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Proposed Rule2024-07646

Federal Motor Vehicle Safety Standards; FMVSS No. 305a Electric-Powered Vehicles: Electric Powertrain Integrity Global Technical Regulation No. 20, Incorporation by Reference

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Published

April 15, 2024

Issuing agencies

Transportation DepartmentNational Highway Traffic Safety Administration

Abstract

Consistent with a Global Technical Regulation on electric vehicle safety, NHTSA proposes to establish Federal Motor Vehicle Safety Standard (FMVSS) No. 305a to replace FMVSS No. 305, "Electric- powered vehicles: Electrolyte spillage and electrical shock protection." Among other improvements, FMVSS No. 305a would apply to light and heavy vehicles and would have performance and risk mitigation requirements for the propulsion battery. Relating to a National Transportation Safety Board recommendation, FMVSS No. 305a would also require manufacturers to submit standardized emergency response information for inclusion on NHTSA's website that would assist first and second responders handling electric vehicles.

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[Federal Register Volume 89, Number 73 (Monday, April 15, 2024)]
[Proposed Rules]
[Pages 26704-26754]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2024-07646]

[[Page 26703]]

Vol. 89

Monday,

No. 73

April 15, 2024

Part V

Department of Transportation

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National Highway Traffic Safety Administration

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49 CFR Part 571

Federal Motor Vehicle Safety Standards; FMVSS No. 305a Electric-Powered
Vehicles: Electric Powertrain Integrity Global Technical Regulation No.
20, Incorporation by Reference; Proposed Rule

Federal Register / Vol. 89 , No. 73 / Monday, April 15, 2024 /
Proposed Rules

[[Page 26704]]

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2024-0012]
RIN 2127-AM43

Federal Motor Vehicle Safety Standards; FMVSS No. 305a Electric-
Powered Vehicles: Electric Powertrain Integrity Global Technical
Regulation No. 20, Incorporation by Reference

AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: Consistent with a Global Technical Regulation on electric
vehicle safety, NHTSA proposes to establish Federal Motor Vehicle
Safety Standard (FMVSS) No. 305a to replace FMVSS No. 305, ``Electric-
powered vehicles: Electrolyte spillage and electrical shock
protection.'' Among other improvements, FMVSS No. 305a would apply to
light and heavy vehicles and would have performance and risk mitigation
requirements for the propulsion battery. Relating to a National
Transportation Safety Board recommendation, FMVSS No. 305a would also
require manufacturers to submit standardized emergency response
information for inclusion on NHTSA's website that would assist first
and second responders handling electric vehicles.

DATES: Comments should be submitted no later than June 14, 2024.
Proposed compliance date: We propose that the compliance date for
the proposed requirements be two years after the date of publication of
the final rule in the Federal Register. Small-volume manufacturers,
final-stage manufacturers, and alterers would be provided an additional
year to comply with the rule beyond the date identified above. We
propose to permit optional early compliance with the rule. After FMVSS
No. 305a is finalized, NHTSA intends to sunset FMVSS No. 305.

ADDRESSES: You may submit comments identified by the docket number in
the heading of this document or by any of the following methods:
<bullet> Federal eRulemaking Portal: Go to <a href="http://www.regulations.gov">http://www.regulations.gov</a>. Follow the instructions for submitting comments on
the electronic docket site by clicking on ``Help'' or ``FAQ.''
<bullet> Mail: Docket Management Facility. M-30, U.S. Department of
Transportation, 1200 New Jersey Avenue SE, West Building, Ground Floor,
Room W12-140, Washington, DC 20590.
<bullet> Hand Delivery: U.S. Department of Transportation, 1200 New
Jersey Avenue SE, West Building, Ground Floor, Room W12-140,
Washington, DC 20590 between 9 a.m. and 5 p.m. Eastern Time, Monday
through Friday, except Federal Holidays.
<bullet> Fax: 202-493-2251.
Instructions: All submissions must include the agency name and
docket number. Note that all comments received will be posted without
change to <a href="http://www.regulations.gov">http://www.regulations.gov</a>, including any personal
information provided. Please see the Privacy Act discussion below. We
will consider all comments received before the close of business on the
comment closing date indicated above. To the extent possible, we will
also consider comments filed after the closing date.
Docket: For access to the docket to read background documents or
comments received, go to <a href="http://www.regulations.gov">www.regulations.gov</a> at any time or to 1200 New
Jersey Avenue SE, West Building Ground Floor, Room W12-140, Washington,
DC 20590, between 9 a.m. and 5 p.m., Monday through Friday, except
Federal Holidays. Telephone: 202-366-9826.
Confidential Business Information: If you claim that any of the
information in your comment (including any additional documents or
attachments) constitutes confidential business information within the
meaning of 5 U.S.C. 552(b)(4) or is protected from disclosure pursuant
to 18 U.S.C. 1905, please see the detailed instructions given under the
Public Participation heading of the SUPPLEMENTARY INFORMATION section
of this document.
Privacy Act: In accordance with 5 U.S.C. 553(c), DOT solicits
comments from the public to better inform its decision-making process.
DOT posts these comments, without edit, including any personal
information the commenter provides, to <a href="http://www.regulations.gov">www.regulations.gov</a>, as
described in the system of records notice (DOT/ALL-14 FDMS), which can
be reviewed at <a href="http://www.transportation.gov/privacy">www.transportation.gov/privacy</a>. In order to facilitate
comment tracking and response, we encourage commenters to provide their
name, or the name of their organization; however, submission of names
is completely optional. Whether or not commenters identify themselves,
all timely comments will be fully considered.

FOR FURTHER INFORMATION CONTACT: For technical issues, you may contact
Ms. Lina Valivullah, Office of Crashworthiness Standards; Telephone:
202-366-8786; Email: <a href="/cdn-cgi/l/email-protection#3975505758176f5855504f4c55555851795d564d175e564f">[email&#160;protected]</a>; Facsimile: (202) 493-
2739. For legal issues, you may contact Ms. K. Helena Sung, Office of
Chief Counsel; Telephone: 202-366-2992; Email: <a href="/cdn-cgi/l/email-protection#e4ac8188818a85cab7918a83a4808b90ca838b92">[email&#160;protected]</a>;
Facsimile: (202) 366-3820. The mailing address of these officials is:
National Highway Traffic Safety Administration, 1200 New Jersey Avenue
SE, Washington, DC 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
II. Background
a. Overview of FMVSS No. 305
b. Overview of GTR No. 20
1. The GTR Process
2. GTR No. 20
III. Proposals Based on GTR No. 20
a. Expanding Applicability of FMVSS No. 305a to Heavy Vehicles
1. Heavy School Buses
2. Heavy Vehicles Other Than School Buses
i. Request for Comment; Mechanical Integrity Test
ii. Request for Comment; Mechanical Shock Test
b. General Specifications Relating To Crash Testing
1. Low Energy Option for Capacitors
2. Assessing Fire or Explosion in Vehicle Post-Crash Test
3. Assessing Post-Crash Voltage Measurements
4. Electrolyte Spillage Versus Leakage
c. REESS Requirements Applicable to All Vehicles
1. Vehicle Controls for Safe REESS Operation
i. Overcharge Protection
ii. Over-Discharge Protection
iii. Overcurrent Protection
iv. Over-Temperature Protection
v. External Short-Circuit Protection
vi. Low-Temperature Protection
2. Mitigating Risk of Thermal Propagation Due to Internal Short
Within a Single Cell in the REESS
i. Safety Need
ii. GTR No. 20 Phase 1 Requirements
iii. NHTSA Proposal
3. Warning Requirements for REESS Operations
i. Thermal Event Warning
ii. Warning in the Event of Operational Failure of REESS Vehicle
Controls
4. Protection Against Water Exposure
i. NHTSA Proposal
A. Vehicle Washing Test
B. Driving Through Standing Water Test
ii. NHTSA's Consideration of Submersions
5. Miscellaneous GTR No. 20 Provisions Not Proposed
i. REESS Vibration Requirements
ii. REESS Thermal Shock and Cycling
iii. REESS Fire Resistance
iv. Low State-of-Charge (SOC) Telltale
IV. Request for Comment on Applying FMVSS No. 305a to Low-Speed
Vehicles
V. Emergency Response Information To Assist First and Second
Responders

[[Page 26705]]

VI. Request for Comment on Placing the Emergency Response
Information and Documentation Requirements in a Regulation Rather
Than in FMVSS No. 305a
VII. Proposed Compliance Dates
VIII. Rulemaking Analyses and Notices
IX. Public Participation
X. Appendices to the Preamble
Appendix A. Table Comparing GTR No. 20, FMVSS No. 305, and FMVSS No.
305a
Appendix B. Request for Comment on Phase 2 GTR No. 20 Approaches
Under Consideration by the IWG

I. Executive Summary

NHTSA is issuing this NPRM to achieve two goals. First, NHTSA
proposes to establish FMVSS No. 305a, ``Electric-powered Vehicles:
Electric Powertrain Integrity,'' to upgrade and replace existing FMVSS
No. 305. Proposed FMVSS No. 305a would have all the requirements of
FMVSS No. 305, but the proposed standard would expand its applicability
to vehicles with a gross vehicle weight rating (GVWR) greater than
4,536 kilograms (kg) (10,000 pounds (lb)) and add requirements and test
procedures covering new aspects of electric vehicle safety, such as the
performance and risk mitigation requirements for the propulsion
battery, referred to as the Rechargeable Electrical Energy Storage
System (REESS). NHTSA is also proposing requirements to ensure first
and second responders have access to vehicle-specific information about
extinguishing REESS fires and mitigating safety risks associated with
stranded energy \1\ when responding to emergencies. The restructured
and upgraded FMVSS No. 305a will facilitate future updates to the
standard as battery technologies and charging systems continue to
evolve. After FMVSS No. 305a is finalized, NHTSA intends to sunset
FMVSS No. 305.
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\1\ Stranded energy is the energy remaining inside the REESS
after a crash or other incident.
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The second goal is to further NHTSA's effort to harmonize the
Federal Motor Vehicle Safety Standards under the Economic Commission
for Europe 1998 Global Agreement (``1998 Agreement''). The efforts of
the U.S. and other contracting parties to the 1998 Agreement culminated
in the establishment of Global Technical Regulation (GTR) No. 20,
``Electric Vehicle Safety.'' \2\ FMVSS No. 305 already incorporates a
substantial portion of GTR No. 20's requirements due to a previous
NHTSA rulemaking. In 2017, NHTSA amended FMVSS No. 305 to include
electrical safety requirements from GTR No. 13, ``Hydrogen and fuel
cell vehicles,'' pertaining to electric vehicle performance during
normal vehicle operation and post-crash.\3\ Because GTR No. 13's
provisions for electric vehicles were later incorporated into what
would become GTR No. 20, the 2017 final rule that adopted GTR No. 13's
provisions adopted what later became many of the requirements of GTR
No. 20. That 2017 rulemaking, however, did not expand the applicability
of FMVSS No. 305 to include heavy vehicles nor did it include
requirements for the REESS. This NPRM proposes these and other GTR No.
20 requirements.
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\2\ GTR No. 20, <a href="https://unece.org/fileadmin/DAM/trans/main/wp29/wp29wgs/wp29gen/wp29registry/ECE-TRANS-180a20e.pdf">https://unece.org/fileadmin/DAM/trans/main/wp29/wp29wgs/wp29gen/wp29registry/ECE-TRANS-180a20e.pdf</a>.
\3\ GTR No. 13 only applied to light vehicles. Normal vehicle
operations include operating modes and conditions that can
reasonably be encountered during typical operation of the vehicle,
such as driving, parking, standing in traffic with vehicle in drive
mode, and charging. Final rule, 82 FR 44950, September 27, 2017.
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High Level Summary of the Proposal

FMVSS No. 305 currently only applies to passenger cars and to
multipurpose passenger vehicles, trucks, and buses with a GVWR of 4,536
kg (10,000 lb) or less (``light vehicles''). Consistent with GTR No.
20, proposed FMVSS No. 305a expands the current applicability of FMVSS
No. 305 to vehicles with a GVWR greater than 4,536 kg (10,000 lb)
(``heavy vehicles''). Under proposed FMVSS No. 305a:
<bullet> Light vehicles would be subject to requirements carried
over from FMVSS No. 305 that ensure the safety of the electrical system
during normal vehicle operations and after a crash (post-crash).\4\
They would also be subject to new requirements for the REESS.
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\4\ Current FMVSS No. 305 light vehicle post-crash test
requirements (front, side, and rear crashes) are aligned with FMVSS
No. 301's light vehicle post-crash test requirements.
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<bullet> Heavy vehicles would be subject to the requirements for
electrical system safety during normal vehicle operations and to
requirements for the REESS. However, except for heavy school buses,
they would not be subject to post-crash requirements. This proposed
exclusion of heavy vehicles, other than school buses, from crash tests,
aligns with similar exclusions in FMVSS No. 301, ``Fuel system
integrity,'' for conventional fuel vehicles and FMVSS No. 303, ``Fuel
system integrity of compressed natural gas vehicles,'' for compressed
natural gas vehicles.
<bullet> Heavy school buses (GVWRs greater than 4,536 kg (10,000
lb)) \5\ would be subject to the requirements for electrical system
safety during normal vehicle operations and to the requirements for the
REESS, and would have to meet post-crash test requirements to ensure
the vehicles protect against unreasonable risk of electric shock and
risk of fire after a crash. The post-crash tests are the same tests
described in FMVSS No. 301 for heavy school buses (impacted at any
point and at any angle by a moving contoured barrier).
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\5\ In the school bus safety area, stakeholders, including
NHTSA, commonly refer to buses with a GVWR over 4,536 kg (10,000 lb)
as ``large'' school buses.
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The post-crash requirements of proposed FMVSS No. 305a for light
vehicles and heavy school buses include electric shock protection
(there are four compliance options--low voltage, electrical isolation,
protective barrier, and low energy for capacitors \6\); REESS
retention; electrolyte leakage; and fire safety. The requirements for
REESS retention and electrolyte leakage are already in FMVSS No. 305,
but this NPRM proposes to enhance some provisions consistent with GTR
No. 20. For example, current FMVSS No. 305 does not specify that there
must be no fire or explosion after a crash test. Electric vehicles may
catch fire long after a collision or other occurrence resulting in a
fault condition. To account for the potential delayed response, NHTSA
is proposing to prohibit fire or explosion for a one-hour post-test
period.
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\6\ FMVSS No. 305 already includes the first three compliance
options for electrical shock protection but not the low energy
option that is available for capacitors in GTR No. 20. This NPRM
would complete the alignment by proposing the low energy option for
capacitors in FMVSS No. 305a. NHTSA had considered this option years
ago and had decided against it. As explained in detail in sections
below, NHTSA has changed its view on the matter after further
considering data and analysis from the GTR.
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A substantial portion of this NPRM focuses on safety provisions for
the propulsion battery, the REESS. For what would be the first time in
an FMVSS, proposed FMVSS No. 305a includes comprehensive performance
requirements and risk mitigation strategies for the REESS. These REESS
requirements would apply to all vehicles, regardless of GVWR. A REESS
provides electric energy for propulsion and may include necessary
ancillary systems for physical support, thermal management, electronic
controls, and casings. The proposed requirements set a level of
protection of the REESS against external fault inputs, ensure the REESS
operations are within the manufacturer-specified functional range, and
increase the likelihood of safe operation of the REESS and other
electrical systems of the vehicle during

[[Page 26706]]

and after water exposure during normal vehicle operations.\7\
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\7\ ``Normal vehicle operation'' means situations such as
driving through a pool of standing water or exposing the vehicle to
an automated car wash. This NPRM does not propose requirements to
address vehicle fires due to vehicle submersions in floods and storm
surges, as GTR No. 20 does not have specific requirements to address
this area. NHTSA is researching this latter area.
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Proposed FMVSS No. 305a addresses some aspects of REESS safety
through documentation measures, consistent with GTR No. 20.
``Documentation measures'' means a list of information provided by
manufacturers, at NHTSA's request, that demonstrate that they
considered, assessed, and mitigated identified risks for safe operation
of the vehicle. These proposed documentation requirements would
address: (a) safety risk mitigation associated with charging and
discharging during low temperature; (b) the safety risks from thermal
propagation in the event of single-cell thermal runaway \8\ (SCTR) due
to an internal short-circuit of a single cell; and (c) providing a
warning if there is a malfunction of vehicle controls that manage REESS
safe operation. The GTR takes a documentation approach on these aspects
of safety because of the rapidly evolving electric vehicle technologies
and the variety of available REESS and electric vehicle designs. The
Informal Working Group experts that drafted the GTR determined there
currently are no objective test procedures to evaluate safety risk
mitigation designs or the operations of warnings of a malfunction of
vehicle controls in a manner that is not design restrictive.
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\8\ Thermal runaway means an uncontrolled increase of cell
temperature caused by exothermic reactions inside the cell.
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NHTSA tentatively agrees with this approach given the current state
of knowledge. Thus, until test procedures and performance criteria can
be developed for all vehicle powertrain architectures, proposed FMVSS
No. 305a would require manufacturers to submit documentation to NHTSA,
at NHTSA's request, that identify all known safety hazards, describe
their risk mitigation strategies for the safety hazards, and, if
applicable, describe how they provide a warning to address a safety
hazard.\9\ The purpose of the documentation approach is two-fold. Given
the variation of battery design and design specific risk mitigation
systems, the documentation requirement would be a means of assuring
that each manufacturer has identified safety risks and safety risk
mitigation strategies. The requirement provides a means for NHTSA to
learn of the risks associated with the REESS, understand how the
manufacturer is addressing the risks, and oversee those safety hazards.
This approach is battery technology neutral, not design restrictive,
and is intended to evolve over time as battery technologies continue to
rapidly evolve. It is an interim measure intended to assure that
manufacturers will identify and address the safety risks of the REESS
until such time objective performance standards can be developed that
can be applied to all applicable REESS designs. NHTSA would also
acquire information from the submissions to learn about the safety of
the REESS and potentially develop the future performance standards for
FMVSS No. 305a. The proposed documentation requirements are based on
the approach of GTR No. 20, but NHTSA proposes to focus the GTR's
documentation requirements to enable the agency to obtain more targeted
information from manufacturers.\10\
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\9\ Section 30166 of the Vehicle Safety Act authorizes the
Secretary of Transportation (NHTSA by delegation) the ability to
request and inspect manufacturer records that are necessary to
enforce the prescribed regulations.
\10\ Given the proposed documentation specifications are more
akin to disclosure requirements that could be issued under general
NHTSA regulation rather than pursuant to an FMVSS with specified
test procedures, the agency also requests comment on whether the
proposed documentation requirements would be better placed in a
general agency regulation than in the proposed FMVSS No. 305a.
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As part of NHTSA's battery initiative \11\ and in response to a
2020 NTSB recommendation,\12\ this NPRM proposes to include in FMVSS
No. 305a a requirement that vehicle manufacturers submit to NHTSA
emergency response guides (ERGs) and rescue sheets for each vehicle
make, model, and model year. The purpose of the requirement is to
provide information to first \13\ and second \14\ responders regarding
the safe handling of the vehicle in emergencies and for towing and
storing operations. The uploaded ERGs and rescue sheets would be
publicly available on NHTSA's website for easy searchable access. ERGs
and rescue sheets communicate vehicle-specific information related to
fire, submersion, and towing, as well as the location of components in
the vehicle that may expose the vehicle occupants or rescue personnel
to risks, the nature of a specific function or danger, and devices or
measures which inhibit a dangerous state.
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\11\ <a href="https://www.nhtsa.gov/battery-safety-initiative">https://www.nhtsa.gov/battery-safety-initiative</a>.
\12\ ``Safety risks to emergency responders from lithium-ion
battery fires in electric vehicles,'' Safety Report NTSB/SR-20/01,
PB2020-101011, National Transportation Safety Board, <a href="https://www.ntsb.gov/safety/safety-studies/Documents/SR2001.pdf">https://www.ntsb.gov/safety/safety-studies/Documents/SR2001.pdf</a>.
\13\ ``First responder'' means a person with specialized
training such as a law enforcement officer, paramedic, emergency
medical technician, and/or firefighter, who is typically one of the
first to arrive and provide assistance at the scene of an emergency.
\14\ ``Second responder'' means a worker who supports first
responders by cleaning up a site, towing vehicles, and/or returning
services after an event requiring first responders.
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NHTSA would require standardized formatting of the information. The
ERG and rescue sheet requirements would meet the layout and format
specified in ISO-17840, ``Road vehicles--Information for first and
second responders,'' which standardize color-coded sections in a
specific order to help first and second responders quickly identify
pertinent vehicle-specific rescue information. The standardized
information would be available and understandable to first and second
responders so they can easily refer to vehicle-specific rescue
information en route to or at the scene of a crash or fire event and
respond to the emergency quickly and safely.
NHTSA believes there are no notable costs associated with this
NPRM. This proposal closely mirrors the electrical safety provisions of
GTR No. 20, which have been voluntarily implemented by manufacturers in
this country. The agency believes that the proposed safety standards
are widely implemented by manufacturers of light and heavy electric
vehicles and heavy electric school buses. Manufacturers are also
already providing emergency response information to the National Fire
Protection Association (NFPA); under proposed FMVSS No. 305a they would
just have to standardize the format and submit the information to
NHTSA.\15\
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\15\ Similar to the issue discussed above regarding having the
proposed documentation requirements in a general regulation rather
than in FMVSS No. 305a, the agency also requests comment on whether
the proposed ERG and rescue sheet requirements would be better
placed in a general agency regulation than in proposed FMVSS No.
305a.
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Lastly, current FMVSS No. 305 does not apply to vehicles that
travel under 40 km/h (25 mph), such as low-speed vehicles.\16\ Given
there are low-speed vehicles that are also electric-powered vehicles,
NHTSA requests comments on the possibility of applying aspects of FMVSS
No. 305a to low-speed vehicles to ensure a level of protection against
shock and fire, particularly during normal vehicle operation, and to
assure the safe operation of the REESS.
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\16\ ``Low-speed vehicle'' is defined in 49 CFR 571.3. See also
FMVSS No. 500, ``Low speed vehicles,'' 49 CFR 500.
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II. Background

a. Overview of FMVSS No. 305

The purpose of FMVSS No. 305, ``Electric-powered vehicles:
electrolyte

[[Page 26707]]

spillage and electrical shock protection,'' is to reduce deaths and
injuries from electrical shock. The standard applies only to light
vehicles (vehicles with a GVWR less than or equal to 4,536 (kg) (10,000
(lb)). The standard's requirements reduce the risk of harmful electric
shock: (a) during normal vehicle operation; \17\ and (b) in post-crash
situations (to protect vehicle occupants, and rescue workers and others
who may come in contact with the vehicle after a crash). The standard's
requirements for the former protect against direct and indirect contact
of high voltage sources during everyday operation of the vehicles. The
focus of this ``in-use'' testing (unlike ``post-crash'' testing,
discussed below) deals with performance criteria that would be assessed
without first exposing the vehicle to a crash test.
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\17\ Normal vehicle operation includes operating modes and
conditions that can reasonably be encountered during typical
operation of the vehicle, such as driving, parking, and standing in
traffic, as well as charging using chargers that are compatible with
the specific charging ports installed on the vehicle. It does not
include conditions where the vehicle is damaged, either by a crash
or road debris, subjected to fire or water submersion, or in a state
where service and/or maintenance is needed or being performed.
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Normal Vehicle Operations. FMVSS No. 305 requires vehicles to
provide the following measures to protect against electric shock during
normal vehicle operations. Vehicles must prevent direct contact of high
voltage sources (those operating with voltage greater than 30 VAC or 60
VDC) \18\; prevent indirect contact of high voltage sources;
electrically isolate high voltage sources from the electric chassis
(500 ohms/volt or higher for alternating current (AC) and 100 ohms/volt
or higher for direct current (DC) sources); mitigate risk of driver
error (indicate to the driver when the vehicle is in possible active
driving mode at startup and when the driver is leaving the vehicle, and
prevent vehicle movement by its own propulsion system when the vehicle
charging system is connected to the external electric power supply).
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\18\ VAC--volts of alternating current; VDC--volts of direct
current.
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Post-Crash Protections. For post-crash protections, FMVSS No. 305
requires vehicles to meet the following provisions during and after the
crash tests specified in the standard. FMVSS No. 305 limits electrolyte
spillage from propulsion batteries and requires the REESS to remain
attached to the vehicle and not enter the passenger compartment. The
standard requires that during and after a crash test, high voltage
sources in a vehicle must be either electrically isolated from the
vehicle's chassis; of a voltage below specified levels considered safe
from electric shock hazards; or prevented from direct or indirect
contact by occupants or emergency services personnel by use of physical
barriers. The standard specifies that the post-crash requirements must
be met after crash tests involving: a frontal impact up to and
including 48 kilometer per hour (km/h) (30 mile per hour (mph)) into a
fixed collision barrier; an impact of a moving barrier at 80 km/h (50
mph) into the rear of the vehicle; an impact of a moving barrier at 53
km/h (33 mph) into the side of the vehicle; and under static rollover
conditions after each such impact.
FMVSS No. 305 already has many of GTR No. 20's requirements for
light vehicles, including requirements for electrical safety during
normal vehicle operation; post-crash electrolyte spillage; post-crash
REESS retention; and most of the GTR's post-crash electrical safety
options for high voltage sources.

b. Overview of GTR No. 20

1. The GTR Process
The United States is a contracting party to the ``1998 Agreement''
(the Agreement concerning the Establishing of Global Technical
Regulations for Wheeled Vehicles, Equipment and Parts which can be
fitted and/or be used on Wheeled Vehicles). This agreement entered into
force in 2000 and is administered by the UN Economic Commission for
Europe's (UN ECE's) World Forum for the Harmonization of Vehicle
Regulations (WP.29). The purpose of this agreement is to establish
Global Technical Regulations (GTRs).
In March 2012, UNECE WP.29 formally adopted the proposal to
establish GTR No. 20 at its one-hundred-and-fifty-eighth session. NHTSA
chaired the development of GTR No. 20 and voted in favor of
establishing GTR No. 20.
As a Contracting Party Member to the 1998 Global Agreement who
voted in favor of GTR No. 20, NHTSA is obligated to initiate the
process used in the U.S. to adopt the GTR as an agency regulation. By
issuing this NPRM, NHTSA is initiating the process to consider adoption
of GTR No. 20. As noted above, under the terms of the 1998 Agreement,
NHTSA is not obligated to adopt the GTR after initiating this process.
In deciding whether to adopt a GTR as an FMVSS, NHTSA follows the
requirements for NHTSA rulemaking, including the Administrative
Procedure Act, the National Traffic and Motor Vehicle Safety Act
(Vehicle Safety Act), Presidential Executive Orders, and DOT and NHTSA
policies, procedures, and regulations. Among other things, FMVSSs
issued under the Vehicle Safety Act ``shall be practicable, meet the
need for motor vehicle safety, and be stated in objective terms.'' \19\
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\19\ 49 U.S.C. 30111.
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2. GTR No. 20
GTR No. 20 establishes performance-orientated requirements that
reduce potential safety risks of electric vehicles (EVs) while in use
and after a crash event. The GTR includes provisions that address
electrical shock associated with high voltage circuits of EVs and
potential hazards associated with lithium-ion batteries and/or other
REESS. One of the principles for developing GTR No. 20 was to address
unique safety risks posed by electric vehicles and their components to
ensure a safety level equivalent to conventional vehicles with internal
combustion engines.
The requirements in GTR No. 20 were developed in Phase 1 of the
GTR. GTR No. 20 was developed in phases due to the differing stages at
which technologies have been developed and evaluated. The informal
working group (IWG) that developed the GTR determined that Phase 1
would address issues relating to the safe operation of the rechargeable
electrical energy storage system (REESS), and for mitigating risks of
fire and other safety risks associated with the REESS. In Phase 2,
which is on-going, the IWG is addressing issues involving long-term
research and verification.\20\ This NPRM pertains to the adoption of
the GTR as developed in Phase 1.
---------------------------------------------------------------------------

\20\ In Appendix B to this preamble, NHTSA requests comments on
some issues under development in Phase 2.
---------------------------------------------------------------------------

GTR No. 20 applies to all electric-powered vehicles regardless of
GVWR, in contrast to FMVSS No. 305, which only applies to light
vehicles. FMVSS No. 305 currently includes the majority of GTR No. 20's
requirements and applies these to light vehicles. GTR No. 20 also has
safety requirements for the REESS beyond those in FMVSS No. 305. These
additional requirements in GTR No. 20 for the REESS include:

<bullet> Safe operation of REESS under the following exposures
during normal vehicle operations:

[cir] REESS protection under external fault conditions and extreme
operating temperatures:

--External short circuit
--Overcharge
--Over-discharge

[[Page 26708]]

--Overcurrent
--High operating temperature
--Low operating temperature

[cir] Management of REESS emitted gases
[cir] Water exposure during vehicle washing and driving through 10-
centimeter (cm) deep water on roadway.
[cir] Thermal shock and cycling (-40 [deg]C to 60 [deg]C) * \21\
---------------------------------------------------------------------------

\21\ The asterisk notes that this NPRM is not proposing to adopt
the GTR No. 20 requirement.
---------------------------------------------------------------------------

[cir] Resistance to short duration external gasoline pool fire *
[cir] Vibration environment during normal vehicle operations *

<bullet> Warning systems for REESS safe operation in case of:

[cir] Low energy content in REESS * \22\
---------------------------------------------------------------------------

\22\ This NPRM does not propose to require a warning for low
energy in REESS. There is no such warning requirement for
conventional fuel vehicles in the event of low-fuel, yet all
conventional fuel vehicles have a low fuel indicator because it is a
consumer convenience feature. The agency expects that, similarly, a
low energy in REESS indicator will be voluntarily provided in all
electric-powered vehicles.
---------------------------------------------------------------------------

[cir] REESS control operational failure
[cir] Thermal runaway propagation due to single cell short circuit in
REESS
[cir] Thermal event in REESS
<bullet> Installation (location) of REESS on the vehicle \23\
---------------------------------------------------------------------------

\23\ This requirement is intended for countries with type
approval systems where a generic REESS can be approved separate from
the vehicle. A vehicle with a pre-approved REESS that complies with
the REESS installation requirement would not have to undergo post-
crash safety assessment for approval. This installation requirement
would not apply in the U.S. with a self-certification system.

This NPRM proposes to complete the alignment of FMVSS No. 305 with
GTR No. 20 by extending the standard's electrical safety requirements
to heavy vehicles. This NPRM also proposes to adopt the above
requirements for the REESS to light and heavy vehicles, except as noted
by an asterisk, because requirements for thermal shock and cycling,
resistance to short duration external pool fire, and vibration
environment are already included under United States Hazardous
Materials Regulations (HMR), 49 CFR parts 171 to 180, in accordance
with the international lithium battery transportation requirements of
UN 38.3, ``Transport of dangerous goods: Manual of tests and
criteria.'' To avoid redundancy, NHTSA is not proposing adding these
requirements into FMVSS No. 305a. NHTSA explains the bases for the
proposals and, for provisions not proposed, the reasons the agency has
not proposed them in this NPRM.
GTR No. 20 includes post-crash requirements but does not specify
the crash tests for post-crash evaluation. Instead, the GTR allows
contracting parties to apply the crash tests in their regulations.
Further, the GTR allows contracting parties to permit regulated
entities to comply with post-crash requirements without conducting
vehicle crash tests. In place of crash tests, a contracting party may
specify tests for ``mechanical integrity'' and ``mechanical shock'' of
the REESS. The mechanical integrity test uses a quasi-static load of
100 kN on the REESS to evaluate the safety performance of the REESS
under contact loads that may occur during vehicle crash. The mechanical
shock test accelerates the REESS on a sled system to evaluate the
safety performance of the REESS and the integrity of the REESS mounting
structures to the vehicle under inertial loads that may occur. NHTSA
discusses its assessment of the component level mechanical integrity
and mechanical shock test procedures and requests comment on these
issues later in this NPRM.

III. Proposals Based on GTR No. 20

a. Expanding Applicability of FMVSS No. 305a to Heavy Vehicles

NHTSA proposes to harmonize the application of FMVSS No. 305a with
GTR No. 20. Currently, FMVSS No. 305 applies to electric-powered
vehicles with a GVWR less than or equal to 4,536 kg (10,000 lb); it
does not apply to electric vehicles with a GVWR greater than 4,536 kg
(10,000 lb). GTR No. 20 applies to both light and heavy electric
vehicles. NHTSA proposes to apply FMVSS No. 305a to both light and
heavy electric vehicles. The fundamentals for protecting against an
electrical shock for light vehicles are the same as for heavy vehicles.
A failure of a high voltage system may cause injurious electric shock
to the human body.
Specifically, NHTSA proposes to apply FMVSS No. 305a to all
passenger cars, multipurpose passenger vehicles, trucks, and buses,
regardless of their GVWR, that use electrical propulsion components
with working voltages greater than or equal to 60 VDC or 30 VAC, and
whose speed attainable over a distance of 1.6 kilometers (km) (1 mile)
on a paved level surface is more than 40 km/h (25 miles per hour
(mph)).\24\ The NPRM proposes to carry over the current requirements
for light vehicles in FMVSS No. 305 to FMVSS No. 305a, except some
provisions as enhanced by this NPRM if adopted by a final rule. To sum,
light vehicles would have to meet the requirements for normal vehicle
operations and the requirements proposed in this NPRM for the REESS.
Further, they would have to meet requirements for post-crash
protections following a crash test. Under proposed FMVSS No. 305a,
heavy school buses would have to meet the requirements for normal
vehicle operations and for the REESS, and, following a specific crash
test, requirements for post-crash protections. The agency is not
adopting the provision in GTR No. 20 that conducts mechanical integrity
and mechanical shock tests (component-level) for light vehicles and for
heavy school buses. NHTSA believes that post-crash safety is better
evaluated at a system level in a crash test than in component-level
tests. Currently there are crash tests for light vehicles and school
buses, thus, NHTSA proposes to conduct post-crash safety after the
specified crash tests.
---------------------------------------------------------------------------

\24\ Current FMVSS No. 305 does not apply to these vehicles that
travel under 40 km/h (25 mph).
---------------------------------------------------------------------------

Heavy vehicles other than heavy school buses would be subject to
the requirements for normal vehicle operations described above and the
requirements for the REESS. They would not be subject to crash testing
requirements because the agency does not know of a crash test that
would be appropriate for the vehicles at this time. However, while
NHTSA does not have a sufficient basis to proceed currently with
dynamic or quasi-static requirements for heavy vehicles other than
school buses, this NPRM requests comment on this issue. NHTSA is
interested in the merits of component-level tests that are
representative of impact loads in heavy vehicle crashes and the
appropriateness of applying the tests to different weight classes of
heavy vehicles. Even in the absence of post-crash testing requirements,
NHTSA tentatively concludes that meeting requirements for normal
vehicle operations and for the REESS, as a starting point, will enhance
the safety of these heavy electric vehicles.
1. Heavy School Buses
NHTSA proposes to distinguish heavy school buses from other types
of heavy vehicles and subject them to crash testing because the school
vehicles will be carrying children. This NPRM proposes to assess the
post-crash safety of heavy school buses (school buses with a GVWR
greater than 4,536 kg (10,000 lb)) in a dynamic moving contoured
barrier test. This proposal would be consistent with current school bus
safety standards. FMVSS No. 301, ``Fuel system integrity,'' and FMVSS
No. 303, ``Fuel system integrity of compressed natural gas vehicles,''
require heavy school buses using

[[Page 26709]]

conventional fuel or compressed natural gas for propulsion,
respectively, to maintain fuel system integrity in a crash test where a
moving contoured barrier traveling at any speed up to 48 km/h (30 mph)
impacts the school bus at any point and angle. These standards set this
high level of safety for heavy school buses even though FMVSS Nos. 301
and 303 do not apply to other types of heavy vehicles.
NHTSA recognizes that FMVSS No. 305 currently does not apply to nor
has a crash test requirement for heavy school buses. When FMVSS No. 305
was first promulgated in September 2000, NHTSA decided not to apply
proposed FMVSS No. 305 to heavy school buses. NHTSA made this decision
after agreeing with commenters that applying the standard to the
vehicles at that time could have substantial effect, in terms of cost
and weight, on heavy school buses and potentially restrict further
development.\25\ The prevailing technology at that time was a series of
conventional lead-acid batteries as the energy source for propulsion.
Since the 1990s and early 2000s, battery technology and electric
powertrains have evolved to include nickel metal hydride and lithium-
ion batteries for electric vehicles. The weight and cost concerns
raised for electric school buses in 2000 are no longer obstacles with
current lithium-ion battery technologies because of their high energy
density and their widespread use. Several school bus manufacturers are
currently manufacturing and offering for sale heavy school buses with
high voltage electric propulsion systems. Given the development of the
technology and practicability of designing and producing heavy electric
school buses, NHTSA tentatively concludes it is appropriate to adopt
requirements to ensure post-crash safety of heavy electric school buses
and maintain the current high level of safety of heavy school buses.
---------------------------------------------------------------------------

\25\ Final rule, 65 FR 57980, September 27, 2000.
---------------------------------------------------------------------------

NHTSA is proposing to include in FMVSS No. 305a a requirement that
heavy school buses with high voltage electric propulsion systems meet
the requirements for normal vehicle operations (assessed prior to a
crash test) and the proposed post-crash electrical safety requirements
when impacted by the moving contoured barrier specified in FMVSS No.
301. The crash test requirement would align FMVSS No. 305a's
requirements for heavy school buses with those of FMVSS Nos. 301 and
303. Due to the number of electric school bus manufacturers and sales
since 2000, NHTSA tentatively concludes that meeting the proposed
standard would have no substantial effect on cost and weight due to
widespread use of lithium-ion battery and conformance to the proposed
post-crash safety requirements.\26\
---------------------------------------------------------------------------

\26\ Currently, all major school bus manufacturers (Blue Bird,
IC Bus, Thomas Built) are offering large and small electric school
buses (see AFDC-electric school bus) and many school districts have
introduced electric powered school buses in their fleets. As of June
2023, there are 2,277 electric school buses that are either on
order, delivered or operating in the U.S. In total, there are now
5,982 committed electric school buses in the U.S. https://
www.wri.org/insights/where-electric-school-buses-
us#:~:text=As%20of%20June%202023%2C%20there,more%20buses%20since%20Ju
ne%202022.
---------------------------------------------------------------------------

2. Heavy Vehicles Other Than School Buses
There are currently no heavy vehicle crash tests in FMVSS. Heavy
vehicles are typically made to order with different configurations \27\
based on the operational needs of the purchaser and are produced in low
volume. Conducting crash tests of various design configurations from a
small volume of representative vehicles would be cost prohibitive.
There could also be practicability constraints for conducting crash
tests on higher weight classes of heavy vehicles.
---------------------------------------------------------------------------

\27\ These differences include the number of fuel containers and
battery packs and the location and attachment of fuel lines and fuel
containers.
---------------------------------------------------------------------------

In this NPRM, NHTSA has proposed requirements to ensure post-crash
safety using full vehicle crash tests for light vehicles and heavy
school buses. Such full vehicle crash tests evaluate post-crash safety
at a system level, so NHTSA is not considering component-level tests of
the REESS for those vehicles. However, since there are no full vehicle
crash tests currently in FMVSSs for heavy vehicles (other than heavy
school buses), NHTSA seeks comment on considerations for component-
level tests (other than the mechanical integrity and mechanical shock
tests in GTR No. 20) that are representative of impact loads in heavy
vehicle crashes and that can be applied to different weight classes of
heavy vehicles.
i. Request for Comment; Mechanical Integrity Test
There are currently no crash tests specified in the FMVSSs \28\ for
evaluating the integrity of the fuel system or propulsion system of
heavy vehicles other than heavy school buses. GTR No. 20 provides an
option for evaluating post-crash safety of light vehicles by way of a
mechanical integrity test (crush test) of the REESS as an item of
vehicle equipment, instead of a full vehicle crash test as in FMVSS No.
305. The loads in the mechanical integrity requirements in the GTR No.
20 were derived from REESS contact loads measured in light passenger
vehicle crash tests per UN Regulations ECE R. No. 12, ``Uniform
provisions concerning the approval of vehicles with regard to the
protection of the driver against the steering mechanism in the event of
impact,'' ECE R.94, ``Uniform provisions concerning the approval of
vehicles with regard to the protection of the occupants in the event of
a frontal collision,'' and ECE R.95, ``Uniform provisions concerning
the approval of vehicles with regard to the protection of occupants in
the event of a lateral collision,'' using electric and hybrid-electric
vehicles available on the market.
---------------------------------------------------------------------------

\28\ FMVSS No. 301, ``Fuel system integrity,'' and FMVSS No.
303, ``Fuel system integrity of compressed natural gas vehicles,''
only applies to light vehicles and to heavy school buses.
---------------------------------------------------------------------------

In the mechanical integrity test, a quasi-static load is applied to
the charged REESS \29\ along with any subsystem components (including
crush protection systems specified by the manufacturer) along the
longitudinal axis of the vehicle (along the direction of vehicle
travel) or the lateral axis (perpendicular to the longitudinal axis). A
peak load of 100 kN is applied within 3 minutes and maintained for at
least 100 milliseconds. During the integrity test, the REESS is
required to have no evidence of electrolyte leakage, fire, or
explosion. The REESS is required to have electric isolation of at least
100 ohms/volt or provide protection level IPXXB against direct contact
of high voltage sources.\30\
---------------------------------------------------------------------------

\29\ The REESS is charged to 95 percent state-of-charge for
REESS designed to be externally charged and charged to no less than
90 percent of state-of-charge for REESS designed to be charged only
by an energy source on the vehicle.
\30\ IPXXB and IPXXD ``protection levels'' refer to the ability
of the physical barriers to prevent entrance of a probe into the
enclosure, to ensure no direct contact with high voltage sources.
``IPXXB'' is a probe representing a small human finger. ``IPXXD'' is
a slender wire probe. Protection degrees IPXXD and IPXXB are
International Electrotechnical Commission specifications for
protection from direct contact of high voltage sources.
---------------------------------------------------------------------------

Because there are no full vehicle crash tests currently in FMVSSs
for heavy vehicles (other than heavy school buses), NHTSA seeks comment
on a mechanical integrity test for REESS on heavy vehicles to evaluate
post-crash safety at a component-level. As noted above, the current
quasi-static loads of the integrity test specified in GTR No. 20 are
specific to light vehicles. NHTSA seeks comment on the parameters for a

[[Page 26710]]

possible quasi-static crush test for the REESS on heavy vehicles.\31\
The agency requests feedback on the merits of the integrity test in
assessing post-crash safety for heavy vehicle REESS. NHTSA seeks
comment on the practicability of such a test and on the specifics of
subsystem components that should be included with the REESS while
conducting the crush test. NHTSA requests that commenters provide data
to substantiate their assertions.
---------------------------------------------------------------------------

\31\ NHTSA's research evaluated the crush resistance of REESS
using a displacement-based loading method. See Ford Safety
Performance of Rechargeable Energy Storage Systems, Appendix A, DOT
HS 812 756, July 2019. <a href="https://rosap.ntl.bts.gov/view/dot/41840">https://rosap.ntl.bts.gov/view/dot/41840</a>.
---------------------------------------------------------------------------

ii. Request for Comment; Mechanical Shock Test
NHTSA seeks comment to inform our research on a mechanical shock
test for REESS on heavy vehicles to evaluate post-crash safety at a
component level. The aim of the mechanical shock requirement in GTR No.
20 is to verify the safety performance of the REESS under inertial
loads which may occur during an impact. The requirement evaluates
specifically the performance of the REESS mountings and fixtures to the
vehicle.
The mechanical shock test is conducted with the REESS along with
any subsystem components installed on a sled system using the mounting
structures that are used for installing the REESS to the vehicle. The
REESS is decelerated or accelerated with an acceleration profile within
the acceleration corridor in Figure 1 and in accordance with
acceleration magnitudes in Table 1 through Table 3 for different
vehicle GVWRs. The test concludes with an observation period of one
hour at the ambient temperature conditions of the test environment.
[GRAPHIC] [TIFF OMITTED] TP15AP24.044

Figure 1--Generic Description of Test Pulses--Mechanical Shock Test

Table 1--Mechanical Shock Test--Acceleration Values for Vehicles With a GVWR Less Than or Equal to 3,500 kg
(7,716 lbs)
----------------------------------------------------------------------------------------------------------------
Acceleration (g)
Point Time (ms) -------------------------------
Longitudinal Transverse
----------------------------------------------------------------------------------------------------------------
A............................................................... 20 0 0
B............................................................... 50 20 8
C............................................................... 65 20 8
D............................................................... 100 0 0
E............................................................... 0 10 4.5
F............................................................... 50 28 15
G............................................................... 80 28 15
H............................................................... 120 0 0
----------------------------------------------------------------------------------------------------------------

Table 2--Mechanical Shock Test--Acceleration Values for Vehicles With a GVWR Greater Than 3,500 kg (7,716 lbs)
and Less Than or Equal to 12,000 kg (26,455 lbs)
----------------------------------------------------------------------------------------------------------------
Acceleration (g)
Point Time (ms) -------------------------------
Longitudinal Transverse
----------------------------------------------------------------------------------------------------------------
A............................................................... 20 0 0
B............................................................... 50 10 5
C............................................................... 65 10 5
D............................................................... 100 0 0

[[Page 26711]]

E............................................................... 0 5 2.5
F............................................................... 50 17 10
G............................................................... 80 17 10
H............................................................... 120 0 0
----------------------------------------------------------------------------------------------------------------

Table 3--Mechanical Shock Test--Acceleration Values for Vehicles With a GVWR Greater Than 12,000 kg (26,455 lbs)
----------------------------------------------------------------------------------------------------------------
Acceleration (g)
Point Time (ms) -------------------------------
Longitudinal Transverse
----------------------------------------------------------------------------------------------------------------
A............................................................... 20 0 0
B............................................................... 50 6.6 5
C............................................................... 65 6.6 5
D............................................................... 100 0 0
E............................................................... 0 4 2.5
F............................................................... 50 12 10
G............................................................... 80 12 10
H............................................................... 120 0 0
----------------------------------------------------------------------------------------------------------------

During the mechanical shock test, the REESS is required to have no
evidence of electrolyte leakage, fire, or explosion. The REESS is
required to have electric isolation of at least 100 ohms/volt or have
protection degree IPXXB.
Since there are no full vehicle crash tests currently in FMVSSs for
heavy vehicles (other than heavy school buses) to evaluate post-crash
safety at a system level, NHTSA seeks comment to inform possible future
research on a mechanical shock test for REESS on heavy vehicles to
evaluate post-crash safety at a component level. Among other matters,
NHTSA requests comment on the following apparent limitations of the GTR
test. The mechanical shock test in GTR No. 20 aims primarily at
evaluating the safety performance of the REESS mounting fixture, which
does not appear to address a safety need presently observed in the
field.\32\ Furthermore, the accelerations captured in the GTR No. 20
for the mechanical shock requirement may be too low, according to a
technical study performed by the Transportation Research
Laboratory.\33\ The aim of the technical study was to review the
appropriateness of the crash pulses used in current European
regulations. This study determined that the crash pulse requirements in
a number of the EU regulations (including R67, R100, and R110) are not
representative of current vehicles. (These are among the reasons NHTSA
is not proposing the mechanical shock test in GTR No. 20 for heavy
vehicles in this NPRM.)
---------------------------------------------------------------------------

\32\ Under the Vehicle Safety Act, the FMVSSs must, among other
things, be practicable, meet the need for motor vehicle safety, and
be stated in objective terms. (49 U.S.C. 30111(a).)
\33\ European Commission, Directorate-General for Internal
Market, Industry, Entrepreneurship and SMEs, Edwards, M., Hylands,
N., Grubor, D., et al., Technical study to review the
appropriateness of crash pulses used in current EU legislation:
final report, Section 4.4, Publications Office, 2021, <a href="https://data.europa.eu/doi/10.2873/58935">https://data.europa.eu/doi/10.2873/58935</a>.
---------------------------------------------------------------------------

NHTSA seeks comment on the relevance of the mechanical shock test
for heavy vehicles. NHTSA seeks comment on how the mechanical shock
test would be performed on heavy vehicle REESSs, the appropriate
accelerations levels that would be representative of acceleration
levels observed in the field or in crash tests, and appropriate
requirements which the REESS would need to meet in a mechanical shock
test.
NHTSA seeks comment on the best approach or test method for
evaluating post-crash safety for electric vehicles with a GVWR greater
than 4,536 kg (10,000 lb). Specifically, NHTSA seeks comment and
recommendations on other applicable safety tests and corresponding
objective performance criteria to evaluate the propulsion system crash
safety performance of vehicles with a GVWR greater than 4,536 kg
(10,000 lb). NHTSA seeks comment on whether the moving contoured
barrier crash test proposed for heavy school buses in the above section
in this preamble can or should be applied to all heavy vehicles.

b. General Specifications Relating To Crash Testing

This NPRM proposes several general provisions from GTR No. 20 that
would apply to various testing and performance requirements. NHTSA
highlights the following proposals below. These provisions pertain to
light vehicles and heavy school buses subject to the crash testing
requirements of proposed FMVSS No. 305a.
1. Low Energy Option for Capacitors
Currently, FMVSS No. 305 S5.3 requires that vehicles meet one of
the following three criteria post-crash: electrical isolation; absence
of high voltage; or physical barrier protection. This NPRM proposes a
low energy option for capacitors in the electric powertrain in FMVSS
No. 305a.
Capacitors store electrical energy and may be connected directly to
the chassis in some electric power trains. In fuel cell electric
vehicles (FCEVs), the high-voltage systems may contain capacitors that
are connected to high voltage buses and are not electrically isolated.
Such capacitors may be high voltage sources post-crash (because a
charged capacitor may not discharge quickly) and may not be able to
comply with post-crash electrical safety requirements using the direct
and indirect contact protection option or the electrical isolation.
However, capacitors may not pose a safety hazard when contacted, even
though they may be high voltage sources post-crash, because they are
low energy high voltage sources.

[[Page 26712]]

NHTSA has previously considered this issue. In a 2007 NPRM
responding to petitions for rulemaking from what were then the Alliance
of Automobile Manufacturers (Alliance) and the Association of
International Automobile Manufacturers (AIAM),\34\ NHTSA sought
comments regarding a request of the petitioners to include 0.2 Joule
(J) as an appropriate low energy threshold for electrical safety
compliance post-crash for high voltage sources.\35\ The petitioners
believed that the low energy option was non-harmful, and argued in
their subsequent comments to the NPRM \36\ that the option is necessary
due to the presence of x- and y-capacitors in the powertrain of fuel
cell vehicles. After evaluating the comments, NHTSA ultimately
disagreed with the petitioners and decided against a low energy option
for post-crash electrical safety because the agency was not convinced
that a low energy option was needed and had concerns about the possible
disparity between the level of safety provided by 0.2 J of energy and
the electrical isolation requirement.\37\ At that time a safety need
for a low energy option was not yet clear and the agency expressed
concerns regarding the practicality of measuring the residual energy in
a crash test environment.
---------------------------------------------------------------------------

\34\ In January 2020, the two industry associations merged to
form the Alliance for Automotive Innovation (generally referred to
as the Auto Innovators).
\35\ 72 FR 57260, October 9, 2007.
\36\ NHTSA-2007-28517-0004.
\37\ Final rule, 75 FR 33515, 33519; June 14, 2010.
---------------------------------------------------------------------------

NHTSA is reconsidering this issue in this NPRM. GTR No. 20 contains
a detailed analysis of the 0.2 Joules energy limit for the low energy
post-crash electrical safety compliance option. While the 2007 NPRM
considered a low energy post-crash electrical safety compliance option
for any high voltage source in the powertrain, GTR No. 20 only provides
this option to capacitors in the powertrain.
NHTSA conducted an analysis using human body resistance charts,
long and short duration capacitance discharge pulse profiles, and the
graphs of physiological effects of AC and DC body current by duration
of exposure from two International Electrotechnical Commission (IEC)
technical publications,\38\ to determine safe energy levels for the
human body. NHTSA has submitted a technical memorandum to the docket
for this NPRM that provides details and results of the agency's
analysis.
---------------------------------------------------------------------------

\38\ IEC 60479-1 and 60479-2 Effects of Current on Human Beings
and Livestock--Part 1: General Aspects, Part 2: Special Aspects,
2005-07, Reference Nos. CEI/IEC/TS 60479-1:2018 and CEI/IEC/TS
60479-2:2019. <a href="https://webstore.iec.ch/publication/62980">https://webstore.iec.ch/publication/62980</a>; <a href="https://webstore.iec.ch/publication/63392">https://webstore.iec.ch/publication/63392</a> (last accessed September 26,
2023).
---------------------------------------------------------------------------

Based on the analysis results, NHTSA tentatively concludes that a
post-crash electrical safety compliance option for capacitors based on
an electrical energy of 0.2 Joules or less provides adequate safety
from electrical shock and long-term harmful effects on the human body.
Providing this post-crash compliance option would allow for practicable
powertrain designs for battery electric and fuel cell vehicles without
any reduction in safety. Automotive high-voltage systems typically
utilize a number of capacitors connected to high voltage buses, and it
is not always practical to discharge every capacitor post-crash. NHTSA
tentatively believes that by providing this compliance option for a
safe energy limit, vehicle manufacturers would have the flexibility to
design products that assure safety. NHTSA seeks comments on the
parameters (human body resistance, discharge profiles) used in the
analysis and the analysis method.
2. Assessing Fire or Explosion in Vehicle Post-Crash Test
After a real-world crash, passengers within the vehicle need time
to safely egress from the vehicle or be rescued by first responders.
During this time, passengers should not be exposed to hazards such as
fire or explosion of the REESS, which may hinder their egress or
rescue.
GTR No. 20 requires that for a period of one hour after a crash
test, there shall be no evidence of fire or explosion of the REESS.
However, such a requirement is not currently in FMVSS No. 305. In
accordance with GTR No. 20, NHTSA proposes to include in FMVSS No. 305a
a requirement that there be no evidence of fire or explosion for the
duration of one hour after the crash test for heavy school buses, and
for the duration of one hour after each crash test and subsequent
quasi-static rollover test for light vehicles. The assessment of fire
or explosion would be verified by inspection without removal of the
REESS or any parts of the vehicle.
3. Assessing Post-Crash Voltage Measurements
This NPRM proposes to clear up a source of ambiguity in FMVSS No.
305. FMVSS No. 305 requires that the post-crash voltage measurements be
made at least 5 seconds after the vehicle comes to rest. However, at
times it is not entirely clear when the vehicle comes to rest because
there is always some vibration and slight vehicle motion post-crash.
For consistency with the GTR No. 20 test procedure, NHTSA proposes that
the voltage measurements in FMVSS No. 305a would be made between 10
seconds and 60 seconds after the impact. The agency tentatively
believes that 10 seconds after impact is sufficient time for voltage
measurement and 60 seconds after impact is early enough that any high
voltage arcing would be detected. NHTSA seeks comment on this approach.
4. Electrolyte Spillage Versus Leakage
Currently, FMVSS No. 305 S5.1 addresses ``electrolyte spillage from
propulsion batteries.'' The standard specifies that following a crash
test, not more than 5.0 liters of electrolyte from propulsion batteries
shall spill outside the passenger compartment, and that no visible
trace of electrolyte shall spill into the passenger compartment. NHTSA
proposes to use terms related to ``leakage'' instead of spillage. When
the electrolyte spillage \39\ requirement was originally adopted in
2000, EV propulsion batteries were envisioned to be a series of lead-
acid batteries. Lead-acid batteries at the time had large quantities of
liquid electrolyte that could spill out of the battery if the battery
structure were compromised in a crash. At that time, it was appropriate
to eliminate the term ``leakage'' due to its synonymity to
``spillage,'' to avoid questions of whether different meanings were
intended by the different words.
---------------------------------------------------------------------------

\39\ Per Section B, ``S5.1 Electrolyte Spillage from Propulsion
Batteries,'' NHTSA stated in 65 FR 57980 that ``leakage'' is
synonymous for ``spillage.'' Both words indicate the escape of
electrolyte from the battery.
---------------------------------------------------------------------------

Current EV propulsion batteries, however, are lithium-ion
batteries. The cells of lithium-ion batteries have small quantity of
electrolyte that could leak out of the battery casing rather than
spill. Thus, NHTSA proposes to use the term ``electrolyte leakage,''
which is more relevant than ``electrolyte spillage'' for these
batteries.
NHTSA seeks comment on the inclusion of a post-crash electrolyte
leakage requirement in FMVSS No. 305a and the necessity and relevance
of such a requirement for current EVs. Specifically, NHTSA seeks
comment on whether this requirement is still relevant given today's
propulsion battery technologies and if it is still necessary based on
the safety incidents observed in the field or in crash tests. NHTSA
seeks comment on whether a 5-liter maximum amount of electrolyte
permitted to be leaked is still relevant and requests commenters to
provide data based on safety incidents observed in the field or in
crash tests to

[[Page 26713]]

substantiate their assertions.\40\ NHTSA seeks comment on and
recommendations regarding electrolyte leakage detection methods and how
these detection methods can discern between the presence of electrolyte
and the presence of other liquids such as coolant.
---------------------------------------------------------------------------

\40\ GTR No. 20 requires that the electrolyte leaking from the
REESS during and after the crash test is no more than 7 percent by
volume of the REESS electrolyte. However, there is no practical way
of measuring the quantity by volume of the electrolyte in the REESS.
---------------------------------------------------------------------------

c. REESS Requirements Applicable to All Vehicles

This section of the NPRM addresses REESS safety performance
requirements during normal vehicle operation. The REESS requirements
would apply to all vehicles subject to FMVSS No. 305a.
Introduction
Currently, FMVSS No. 305 does not have any requirements for the
safe operation of the REESS and for mitigating risks of fire and other
safety risks associated with it. This NPRM's proposed requirements
would protect the REESS against external fault inputs, ensure the REESS
operations are within the manufacturer-specified functional range,
provide protection from thermal propagation in the event of single-cell
thermal runaway (SCTR) due to an internal short-circuit, provide a
warning if there is a thermal event within the REESS or a malfunction
of vehicle controls that manage REESS safe operation, and ensure safe
REESS operation during and after water exposure.
While REESS is a general term to represent any rechargeable
electrical energy storage system, currently all electric powered
vehicles use REESS with lithium-ion chemistry. Therefore, the current
safety hazards associated with REESS identified in literature and in
the field are those specific to lithium-ion chemistry REESS. However,
the proposed requirements in this NPRM will apply regardless of REESS
chemistry.
REESSs are designed and manufactured to operate safely within a
range of operating parameters, including temperature ranges, charge
levels, and current levels. If the REESS is subjected to fault
conditions outside these operating ranges such as overcharge, over-
discharge, overcurrent, over-temperature, external short-circuit, or
low temperature, these conditions can result in damage to the cells.
Cell damage increases the risk of hazardous conditions such as
electrolyte leakage, reduced electrical isolation, and fire in the
REESS (thermal runaway). Manufacturers include controls in electric
vehicles to manage REESS operation to ensure they stay within the
specified safe operating range, thereby mitigating damage to the REESS.
The system that monitors and controls the REESS is referred to as the
battery management system (BMS). NHTSA proposes requirements to assure
that the BMS has controls that protect the REESS against these faults
by, e.g., stopping the vehicle from charging to prevent overcharge.
Performance Criteria For Normal Vehicle Operations--General
The performance criteria specified in GTR No. 20 for each of the
vehicle control performance tests specify no evidence of electrolyte
leakage, rupture (applicable to high voltage REESSs only), venting
(applicable to REESSs other than open-type traction batteries \41\),
fire, or explosion. For high voltage REESSs, the electrical isolation
is required to be greater than or equal to 100 ohms per volt, for a DC
high voltage source. This NPRM proposes the same performance criteria
to protect the REESS against external faults, such as a fault in an
external charger that could result in the charger supplying greater
current than requested by the vehicle and/or charging the REESS beyond
full state of charge.\42\
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\41\ Open-type traction batteries are a type of battery which
are filled with liquid and generate hydrogen gas that is released
into the atmosphere.
\42\ The control pilot pin of the charger communicates with the
vehicle during charging. Based on the state of charge (SOC), the
vehicle requests a certain level of current and the vehicle charger
provides that level. Other external faults could arise when
attempting to drive the vehicle beyond the lowest safe operating SOC
of the REESS (over-discharge of the REESS), driving fast up a steep
hill for a long period of time that could cause the REESS to heat
beyond its highest safe operating temperature, and charging a REESS
at very cold temperatures that could cause lithium plating.
---------------------------------------------------------------------------

Under proposed FMVSS No. 305a, the evidence of electrolyte leakage,
venting,\43\ or rupture is verified by visual inspection without
disassembly of any part of the vehicle. Visible smoke during and after
the test, and/or the presence of soot and/or electrolyte residue in
post-test visual inspection are indicators of venting and electrolyte
leakage. The overcharge, over-discharge, overcurrent, over-temperature,
and external short-circuit test procedures specify that the agency
would perform a standard cycle after completing exposure to each of the
external faults, provided that the vehicle permits charging and
discharging at that time. A standard cycle, as specified in GTR No. 20
and proposed FMVSS No. 305a, consists of a standard discharge and
followed by a standard charge. If the vehicle is operable after
exposure to the external fault, running the standard cycle after
exposure to the external fault condition--while observing the vehicle
for one hour for evidence of electrolyte leakage, rupture, venting,
fire, or explosion, followed by voltage measurements for determining
electrical isolation--would ensure that continuing operating the
vehicle would not result in safety hazards.
---------------------------------------------------------------------------

\43\ NHTSA elaborates on the proposed venting requirement at the
end of this section.
---------------------------------------------------------------------------

The vehicle might not permit charging and discharging after
detecting a dangerous condition; NHTSA considers this a safety feature
and that such a test outcome would not amount to an apparent
noncompliance. The inability to perform a standard cycle after exposure
to the external fault does not terminate the test. If the vehicle does
not permit charging and discharging after exposure to an external
fault, then the standard cycle is simply not performed and the test
proceeds. Specifically, the test ends with the vehicle observed for one
hour for evidence of electrolyte leakage, rupture, venting, fire, or
explosion, followed by voltage measurements for determining electrical
isolation.
The standard cycle would be conducted with the breakout harness
connected to the manufacturer-specified location(s) on the traction
side of the REESS \44\ on the vehicle's electric power train. The REESS
is charged and discharged using a high voltage battery tester/cycler
(with appropriate power and voltage ranges) which is connected to the
vehicle through the breakout harness, as shown in Figure 2 below (for
illustration purposes only).
---------------------------------------------------------------------------

\44\ The manufacturer is required by proposed FMVSS No. 305a to
specify the location for connecting the breakout harness and may
also provide appropriate breakout harnesses for testing the vehicle.
If the manufacturer does not provide a breakout harness, NHTSA would
use a generic breakout harness to connect to the traction side of
the REESS.

---------------------------------------------------------------------------

[[Page 26714]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.045

Figure 2--Connection of the Breakout Harness & Laboratory Test
Equipment to the Vehicle

NHTSA proposes that the discharge and charge rates for the standard
cycle would be provided by the vehicle manufacturer. NHTSA proposes
that, if the discharge rate is not specified by the manufacturer, NHTSA
would use a discharge rate (C-Rate) of 1C current. A ``nC Rate'' is the
magnitude of constant current that would charge or discharge the REESS
in 1/n hour between 0 percent state of charge (SOC) and 100 percent
SOC. Discharge would continue until automatically terminated by vehicle
controls at the manufacturer-specified minimum operating SOC of the
REESS. After discharge, the standard cycle would include a 15-minute
rest period before the charging procedure commences. If a charge
procedure is not specified, then a charge rate (i.e., C-Rate) of \1/3\C
current would be used. Charging is continued until automatically
terminated by vehicle controls at the manufacturer-specified maximum
operating SOC of the REESS.
REESS Venting
Venting is the release of excessive internal pressure from a cell
or REESS in a manner intended by design to preclude rupture or
explosion. Venting during normal vehicle use may be associated with (a)
combustion and/or decomposition of electrolyte, or (b) vaporization of
the electrolyte. In case of condition (a), the emissions from the cells
may increase the risk to vehicle occupants if they are exposed to such
substances. In case of condition (b), the amount of the gases released
is considered less likely to pose a safety risk to the occupants.
Venting in the case of condition (a) may result in the release of gases
and particulates from the REESS, thereby potentially exposing vehicle
occupants to the emissions (gases and particulate matter).\45\ Hazards
associated with toxicity, corrosiveness, and flammability of the gases
emitted from the REESS and associated human health exposure limits vary
considerably. As noted above, NHTSA proposes to include a provision in
FMVSS No. 305a to limit the safety risks to vehicle occupants due to
venting during normal vehicle operations. The provision is based on GTR
No. 20 requirements described below.
---------------------------------------------------------------------------

\45\ Gases generated in and vented from lithium-ion (Li-ion)
batteries typically include carbon dioxide (CO<INF>2</INF>), carbon
monoxide (CO), hydrogen (H<INF>2</INF>), oxygen (O<INF>2</INF>),
light C<INF>1</INF>-C<INF>5</INF> hydrocarbons, e.g., methane and
ethane, and fluorine-containing compounds such as hydrogen fluoride
(HF) and fluoro-organics, e.g., ethyl-fluoride.
---------------------------------------------------------------------------

GTR No. 20 specifies that under normal vehicle operation, the
vehicle occupants are not exposed to any hazardous environment caused
by venting from the REESS. To avoid human harm that may occur due to
potential toxic or corrosive emissions, GTR No. 20 specifies that there
be no venting from the REESS for the following normal vehicle
operations tests: vibration, thermal shock and cycling, external short
circuit protection, overcharge protection, over-discharge protection,
over-temperature protection and overcurrent protection. GTR No. 20
includes a no-fire requirement in these tests which addresses the issue
of vented gas flammability. During the development of GTR No. 20, a
robust and repeatable method to verify the occurrence of

[[Page 26715]]

venting and the potential exposure of vehicle occupants to various
gases from the venting was sought, but no suitable method was found.
Visual inspection was found to be the best approach at this time for
verifying the occurrence of venting for assessing the influence of
vented gases on vehicle occupants. Therefore, GTR No. 20 specifies that
evidence of venting in these tests is verified by visual inspection
(evidence of soot, electrolyte residues) without disassembling any part
of the REESS.
NHTSA proposes to use a similar approach in FMVSS No. 305a to
evaluate the safety risks to vehicle occupants resulting from venting
from the REESS. The agency acknowledges that research is needed to
develop a repeatable, reproducible, and practical method to verify the
occurrence of various vented gases and the potential exposure and harm
to vehicle occupants. However, NHTSA tentatively concludes that in the
absence of such a method, the requirement that there must be no fire,
electrolyte leakage or venting during the tests evaluating vehicle
controls for safe REESS operation (external short-circuit protection,
overcharge protection, over-discharge protection, over-temperature, and
overcurrent protection) would reduce some safety risks to vehicle
occupants due to venting from the REESS. The evidence of venting in
these tests would be verified by visual inspection (evidence of soot,
electrolyte residues) without disassembling any part of the REESS.
NHTSA also requests comment in an Appendix to this preamble on the
IWG's continuing work on venting in Phase 2 of the GTR.
1. Vehicle Controls for Safe REESS Operation
This NPRM proposes the following performance requirements and
associated test procedures for vehicles to ensure they have controls
managing safe REESS operations. There are some minor differences
between the GTR No. 20 test procedures and those proposed in this NPRM
that are based on the lessons learned from NHTSA's test program. Those
differences pertain to the ease of conducting the test.\46\
---------------------------------------------------------------------------

\46\ For example, the state of charge of the REESS at the
beginning of the test differed in some instances from that in GTR
No. 20 to enable completing the test more readily.
---------------------------------------------------------------------------

NHTSA funded research to validate a collection of test procedures
that assess safety hazards to electric vehicles while being charged or
when the REESS exceeds its recommended operational
limits.47 48 The research independently evaluated, refined,
and validated vehicle-level test procedures that could be robustly
applied to a wide range of vehicle technologies and battery
configurations. Based on the results of NHTSA's research, the agency
proposes to conduct full vehicle-level tests using a breakout harness
connected to a battery tester/cycler \49\ to evaluate vehicle controls
for safe REESS operation, rather than conducting the tests on the REESS
as a separate component. NHTSA is proposing vehicle-level testing
because evaluating REESS safe operation at the vehicle level would
evaluate the entire vehicle system and the associated vehicle controls,
whereas conducting the tests at the equipment level would not evaluate
all the relevant vehicle controls or any interaction or interference
between vehicle controls.
---------------------------------------------------------------------------

\47\ DC Charging Safety Evaluation Procedure Development,
Validation, And Assessment, and Preliminary AC Charging Evaluation
Procedure--DOT HS 812 754 and DOT HS 812 778--July 2019. <a href="https://rosap.ntl.bts.gov/view/dot/41933">https://rosap.ntl.bts.gov/view/dot/41933</a>.
\48\ System-Level RESS Safety and Protection Test Procedure
Development, Validation, and Assessment--Final Report--DOT HS 812
782 October 2019 <a href="https://rosap.ntl.bts.gov/view/dot/42551">https://rosap.ntl.bts.gov/view/dot/42551</a>.
\49\ A battery tester/cycler is equipment that can be used for
charging and discharging REESS and for conducting specialized tests
on the REESS. An example of a battery tester with hybrid and battery
electric vehicles is the NHR 9300 battery test system (NHR 9300).
---------------------------------------------------------------------------

NHTSA evaluated the GTR No. 20 test procedures for feasibility,
practicability, and objectivity by conducting the test procedures on a
2019 Chevy Bolt, 2020 Tesla Model 3, and 2020 Nissan Leaf S
Plus.50 51 52 NHTSA's test program demonstrated the ease of
conducting tests at a vehicle level using breakout harnesses connected
to a battery cycler/tester for the external inputs to the REESS without
having to remove the REESS from the vehicle to conduct component level
tests. The proposed test procedures for overcharge, over-discharge,
overcurrent, over-temperature, and external short-circuit tests are
non-destructive tests intended to evaluate vehicle controls to protect
the REESS and can be conducted in serial order on the same vehicle.
---------------------------------------------------------------------------

\50\ NHTSA Test Report on the 2020 Tesla Model 3 Standard Range
4-Door Sedan can be accessed here: <a href="https://downloads.regulations.gov/NHTSA-2021-0029-0003/attachment_2.pdf">https://downloads.regulations.gov/NHTSA-2021-0029-0003/attachment_2.pdf</a>.
\51\ NHTSA Test Report on the 2020 Nissan Leaf S Plus (62kWh
Battery) 5-Door Hatchback can be accessed here: <a href="https://downloads.regulations.gov/NHTSA-2021-0029-0002/attachment_2.pdf">https://downloads.regulations.gov/NHTSA-2021-0029-0002/attachment_2.pdf</a>.
\52\ NHTSA Test Report on the 2019 Chevy Bolt can be accessed
here: <a href="https://downloads.regulations.gov/NHTSA-2021-0029-0001/attachment_2.pdf">https://downloads.regulations.gov/NHTSA-2021-0029-0001/attachment_2.pdf</a>.
---------------------------------------------------------------------------

i. Overcharge Protection
A battery pack experiences an overcharge when a charger forces its
state of charge (SOC) level to rise above 100 percent. Overcharge of a
REESS can occur because of a failure of the charging system, such as a
fault in an external charger, a fault in the vehicle's regenerative
braking system, a sensor failure, or a voltage reference drift.\53\
Overcharge can lead to swelling of an electrochemical cell, lithium
plating, stability degradation, or over-heating, and ultimately can
lead to thermal runaway.\54\ Severe events such as fire or explosion
may occur. Therefore, vehicle controls to ensure the REESS does not get
overcharged are important for long-term safe operation of the REESS.
---------------------------------------------------------------------------

\53\ Voltage can drift based on temperature. Higher temperature
can result in lower voltage.
\54\ Thermal runaway of a lithium-ion cell in a REESS occurs
when the thermal stability limit of the cell chemistry is exceeded,
and the cell releases its energy via an exothermic reaction at an
uncontrolled rate such that the heat generated is faster than that
dissipated.
---------------------------------------------------------------------------

Vehicle level controls or the BMS typically prevent charging when
the manufacturer-specified maximum operating SOC of the REESS is
achieved. GTR No. 20 includes a test to evaluate the performance of
vehicle controls to prevent overcharge of the REESS. NHTSA tentatively
concludes that GTR No. 20's overcharge test is practical and feasible
based on the agency's own testing.\55\ NHTSA proposes to include the
overcharge protection requirement and test procedure in FMVSS No. 305a.
---------------------------------------------------------------------------

\55\ See Test reports in docket no. NHTSA-2021-0029, available
at <a href="http://www.regulations.gov">www.regulations.gov</a>. Detailed test procedures are provided in the
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

The proposed overcharge test would be performed on a complete
vehicle as follows. The test is conducted with the REESS initially set
at 90 to 95 percent SOC \56\ and at ambient temperatures between 10
[deg]C and 30 [deg]C. The breakout harness is attached on the traction
side of the REESS at the vehicle manufacturer's recommended location(s)
and attachment point(s), and the battery tester/cycler is connected to
the breakout harnesses to supply the charge current. Temperature probes
are connected to the REESS case to monitor changes in the REESS
temperature. Temperature measurements may also be

[[Page 26716]]

obtained through communication with the REESS control module.\57\
---------------------------------------------------------------------------

\56\ Ranges in temperature and SOC are provided for this and
other test procedures for practicability and ease of conducting the
tests. In the overcharge test, the REESS is initially set at a high
SOC (90 to 95 percent) to enable fully charging the REESS in a
shorter period of time.
\57\ Commercial diagnostic tools or tools supplied by the
manufacturer may be used to read the Temperature measurements within
the REESS from the vehicle's Controller Area Network (CAN bus).
---------------------------------------------------------------------------

The vehicle is turned on and the REESS is charged using the battery
tester/cycler in accordance with the manufacturer's recommended maximum
charge current \58\ until one of the following has occurred:
---------------------------------------------------------------------------

\58\ If the manufacturer does not provide an appropriate charge
current, then a charge rate (i.e., C-Rate) of C/3 current would be
used.
---------------------------------------------------------------------------

(a) the REESS overcharge protection control terminates the charge
current;
(b) the REESS temperature is 10 [deg]C above its maximum operating
temperature specified by the manufacturer; \59\ or,
---------------------------------------------------------------------------

\59\ The manufacturer would specify the procedure for monitoring
the temperature of the REESS during testing. This could be measured
by attaching thermocouples to the casing of the REESS or obtained
from the CAN bus using appropriate tools.
---------------------------------------------------------------------------

(c) 12 hours have passed since the start of charging the vehicle.
After the overcharge condition is terminated, a standard cycle is
performed if possible. The test concludes with a 1-hour observation
period in which the vehicle is observed for any evidence of electrolyte
leakage, rupture, venting, fire, or explosion. At the conclusion of the
post-test observation period, the electrical isolation is determined in
the same manner as currently in FMVSS No. 305 S7.6 using a voltmeter to
measure voltages.
ii. Over-Discharge Protection
Over-discharging a REESS, which means discharging it below its
lowest state of charge specified by the manufacturer, can lead to
undesirable aging, electrolyte leakage, swelling, solid electrolyte
interphase (SEI) decomposition, internal short-circuit, and damaged
cell stability and safety on subsequent recharges. Even though the
initial over-discharge response of lithium-ion cells generally appears
benign, it can cause damage to cell electrodes that can compromise cell
stability and safety on subsequent recharge. Subsequent charging of an
over-discharged REESS may lead to fire or explosion.
Vehicle controls or the BMS typically prevent over-discharging when
the manufacturer specified minimum operating SOC of the REESS is
achieved. GTR No. 20 includes a test to evaluate the performance of
vehicle controls to prevent over-discharge of the REESS. NHTSA
tentatively concludes that GTR No. 20's over-discharge test is
practical and feasible based on the agency's own testing.\60\ NHTSA
proposes to include the over-discharge protection requirement and test
procedure in FMVSS No. 305a.
---------------------------------------------------------------------------

\60\ See Test reports in Docket No. NHTSA-2021-0029, available
at <a href="http://www.regulations.gov">www.regulations.gov</a>. Detailed test procedures are provided in the
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

The over-discharge test is performed at ambient temperatures
between 10 [deg]C and 30 [deg]C on a complete vehicle. The SOC of the
REESS at the beginning of the test is set at 10 to 15 percent.\61\ For
a vehicle with on-board energy conversion systems (e.g., internal
combustion engine, fuel cell, etc.), the fuel supply is set to the
minimum level \62\ where active driving mode is permitted. Similar to
the overcharge test, the breakout harness is attached on the traction
side of the REESS at the vehicle manufacturer's recommended location(s)
and attachment point(s), and the battery tester/cycler is connected to
the breakout harness to discharge the REESS.\63\ Temperature probes are
connected to the REESS case to monitor changes in the REESS
temperature. Temperature measurements may also be obtained through
communication with the REESS control module.
---------------------------------------------------------------------------

\61\ Ranges in temperature and SOC are provided for this and
other test procedures for practicability and ease of conducting the
tests. In this case, the test is initiated with the REESS at a low
SOC (10 to 15 percent) to enable discharging the REESS in a shorter
period of time.
\62\ Minimum level of fuel supply needed would be provided by
the manufacturer.
\63\ A discharge resistor may also be used for this purpose.
---------------------------------------------------------------------------

The vehicle is turned on and the REESS is discharged using the
battery tester/cycler in accordance with the manufacturer's recommended
discharging rate \64\ under normal operating conditions until one of
the following has occurred:
---------------------------------------------------------------------------

\64\ If the manufacturer does not specify a discharge rate, a
power load of 1kW is used.
---------------------------------------------------------------------------

(a) vehicle controls terminate the discharge current,
(b) the temperature gradient of the REESS is less than 4 [deg]C
\65\ through two hours, or
---------------------------------------------------------------------------

\65\ Temperature variation of 4 [deg]C indicates stable
operation of the REESS. As noted earlier, the manufacturer specifies
the procedure for monitoring the temperature of the REESS during
testing. This could be measured by attaching thermocouples to the
casing of the REESS or obtained from the CAN bus using appropriate
tools.
---------------------------------------------------------------------------

(c) if the vehicle is discharged to 25 percent of its nominal
voltage level.
At the conclusion of the discharge termination, one standard charge
is performed, followed by one standard discharge. The test concludes
with a 1-hour observation period in which the vehicle is observed for
any evidence of electrolyte leakage, rupture, venting, fire, or
explosion. At the conclusion of the observation period, the electrical
isolation is determined in a similar manner as that in current FMVSS
No. 305 S7.6 using a voltmeter to measure voltages.
iii. Overcurrent Protection
As noted earlier, the vehicle and the charging system communicate
the level of current needed to charge the REESS. If there is a problem
in the communication or if the charging system malfunctions, higher
current may be provided though not requested by the vehicle. During
direct current (DC) fast-charging, failure of the external charge
equipment could cause over-current conditions in which the REESS
receives higher current than it was designed to manage at a given state
of charge of the REESS. Overcurrent conditions could result in heating
of the REESS, electrochemical damage to the cells, and a risk of
thermal runaway.
GTR No. 20 includes a test to evaluate the performance of vehicle
controls to protect the REESS from overcurrent conditions. NHTSA
tentatively concludes that GTR No. 20's overcurrent test is practical
and feasible based on the agency's own testing.\66\ NHTSA proposes to
include the overcurrent protection requirement in FMVSS No. 305a. In
accordance with GTR No. 20, NHTSA proposes to apply the overcurrent
test to vehicles that have capability of charging by DC external
electricity supply. The test is unnecessary for vehicles that only
charge by alternating current (AC) supply because AC charging is slower
and the inverters for AC charging manage any overcurrent. Also,
overcurrent issues have not been observed in AC charging.
---------------------------------------------------------------------------

\66\ See Test reports in docket no. NHTSA-2021-0029, available
at <a href="http://www.regulations.gov">www.regulations.gov</a>. Detailed test procedures are provided in the
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

The overcurrent test is performed with a complete vehicle. To avoid
the overcharge protection terminating the over-current condition, the
SOC of the REESS is set between 40 to 50 percent. The test is conducted
at ambient temperatures between 10 [deg]C and 30 [deg]C. The breakout
harness is attached on the traction side of the REESS at the vehicle
manufacturer's recommended location(s) and attachment point(s), and the
battery tester/cycler is connected to the breakout harnesses to supply
the charge current. Temperature probes are connected to the REESS case
to monitor changes in the REESS temperature.

[[Page 26717]]

Temperature measurements may also be obtained through communication
with the REESS control module. The vehicle manufacturer specifies the
highest normal charge current and the over-current level that is
applied. The battery tester/cycler is programmed to supply an over-
current during charging at the level specified by the manufacturer.
The vehicle is turned on and the REESS is charged using the battery
tester/cycler in accordance with manufacturer's recommended charging
procedure with the highest normal charge current specified by the
manufacturer.\67\ After charging is initiated, an over-current
specified by the manufacturer \68\ is supplied above that requested by
the vehicle. The charge current is increased over the course of 5
seconds from the highest normal charge current to the over-current
level. The charge current and the overcurrent supply is continued until
one of the following has occurred: (a) vehicle over-current protection
controls terminate the charging, or (b) the temperature gradient of the
REESS is less than or equal to 4 [deg]C for a two-hour period.
---------------------------------------------------------------------------

\67\ The manufacturer supplied information define the constant
current level and/or constant voltage level combination to charge
the REESS. If a charge procedure is not specified, then a charge
rate (i.e., C-Rate) of C/3 current is used.
\68\ If the vehicle manufacturer does not supply an appropriate
over-current level, the battery test/cycler will be programmed to
initially apply a 10 Ampere over-current. If charging is not
terminated, the over-current level of 20 amps will be applied.
Subsequently, the over-current supply is increased in steps of 10
amperes.
---------------------------------------------------------------------------

If possible, a standard cycle is performed using the connected
breakout harness and battery cycler. The test concludes with an
observation period of one hour in which the vehicle is observed for
electrolyte leakage, rupture, venting, fire, or explosion. At the
conclusion of the observation period, the electrical isolation is
determined in a similar manner as that in current FMVSS No. 305 S7.6,
using a voltmeter to measure voltages.
iv. Over-Temperature Protection
While the impacts of over-temperature operation vary by chemistry,
most battery chemistries can be negatively affected if operation by the
driver is attempted at high temperatures (per the limits of a specific
chemistry) or if aggressive operation is attempted at high temperatures
(high-rate charging or discharging). A temperature imbalance or
continued operation at elevated temperatures may even lead to thermal
runaway of cells if appropriate countermeasures, such as de-rating,\69\
are not taken.
---------------------------------------------------------------------------

\69\ De-rating is the reduction of a battery's available power
and is typically due to a state that indicates an undesirable
condition such as rapidly increasing cell temperature, elevated
temperatures, or very cold cell temperatures. By temporarily
reducing a battery's ability to provide and/or absorb power, de-
rating allows the battery to cool down (or at least stop increasing
in temperature) in situations with elevated temperatures and reduces
operation when the battery is so cold that certain usage levels
could cause damage.
---------------------------------------------------------------------------

Vehicle controls such as thermal management systems or the BMS
continuously monitor temperature conditions to prevent REESS operation
at elevated temperatures above the upper temperature boundary for safe
REESS operations. GTR No. 20 includes a test to evaluate the
performance of vehicle controls to prevent REESS temperatures exceeding
the upper temperature boundary for safe REESS operations. NHTSA
tentatively concludes that GTR No. 20's over-temperature test is
practical and feasible based on the agency's own testing.\70\ NHTSA
proposes to include the over-temperature protection requirement and
test procedure in FMVSS No. 305a, which aligns with GTR No. 20.
---------------------------------------------------------------------------

\70\ See Test reports in Docket No. NHTSA-2021-0029, available
at <a href="http://www.regulations.gov">www.regulations.gov</a>. Detailed test procedures are provided in the
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

In the proposed FMVSS No. 305a, the over-temperature test is
performed on a chassis dynamometer \71\ with a complete vehicle. The
SOC of the REESS at the beginning of the test is set between 90 to 95
percent. The test is conducted at ambient temperatures between 10
[deg]C and 30 [deg]C. For vehicles with on-board energy conversion
systems (e.g., internal combustion engine, fuel cell, etc.), the fuel
system must have sufficient supply to allow operation of the energy
conversion system for about one hour of driving. The cooling system for
the REESS is disabled (or significantly reduced for a REESS that will
not operate with the cooling system disabled) per manufacturer-supplied
information.\72\ For REESSs that will not operate if the cooling system
is disabled, the maximum amount of coolant is removed to minimize the
cooling system's operation for the test.
---------------------------------------------------------------------------

\71\ A chassis dynamometer is a mechanical device that uses one
or more fixed roller assemblies to simulate different road
conditions within a controlled environment and is used for a wide
variety of vehicle testing.
\72\ Methods for disabling the cooling system may include
crimping the liquid cooling hose or in the case of a refrigerant
cooled package, removing the refrigerant fluid. For REESS cooled by
cabin air, block the cabin air intakes used to provide cooling air
flow to the REESS.
---------------------------------------------------------------------------

Temperature probes are connected to the REESS case to monitor
changes in the REESS temperature. Temperature measurements may also be
obtained through communication with the REESS control module.
GTR No. 20 specifies that the vehicle be soaked for at least 6
hours in a thermally controlled chamber at 45 [deg]C. However, NHTSA's
testing \73\ demonstrated that the presoaking of the vehicle at
elevated temperatures does not raise the temperature of the REESS as
significantly as by driving the vehicle under high acceleration and
deceleration drive modes. Therefore, to reduce the test time and test
burden, the agency does not believe it needs to specify presoaking of
the vehicle.
---------------------------------------------------------------------------

\73\ System-Level RESS Safety and Protection Test Procedure
Development, Validation, and Assessment-Final Report. DOT HS 812 782
October 2019. <a href="https://rosap.ntl.bts.gov/view/dot/42551">https://rosap.ntl.bts.gov/view/dot/42551</a>.
---------------------------------------------------------------------------

The vehicle is installed on the chassis dynamometer and is placed
into driving mode. The vehicle is driven on the dynamometer using the
vehicle manufacturer-recommended appropriate drive profile for
discharge and charge of the REESS that would raise the temperature of
the REESS (with cooling system disabled or reduced function) above its
safe operating temperature within one hour. If the vehicle manufacturer
does not supply an appropriate drive profile, NHTSA will drive the
vehicle over back-to-back aggressive acceleration (near 100% pedal
application) and decelerations (near or above regenerative braking
limits) such as the one shown in Figure 3 below, where the vehicle is
accelerated to 80 mph and then decelerated to 15 mph within 40 seconds.

[[Page 26718]]

[GRAPHIC] [TIFF OMITTED] TP15AP24.046

Figure 3--Drive Profile on Dynamometer To Quickly Raise the Temperature
of the REESS. (For Illustration Purposes Only)

Vehicle battery designs and controls mitigate overheating of the
REESS in different ways: (1) Terminate discharge/charge operations when
the REESS temperature reaches its operating bounds; (2) Derate (reduce
acceleration/speed of the vehicle) to prevent the REESS reaching its
maximum operating temperature; (3) REESS cell chemistries are stable at
higher REESS temperature. In order to accommodate different approaches
to address hazards associated with overheating of REESS, GTR No. 20
provides three different options for terminating the discharge/charge
cycles:
(a) the vehicle terminates the charge-discharge cycle,
(b) the REESS temperature gradient is less than or equal to 4
[deg]C for a two-hour period, or
(c) 3 hours have elapsed from the time of starting the discharge-
charge cycles on the chassis dynamometer.
In accordance with GTR No. 20, the agency proposes to use the same
three options listed above to terminate the discharge/charge cycle.
At the conclusion of the over-temperature evaluation, a standard
cycle is performed if possible. The test concludes with a 1-hour
observation period in which the vehicle is observed for electrolyte
leakage, rupture, venting, fire, or explosion. At the conclusion of the
observation period, the electrical isolation is determined in a similar
manner as that in FMVSS No. 305 S7.6, using a voltmeter to measure
voltages.
v. External Short-Circuit Protection
The purpose of the external short-circuit protection test is to
verify the performance of the vehicle controls (protection measure)
against a short-circuit occurring externally to the REESS. During an
external short-circuit event, large amounts of instantaneous current
can be readily drawn generating copious amounts of heat. Associated
safety risks include over-heating, gas venting, or arcing that can
occur under fault conditions which can potentially lead to fire or
explosion.
Vehicle controls or the BMS typically protect the REESS from an
external short-circuit. GTR No. 20 includes a test to evaluate the
performance of vehicle controls to protect the REESS from an external
hard short-circuit (shorting resistance less than 5 milliohms). NHTSA
tentatively concludes that GTR No. 20's external short-circuit test is
practical and feasible based on the agency's own testing.\74\ NHTSA
proposes to include the GTR No. 20 external short-circuit protection
requirement and test procedure in FMVSS No. 305a.
---------------------------------------------------------------------------

\74\ See Test reports in Docket No. NHTSA-2021-0029, available
at <a href="http://www.regulations.gov">www.regulations.gov</a>. Detailed test procedures are provided in the
test reports of the 2021 Chevrolet Bolt (NHTSA-2021-0029-0001), 2020
Nissan Leaf (NHTSA-2021-0029-0002), and the 2020 Tesla Model 3
(NHTSA-2021-0029-0003).
---------------------------------------------------------------------------

The external short-circuit test is performed on a complete vehicle.
The SOC of the REESS at the beginning of the test is set at 90 to 95
percent SOC. The test is conducted at ambient temperatures between 10
[deg]C and 30 [deg]C. The breakout harness is installed on the vehicle
at the manufacturer specified location(s).\75\ Temperature probes are
connected to the REESS case to monitor changes in the REESS
temperature. Temperature measurements may also be obtained through
communication with the REESS control module. The short circuit
contactor (with the contactors in open position) is connected to the
breakout harnesses. The total resistance of the equipment to create the
external short circuit (short circuit contactor and breakout harnesses)
is verified to be between 2 to 5 milliohms.\76\ To begin the short-
circuit evaluation, the short-circuit contactors are closed. The short-
circuit condition is continued until (1) current is no longer present
or (2) one hour after the temperature probe on the REESS has stabilized
with a temperature change of less than 4 [deg]C for a two-hour period.
---------------------------------------------------------------------------

\75\ If the manufacturer does not provide information on the
location to connect the breakout harness for the external short
circuit test, the breakout harnesses may be connected on either side
of the positive and negative terminals of the pack.
\76\ GTR No. 20 specifies the external short circuit resistance
not exceeding 5 milliohms. The agency is specifying a range from 2
to 5 milliohms for ease of conducting the tests and to ensure
objectivity of the test.
---------------------------------------------------------------------------

If possible, a standard cycle is performed after termination of the
short-circuit. Fuses that opened during the short-circuit are not
replaced, and the standard cycle procedure is not performed if it is
not possible to charge and discharge the vehicle.
The vehicle is observed for one hour for electrolyte leakage,
rupture, venting, fire, or explosion. The external short-circuit test
concludes with an electrical isolation determination in a similar
manner as that in current FMVSS No. 305a S7.6 using a voltmeter to
measure voltages.
vi. Low-Temperature Protection
Uncontrolled repeated operation at low temperatures, especially
charging

[[Page 26719]]

for lithium-ion battery chemistries, may result in lithium plating or
cell damage that could eventually lead to reduced performance or
degraded life during subsequent operation. While single time operation
of REESS in very cold temperatures would not lead to a severe event,
some REESS designs use special chemical reactions which can damage the
REESS if it is charged at high rates in very cold temperatures. A
subsequent high rate of charging of such a damaged REESS may lead to
fire or explosion. Therefore, the rate of charging may need to be
terminated or limited in very cold temperatures.
Currently, no practical test procedure is available to evaluate the
performance of vehicle controls in low temperature conditions because
the effects of repeated charging at very low temperatures occur over a
very long period of time. Therefore, GTR No. 20 requires manufacturers
to provide documentation that includes a system diagram, a written
explanation on the lower boundary temperature for safe REESS operation,
the method of detecting REESS temperature, and the action taken when
the REESS temperature is at or below the lower boundary for safe REESS
operation.
NHTSA proposes to include documentation requirements based on GTR
No. 20 into FMVSS No. 305a. NHTSA proposes that the manufacturer
provide documentation, upon NHTSA's request, to demonstrate how the
vehicle monitors and appropriately controls REESS operations at low
temperatures at or below the lower temperature boundary for safe REESS
operation. The proposed requirements would indicate how manufacturers
identify, verify, and ensure vehicles have low-temperature protections
in place. Specifically, the proposal requires the manufacturer-supplied
documentation for a specific vehicle make, model, and model year would
include the following:
(1) A description of the lower temperature boundary for safe REESS
operation in all vehicle operating modes.
(2) A description and explanation of C-rates at the lower
temperature boundary for safe REESS operation.
(3) A description of the method used to detect REESS temperature.
(4) A system diagram with key components and subsystems involved in
maintaining safe REESS charging and discharging operation for
temperatures at or below the lower temperature boundary for safe REESS
operation.
(5) A description of how the vehicle controls, ancillary equipment,
and design features were validated and verified for maintaining safe
REESS operations at or below the lower temperature boundary for safe
REESS operation.
(6) A description of the final review/audit process of the
manufacturer, and the accompanying results of the manufacturer's final
assessment of risk management, and risk mitigation strategies.
NHTSA intends these documentation measures to demonstrate that the
manufacturer has considered, assessed, and mitigated identified risks
for safe operation of the vehicle. NHTSA tentatively agrees with GTR
No. 20 that there is a safety need for low temperature protections for
the REESS. Without protections, uncontrolled repeated operation at low
temperatures poses an unreasonable risk of fire or explosion. In the
absence of information enabling NHTSA to propose a practical test
procedure to evaluate the performance of vehicle controls in low
temperature conditions, the agency is proposing to require
manufacturers to submit documentation to NHTSA about pertinent low
temperature safety hazards, describe their risk mitigation strategies
for the safety hazards, and how they assessed the effectiveness of
their mitigation strategies.
NHTSA would review the documentation to understand the safety
hazards associated with the particular REESS in the vehicle, see
whether the manufacturer conducted an assessment of the risks, and
understand the measures the manufacturer undertook to mitigate those
known risks. This approach is intended to evolve over time as battery
technologies continue to rapidly evolve. It is an interim measure
intended to assure that manufacturers will identify and address the low
temperature safety risks of the REESS. In section VI., NHTSA requests
comments on whether the proposed document requirement would be better
placed in a general agency regulation than in proposed FMVSS No. 305a.
2. Mitigating Risk of Thermal Propagation Due to Internal Short Within
a Single Cell in the REESS
i. Safety Need
The potential for thermal runaway is a characteristic of the
lithium-ion cells currently used in REESSs for electric vehicle
propulsion. Thermal runaway of a lithium-ion cell in a REESS occurs
when the thermal stability limit of the cell chemistry is exceeded, and
the cell releases its energy via an exothermic reaction at an
uncontrolled rate such that heat is generated faster than it is
dissipated. The thermal runaway in a single cell may propagate to the
surrounding cells through conductive, convective, and radiative heat
transfer modes, causing reactions which create smoke, fire or, in very
rare circumstances, explosion. Lithium-ion cells have flammable
electrolyte that upon decomposition provides oxygen to the fire caused
by the thermal runaway, which increases the likelihood of its
propagation to other cells and even outside the REESS. The self-
oxygenating fires involving the cells in a REESS are therefore
difficult to extinguish. The smoke, fire, toxic gas emissions, and
explosion resulting from the thermal runaway can cause hazardous
conditions for vehicle occupants and those near the vehicle.
One root-cause of single-cell thermal runaway (SCTR) and
propagation due to an internal short-circuit relates to problems within
the cells. While this NPRM contains many performance tests for the safe
operation of the REESS, none of these tests would mitigate or prevent
thermal runaway due to an internal short-circuit within a cell of the
REESS and subsequent fire propagation. The mechanism of an internal
short circuit in a cell is complex and requires further study.
Currently, the risk of a spontaneous internal short circuit is heavily
dependent on battery design, such as use of non-flammable electrolytes,
ionic liquids, heat resistant and puncture-proof separators, and anode
and cathode materials. However, as discussed below, a performance test
that would establish a minimum standard of performance for the
materials is not available now.
GTR No. 20 addresses the hazards associated with SCTR due to an
internal short circuit through a documentation approach that requires
manufacturers to provide (to the testing authority) information on risk
mitigation strategies used in vehicle design to counteract the safety
risk. GTR No. 20 also requires a warning system to allow vehicle
occupants sufficient time to egress the vehicle before hazardous
conditions are present in the passenger compartment due to SCTR within
the REESS. GTR No. 20 requires documentation of the warning system, and
requires operation of the warning system only when the vehicle
propulsion system is turned on.
NHTSA tentatively generally agrees that a documentation approach on
risk mitigation strategies currently has merit, given there is no
suitable performance test to validate mitigation or prevention of SCTR
within a REESS. NHTSA is proposing a documentation approach based on
GTR No. 20 but has focused the GTR's requirements to better address
this safety need pending development of an objective performance test
that can

[[Page 26720]]

be applied to all REESSs in vehicles. In section VI., NHTSA requests
comments on whether the proposed document requirement would be better
placed in a general agency regulation than in proposed FMVSS No. 305a.
NHTSA is not proposing to require a warning system, or
documentation of the warning system, as specified in GTR No. 20. As
explained fully later in this section, NHTSA believes such a
requirement would not mitigate the safety hazards observed in the
field.
ii. GTR No. 20 Phase 1 Requirements
GTR No. 20 recognizes that, in general, REESS cells are
manufactured with manufacturing controls to mitigate safety problems.
Based on current manufacturing control processes, the probability of
manufacturing problems within a cell is generally considered to be less
than one in a million.\77\ Since the likelihood of two cells in a REESS
going into spontaneous single-cell thermal runaway (SCTR)
simultaneously is significantly lower,\78\ the focus of GTR No. 20 is
to mitigate the hazards associated with SCTR due to an internal short-
circuit within a single cell.
---------------------------------------------------------------------------

\77\ A REESS consists of a number of cells (n) in the range of
100 to 500. Therefore, the probability of a single-cell thermal
runaway and propagation event due to an internal short-circuit is
estimated to be the product of the number of cells times one in a
million (n x 10-6). https://batteryuniversity.com/
article/bu-304a-safety-concerns-with-li-
ion#:~:text=Lithium%2Dion%20batteries%20have%20a,than%20those%20in%20
consumer%20products.
\78\ The probability of two cells simultaneously undergoing
single-cell thermal runaway and propagation due to an internal
short-circuit is equal to the product of the probability of a
single-cell thermal runaway (n\2\ x 10-12).
---------------------------------------------------------------------------

GTR No. 20 addresses the SCTR safety hazard through a documentation
approach that requires manufacturers to provide (to the testing
authority on request) information on risk mitigation strategies used in
vehicle design to counteract the safety risk, and documentation on a
warning system that warns occupants to egress the vehicle. The
documentation requirements for risk mitigation strategies are only
generally described, however. This is because during the development of
GTR No. 20, there was no significant evidence of electric vehicle fires
due to SCTR and propagation due to an internal short-circuit. At that
time, the thought was that vehicle occupants would be exposed to
hazardous conditions if the SCTR propagates outside of the REESS to
other parts of the vehicle. Therefore, GTR No. 20 focuses primarily on
the warning and less on mitigating the risk of the SCTR within the
cell. The GTR requires that a warning be provided to the driver 5
minutes before hazardous conditions are present in the passenger
compartment due to SCTR and subsequent fire propagation. Five minutes
was considered sufficient time for vehicle occupants to egress the
vehicle before exposure to hazardous conditions. Under the GTR,
manufacturers would satisfy the requirement for a warning by providing
documentation that the vehicle provides the required warning.
GTR No. 20 uses a documentation approach for both the risk
mitigation strategies and the warning because an objective test
procedure is not available. Existing methods of initiating thermal
runaway simulating an internal short-circuit within a single cell in a
REESS are intrusive and dependent on the type of cell chemistry and
cell type.\79\ Additionally, different methods of initiation could
result in different results.\80\ NHTSA funded research to evaluate
different thermal runaway propagation test methods by examining various
existing methods of initiating thermal runaway, including heating
element method, rapid heater method, nail penetration, and laser
method, on batteries with a variety of chemistries, formats, and
configurations.\81\ The research indicated that the thermal runaway
initiation methods may influence the test results and the most
appropriate initiation method for a battery may depend on battery
chemistries, formats, and configurations.
---------------------------------------------------------------------------

\79\ One common method of initiating a thermal runaway is to
heat a cell externally using a heating element. This would require
disassembly of the casing of the REESS, adhering a heating element
to the surface of a cell, and adding thermocouples to verify the
heating element only provides heat to a single cell and not to
adjacent cells. The amount of heat applied to initiate a thermal
runaway depends on the cell chemistry (more volatile chemistries
requiring less heat input), and the cell design/type (thick wall
cells needing more heat input). The disassembly of the REESS, the
addition of a heating element, and the heat input is intrusive to
the REESS.
\80\ Another method of initiating a thermal runaway in a cell is
to penetrate a nail into a cell in the REESS. The orientation of the
nail penetration depends on the cell design and in some instances,
nail penetration may not cause a thermal runaway. While this method
may not require the REESS casing to be opened, the penetrating nail
compromises the casing and the cell structure. Additionally, the
depth of nail penetration may result in differences in heat release
that may not be similar in repeat tests and in tests using a heating
element.
\81\ Lamb, J., Torres-Castro, L., Stanley J., Grosso, C, Gray,
L., ``Evaluation of Multi-Cell Failure Propagation,'' Sandia Report
SAND2020-2802, March 2020. <a href="https://www.osti.gov/servlets/purl/1605985">https://www.osti.gov/servlets/purl/1605985</a>.
---------------------------------------------------------------------------

The repeatability and reproducibility of a potential performance
test using existing methods of thermal runaway initiation, and whether
such a test could be conducted on all applicable vehicles, are unknown.
Due to the rapid development of electric vehicle propulsion technology,
it was unclear during development of the GTR if any existing
performance test could apply to future vehicle designs without
restricting further enhancement of electric vehicle propulsion systems.
Therefore, instead of specifying a performance test for thermal runaway
and propagation due to an internal short-circuit in a single cell of a
REESS, GTR No. 20 requires manufacturers to submit documentation. Such
documentation must show risk mitigation strategies in their vehicle
designs for reducing hazards to vehicle occupants associated with
thermal runaway due to an internal short-circuit in a single cell in
the REESS. The documentation must also detail how the vehicle's warning
system activates a warning at least 5 minutes before hazardous
conditions arise in the passenger compartment.
Specifically, GTR No. 20 specifies the following documentation
requirements:
<bullet> A description of the warning system.
<bullet> Parameters (such as voltage, temperature, or current) that
trigger the warning indicator (telltale).
<bullet> A risk reduction analysis using appropriate industry
standard methodology (for example, IEC 61508,\82\ MIL-STD 882E,\83\
ISO-26262,\84\ fault analysis as in SAE J2929,\85\ or similar), which
documents the risk to vehicle occupants caused by a single-cell thermal
runaway triggered by an internal short-circuit leading to thermal
propagation and the expected risk reduction resulting from
implementation of the identified risk mitigation functions or
characteristics.
---------------------------------------------------------------------------

\82\ IEC-61508:2010, ``Functional Safety of Electrical/
Electronic/Programmable Electronic Safety-related Systems''. <a href="https://webstore.iec.ch/searchform&q=IEC%2061508">https://webstore.iec.ch/searchform&q=IEC%2061508</a>.
\83\ MIL-STD-882E:2012, ``System Safety''. <a href="https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=36027">https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=36027</a>.
\84\ ISO-26262 series:2018, ``Road vehicles--Functional
Safety''. <a href="https://www.iso.org/search.html?q=ISO-26262&hPP=10&idx=all_en&p=0&hFR%5Bcategory%5D%5B0%5D=standard">https://www.iso.org/search.html?q=ISO-26262&hPP=10&idx=all_en&p=0&hFR%5Bcategory%5D%5B0%5D=standard</a>.
\85\ SAE J2929:2013, ``Safety Standard for Electric and Hybrid
Vehicle Propulsion Battery Systems Utilizing Lithium-based
Rechargeable Cells''. <a href="https://www.sae.org/standards/content/j2929_201302/">https://www.sae.org/standards/content/j2929_201302/</a>.
---------------------------------------------------------------------------

<bullet> A system diagram of all relevant physical systems and
components which contribute to the protection of vehicle occupants from
hazardous effects caused by thermal propagation triggered by a single-
cell thermal runaway event due to an internal short-circuit.

[[Page 26721]]

<bullet> A diagram showing the functional operation of the relevant
systems and components and identifying all relevant risk mitigation
functions or characteristics.
<bullet> For each identified risk mitigation function or
characteristic:
[cir] A description of its operation strategy,
[cir] Identification of the physical system(s) or component(s)
which implements the function,
[cir] One or more of the following engineering documents relevant
to the manufacturers design which demonstrates the effectiveness of the
risk mitigation function:
[ssquf] Tests performed including procedure used and conditions and
resulting data,
[ssquf] Analysis or validated simulation methodology and resulting
data.
iii. NHTSA Proposal
NHTSA tentatively agrees with GTR No. 20's rationale for the
documentation requirements for risk mitigation of thermal propagation
events resulting from SCTR due to an internal short-circuit within a
cell in the REESS. NHTSA tentatively concludes that due to the rapidly
evolving REESS technology and control systems to manage the performance
condition and safety of the REESS, a performance test to validate
mitigation of thermal propagation resulting from SCTR within the REESS
is not currently feasible. A performance test for a warning, when the
vehicle propulsion system is turned on, that provides sufficient time
for vehicle occupants to egress the vehicle before hazardous conditions
arise in the passenger compartment after a thermal runaway is initiated
in a cell of the REESS would be unduly design restrictive, not
applicable to all vehicle/REESS types, and not relevant to real world
incidents.\86\
---------------------------------------------------------------------------

\86\ In most real-world incidents resulting in fire due to
thermal runaway of a single cell in the REESS, the vehicle was
parked, with propulsion system turned off, and with no occupants in
the vehicle. In some cases, the vehicles were parked in garages of
homes. Therefore, a requirement for a warning to vehicle occupants
in the vehicle with propulsion system turned on would not have
helped prevent the fire or mitigated hazards to people in homes or
in the vicinity of the burning parked vehicle.
---------------------------------------------------------------------------

This NPRM proposes a documentation requirement for FMVSS No. 305a
to require manufacturers to provide to NHTSA, upon NHTSA's request,
information about their efforts to identify and address potential
safety problems with SCTR and propagation due to an internal short-
circuit. The information would be provided by a manufacturer in
accordance with NHTSA's specified structure in four parts. NHTSA's
proposed documentation component structure is based on elements from
the GTR No. 20, ISO-6469-1: Amendment 1 2022-11,\87\ and ISO-26262.\88\
The documentation submitted by the manufacturer is required to include
all known risks to vehicle occupants and bystanders, risk assessment,
risk management, and risk mitigation strategies in three vehicle
operational modes (i.e., external charging mode,\89\ active driving
possible mode,\90\ and parking mode \91\). NHTSA's proposal goes beyond
GTR No. 20's active driving possible mode to ensure manufacturers
consider all risks known to it in three vehicle operational modes. The
assessment and validation of these strategies may involve a combination
of physical testing and simulations at the component level and/or full
vehicle level. The reporting requirements would apply to REESSs of all
types (including REESS with non-flammable electrolyte).
---------------------------------------------------------------------------

\87\ ISO 6469-1:Third Edition 2019-04 Amendment 1 2022-11,
``Electrically propelled road vehicles--Safety specifications--Part
1: Rechargeable energy storage system (RESS),'' specifies safety
requirements for REESS, including test methodology for initiating
thermal runaway in a cell for the purpose of conducting a thermal
runaway propagation test and a format for reporting on risk
mitigation strategies of thermal propagation resulting from a
thermal runaway in a single cell of an REESS due to an internal
short within the cell.
\88\ ISO 26262: 2018, ``Road vehicles--Functional safety,''
provides a comprehensive collection of standards to manage and
implement road vehicle functional safety from concept phase to
production and operation. The standard provides guidelines for
overall risk management, individual component development,
production, operation, and service.
\89\ External charging mode is the vehicle operational mode in
which the charge connector is connected to the vehicle charge inlet
for the purpose of charging the REESS.
\90\ Active driving possible mode is the vehicle mode when
application of pressure to the accelerator pedal (or activation of
an equivalent control) or release of the brake system causes the
electric powertrain to move the vehicle.
\91\ Parking mode is the vehicle mode in which the vehicle power
is turned off, the vehicle propulsion system and ancillary equipment
such as the radio are not operational, and the vehicle is
stationary.
---------------------------------------------------------------------------

The objective of the documentation is for vehicle manufacturers to
identify the risks of single-cell thermal runaway and propagation for
their REESS type, identify strategies to mitigate those risks, and
demonstrate how those strategies work. The documentation would
accomplish the following goals:
<bullet> It would identify all risks known to the manufacturer
related to single-cell thermal runaway and propagation due to an
internal short-circuit;
<bullet> It would discuss whether and how each identified risk is
managed and/or mitigated by at least one risk mitigation strategy;
<bullet> It would explain the reasons the manufacturer believes
each risk mitigation strategy is effective (measures taken to verify
and/or validate them, including any final review/audit results); and,
<bullet> It would identify, describe, and provide any review/audit
process and results that accompany the final assessment of risk
management and risk mitigation strategies.
Proposed provisions to achieve the above goals are discussed in
detail below.
The documentation requirement proposed by NHTSA is divided into
four sections with more detailed requirements than GTR No. 20. Under
the agency's requirements, in Part I, System Analysis, the vehicle
manufacturer would provide information describing which conditions
specific to the vehicle could lead to a SCTR event caused by an
internal short-circuit. The conditions identified serve as the inputs
to identify the functions and failure modes for the risk identification
in Part II.
Part I would require the following documentation:
<bullet> A system diagram and a description of all relevant
physical systems and components of the REESS, including information
about the cell type and electrical configuration, cell chemistry,
electrical capacity, voltage, current limits during charging and
discharging, thermal limits of the components that are critical for
thermal propagation safety;
<bullet> A system diagram, operational description of sensors,
components, functional units relevant to single-cell thermal runaway
due to internal short-circuit and thermal propagation, and the
interrelationship between the identified sensors, components, and
functional units;
<bullet> A description of conditions under which a single-cell
thermal runaway and propagation event due to an internal short-circuit
could occur;
<bullet> A description of how the identified conditions are
allocated to each identified component, functional unit, and subsystem;
<bullet> A description of the process used to review the identified
conditions and their allocation to the identified sensors, components,
and functional units, for completeness and validity; and
<bullet> A description of any system for warning or notification
prior to the occurrence of thermal runaway in a cell, including a
description of the detection technology and mitigation strategies, if
any.
Part II, Safety Risk Assessment and Mitigation Process, provides a
description of all identified safety risks and strategies to mitigate
and manage

[[Page 26722]]

these risks. Part II distinguishes between primary and secondary risk
mitigation strategies. Primary risk mitigation strategies mitigate the
risk of SCTR due to an internal short-circuit and the occurrence of
thermal propagation that may result from SCTR. Primary risk mitigation
strategies include manufacturing quality control to mitigate defects in
cells of REESS, REESS design features such as heat sinks, cell spacing,
coolant, advanced battery management system with prognostics and
diagnostics systems \92\ to manage the health of the cells of an REESS
and detect a possible thermal runaway condition before it occurs. In
contrast, secondary risk mitigation strategies may not reduce the risk
of thermal runaway or thermal propagation but reduce the hazards
associated with thermal propagation. Secondary risk mitigation
strategies include warning systems to vehicle occupants/bystanders and/
or notification to emergency personnel in the event of thermal
propagation (e.g., automatic notification to 911 operators). NHTSA
anticipates that secondary risk mitigation strategies would be employed
as an addition to primary risk mitigation strategies in the overall
safety strategy.
---------------------------------------------------------------------------

\92\ Prognostic technologies predict the health of a system or a
component of a system in the future and diagnostic technologies
determine a specific problem with a system or component of a system.
---------------------------------------------------------------------------

Part II would require the following documentation:
<bullet> A description of safety risks and safety risk mitigation
strategies, and how these were identified (e.g., Failure Mode and
Effects Analysis (FMEA), or Failure Modes, Effects, and Criticality
Analysis (FMECA)); \93\
---------------------------------------------------------------------------

\93\ FMEA and FMECA are established methodologies to identify
failure modes and postulate the effects of those failures on the
system. Refer to <a href="https://www.dau.edu/acquipedia-article/failure-modes-effects-analysis-fmea-and-failure-modes-effects-criticality">https://www.dau.edu/acquipedia-article/failure-modes-effects-analysis-fmea-and-failure-modes-effects-criticality</a>.
---------------------------------------------------------------------------

<bullet> A description of how each risk mitigation manages/
mitigates the identified safety risks.
In Part III, Verification and Validation of Effective Risk
Mitigation Strategies, the manufacturer provides information showing
how they verify the effectiveness of the identified mitigation
strategies in Part II to mitigate the identified safety risks. The
vehicle level assessment examines how the entire vehicle monitors and
mitigates safety risks. The vehicle level assessment is the culmination
of the verification/validation results of each individual risk
mitigation strategy.
Part III would require the following documentation:
<bullet> A summary of the process used to verify each identified
risk is addressed by at least one risk mitigation strategy;
<bullet> A description of how each risk mitigation strategy was
verified and validated for effectiveness; \94\
---------------------------------------------------------------------------

\94\ Possible verification/validation methods for Part III
include (but are not limited to) fault injection tests, software,
and hardware performance tests at component and/or system level, and
system level performance evaluation using validated mathematical
models.
---------------------------------------------------------------------------

<bullet> A description of the verification and validation results
for each risk mitigation strategy; and
<bullet> A vehicle level assessment evaluating the system response
to safety risks associated with the REESS. Vehicle level assessment and
validation could be the use of physical tests and/or validated models/
simulations at a component level scaled up to evaluate the system
response.
Part IV, Overall Evaluation of Risk Mitigation, shall address:
<bullet> Results of any final review/audit responsible for
reviewing the technical content, completeness, and verity of the
documentation submitted by the manufacturer.
The risk-based methodology outlined above is intended to mitigate
the safety hazards associated with SCTR and propagation from an
internal short-circuit. The requirement is intended to ensure that
manufacturers are aware of the safety risks at issue and have
considered safety risk mitigation strategies. The documentation
submitted by the manufacturer will inform NHTSA of the safety risk
mitigation strategies manufacturers have utilized for the identified
safety hazards, enable NHTSA to oversee those safety hazards, and
inform future regulatory measures.. This approach is battery technology
neutral, not design restricted, and is intended to adapt over time as
battery technologies continue to rapidly evolve. NHTSA seeks comment on
the documentation requirements described above. In section VI., NHTSA
requests comments on whether the proposed document requirement would be
better placed in a general agency regulation than in proposed FMVSS No.
305a.
NHTSA's Decision Not To Propose a Warning Requirement
GTR No.20's warning requirement rationale is that the warning would
allow vehicle occupants sufficient time to egress the vehicle before
hazardous conditions are present in the occupant compartment. NHTSA
does not agree with GTR No.20's rationale for a warning requirement
related to SCTR due to an internal short-circuit within the cell. NHTSA
is not proposing to require such a warning system, or documentation of
the warning system, as specified in GTR No. 20 because such a
requirement would not mitigate the safety hazards observed in the
field, as described in detail below.
Field data and incidents related to SCTR and propagation due to an
internal short-circuit in lithium-ion REESSs are sparse and anecdotal.
However, when reviewing the limited number of non-crash and non-abuse
related electric vehicle fire incidents in the United States,\95\ the
following trends emerge:
---------------------------------------------------------------------------

\95\ E.g., Bolt EV Recall Information <a href="https://experience.gm.com/recalls/bolt-ev">https://experience.gm.com/recalls/bolt-ev</a>.
---------------------------------------------------------------------------

<bullet> The vehicle operation mode is in the usual parking
mode.\96\
---------------------------------------------------------------------------

\96\ Usual parking mode is the vehicle operational mode in which
the main software is ``Off'', the gear selector is in ``P'' (park),
the energy supply is disconnected, the REESS power line is
disconnected, the cooling system is not operational, the vehicle
controls that manage safe operation of the REESS (e.g., Battery
Manage System) are not energized, and the vehicle occupants are
typically not present.
---------------------------------------------------------------------------

<bullet> The vehicle is parked in a garage attached to a house, a
parking garage, or on the street.
<bullet> The state of charge (SOC) of the REESS was generally in
the upper range.
Fire statistics reports by South Korea identified 35 electric
vehicle fires since 2018, among which 20 electric vehicle fires
originated in the REESS of the vehicles when the vehicle was parked and
the SOC was greater than 90 percent.\97\ In the electric vehicle fire
incidents in the United States and South Korea, the vehicle fire
propagated to adjacent vehicles and structures with release of copious
amounts of smoke, resulting in significant property damage. The GTR No.
20 requirement for a warning to the driver would not have helped
mitigate the electric vehicle fires and would not have mitigated
property damage.
---------------------------------------------------------------------------

\97\ EVS23-E1TP-0200 [KR] EV Fire Records of Korea.pptx. <a href="https://wiki.unece.org/display/trans/EVS+23rd+session">https://wiki.unece.org/display/trans/EVS+23rd+session</a>.
---------------------------------------------------------------------------

Accordingly, this NPRM does not propose to require a warning to
occupants or documentation pertaining to a warning, as such
requirements would not sufficiently address a safety need. NHTSA
believes the documentation requirements in GTR No. 20 for a warning to
the driver are not relevant to the field-observed electric vehicle
fires likely resulting from SCTR. NHTSA believes that vehicle designs
using a risk mitigation strategy to mitigate or prevent the occurrence
of SCTR incidents would better address the risks and hazards associated
with spontaneous electric

[[Page 26723]]

vehicle fires that originate within the REESS than a warning to egress
the vehicle. This NPRM proceeds with NHTSA's preferred approach which
would require documentation demonstrating that the manufacturer has
considered and developed risk mitigation strategies to address SCTR in
developing their electric vehicles.
GTR No. 20 Phase 2 Test Procedure Currently Under Consideration
The IWG is continuing work on developing a test-based approach for
SCTR due to an internal short-circuit in a single cell within the
REESS. The plan is for a future regulation to require that the thermal
propagation test procedure fulfill the following conditions:
1. Triggering of thermal runaway at a single-cell level must be
repeatable, reproducible, and practicable,
2. Judgment of thermal runaway through common sensors, e.g.,
voltage and temperature, needs to be practical, repeatable, and
reproducible, and
3. Judgment of whether consequent thermal events involve severe
thermal propagation hazards, needs to be unequivocal and evidence
based.
NHTSA discusses this work in the Appendix B to this preamble.
Comments are requested that could assist the agency in future decisions
on this matter.
3. Warning Requirements for REESS Operations
As part of a risk-mitigation approach addressing multiple aspects
of electrical system safety, NHTSA proposes requiring: (a) a thermal
event warning; and (b) a vehicle control malfunction warning for
drivers. The thermal event warning would be assessed by a performance
requirement, while the vehicle control malfunction warning would be a
documentation requirement.
i. Thermal Event Warning
A ``thermal event'' presents an urgent safety critical situation.
The term refers to a condition when the temperature within the REESS is
significantly higher (as defined by the manufacturer) than the maximum
operating temperature specified by the manufacturer. Thermal events
within REESS could occur due to moisture and dust accumulation within
the REESS that cause a short circuit at the connections or electronic
components within the REESS. A thermal event within a battery pack can
be a safety critical event, as it can lead to smoke, fire, and/or
explosion. A warning provided about a thermal event within the REESS
would reduce the likelihood of occupant exposure to smoke, fire, and/or
explosion.
GTR No. 20 requires the vehicle to provide a warning to the driver
in the case of a ``significant thermal event'' in the REESS (as
specified by the manufacturer) when the vehicle is in active driving
possible mode.\98\ The GTR does not contain a performance test for the
warning but instead requires manufacturers to provide documentation on
the parameters that trigger the warning and a description of the system
for triggering the warning. Specifically, the documentation
requirements include:
---------------------------------------------------------------------------

\98\ Active driving possible mode means the vehicle mode when
application of pressure to the accelerator pedal (or activation of
an equivalent control) or release of the brake system causes the
electric power train to move the vehicle.
---------------------------------------------------------------------------

(1) Parameters and associated threshold levels that are used to
indicate a thermal event (e.g., temperature, temperature rise rate, SOC
level, voltage drop, electrical current, etc.) to trigger the warning.
(2) A system diagram and written explanation describing the sensors
and operation of the vehicle controls which manage the REESS in the
event of a thermal event.
NHTSA Proposal
NHTSA proposes to include a requirement for an audio and visual
warning to the driver if a thermal event occurs in the REESS during the
active driving possible mode. Instead of a documentation requirement as
in the current GTR No. 20, NHTSA proposes a performance test to
evaluate the required warning of a thermal event originating within the
REESS.
NHTSA proposes to initiate the thermal event in the REESS by
inserting a heater within the REESS that achieves a peak temperature of
600[deg]C within 30 seconds. In the proposed test procedure, the REESS
is removed from the vehicle, if possible, and the REESS casing is
opened to attach the heater to a cell or cells in the REESS in a manner
to put at least one cell in the REESS into thermal runaway. In this
test, there is no need to restrict heating to a single cell within the
REESS as the test is verifying activation of a warning when a thermal
event occurs in the REESS regardless of the cause (e.g., an electric
short between electronic components in the REESS, thermal runaway of
multiple cells, etc.). Following installation of the heater in the
REESS, the REESS casing is closed, the REESS is re-installed in the
vehicle, and the vehicle propulsion system is turned on. The heater
within the REESS is then activated. NHTSA proposes that the audio-
visual warning must be activated within three minutes \99\ of
initiating the heater in the REESS. NHTSA has tentatively decided not
to specify characteristics of the audio-visual warning to provide
flexibility in how manufacturers communicate this safety critical
information to vehicle occupants so they quickly egress the vehicle.
---------------------------------------------------------------------------

\99\ 3 to 5 minutes is considered to be sufficient time for able
body individuals to evacuate light and heavy passenger vehicles
before the occurrence of a hazardous event. <a href="https://one.nhtsa.gov/reports/0900006480b01bbc.pdf">https://one.nhtsa.gov/reports/0900006480b01bbc.pdf</a>.
---------------------------------------------------------------------------

The proposed test is for evaluating appropriate activation of a
required warning system when there is a thermal event in the REESS that
could be hazardous to vehicle occupants.\100\ NHTSA tentatively
concludes that the proposed performance test to evaluate the warning
system would not be design restrictive and can be conducted on all
applicable vehicles. Therefore, a performance test is proposed instead
of adopting the documentation requirement in GTR No. 20. NHTSA seeks
comment on the merits of the proposed performance test to evaluate the
thermal event warning system instead of the documentation requirement
in GTR No. 20. In addition, NHTSA seeks input on the type of heater,
the heater characteristics (power, peak temperature) and possible
locations of the heater within the REESS to simulate a thermal event to
trigger the warning. While this NPRM does not require specific features
of the audio-visual warning itself, comments are requested on what
characteristics an effective audio-visual warning should have.
---------------------------------------------------------------------------

\100\ This is unlike the risk management approach for SCTR where
the goal is to mitigate hazards of thermal propagation (fire, smoke,
gas emissions). Because risk management strategies for mitigating
thermal propagation hazards due to SCTR differ considerably in
vehicle designs, an objective performance test that can be conducted
on all applicable vehicles is not available and so a documentation
requirement is proposed.
---------------------------------------------------------------------------

ii. Warning in the Event of Operational Failure of REESS Vehicle
Controls
NHTSA is proposing to require that drivers be warned if there is a
malfunction of vehicle controls that manage the safe operation of the
REESS. This NPRM proposes a documentation approach for this type of
warning, similar to GTR No. 20.
GTR No. 20 specifies that when the vehicle is in the active driving
possible mode, the vehicle shall provide a warning telltale to the
driver in the event of a malfunction of the vehicle controls that
manage the safe operation of the REESS. GTR No. 20 requires
manufacturers to provide

[[Page 26724]]

documentation demonstrating that a warning to the driver will be
provided in the event of malfunction of one or more aspects of vehicle
controls that manage REESS safe operation. Specifically, vehicle
manufacturers shall make the following documentation available to the
testing authority:
(1) A system diagram that identifies all the vehicle controls that
manage REESS operation. The diagram must identify what components are
used to generate a warning telltale indicating malfunction of vehicle
controls to conduct one or more basic operations.
(2) A written explanation describing the basic operation of the
vehicle controls that manage REESS operation. The explanation must
identify the components of the vehicle control system, provide
description of their functions and capability to manage the REESS, and
provide a logic diagram and description of conditions that would lead
to triggering the warning telltale.
NHTSA Proposal
Vehicle controls manage several REESS operations, some of which are
safety critical. There are multiple external fault scenarios \101\ that
could trigger a vehicle control to take corrective actions to ensure
safe REESS operations. This NPRM includes performance requirements to
address these external fault scenarios that assume proper functioning
of the vehicle controls that manage safe REESS operations. However, if
the vehicle controls that manage safe REESS operation are not
functioning properly, the REESS may not be adequately protected from
fault scenarios, which could lead to REESS degradation and eventually
result in thermal propagation and other safety hazards. Therefore, it
is important to notify the driver or front row occupants in the event
there is malfunction of these vehicle controls that manage safe REESS
operations.
---------------------------------------------------------------------------

\101\ These fault scenarios include overcharge, over-discharge,
overcurrent, external short-circuit, and overheating of the REESS.
---------------------------------------------------------------------------

Due to the complexity and varied designs of vehicle controls that
manage REESS safe operation, no single test procedure could be
developed that would fully evaluate whether a warning turns on in the
event of operational failure of vehicle controls. Therefore, in
accordance with GTR No. 20, this NPRM proposes to require manufacturers
to provide a visual warning to the driver (e.g., like a check engine
light) and documentation demonstrating that the visual warning will be
provided in the event of operational failure of one or more aspects of
vehicle controls that manage REESS safe operation.
NHTSA proposes the GTR No. 20 requirements for a visual warning to
the driver of any malfunction of the REESS vehicle controls, and
manufacturer documentation. In addition, NHTSA proposes to include two
additional requirements that ensure manufacturers have validated
functionality of the warning system:
(1) Any validation test results by the vehicle manufacturer to
confirm a visual warning is displayed in the presence of malfunction of
the REESS operation vehicle controls.
(2) A description of the final manufacturer review or audit process
and results of any final review or audit evaluating the technical
content and the completeness and verity of the documentation submitted
by the manufacturer.
NHTSA tentatively concludes that a documentation approach is
merited to demonstrate that the manufacturer has considered the
effectiveness of a visual warning of the malfunction of the REESS
operational vehicle controls. In the absence of information enabling
NHTSA to propose a practical test procedure to evaluate the performance
of a warning, the documentation approach ensures that manufacturers are
aware of the safety risks at issue and have considered ways to address
the risks. NHTSA would review the documentation to understand the
visual warning associated with the particular REESS in the vehicle, see
whether the manufacturer conducted an assessment of its effectiveness,
and understand the measures the manufacturer undertook to validate such
performance.
This approach is an interim measure intended to assure that
manufacturers will identify, address, and validate the effectiveness of
their visual warnings that help manage safe REESS operation. The
approach is intended to evolve over time as battery technologies and
NHTSA's information about the REESS safety risk mitigation strategies
evolve. In section VI., NHTSA requests comments on whether the proposed
document requirement would be better placed in a general agency
regulation than in proposed FMVSS No. 305a.
4. Protection Against Water Exposure
NHTSA proposes to adopt GTR No. 20's physical water test
requirement, where a vehicle shall maintain electrical isolation
resistance after the vehicle is exposed to water under normal vehicle
operation, such as in a car wash or while driving through a pool of
standing water. However, the agency is not proposing to adopt GTR No.
20's two other water exposure methods: documentation measures and
warning requirements.
Environmental effects such as exposure to water and moisture may
deteriorate the electrical isolation of high voltage components in the
powertrain. This may first lead to an electric system degradation and
eventually lead to an unsafe electrical system for vehicle occupants,
operators (during charging) or by-standers. Under extreme conditions,
fire can originate from compromised electrical components due to water
ingress. GTR No. 20 contains water exposure shock protection
specifications in which a vehicle shall maintain electrical isolation
resistance after the vehicle is exposed to water under normal vehicle
operation, such as during a car wash or driving through a pool of
standing water.
NHTSA begins by noting that GTR No. 20 does not have specific
requirements to address vehicle fires due to vehicle submersion such as
floods and storm surges, and this NPRM is not covering that area.
Floods are considered as catastrophic events, and as noted above, one
of the principles for developing GTR No. 20 was to address unique
safety risks posed by electric vehicles and their components to ensure
a safety level equivalent to conventional vehicles with internal
combustion engine (ICE). NHTSA continues to research the area of REESS
performance post-submersions. This issue is discussed in more detail
later in this section.
GTR No. 20 Requirements
GTR No. 20 contains water exposure shock protection specifications
in which a vehicle shall maintain electrical isolation resistance after
the vehicle is exposed to water under normal vehicle operation. GTR No.
20 specifies three compliance options contracting parties may use in
their regulations:
<bullet> Physical tests--(1) the vehicle is subjected to normal
washing using a hose nozzle and conditions in accordance with IPX5,
after which (2) the vehicle is driven in a freshwater wade pool (10 cm
depth) over a total distance of 500 m at a speed of 20 km/hr for
approximately 1.5 minutes (min). The electrical isolation of high
voltage sources in the electric powertrain are verified at the
conclusion of each test and once again after 24 hours.
<bullet> Documentation--The vehicle manufacturers provide
documentation

[[Page 26725]]

certifying to IPX5 \102\ level waterproofing for protection of high
voltage components in the vehicle. IPX5 is a waterproof rating that
ensures protection against water ingress under sustained low pressure
water jet stream (12.5 liters per minute at a pressure of 30
kilopascals (4.4 psi) from a distance of 3 meters) from any angle. The
duration of the jet stream exposure is 1 minute per square meter
surface area of the high voltage component.
---------------------------------------------------------------------------

\102\ IEC 60529:1989/AMD2:2013, ``Degrees of protection provided
by enclosures (IP Code).'' <a href="https://webstore.iec.ch/publication/2446">https://webstore.iec.ch/publication/2446</a>.
---------------------------------------------------------------------------

<bullet> Warning--The vehicle has an electrical isolation loss
warning system that warns the driver when electrical isolation falls
below 100 ohms per volt for DC electrical components or 500 ohms per
volt for AC electrical components. This option is available for
individual countries to adopt if they so choose.
i. NHTSA Proposal
NHTSA tentatively concludes that the GTR No. 20's physical test
option is a practical and feasible means of evaluating the effects of
water exposure under normal vehicle operating conditions. It has
advantages of a performance standard in assessing compliance over a
documentation approach. Thus, the agency is not proposing the
compliance option in GTR No. 20 of providing documentation on high
voltage components meeting IPX5 level of protection.
Regarding the electrical isolation loss warning system option in
GTR No. 20, NHTSA believes the warning signals alone are not sufficient
for addressing loss of electrical isolation concerns. Where objective
performance criteria are available and are appropriate for all types of
vehicles to which the standard applies, NHTSA believes objective
performance criteria should govern when compared to the approach of
solely using a warning. The existence of the visual warning cannot
necessarily be considered a safety prevention system, as the root cause
of the safety hazard remains unaddressed, and the visual warning may be
ignored by the driver. Although visual warning indicators triggered
from an isolation monitoring system could help mitigate safety
concerns, NHTSA believes that this approach is not sufficient to solely
mitigate a shock or fire hazard caused by the effects of water
exposure. Thus, the agency does not propose this alternative as a
compliance option in FMVSS No. 305a.
NHTSA Proposed Vehicle-Level Physical Test Procedures
The proposed physical test procedure is comprised of two series of
tests, informally referred to as the ``vehicle washing'' test and the
``driving through standing water'' test. Electrical isolation is
determined at the conclusion of each test, and once again after 24
hours.
A. Vehicle Washing Test
The washing test exposes the vehicle to a stream of water such as
when washing a car. The vehicle external surface, including the vehicle
sides, front, rear, top, and bottom is exposed to the water stream. GTR
No. 20 excludes the vehicle underbody from exposure to the water
stream. However, since the vehicle underbody is often exposed to water
when the vehicle is washed, NHTSA proposes to also expose the vehicle
underbody to the water stream to make this test more representative of
vehicle washing. The areas of the vehicle that are exposed to the water
stream in any possible direction include border lines, i.e., a seal of
two parts such as flaps, glass seals, outline of opening parts
(windows, doors, vehicle inlet cover), outline of front grille and
seals of lamps.
During the test, the vehicle is sprayed from any practicable
directions with a stream of freshwater from a standard test nozzle as
shown in Figure 4 below. The standard nozzle, with an internal diameter
is 6.3 mm, shall provide a delivery rate of 11.9-13.2 liters/minute (l/
min) with water pressure at the nozzle of 30-35 kilopascals (kPa) or
0.30-0.35 bar. These standard nozzle specifications are from IEC 60529
for IPX5 water jet nozzle.
[GRAPHIC] [TIFF OMITTED] TP15AP24.047

Figure 4--Standard Nozzle (IEC 60529) for IPX5 Water Exposure Test

The vehicle surface is exposed to the water stream from the
standard nozzle for a duration of 1 minute per square meter or for 3
minutes, whichever is greater. The distance from the nozzle to the
tested vehicle is 3 meters, which may be reduced, if necessary, to
ensure the surface is wet when spraying upwards.
After the ``vehicle washing'' test and with the vehicle surface
still wet, electrical isolation is determined for high voltage sources
in the same manner as that currently in S7.6 of FMVSS No. 305. The high
voltage sources are required to meet the electrical isolation
requirements as specified in S5.4.3 of current FMVSS No. 305.
Comments are requested on the merits of including the test in FMVSS
No. 305a. NHTSA seeks comment on the representativeness of the washing
test, including but not limited to the proposed test conditions (e.g.,
30-35

[[Page 26726]]

kPa versus 80-100 kPa water pressure conditions, water salinity levels,
and water exposure durations, etc.).
B. Driving Through Standing Water Test
NHTSA proposes that vehicles should also be subjected to GTR No.
20's ``driving through standing water'' test. The vehicle is driven
through a pool of standing freshwater,\103\ 10 centimeters (cm) (4
inches) deep, for a total range of 500 meters (m), at a vehicle speed
of 20 km/hr.\104\ The pool represents a low-lying portion of a road
that can get flooded in excessive rain. Meeting the test is a
reasonable indication that the vehicle has safeguards to ensure
electrical safety when driven through roads in inclement weather.
---------------------------------------------------------------------------

\103\ Freshwater means water containing less than 1,000
milligrams per liter of dissolved solids, most often salt.
\104\ NHTSA tentatively concludes that the 10 cm (approximately
four-inch) depth is reasonable, as national weather advisories
(<a href="https://www.weather.gov/tsa/hydro_tadd">https://www.weather.gov/tsa/hydro_tadd</a>) recommend not driving on
flooded roads with more than four inches of water. Six inches of
water on the road could reach the bottom of most passenger cars
causing loss of control and possible stalling. A foot of water can
float many vehicles.
---------------------------------------------------------------------------

If the wade pool used is less than 500 m in length, then the
vehicle is driven through the wade pool several times. The total time,
including the periods outside the wade pool, would have to be less than
5 minutes. GTR No. 20 specifies a maximum test time of 10 minutes, but
NHTSA believes that 5 minutes is preferable. Traversing 500 m at 20 km/
hr takes 90 seconds. A maximum test duration of 10 minutes would allow
for an excessive amount of time out of the water and may not be
equivalent to a continuous 500 m exposure. NHTSA seeks comment on the
maximum duration of this test. NHTSA also seeks comment on the
availability and geometric dimensions of different types of wade pools
(long rectangular, circular) to accomplish this type of test.
Just after the standing water test is completed and with the
vehicle still wet, the vehicle would be required to meet the electrical
isolation requirements now specified in FMVSS No. 305 S5.4.3 when
tested in the same manner as described in S7.6 of current FMVSS No.
305. The vehicle is also required to meet the electrical isolation
requirements that are in S5.4.3 of current FMVSS No. 305, 24 hours
after the washing test and the standing water test are completed.
NHTSA seeks comment on the water salinity requirements for the
physical tests as described above, including tolerances for the test
parameters listed above.
ii. NHTSA's Consideration of Submersions
In the U.S., floods resulting from Hurricane Sandy (2012),
Hurricane Harvey (2017) and Hurricane Ian (2022) have led to electric
vehicles submerged in flood waters for varying periods of time, with
varying reports of vehicle fires in the aftermath. In developing this
NPRM, the agency considered whether it could propose requirements to
address these types of vehicle submersions and the resulting risk of
fire. NHTSA analyzed field data from these hurricanes and made the
following key observations of vehicle fires resulting from the vehicle
submersions:
(1) Not all electric vehicles submerged in floods catch on fire.
The type of water (water salinity), the level of submersion, and
duration of submersion are likely factors;
(2) Fire and other hazards are more likely after water exposure
(days after flood waters recede) rather than during the exposure;
(3) Fire may not originate in the REESS and may spread to the REESS
from another vehicle component; and
(4) While 12V systems may also short circuit and result in vehicle
fire, fires involving lithium-ion REESS are more difficult to
extinguish and more hazardous because of the self-oxygenating nature of
the lithium-ion cells and the energy density of the REESS.
NHTSA evaluated the regulatory approaches taken by other countries
to determine if such standards could assist NHTSA in addressing the
challenges posed by the submersions and fires resulting from Hurricanes
Sandy, Harvey, and Ian. NHTSA analyzed China and Korea's water exposure
requirements but determined the focus of those standards do not appear
to address the safety matter at issue. Key observations and findings
from the field data in the U.S. and the exploratory investigation into
the water exposure posed by the hurricanes suggest that the test
procedure and parameters and the performance requirements in China GB-
38031 \105\ and the Korean Motor Vehicle Safety Standard (KMVSS) \106\
may not be representative of field events of vehicle fires resulting
from Hurricanes Sandy, Harvey, and Ian water exposure. If the standards
are not representative of the harm NHTSA wishes to address from the
hurricanes, the concern is the countermeasures to meet the performance
test requirements of GB-38031 and KMVSS may not be effective at
mitigating thermal events resulting from the water exposure at
issue.\107\
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\105\ GB-38031 water immersion test contains two options. Option
1 is based on ISO-6469-1:2019 where the REESS is submerged in 1
meter of seawater (salinity of 3.5 percent) for two hours. The
performance requirement for this test option is for no fire or
explosion of the REESS during the submersion. Option 2 is based on
ISO-20653, and requires IPX7 level waterproofing. In this test
option, the REESS is completely submerged in regular water for 30
minutes such that the lower point of the battery is one meter below
the surface or the highest point is 150 mm below the surface (for
battery packs with a height greater than 850 mm). The performance
requirement in this test option is for no water ingress, fire, or
explosion, and the REESS maintains an electrical isolation of 100
ohms per volt after submersion. Option 1 of GB-38031 is intended for
most current REESS (open-type or partially sealed) while Option 2
would necessitate a fully sealed REESS.
\106\ KMVSS contains requirements for REESS, including a water
immersion test that has been implemented in South Korea since 2009.
In the water immersion test, the REESS is fully submerged in
seawater (salinity of 3.5 percent) for one hour. The performance
requirement in this test is for the REESS to not explode or catch on
fire during the immersion. EVS19-E4WI-0300 [KR] Water Immersion
Test.pptx. <a href="https://wiki.unece.org/display/trans/EVS+19th+session">https://wiki.unece.org/display/trans/EVS+19th+session</a>.
\107\ For instance, NHTSA's understanding is that most of the
vehicles involved in Hurricane Ian's post-submersion fires had met
China GB-38031.
---------------------------------------------------------------------------

Specifically, in both standards, the REESS is submerged in 3.5
percent salinity water representing seawater for a long period of time
(two hours for GB-38031 and one hour for KMVSS). NHTSA's exploratory
investigation of current REESS designs \108\ suggests submersion in
lower salinity water for a shorter duration may result in higher risk
of thermal event. Longer immersion times in seawater salinity levels
allow the batteries to safely discharge under water without adverse
reactions such as arcing, venting, or underwater fires. Additionally,
the requirements for no fire and explosion in these two standards are
evaluated during the REESS immersion and not after the REESS is pulled
out of the water. Such a requirement is not relevant to the electric
vehicle fires observed after the flood waters in Hurricane Sandy and
Hurricane Ian receded.
---------------------------------------------------------------------------

\108\ Li-Ion Battery Pack Immersion Exploratory Investigation,
DOT HS 813 136, July 2021. <a href="https://rosap.ntl.bts.gov/view/dot/57013">https://rosap.ntl.bts.gov/view/dot/57013</a>.
---------------------------------------------------------------------------

NHTSA acknowledges that the batteries in conventional vehicles with
internal combustion engines (ICE) may also catch fire due to
submersion. However, the post-submersion vehicle fires after Hurricane
Ian demonstrated that electric vehicle fires are more difficult to put
out and therefore more hazardous than ICE vehicle fires. NHTSA believes
that a better understanding of the field incidences of electric vehicle
fires is needed before a field relevant test and performance
requirements can be developed that addresses the observed safety risks

[[Page 26727]]

associated with submersion of REESS and high voltage components in
events such as floods.
The agency seeks comment on test conditions and test procedures
that would address observed safety risks associated with submersion of
REESS and high voltage components.
Going Forward
Shortly after Hurricane Ian, NHTSA and other DOT agencies
coordinated with emergency personnel in Florida to collect in-depth
information on vehicle fire incidences and REESSs involved in the
flooding.\109\ This activity and others like it provided critical
information that informed approaches to better protect vehicle owners,
responders, and other stakeholders in the future.
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\109\ NHTSA has purchased ten electric vehicles damaged during
Hurricane Ian and plans to perform a teardown analysis to understand
the root cause of the vehicle fires. The teardown analysis will
inform the next steps to address the safety risks associated with
vehicle submersions.
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In the near term, as discussed in sections below, this NPRM
proposes to require that electric vehicle manufacturers submit
standardized emergency response information to a NHTSA central
depository, to assist first and second responders to respond to
emergencies as quickly and safely as possible. The agency tentatively
concludes that such a requirement would be an important and achievable
near-term measure that NHTSA and the industry can take to mitigate the
harm from these fires as work continues on vehicle-based mitigation
methods. As part of NHTSA's activity going forward, NHTSA will document
EV battery conditions after catastrophic flooding events and will
commence new research into mitigation methods. The agency will obtain
data to develop and improve EV tests relevant to salt-water immersion.
5. Miscellaneous GTR No. 20 Provisions Not Proposed
There are several GTR No. 20 provisions for REESS performance
during normal vehicle operations that NHTSA has not included in this
NPRM. These provisions relate to requirements for: vibration, thermal
shock and cycling, fire resistance, and low state-of-charge (SOC).
Below is a description of the requirements and explanations of why
NHTSA is proposing not to include the requirements. NHTSA requests
comments on these views.
i. REESS Vibration Requirements
GTR No. 20 contains a vibration requirement and test procedure to
verify the safety performance of the REESS under a prescribed
sinusoidal vibration environment that applies a generic vibration
profile to the tested vehicle. NHTSA believes the vibration profile
accelerations and frequencies are unique for each vehicle model and so
applying a generic vibration profile to all vehicle models may not be
appropriate. Additionally, the vibration environment in the test
specified in GTR No. 20 is applied only in the vertical direction while
in real world driving conditions, the REESS is subject to vibration
along all three orthogonal axes. Therefore, the agency tentatively
concludes that the vibration test in GTR No. 20 is not representative
of the actual vibration environment for different vehicle models, or
representative of real-world conditions that the REESS experiences.
Furthermore, vibration appears sufficiently addressed through other
means. The market addresses this matter, as manufacturers routinely
perform vibration testing to ensure customer satisfaction and
reliability. Vehicle manufacturers assess the durability of the vehicle
and its components (not just the REESS) through various road conditions
with full vehicle simulation, either by driving on a rough road test
track or simulating the lifetime fatigue on a vibration rig. Further,
at the component level, electric vehicle batteries are currently
subject to similar vibration test requirements for transportation under
the United States Hazardous Materials Regulations (HMR) \110\ but along
all three orthogonal axes and for frequencies up to 200 Hz.\111\ Thus,
NHTSA believes that the GTR No. 20 vibration test would not address an
additional safety need beyond what is already provided by HMR.
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\110\ 49 CFR parts 171 to 180, incorporated requirements for
lithium batteries from UN 38.3 ``Transport of dangerous goods:
manual tests and criteria.''
\111\ 49 CFR 173.185 incorporated the vibration test 38.3.4.3
from the UN's ``Recommendations on the Transport of Dangerous Goods,
Manual of Tests and Criteria,'' <a href="https://digitallibrary.un.org/record/483552?ln=en">https://digitallibrary.un.org/record/483552?ln=en</a>.
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For the reasons stated in the paragraph above, NHTSA is not
proposing the vibration test at a component level or the vehicle
level.\112\ Currently, during Phase 2 development of GTR No. 20, there
are discussions for updating the vibration test to include vibration in
all three orthogonal axes and at higher amplitudes and frequency range.
In Appendix B of this preamble, the agency seeks public comment on the
work in Phase 2 on the vibration test.
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\112\ NHTSA and Transport Canada discussed in detail their
positions for not including this vibration test during the
development of GTR No. 20. See <a href="https://wiki.unece.org/download/attachments/117508721/EVS21-E3VP-0101%5BOICA_UC_CA%5Dconsideration_of_vibration.pdf?api=v2">https://wiki.unece.org/download/attachments/117508721/EVS21-E3VP-0101%5BOICA_UC_CA%5Dconsideration_of_vibration.pdf?api=v2</a>.
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ii. REESS Thermal Shock and Cycling
GTR No. 20's thermal shock and cycling requirement and test
procedure aim to verify that the REESS is robust against thermal
fatigue and contact degradation caused by temperature changes and
potential incompatibilities of materials with varying thermal expansion
characteristics.
At the component level, REESSs are already subject to thermal
cycling test requirements for transportation under the HMR. 49 CFR
173.185 requires lithium-ion cells and batteries to comply with the
test requirements in UN 38.3, including Test T2: Thermal test, which is
the basis of the GTR No. 20 thermal shock and cycling test. In the
UN38.3 Test T2, the REESS would be subject to temperature changes from
-40 [deg]C to +75 [deg]C. This temperature range is greater than that
prescribed in GTR No. 20. To avoid redundancy, NHTSA is not proposing
the thermal shock and cycling test for the REESS. NHTSA tentatively
concludes that incorporating the GTR No. 20 thermal shock and cycling
test into FMVSS would not address additional safety needs beyond that
already provided by HMR and 49 CFR 173.185. The agency seeks public
comment on the safety need of a REESS thermal shock and cycling
requirement, and requests commenters provide data to substantiate their
comments and/or assertions.
iii. REESS Fire Resistance
This GTR No. 20 requirement is based on UN Regulation No. 34,
``Uniform provision concerning the approval of vehicles with regard to
the prevention of fire risks,'' \113\ which contains a fire resistance
requirement for liquid fueled vehicle with plastic tanks. This test is
required for REESSs installed in a vehicle at a height lower than 1.5 m
above the ground and contain flammable electrolyte. During the test,
the REESS is placed on a grating table positioned above the fire source
in a pan. The pan filled with fuel is placed under the REESS in such a
way that the distance between the level of the fuel in the pan and the
bottom of the REESS corresponds to the design height of the REESS above
the road surface at the unladed mass. The REESS is exposed directly to
the flame for 70 seconds. A screen made of refractory material is then
moved over the pan with the flame,

[[Page 26728]]

such that the REESS is indirectly exposed to the flame for an
additional 60 seconds. The screen and pan are then moved away from the
REESS. The REESS is observed until the surface temperature of the REESS
has decreased to the ambient temperature of the test environment.
During the test, the REESS shall exhibit no evidence of explosion.
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\113\ UN Regulation No. 34. <a href="https://unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2013/R034r2e.pdf">https://unece.org/fileadmin/DAM/trans/main/wp29/wp29regs/2013/R034r2e.pdf</a>.
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NHTSA tentatively concludes that the short duration of the GTR No.
20 fire resistance test would not address any safety risks associated
with explosion resulting from external fire to the battery pack.
Transport Canada conducted full vehicle gasoline pool fire tests of
electric powered vehicles and similar vehicles with internal combustion
engines and found that there was no explosion in tests of vehicles with
REESS and those without. The Transport Canada tests indicated that the
short duration of the GTR No. 20 external fire test would not result in
explosion.\114\ During Phase 1 of the GTR No. 20 discussions, the
United States and Canada noted that including the short duration
component level test in GTR No. 20 would not address a safety need and
recommended removing it from GTR No. 20.\115\ For these reasons, NHTSA
is tentatively not proposing the short duration fire resistance test
from GTR No. 20. The agency seeks comment on excluding this fire
resistance requirement from the FMVSS, and requests commenters provide
data to substantiate their comments and/or assertions.
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\114\ <a href="https://wiki.unece.org/download/attachments/29884786/EVSTF-07-02e.pdf?api=v2">https://wiki.unece.org/download/attachments/29884786/EVSTF-07-02e.pdf?api=v2</a>.
\115\ <a href="https://wiki.unece.org/download/attachments/29884786/EVSTF-07-02e.pdf?api=v2">https://wiki.unece.org/download/attachments/29884786/EVSTF-07-02e.pdf?api=v2</a>.
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iv. Low State-of-Charge (SOC) Telltale
GTR No. 20 requires a telltale to the driver in the event of low
REESS SOC.\116\ The agency is tentatively not including this telltale
requirement for electric powered vehicles because there is no
corresponding low fuel warning requirement for conventional vehicles
with internal combustion engines. Low-fuel telltales are presently
provided in all conventional vehicles due to consumer demand.
Similarly, all electric-powered vehicles already provide low SOC
telltales due to consumer demand. NHTSA seeks comment on whether this
GTR No. 20 requirement should be incorporated into proposed FMVSS No.
305a, and if yes, what the telltale should look like.
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\116\ The GTR does not standardize the appearance of the
telltale.
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IV. Request for Comment on Applying FMVSS No. 305a to Low-Speed
Vehicles

Current FMVSS No. 305 applies to electric vehicles whose speed,
attainable over a distance of 1.6 kilometers (km) (1 mile) on a paved
level surface, is more than 40 km/h (25 miles per hour (mph)). It does
not apply to vehicles that travel under 40 km/h (25 mph), such as low-
speed vehicles.\117\
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\117\ ``Low-speed vehicle'' is defined in 49 CFR 571.3. See also
FMVSS No. 500, ``Low speed vehicles,'' 49 CFR 500.
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There are low-speed vehicles that are also electric-powered
vehicles. NHTSA requests comments on applying aspects of FMVSS No. 305a
to low-speed vehicles to ensure a level of protection against shock and
fire, particularly during normal vehicle operation, and to assure the
safe operation of the REESS. The agency requests comment on the
possible applicability of FMVSS No. 305a to low-speed vehicles and its
relevant safety needs, including any supporting research on low-speed
vehicles.

V. Emergency Response Information To Assist First and Second Responders

Fires in electric vehicles are harder to extinguish than fires in
vehicles with internal combustion engines and can reignite. These risks
are also dependent on the specific vehicle design. Easy access to
pertinent vehicle specific and emergency response information is vital
for first and second responders when encountering electric vehicles.
Safety is impeded when first and secondary responders are on scene but
are delayed in their mitigation efforts because information on vehicle-
specific safety mitigation methods are not easily accessible.

a. NTSB Report

In 2020, NTSB published a safety report following a detailed
investigation of four electric vehicle fires.\118\ The investigation
identified safety risks to first and second responders \119\ from
exposure to high voltage components and from vehicle fire due to
damaged cells in the REESS that could reignite as a result of stranded
energy in the REESS.\120\ The NTSB investigation further identified the
lack of a clear and standardized format in vehicle manufacturers'
emergency response guides (ERGs) \121\ and inadequacy in the
information provided in the ERGs for first and second responders to
minimize safety risks posed by stranded energy in the REESS while
handling electric vehicles.
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\118\ Three of the vehicle fires occurred following severe
crashes that resulted in significant damage to the REESS casing. One
vehicle fire was caused by internal failure of the REESS during
normal driving operations. ``Safety risks to emergency responders
from lithium-ion battery fires in electric vehicles,'' Safety Report
NTSB/SR-20/01, PB2020-101011, National Transportation Safety Board,
<a href="https://www.ntsb.gov/safety/safety-studies/Documents/SR2001.pdf">https://www.ntsb.gov/safety/safety-studies/Documents/SR2001.pdf</a>.
\119\ The NTSB report states, ``First responders in this context
refers to firefighters, but emergency medical technicians,
paramedics, and police officers are also classified as first
responders. Second responders in this context refers to tow truck
drivers or tow yard operators, but they can also include those
responsible for temporary traffic control or other support functions
at a crash site.''
\120\ Stranded energy is the energy remaining inside the REESS
after a crash or other incident. Cells in a compromised REESS could
undergo thermal runaway at a later time and reignite the vehicle
fire after firefighters extinguish the initial vehicle fire.
\121\ Emergency Response Guides (ERGs) contain in-depth vehicle-
specific information related to fire, submersion, leakage of fluids,
towing, and storage of vehicles. The information is presented in a
specific format with color-coded sections in a specific order to
help first and second responders quickly identify pertinent rescue
information. Rescue sheets contain abbreviated emergency response
information about a vehicle's construction. Rescue sheets are most
likely to be referenced first by emergency responders upon arrival
at the scene of a crash. ERGs contain more information than rescue
sheets.
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NTSB issued recommendations to vehicle manufacturers, first and
second responder organizations, and NHTSA. NTSB recommended
manufacturers of electric vehicles to model their emergency response
guides on International Standards Organization (ISO)-17840 \122\ and
SAE International recommended practice SAE J2990, ``Hybrid and EV first
and second responder recommended practice.'' \123\ It recommended
incorporating vehicle-specific information on (1) extinguishing REESS
fires, (2) mitigating risk of REESS reignition, (3) mitigating safety
risks (electric shock and fire) associated with stranded energy during
emergency response and transport of damaged vehicle, and (4) storing
damaged electric vehicles.
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\122\ ISO-17840, ``Road vehicles--Information for first and
second responders,'' consists of 4 parts: (1) Part 1 (2015): Rescue
sheet for passenger cars and light commercial vehicles, (2) Part 2
(2019): Rescue sheet for buses, coaches, and heavy commercial
vehicles, (3) Part 3 (2019): Emergency response guide template, and
(4) Part 4 (2018): Propulsion energy identification. <a href="https://webstore.ansi.org/standards/iso/iso178402015?gclid=Cj0KCQiAtbqdBhDvARIsAGYnXBMNT9mR9gjsrKxd5kK8dK6V21Ql9bDr8q2OI0fncMQHHpX_D8bQCxAaAhbUEALw_wcB">https://webstore.ansi.org/standards/iso/iso178402015?gclid=Cj0KCQiAtbqdBhDvARIsAGYnXBMNT9mR9gjsrKxd5kK8dK6V21Ql9bDr8q2OI0fncMQHHpX_D8bQCxAaAhbUEALw_wcB</a>.
\123\ SAE J2990 provides format and content recommendations for
emergency response guides and quick reference sheets in accordance
with ISO 17840. <a href="https://www.sae.org/standards/content/j2990/2_202011/">https://www.sae.org/standards/content/j2990/2_202011/</a>.
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NTSB recommended to the vehicle manufacturers to follow the
practices for first and second emergency responders

[[Page 26729]]

available in SAE J2990 \124\ and ISO-17840. SAE J2990 mainly refers to
the ISO-17840 for the emergency response information. As indicated
earlier, ISO-17840 is comprised of four parts:
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\124\ SAE J2990 recommended practice provides common procedures
to help protect emergency responders and personnel supporting towing
and/or recovery, storage, repair, and salvage after an incident has
occurred with an electric powertrain vehicle.
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<bullet> ISO 17840-1:2022(E) standardizes the content and layout of
rescue sheets for passenger cars and light commercial vehicles.
<bullet> ISO 17840-2:2019(E) standardizes the rescue sheets for
buses, coaches, and heavy commercial vehicles.
<bullet> ISO 17840-3:2019(E) establishes a template and defines the
general content for manufacturers' emergency response guides for all
vehicle types--longer documents that give in-depth ``necessary and
useful information'' about a vehicle for emergency incidents.
<bullet> ISO 17840-4:2018 defines the labels and colors used to
indicate the fuel or energy used to propel a vehicle for both the
rescue sheets and the ERGs.
NTSB had two recommendations to NHTSA. The first recommendation was
to factor the availability of a manufacturer's ERG and its adherence to
ISO 17840 and J2990 when determining a vehicle's U.S. New Car
Assessment Program (NCAP) score.\125\ The second recommendation was to
convene a coalition of stakeholders to continue research and publish
the results on ways to mitigate or deenergize the stranded energy in
high-voltage lithium-ion batteries and to reduce the hazards associated
with thermal runaway resulting from high-speed, high-severity crashes.
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\125\ NHTSA's NCAP is a consumer information program that
evaluates the safety performance of vehicles and provides
comparative information on new vehicles. NCAP also provides
consumers with information on the availability of new vehicle safety
features. This information is provided to assist consumers with
vehicle purc

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