ISO/DTS 25344-1

• Status: Not Published
• ICS: 43.120 - Electric road vehicles
• Technical Committee: ISO/TC 22/SC 37 - Electrically propelled vehicles
• Drafting Committee: ISO/TC 22/SC 37/WG 3 - Rechargeable energy storage
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 27-Aug-2026
• Completion Date: 27-Aug-2026

Overview

ISO/DTS 25344-1 is a key international document that specifies standardized general test methods for the thermal management systems (BTMS) of traction battery packs and systems in electrically propelled road vehicles. Developed by the International Organization for Standardization (ISO), this document establishes unified procedures to evaluate the performance, safety, and reliability of battery thermal management across the electric vehicle (EV) industry.

As the importance of electric vehicles grows, consistent benchmarking for battery thermal management has become critical. Effective BTMS ensures optimal battery performance, enhances lifespan, and maintains safety through regulated cooling, heating, and thermal insulation-directly affecting vehicle efficiency and safety.

Key Topics

• Thermal Management System Basics: Defines battery thermal management systems (BTMS), including functions for cooling, heating, and insulation of EV battery packs and systems.
• Test Methodologies: Establishes unified procedures for:
  • Cooling performance tests at standard and elevated temperatures
  • Heating performance tests (with and without charging/discharging scenarios)
  • Thermal insulation performance tests at both low and high temperatures
• Technical Requirements:
  • Guidelines for environmental conditions during testing (temperature, humidity, pressure)
  • Specifications for measurement equipment accuracy and data recording intervals
  • Procedures for thermal equilibration and preconditioning of devices under test
• Terminology and Definitions: Adopts consistent terms and symbols across the EV industry for clarity and reproducibility, referencing key standards such as ISO/TR 8713.
• Test Configuration: Outlines preparation steps for battery packs/systems, including bench testing setups and agreement on monitoring locations.

Applications

ISO/DTS 25344-1 serves stakeholders across the EV supply chain, including:

• Automotive Manufacturers: Assures that thermal management system designs for battery packs and systems meet objective international criteria for safety, durability, and performance.
• Battery System Suppliers: Provides clear test benchmarks when communicating with automotive customers, facilitating transparent quality and performance agreements.
• Research and Development: Supports R&D teams in evaluating and improving BTMS performance, reducing development costs, and accelerating time-to-market for new EV technologies.
• Testing Laboratories: Enables third-party labs to conduct reliable, standardized assessments of battery thermal management systems, ensuring impartial test results.
• Regulators and Certification Bodies: Offers authorities an internationally recognized basis for evaluating compliance with safety and performance standards for EV battery systems.

Key practical values include enhanced battery safety, improved battery life, consistent data reporting across different organizations, and easier comparability of EV battery solutions.

Related Standards

• ISO/TR 8713 - Electrically propelled road vehicles-Vocabulary: Essential reference for terms and definitions used across all documents related to electric vehicles.
• ISO/TR 25344-2: Specifies test methods focused specifically on liquid-based cooling and heating systems for batteries.
• IEC Standards: The thermal management test strategies are often aligned with or complement the International Electrotechnical Commission's guidance on electrical and electronic equipment testing.

Organizations involved in manufacturing or testing electric vehicles or components should also be aware of evolving standards in the ISO 25344 series and participate in periodic reviews for ongoing alignment and compliance.

---

By adhering to ISO/DTS 25344-1, stakeholders ensure robust, consistent assessment of electric vehicle battery thermal management, promoting global collaboration, enhanced safety, and technological innovation in the EV industry.

FINAL DRAFT
Technical
Specification
ISO/TC 22/SC 37
Electrically propelled road
Secretariat: DIN
vehicles - Test methods for thermal
Voting begins on:
management system of traction
2026-08-27
battery packs and systems —
Voting terminates on:
2026-10-22
Part 1:
General tests
Véhicules à propulsion électrique — Méthodes d'essai des
batteries de traction et des systèmes de gestion thermique —
Partie 1: Essais généraux
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
Technical
Specification
ISO/TC 22/SC 37
Electrically propelled road
Secretariat: DIN
vehicles - Test methods for thermal
Voting begins on:
management system of traction
battery packs and systems —
Voting terminates on:
Part 1:
General tests
Véhicules à propulsion électrique — Méthodes d'essai des
batteries de traction et des systèmes de gestion thermique —
Partie 1: Essais généraux
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO-
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 3
4.1 Symbols .3
4.2 Abbreviated terms .3
5 Technical requirements . 3
5.1 General requirements .3
5.2 Accuracy of measurement equipment and measured values .4
5.3 Thermal equilibration .4
5.4 Preparation for bench testing .5
5.4.1 Preparation of battery pack .5
5.4.2 Preparation of battery system .5
5.4.3 Preparation of cooling/heating device .5
5.5 Preconditioning cycles .5
6 General tests . 6
6.1 Cooling performance test . .6
6.1.1 Cooling performance test at ambient temperature .6
6.1.2 Cooling performance test at high temperature .6
6.2 Heating performance test .6
6.2.1 Heating performance test without charging or discharging .6
6.2.2 Heating performance test in fast charging state .7
6.2.3 Heating performance test in general charging state .8
6.2.4 Heating performance test in discharging state .8
6.3 Thermal insulation performance test . .9
6.3.1 Thermal insulation performance test at low temperature .9
6.3.2 Thermal insulation performance test at high temperature .9
Annex A (informative) An example of the temperature monitoring location .11
Annex B (informative) An example of the test bench layout .12
Bibliography .13

iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out through
ISO technical committees. Each member body interested in a subject for which a technical committee
has been established has the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely
with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the different types
of ISO document should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 22, Road Vehicles, Subcommittee SC 37,
Electrically propelled vehicles.
A list of all parts in the ISO 25344 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
Introduction
Temperature significantly influences the performance, life, and safety of electric vehicle traction battery
packs and systems. The battery thermal management system (BTMS) is designed to adjust battery
temperature through cooling, heating, and insulation, effectively managing the heat generated during
electrochemical processes within the cells. This ensures that the battery operates safely and efficiently.
Universal, widely accepted, and feasible test methods are essential to enable objective evaluation of BTMS
and reduce development costs. ISO/TS 25344-1 specifies general test methods for the thermal management
system of traction battery packs and systems used in electrically propelled road vehicles. The objective of
ISO 25344-1 is to provide general test procedures to evaluate BTMS performance at the pack and system
levels. The test procedure provided have certain boundary conditions and limitations, which should be fully
understood by both the supplier and the customer before testing.
NOTE 1 Test methods applicable only to liquid-based cooling/heating systems are specified in ISO/TR 25344-2.

v
FINAL DRAFT Technical Specification ISO/DTS 25344-1:2026(en)
Electrically propelled road vehicles - Test methods for
thermal management system of traction battery packs and
systems —
Part 1:
General tests
1 Scope
This document specifies the general test methods for the thermal management system of electrically
propelled road vehicle traction battery packs and systems.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/TR 8713, Electrically propelled road vehicles—Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/TR 8713 and the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
battery control unit
BCU
electronic device that controls or manages or measures or calculates electric and thermal functions of the
battery system and that provides communication between the battery system and other vehicle controllers
3.2
battery pack
energy storage device that includes cells or cell assemblies normally connected with cell electronics and
overcurrent shut-off device including electrical interconnections and interfaces for external systems
Note 1 to entry: Examples for interfaces are cooling, high voltage, auxiliary low voltage and communication.
3.3
battery system
energy storage device that includes cells or cell assemblies or battery pack(s) as well as electrical circuits
and electronics
EXAMPLE BCU, contactors.
3.4
battery thermal management system
BTMS
system that adjusts the temperature of batteries through cooling, heating, and insulation
Note 1 to entry: There are different architectures of battery thermal management system, including passive air
cooling/heating system, active air cooling/heating system, liquid cooling/heating system, phase change material
cooling/heating system, refrigerant cooling/heating system, etc.
3.5
customer
party that is interested in using the battery pack or system and therefore orders or performs the test
3.6
capacity
total number of ampere hours that can be withdrawn from a fully charged battery pack (3.2) under specified
conditions
3.7
device under test
DUT
battery pack or battery system
3.8
rated capacity
supplier's specification of the total number of ampere hours that can be withdrawn from a fully charged
battery pack or system for a specified set of test conditions such as discharge rate, temperature and
discharge cut-off voltage
3.9
state of charge
SOC
available capacity in a battery pack or system expressed as a percentage of rated capacity (3.8)
3.10
supplier
party that provides battery systems and packs
3.11
temperature difference
difference between the highest and lowest temperature of cells collected in the battery pack at the same
time, which is calculated according to Formula (1):
t ttt t t ttt t t
TM ax TT,,,TTT., ,., Min TTT,,,.,,,TT., (1)
 
diff 12 31k n 23 k n
Where
t
T is the temperature difference at time t, in degree Celsius (°C).
diff
t
T is the temperature value collected by the kth cell temperature sensor at time t, in degree Celsius
k
(°C).
k is the index number of considered cell temperature sensor.
n is the total number of cell temperature sensor.
Note 1 to entry: The supplier and the customer should agree on which cells and which specific locations within the
cells should be monitored for temperature with evidence that the minimum temperature of the cell and the maximum
temperature have been measured. An example of the temperature monitoring location is provided in Annex A.

4 Symbols and abbreviated terms
4.1 Symbols
t
is the temperature difference at time t, in degree Celsius (°C).
T
diff
t
is the temperature value collected by the kth cell temperature sensor at time t, in degree Celsius
T
k
(°C).
t is the minimum cell temperature at start time.
start
T
min
t is the minimum cell temperature at end time.
end
T
min
t is the minimum cell temperature at the time when the heating system starts working (°C).
hs− tart
T
min
t
is the minimum cell temperature at the time when the heating system stops working (°C).
he− nd
T
min
t
is the maximum cell temperature at start time of the test.
start
T
max
t is the maximum cell temperature at end time of the test.
end
T
max
is the start time.
t
start
is the end time.
t
end
is the time when the heating system starts working (s).
t
hs− tart
is the time when the heating system stops working (s).
t
he− nd
4.2 Abbreviated terms
BCU battery control unit
BTMS battery thermal management system
DUT device under test
nC current rate equal to n times the one hour discharge capacity expressed in ampere (e.g. 3C is equal
to three times the 1 h current discharge rate, expressed in ampere)
SOC state of charge
5 Technical requirements
5.1 General requirements
Unless otherwise required, the test shall be conducted under the following environmental conditions:
— Maintain environmental temperature: 25 °C ± 2 °C;
— Maintain relative humidity
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Secretariat: DIN .
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Date: 2026-05-3108-13
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Electrically propelled road vehicles —- Test methods for thermal
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management system of traction battery packs and systems —
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General tests
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2 © ISO #### – All rights reserved

Véhicules à propulsion électrique — Méthodes d'essai des batteries de traction et des systèmes de gestion
thermique —
Partie 1: Essais généraux
Formatted: Font: Bold
© ISO #### – All rights reserved

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this
Formatted: French (France)
publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical,
Formatted: Indent: Left: 0 cm, Right: 0 cm, Adjust
including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can
space between Latin and Asian text, Adjust space
be requested from either ISO at the address below or ISO’s member body in the country of the requester.
between Asian text and numbers
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Formatted: French (France)
EmailE-mail: [e-mail]
Formatted: French (France)
Website: www.iso.orgwww.iso.org
Formatted: French (France)
Published in Switzerland
Formatted: English (United Kingdom)
Formatted: English (United Kingdom)

iv © ISO #### – All rights reserved

Contents Formatted: Space Before: 48 pt
Foreword . vii
Introduction . ix
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
4.1 Symbols . 3
4.2 Abbreviated terms . 3
5 Technical requirements . 3
5.1 General requirements . 3
5.2 Accuracy of measurement equipment and measured values . 4
5.3 Thermal equilibration . 5
5.4 Preparation for bench testing . 5
5.5 Preconditioning cycles . 6
6 General tests . 6
6.1 Cooling performance test . 6
6.2 Heating performance test . 7
6.3 Thermal insulation performance test . 10
Annex A (informative) An example of the temperature monitoring location . 12
Annex B (informative) An example of the test bench layout . 13
Bibliography . 15

Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 3
4.1 Symbols . 3
4.2 Abbreviated terms . 3
5 Technical requirements . 3
5.1 General requirements . 3
5.2 Accuracy of measurement equipment and measured values . 4
5.3 Thermal equilibration . 4
5.4 Preparation for bench testing . 4
5.4.1 Preparation of battery pack . 4
5.4.2 Preparation of battery system . 5
5.4.3 Preparation of cooling/heating device . 5
5.5 Preconditioning cycles . 5
6 General tests . 5
6.1 Cooling performance test . 5
6.1.1 Cooling performance test at ambient temperature . 5
6.1.2 Cooling performance test at high temperature . 6
© ISO #### – All rights reserved v

6.2 Heating performance test . 6
6.2.1 Heating performance test without charging or discharging . 6
6.2.2 Heating performance test in fast charging state . 7
6.2.3 Heating performance test in general charging state . 7
6.2.4 Heating performance test in discharging state . 8
6.3 Thermal insulation performance test . 8
6.3.1 Thermal insulation performance test at low temperature . 8
6.3.2 Thermal insulation performance test at high temperature . 9
Annex A(informative) An example of the temperature monitoring location .10
Annex B(informative) An example of the test bench layout .11
Bibliography .12
vi © ISO #### – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documentsdocument should be Notednoted. This document was drafted in
accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see
www.iso.org/directiveswww.iso.org/directives).
Attention is drawnISO draws attention to the possibility that some of the elementsimplementation of this
Formatted: English (United Kingdom)
document may beinvolve the subjectuse of (a) patent(s). ISO takes no position concerning the evidence,
Formatted: English (United Kingdom)
validity or applicability of any claimed patent rights. in respect thereof. As of the date of publication of
Formatted: English (United Kingdom)
this document, ISO had not received notice of (a) patent(s) which may be required to implement this
document. However, implementers are cautioned that this may not represent the latest information,
Formatted: English (United Kingdom)
which may be obtained from the patent database available at www.iso.org/patents. ISO shall not be held
Formatted: English (United Kingdom)
responsible for identifying any or all such patent rights. Details of any patent rights identified during the
Formatted: English (United Kingdom)
development of the document will be in the Introduction and/or on the ISO list of patent declarations
received. www.iso.org/patents
Formatted: English (United Kingdom)
Formatted: English (United Kingdom)
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the World
Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
Formatted: Font color: Auto
www.iso.org/iso/foreword.htmlwww.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 22, Road Vehicles, Subcommittee SC 37,
Formatted: Font: Not Italic
Electrically propelled vehicles.
Formatted: Font: Not Italic
A list of all parts in the ISO 25344 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
© ISO #### – All rights reserved vii

www.iso.org/members.html.
viii © ISO #### – All rights reserved

Formatted: Font: Bold
Introduction
Formatted: Intro Title
Temperature significantly influences the performance, life, and safety of electric vehicle traction battery
packs and systems. The battery thermal management system (BTMS) is designed to adjust battery
temperature through cooling, heating, and insulation, effectively managing the heat generated during
electrochemical processes within the cells. This ensures that the battery operates safely and efficiently.
Universal, widely accepted, and feasible test methods are essential to enable objective evaluation of BTMS
and reduce development costs. ISO/TS 25344-1 specifies general test methods for the thermal
management system of traction battery packs and systems used in electrically propelled road vehicles.
The objective of ISO 25344-1 is to provide general test procedures to evaluate BTMS performance at the
pack and system levels. The test procedure provided have certain boundary conditions and limitations,
Formatted: Font: English (United Kingdom)
which should be fully understood by both the supplier and the customer before testing.
NOTE 1: Test methods applicable only to liquid-based cooling/heating systems are specified in
ISO/TR 25344-2.
© ISO #### – All rights reserved ix

x © ISO #### – All rights reserved

ISO/DTS 25344-1:####(X:(en)
Formatted: Font: 11 pt, Bold
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© ISO #### 2026 – All rights reserved
xi
ISO/DTS 25344-1:####(X:(en)
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Electrically propelled road vehicles —- Test methods for thermal
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management system of traction battery packs and systems — —
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Part 1:
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General tests
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1 Scope
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This document specifies the general test methods for the thermal management system of electrically propelled
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road vehicle traction battery packs and systems.
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2 Normative references
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The following documents are referred to in the text in such a way that some or all of their content constitutes
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requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/TR 8713, Electrically propelled road vehicles—Vocabulary
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Formatted: Font: Not Italic
3 Terms and definitions
Formatted: RefNorm
For the purposes of this document, the terms and definitions given in ISO/TR 8713 and the following apply.
Formatted: Indent: Left: 0 cm, First line: 0 cm
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obphttps://www.iso.org/obp
Formatted: No underline, Font color: Auto
Formatted: List Continue 1, No bullets or numbering,
— IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
Don't keep with next
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3.1 3.1
battery control unit
Formatted: TermNum2
BCU
electronic device that controls or manages or measures or calculates electric and thermal functions of the
battery system and that provides communication between the battery system and other vehicle controllers
3.2 3.2
Formatted: TermNum2
battery pack
energy storage device that includes cells or cell assemblies normally connected with cell electronics and
overcurrent shut-off device including electrical interconnections and interfaces for external systems
Note 1 to entry: Examples for interfaces are cooling, high voltage, auxiliary low voltage and communication.
3.3 3.3
Formatted: TermNum2
battery system
energy storage device that includes cells or cell assemblies or battery pack(s) as well as electrical circuits and
Formatted: Example
electronics
Formatted: Space Before: 0 pt, After: 0 pt
EXAMPLE    BCU, contactors.
Formatted: Font: 10 pt
Formatted: Font: 10 pt
3.4 3.4
battery thermal management system Formatted: Font: 11 pt
BTMS
Formatted: FooterPageNumber, Space After: 0 pt, Line
system that adjusts the temperature of batteries through cooling, heating, and insulation
spacing: single
© ISO #### 2026 – All rights reserved
ISO/DTS 25344-1:####(X:(en)
Formatted: Font: 11 pt, Bold
Formatted: Font: 11 pt, Bold
Formatted: HeaderCentered, Space After: 0 pt, Line
Note 1 to entry: There are different architectures of battery thermal management system, including passive air
spacing: single
cooling/heating system, active air cooling/heating system, liquid cooling/heating system, phase change material
cooling/heating system, refrigerant cooling/heating system, etc.
3.5 3.5
Formatted: TermNum2
customer
party that is interested in using the battery pack or system and therefore orders or performs the test
3.6 3.6
Formatted: TermNum2
capacity
total number of ampere hours that can be withdrawn from a fully charged battery pack (3.2)(3.2) under
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specified conditions
3.7 3.7
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device under test
DUT
battery pack or battery system
3.8 3.8
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rated capacity
supplier's specification of the total number of ampere hours that can be withdrawn from a fully charged
battery pack or system for a specified set of test conditions such as discharge rate, temperature and discharge
cut-off voltage
3.9 3.9
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state of charge
SOC
available capacity in a battery pack or system expressed as a percentage of rated capacity (3.8)(3.8)
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3.10 3.10
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supplier
party that provides battery systems and packs
3.11 3.11
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temperature difference
difference between the highest and lowest temperature of cells collected in the battery pack at the same time,
which is calculated according to formula (1):Formula (1):
𝑡𝑡 𝑡𝑡 𝑡𝑡 𝑡𝑡 𝑡𝑡 𝑡𝑡 𝑡𝑡 𝑡𝑡 𝑡𝑡 𝑡𝑡 𝑡𝑡
𝑇𝑇 =𝑀𝑀𝑀𝑀𝑀𝑀(𝑇𝑇 ,𝑇𝑇 ,𝑇𝑇 , . . . ,𝑇𝑇 , . . . ,𝑇𝑇 )−𝑀𝑀𝑀𝑀𝑀𝑀(𝑇𝑇 ,𝑇𝑇 ,𝑇𝑇 , . . . ,𝑇𝑇 , . . . ,𝑇𝑇 )
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𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 1 2 3 𝑘𝑘 𝑛𝑛 1 2 3 𝑘𝑘 𝑛𝑛
(1)
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Where
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𝑡𝑡
is the temperature difference at time t, in degree Celsius (℃).
𝑇𝑇
𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑
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𝑡𝑡
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𝑇𝑇 is the temperature value collected by the kth cell temperature sensor at time t, in degree
𝑘𝑘
Celsius (℃).
k is the index number of considered cell temperature sensor.
n is the total number of cell temperature sensor.
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𝑡𝑡
𝑇𝑇 is the temperature difference at time t, in degree Celsius (°C).
𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑
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𝑡𝑡
𝑇𝑇 is the temperature value collected by the kth cell temperature sensor at time t, in degree Celsius (°C).
𝑘𝑘
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k is the index number of considered cell temperature sensor.
spacing: single
2 © ISO #### 2026 – All rights reserved
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ISO/DTS 25344-1:####(X:(en)
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n is the total number of cell temperature sensor.
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Note 1 to entry: The supplier and the customer should agree on which cells and which specific locations within the cells
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should be monitored for temperature with evidence that the minimum temperature of the cell and the maximum
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temperature have been measured. An example of the temperature monitoring location is provided in Annex A.Annex A.
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4 Symbols and abbreviated terms
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4.1 Symbols
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𝑡𝑡
is the temperature difference at time t, in degree Celsius (℃).(°C).
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𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑
𝑡𝑡 Formatted
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𝑇𝑇 is the temperature value collected by the kth cell temperature sensor at time t, in degree
𝑘𝑘
Celsius (℃).(°C).
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𝑡𝑡
𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠
is the minimum cell temperature at start time. Formatted
𝑇𝑇 .
𝑚𝑚𝑑𝑑𝑛𝑛
Formatted
𝑡𝑡
𝑒𝑒𝑒𝑒𝑒𝑒 .
is the minimum cell temperature at end time.
𝑇𝑇
𝑚𝑚𝑑𝑑𝑛𝑛
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𝑡𝑡
ℎ−𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠
is the minimum cell temperature at the time when the heating system starts working
𝑇𝑇
𝑚𝑚𝑑𝑑𝑛𝑛
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(℃).(°C).
Formatted
𝑡𝑡 .
ℎ−𝑒𝑒𝑒𝑒𝑒𝑒
is the minimum cell temperature at the time when the heating system stops working
𝑇𝑇
𝑚𝑚𝑑𝑑𝑛𝑛
Formatted
(℃).(°C). .
𝑡𝑡 Formatted
𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠𝑠
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is the maximum cell temperature at start time of the test.
𝑇𝑇
𝑚𝑚𝑚𝑚𝑚𝑚
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𝑡𝑡
𝑒𝑒𝑒𝑒𝑒𝑒
is the maximum cell temperature at end time of the test.
𝑇𝑇
𝑚𝑚𝑚𝑚𝑚𝑚
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𝑡𝑡 is the start time.
𝑠𝑠𝑡𝑡𝑚𝑚𝑠𝑠𝑡𝑡
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𝑡𝑡 is the end time.
𝑒𝑒𝑛𝑛𝑑𝑑
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𝑡𝑡 is the time when the heating system starts working (s).
ℎ−𝑠𝑠𝑡𝑡𝑚𝑚𝑠𝑠𝑡𝑡 Formatted
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𝑡𝑡 is the time when the heating system stops working (s).
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ℎ−𝑒𝑒𝑛𝑛𝑑𝑑
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4.2 Abbreviated terms
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BCU battery control unit
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BTMS battery thermal management system
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DUT device under test
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nC current rate equal to n times the one hour discharge capacity expressed in ampere (e.g. 3C is
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equal to three times the 1 h current discharge rate, expressed in ampere);) .
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SOC state of charge
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5 Technical requirements
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5.1 General requirements
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Unless otherwise required, the test shall be conducted under the following environmental conditions:
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— —Maintain environmental temperature: 25 ℃± °C ± 2 ℃; °C; .
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— —Maintain relative humidity: 10 % to 90 %;
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— —Maintain atmospheric pressure: 86 kPa to 106 kPa (sea level equivalent). .
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© ISO #### 2026 – All rights reserved
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F tt d
ISO/DTS 25344-1:####(X:(en)
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The supplier of DUT shall provide necessary operating documents, safe operating limits of DUT and interface
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components required to connect with the test equipments (such as connectors, plugs, etc.).
spacing: single
When the target environmental temperature changes during test, the DUT shall be thermal equilibrated at the
required ambient temperature as specified in 5.35.3 before the test.
It is recommended that on-board location and heat dissipation environment of the battery pack/system
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should be simulated in the test. For example, for the battery pack/system located at the bottom of an electric
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vehicle, it is recommended to arrange a tray at the bottom of the DUT and maintain smooth air circulation at
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the bottom of the DUT during the test. At the same time, windproof and thermal insulation materials should
be covered on the surface of the battery pack/system. The size of the tray, thickness, and properties of the
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windproof and thermal insulation materials should simulate the battery pack/system on-board location and
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heat dissipation environment.
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The supplier and the customer should agree on the boundary conditions for measurement in order to clarify
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the differences between the environment on the vehicle and the environment on the platform (e.g., shape,
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thermal resistance).
If the battery pack/system is not suitable for some tests due to certain reasons (such as size or mass), it is
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allowed to use the subsystem of the battery pack/system as DUT to conduct all or part of the tests. However,
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the subsystem as a DUT shall comprise all parts specified by the customer (e.g., including mechanical and
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electrical connecting points for mechanical tests).
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Charging and discharging cut-off conditions during the test shall be provided by the supplier.
Method for adjusting the SOC to n %: Firstly, fully charge the battery pack/system according to the charging
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method provided by the supplier. After resting for 1 hour, discharge at 1/3C for (3 - 0,03n) hours. After SOC
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adjustment, the DUT should rest for 30 minutes before the following test procedure.
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Unless otherwise required, the recording interval of test data (such as time, temperature, current, voltage,
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etc.) should not exceed 100 seconds.
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