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

ISO/DTS 25344-1 is an ISO draft technical specification for general test methods for the thermal management system of traction battery packs and systems in electrically propelled road vehicles. It is written for suppliers, customers and test labs that need a common way to prepare the device under test, run cooling, heating and insulation tests, and compare results at pack and system level.

What does ISO/DTS 25344-1 specify?

ISO/DTS 25344-1 specifies the general test methods used to evaluate battery thermal management system (BTMS) performance for electrically propelled road vehicle traction battery packs and battery systems. It focuses on bench testing, test preparation and repeatable thermal tests, so different parties can assess similar hardware in the same way.

The document is organized into six clauses, two informative annexes and a bibliography:

Annex	What it covers
Annex A	An example of the temperature monitoring location
Annex B	An example of the test bench layout

Clause 1 gives the scope, Clause 2 lists the normative reference, Clause 3 defines the key terms, Clause 4 covers symbols and abbreviated terms, Clause 5 sets the technical requirements, and Clause 6 gives the general tests. The introduction also points readers to ISO/TR 25344-2 for test methods that apply only to liquid-based cooling/heating systems.

What are the key requirements of ISO/DTS 25344-1?

ISO/DTS 25344-1 is built around controlled bench testing, agreed operating limits, and consistent reporting of cell temperatures. In practice, that means the supplier and customer need to agree on the test boundary conditions before any data is used for comparison.

Test conditions and bench setup

Clause 5 requires the test to be run under controlled ambient conditions, with the supplier providing the operating documents, safe operating limits and interface information needed to connect the DUT. The document also says the test should reflect the battery pack or system’s on-vehicle thermal environment as closely as practical.

That matters because thermal results can change with mounting position, airflow and heat dissipation. The supplier and customer are expected to agree how the bench represents the vehicle environment, especially when the pack is mounted in a location with special airflow or insulation conditions.

Clause 5 also allows a subsystem to be used as the DUT when the full pack or system is not practical for a test because of size or mass. If that happens, the subsystem still has to include the parts the customer specifies, such as mechanical and electrical connection points.

Measurement quality and thermal equilibration

Clause 5.2 sets accuracy expectations for the measurement system and for externally controlled or measured values. The practical effect is that temperature, current, voltage and time data need to be trustworthy enough for performance comparisons, not just for rough observation.

Clause 5.3 requires thermal equilibration before testing when the target ambient temperature changes. The BTMS must be idle long enough for temperatures to settle, and the spread between cells has to be small enough to show the DUT is stable.

Preparation before testing

Clause 5.4 describes how to prepare a battery pack, battery system and cooling or heating device on the bench. The battery pack or system is connected to the test equipment, the BCU is used where applicable, and overcurrent protection must remain active.

This is important because the test bench must not defeat normal protection or control functions. For a battery system, the test equipment follows the BCU’s operational limits and the cooling loop must work as commanded by the BCU unless the specific test says otherwise.

Clause 5.5 requires preconditioning cycles before the general tests. The purpose is to stabilize performance so that the test results reflect the DUT’s thermal behavior rather than its first-cycle behavior.

Cooling performance tests

Clause 6.1 contains two cooling performance tests: one at ambient temperature and one at high temperature. Both use a controlled sequence that adjusts state of charge (SOC), allows thermal equilibration, charges with the supplier’s fastest approved profile, rests, and then discharges.

The key output is the temperature response during the charging, rest and discharge steps. The document asks for maximum cell temperature, minimum cell temperature and temperature difference, with a short data-recording interval during the charging step so that rapid thermal changes are captured.

Heating performance tests

Clause 6.2 covers four heating performance tests: without charging or discharging, in fast charging state, in general charging state, and in discharging state. These tests apply to battery packs or systems with a heating function.

In these tests, the BTMS starts according to the supplier’s strategy and the test records how quickly the battery warms up. Clause 6.2 uses the temperature increase rate as a key result, which tells the reader whether the heating function can bring the battery into a usable temperature range fast enough.

Thermal insulation performance tests

Clause 6.3 covers thermal insulation performance at low and high temperature. The low-temperature test disables the heating function during the soak period, while the high-temperature test disables the active function during the soak period.

These tests show how well the battery keeps its temperature when the BTMS is not actively changing it. The customer and supplier also need to agree on the start time definition and sensor positions, because those choices affect the calculated temperature change rate.

What terms does ISO/DTS 25344-1 define?

ISO/DTS 25344-1 defines the main battery and test terms used throughout the document.

• Battery control unit (BCU) - The electronic device that controls, manages, measures or calculates electric and thermal functions of the battery system and communicates with other vehicle controllers.
• Battery pack - An energy storage device made up of cells or cell assemblies, together with interfaces such as cooling, high-voltage, auxiliary low-voltage and communication connections.
• Battery system - An energy storage device that includes cells or battery packs plus electrical circuits and electronics, such as a BCU and contactors.
• Battery thermal management system (BTMS) - The system that adjusts battery temperature through cooling, heating and insulation.
• Device under test (DUT) - The battery pack or battery system being tested.
• State of charge (SOC) - The available capacity expressed as a percentage of rated capacity.
• Temperature difference - The difference between the highest and lowest cell temperatures measured at the same time.
• nC - A current rate equal to n times the one-hour discharge capacity.

Who uses ISO/DTS 25344-1?

ISO/DTS 25344-1 is used by battery pack and battery system suppliers, vehicle manufacturers, test laboratories and customers who order or witness thermal performance tests. It is relevant for development, validation, bench testing and acceptance work on electrically propelled road vehicles.

Quality and engineering teams use it to agree test conditions, select the DUT configuration, and define what data must be reported. Buyers and technical reviewers use it to check whether a supplier’s thermal management claims are being tested under a common procedure.

Which standards are used with ISO/DTS 25344-1?

ISO/DTS 25344-1 cites ISO/TR 8713 as its normative vocabulary reference. That document provides the shared road-vehicle terminology used in the text.

The introduction also names ISO/TR 25344-2 as the companion part for test methods that apply only to liquid-based cooling/heating systems. In the bibliography, ISO 12405-4:2018 is listed for performance testing of lithium-ion traction battery packs and systems, and SAE J3073 is listed as a reference on battery thermal management.

What does the ISO/DTS 25344-1 document contain?

ISO/DTS 25344-1 contains the test conditions, preparation steps and reporting items needed to run general BTMS evaluations at pack and system level. Clause 5 gives the technical requirements for environment, measurement accuracy, equilibration, bench preparation and preconditioning.

Clause 6 provides the test sequences for cooling, heating and thermal insulation performance, including the operating state for each test and the data to record. The document also includes formulas for temperature difference and temperature change rate, plus tables that define the step-by-step test sequences and reporting points.

Annex A gives an example of where to place temperature monitoring sensors, and Annex B gives an example of a test bench layout showing the main bench elements and signal and medium flows. These annexes support setup and communication between supplier, customer and test lab without replacing the detailed test procedure in the main clauses.

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
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AND TO PROVIDE SUPPOR TING DOCUMENTATION.
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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
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Phone: [phone]
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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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ISO/DTS 25344-1:####(X) .
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ISO /TC 22/SC 37/WG 3
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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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Part 1:
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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
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© ISO #### – All rights reserved

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this
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publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical,
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including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can
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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
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EmailE-mail: [e-mail]
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Website: www.iso.orgwww.iso.org
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Published in Switzerland
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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)
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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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3 Terms and definitions
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For the purposes of this document, the terms and definitions given in ISO/TR 8713 and the following apply.
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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
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— IEC Electropedia: available at https://www.electropedia.org/https://www.electropedia.org/
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3.1 3.1
battery control unit
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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
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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
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battery system
energy storage device that includes cells or cell assemblies or battery pack(s) as well as electrical circuits and
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electronics
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EXAMPLE    BCU, contactors.
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3.4 3.4
battery thermal management system Formatted: Font: 11 pt
BTMS
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system that adjusts the temperature of batteries through cooling, heating, and insulation
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© ISO #### 2026 – All rights reserved
ISO/DTS 25344-1:####(X:(en)
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Note 1 to entry: There are different architectures of battery thermal management system, including passive air
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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
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customer
party that is interested in using the battery pack or system and therefore orders or performs the test
3.6 3.6
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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.
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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).
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𝑡𝑡 .
ℎ−𝑒𝑒𝑒𝑒𝑒𝑒
is the minimum cell temperature at the time when the heating system stops working
𝑇𝑇
𝑚𝑚𝑑𝑑𝑛𝑛
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(℃).(°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).
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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.).
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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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