oSIST prEN IEC 62973-4:2025

Railway applications – Rolling stock – Batteries for auxiliary power supply systems – Part 4: Secondary sealed nickel-metal hydride batteries

No changes compare the IEC 62973-4 Version.
No European Annex is necessary for Part 4. Ni-MH-batteries for auxiliary power supply systems have no future importance in Europe in the railway rolling stock sector

Bahnanwendungen - Fahrzeuge - Batterien für Bordnetzversorgungssysteme – Teil 4: Gasdichte Nickel-Metallhydrid-Sekundärbatterien

Applications ferroviaires - Matériel roulant -Batteries pour systèmes d'alimentation auxiliaire - Partie 4: Batterie d'accumulateurs nickel-hydrure métallique étanche

IEC 62973-4:2021 s'applique aux différentes technologies de batterie d'accumulateurs nickel-hydrure métallique étanche destinées aux systèmes d'alimentation auxiliaire utilisés sur le matériel roulant.
Le présent document spécifie les exigences des caractéristiques et essais des éléments nickel-hydrure métallique étanches et complète l'IEC 62973-1 qui s'applique au matériel roulant de tous types (par exemple, véhicules ferroviaires de métro léger, tramways, véhicules de métro, trains de banlieue, trains régionaux, trains à grande vitesse, locomotives, etc.). Sauf spécification contraire, les exigences de l'IEC 62973-1 s'appliquent. Le présent document spécifie également les exigences de l'interface entre les batteries et les chargeurs de batterie. Ce document doit être utilisé conjointement avec l'IEC 62675, l'IEC 63115-1 et l'IEC 63115-2.

Železniške naprave - Vozna sredstva - Baterije za pomožne močnostne napajalne sisteme - 4. del: Sekundarne zatesnjene nikelj-kovinske hidridne baterije

General Information

• Status: Not Published
• Public Enquiry End Date: 21-Dec-2025
• ICS: 29.220.99 - Other cells and batteries
• ICS: 45.060.01 - Railway rolling stock in general
• Technical Committee: ŽEN - Electrical applications for railways
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 16-Oct-2025
• Due Date: 05-Mar-2026
• Completion Date: 05-Dec-2025
• Ref Project: prEN IEC 62973-4:2025 - Railway applications – Rolling stock – Batteries for auxiliary power supply systems – Part 4: Secondary sealed nickel-metal hydride batteries

Standards Content (Sample)

SLOVENSKI STANDARD
01-december-2025
Železniške naprave - Vozna sredstva - Baterije za pomožne močnostne napajalne
sisteme - 4. del: Sekundarne zatesnjene nikelj-kovinske hidridne baterije
Railway applications – Rolling stock – Batteries for auxiliary power supply systems – Part
4: Secondary sealed nickel-metal hydride batteries
Bahnanwendungen - Fahrzeuge - Batterien für Bordnetzversorgungssysteme – Teil 4:
Gasdichte Nickel-Metallhydrid-Sekundärbatterien
Applications ferroviaires - Matériel roulant -Batteries pour systèmes d'alimentation
auxiliaire - Partie 4: Batterie d'accumulateurs nickel-hydrure métallique étanche
Ta slovenski standard je istoveten z: prEN IEC 62973-4:2025
ICS:
29.220.99 Drugi členi in baterije Other cells and batteries
45.060.01 Železniška vozila na splošno Railway rolling stock in
general
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD DRAFT
prEN IEC 62973-4
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 45.060.01 -
English Version
Railway applications - Rolling stock - Batteries for auxiliary
power supply systems - Part 4: Secondary sealed nickel-metal
hydride batteries
(IEC 62973-4:2021)
Applications ferroviaires - Matériel roulant -Batteries pour Bahnanwendungen - Fahrzeuge - Batterien für
systèmes d'alimentation auxiliaire - Partie 4: Batterie Bordnetzversorgungssysteme - Teil 4: Gasdichte Nickel-
d'accumulateurs nickel-hydrure métallique étanche Metallhydrid-Sekundärbatterien
(IEC 62973-4:2021) (IEC 62973-4:2021)
This draft European Standard is submitted to CENELEC members for enquiry.
Deadline for CENELEC: 2026-01-02.

The text of this draft consists of the text of IEC 62973-4:2021 (9/2638(F)/FDIS).

If this draft becomes a European Standard, CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which
stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CENELEC in three official versions (English, French, German).
A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to
the CEN-CENELEC Management Centre has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the
Netherlands, Norway, Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.

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 supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.

European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Project: 81986 Ref. No. prEN IEC 62973-4:2025 E

European foreword
This document (prEN IEC 62973-4:2025) consists of the text of IEC 62973-4:2021 prepared by IEC/TC 9
"Electrical equipment and systems for railways".
This document is currently submitted to the Enquiry.
The following dates are proposed:
• latest date by which the existence of this document has (doa) dav+ 6 months
to be announced at national level
• latest date by which this document has to be (dop) dav+ 12 months
implemented at national level by publication of an
identical national standard or by endorsement
• latest date by which the national standards conflicting (dow) dav+ 36 months
with this document have to be withdrawn (to be confirmed or
modified when voting)
This document is read in conjunction with EN 62675, EN IEC 63115-1 and EN IEC 63115-2.
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1  Where an International Publication has been modified by common modifications, indicated by (mod), the
relevant EN/HD applies.
NOTE 2  Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 60051 series Direct acting indicating analogue electrical EN 60051 series
measuring instruments and their
accessories
IEC 60077-1 - Railway applications - Electric equipment EN 60077-1 -
for rolling stock - Part 1: General service
conditions and general rules
IEC 62485-2 - Safety requirements for secondary EN IEC 62485-2 -
batteries and battery installations - Part 2:
Stationary batteries
IEC 62675 - Secondary cells and batteries containing EN 62675 -
alkaline or other non-acid electrolytes -
Sealed nickel-metal hydride prismatic
rechargeable single cells
IEC 62902 2019 Secondary cells and batteries - Marking EN IEC 62902 2019
symbols for identification of their chemistry
IEC 62973-1 2018 Railway applications - Rolling stock - EN IEC 62973-1 —
Batteries for auxiliary power supply
systems - Part 1: General Requirements
IEC 63115-1 2020 Secondary cells and batteries containing EN IEC 63115-1 2020
alkaline or other non-acid electrolytes -
Sealed nickel-metal hydride cells and
batteries for use in industrial applications -
Part 1: Performance
IEC 63115-2 2021 Secondary cells and batteries containing EN IEC 63115-2 2021
alkaline or other non-acid electrolytes -
Sealed nickel-metal hydride cells and
batteries for use in industrial applications -
Part 2: Safety
Under preparation. Stage at the time of publication: prEN IEC 62973-1:2025.
IEC 62973-4 ®
Edition 1.0 2021-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Railway applications – Rolling stock – Batteries for auxiliary power supply

systems –
Part 4: Secondary sealed nickel-metal hydride batteries

Applications ferroviaires – Materiel roulant –Batteries pour systemes

d'alimentation auxiliaire –
Partie 4: Batterie d'accumulateurs nickel-hydrure métallique étanche

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 45.060.01 ISBN 978-2-8322-9279-2

– 2 – IEC 62973-4:2021 © IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions and abbreviated terms . 7
3.1 Terms and definitions . 7
3.2 Abbreviated terms . 9
4 General requirements . 9
4.1 Definitions of components of a battery system (images are examples) . 9
4.2 Definition of battery type . 10
4.2.1 General . 10
4.2.2 Cell designation . 10
4.2.3 Prismatic cells . 10
4.2.4 Cylindrical cells . 10
4.3 Environmental conditions . 10
4.3.1 Battery system . 10
4.3.2 Battery module . 10
4.4 System requirements . 11
4.4.1 System voltage . 11
4.4.2 Charging requirements . 12
4.4.3 Discharging requirements . 15
4.4.4 Charge retention (self-discharge) . 16
4.4.5 Requirements for battery capacity sizing. 16
4.5 Safety and protection requirements . 17
4.5.1 General . 17
4.5.2 Deep discharge of batteries . 17
4.5.3 Temperature compensation during charging . 17
4.6 Fire protection . 17
4.7 Maintenance . 17
5 Mechanical design of battery system . 17
6 Electrical interface . 18
7 Markings. 18
7.1 Safety signs . 18
7.2 Nameplate . 18
7.2.1 General . 18
7.2.2 Battery modules and cells . 18
8 Storage and transportation conditions . 18
8.1 Transportation . 18
8.2 Storage of battery . 18
9 Testing . 19
9.1 General . 19
9.2 Parameter measurement tolerances . 19
9.3 Type test . 20
9.3.1 General . 20
9.3.2 Electrical characteristic tests . 20
9.3.3 Dielectric test . 21
9.3.4 Load profile test . 21

IEC 62973-4:2021 © IEC 2021 – 3 –
9.3.5 Shock and vibration test . 21
9.3.6 Reliability test . 21
9.4 Routine test . 21
9.4.1 General . 21
9.4.2 Visual checks . 21
9.4.3 Dielectric test . 21
9.4.4 Measurement of open circuit voltage . 22
9.4.5 Measurement of Internal resistance . 22
Annex A (informative) Other configuration of the battery charging system . 23
A.1 General . 23
A.2 Charging requirements for the main charger . 23
A.3 Charging requirements for the additional charger . 24
A.3.1 General . 24
A.3.2 Temperature compensation during charging . 25
Annex B (informative) Declaration of cell model range representative of the testing . 26
B.1 Electrical performance declaration . 26
B.2 Shock and vibration declaration . 26
Bibliography . 27

Figure 1 –Definition of cell(s), battery module, crate, tray and battery box . 9
Figure 2 – Example of discharge curves at various constant discharge currents based
on percentage of capacity . 11
Figure 3 – Examples of Ni-MH charge curves. 12
Figure 4 – Example of interfaces between battery box and battery charging system. 13
Figure 5 – Typical charging characteristic of secondary sealed nickel-metal hydride

battery . 15
Figure A.1 – Example of interface with the additional charger in the battery box . 24
Figure A.2 – Examples of Ni-MH charge curves . 25

Table 1 – Requirements of the charging characteristics . 12
Table 2 – Typical Ni-MH battery charging characteristics . 14
Table 3 – Parameters and responsibility for battery capacity sizing . 16
Table 4 – Type test and routine test . 19
Table A.1 – Requirements of the charging characteristics for the main charger outside
the battery box with the additional charger in the battery box . 23

– 4 – IEC 62973-4:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RAILWAY APPLICATIONS – ROLLING STOCK –
BATTERIES FOR AUXILIARY POWER SUPPLY SYSTEMS –

Part 4: Secondary sealed nickel-metal hydride batteries

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 62973-4 has been prepared by IEC technical committee 9:
Electrical equipment and systems for railways.
The text of this International Standard is based on the following documents:
FDIS Report on voting
9/2638/FDIS 9/2665/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
This document is to be used in conjunction with IEC 62675, IEC 63115-1 and IEC 63115-2.

IEC 62973-4:2021 © IEC 2021 – 5 –
A list of all parts in the IEC 62973 series, published under the general title Railway
applications – Rolling stock – Batteries for auxiliary power supply systems, can be found on
the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC 62973-4:2021 © IEC 2021
RAILWAY APPLICATIONS – ROLLING STOCK –
BATTERIES FOR AUXILIARY POWER SUPPLY SYSTEMS –

Part 4: Secondary sealed nickel-metal hydride batteries

1 Scope
This part of IEC 62973 applies to secondary sealed nickel-metal hydride battery technologies
for auxiliary power supply systems used on rolling stock.
This document specifies the requirements of the characteristics and tests for the sealed
nickel-metal hydride cells and supplements IEC 62973-1 which applies to any rolling stock
types (e.g. light rail vehicles, tramways, streetcars, metros, commuter trains, regional trains,
high speed trains, locomotives, etc.). Unless otherwise specified, the requirements of
IEC 62973-1 apply.
This document also specifies the requirements of the interface between the batteries and the
battery chargers.
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.
IEC 60051 (all parts), Direct acting indicating analogue electrical measuring instruments and
their accessories
IEC 60077-1, Railway applications – Electric equipment for rolling stock – Part 1: General
service conditions and general rules
IEC 62485-2, Safety requirements for secondary batteries and battery installations – Part 2:
Stationary batteries
IEC 62675, Secondary cells and batteries containing alkaline or other non-acid electrolytes –
Sealed nickel-metal hydride prismatic rechargeable single cells
IEC 62902:2019, Secondary cells and batteries – Marking symbols for identification of their
chemistry
IEC 62973-1:2018, Railway applications – Rolling stock – Batteries for auxiliary power supply
systems – Part 1: General requirements
IEC 63115-1:2020, Secondary cells and batteries containing alkaline or other non-acid
electrolytes – Sealed nickel-metal hydride cells and batteries for use in industrial applications
– Part 1: Performance
IEC 63115-2:2021, Secondary cells and batteries containing alkaline or other non-acid
electrolytes – Sealed nickel-metal hydride cells and batteries for use in industrial applications
– Part 2: Safety
IEC 62973-4:2021 © IEC 2021 – 7 –
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/;
• ISO Online browsing platform: available at http://www.iso.org/obp.
NOTE All typical battery related descriptions are defined in IEC 60050-482.
3.1.1
nickel-metal hydride battery
Ni-MH battery
secondary battery with an electrolyte of aqueous potassium hydroxide, a positive electrode
containing nickel as nickel hydroxide and a negative electrode of hydrogen in the form of a
metal hydride
Note 1 to entry: Nickel-metal hydride battery contains assembly of sealed cells.
[SOURCE: IEC 60050-482:2004, 482-05-08, modified – Abbreviation and Note 1 to entry have
been added.]
3.1.2
cell
basic functional unit, consisting of an assembly of electrodes, electrolyte, container, terminals
and usually separators, that is a source of electric energy obtained by direct conversion of
chemical energy
Note 1 to entry: In this document cell means secondary sealed nickel-metal hydride cell,
[SOURCE: IEC 60050-482:2004, 482-01-01, modified – Note 1 to entry has been replaced.]
3.1.3
sealed cell
cell which remains closed and does not release either gas or liquid when operated within the
limits specified by the manufacturer
Note 1 to entry: A sealed cell may be equipped with a safety device to prevent a dangerously high internal
pressure and is designed to operate during its life in its original sealed state.
[SOURCE: IEC 60050-482:2004, 482-05-17]
3.1.4
secondary cell
cell which is designed to be electrically recharged
Note 1 to entry: The recharge is accomplished by way of a reversible chemical reaction.
[SOURCE: IEC 60050-482:2004, 482-01-03]
3.1.5
battery module
group of cells connected together either in series and/or parallel configuration with or without
protective devices (e.g. fuse or PTC) and monitoring circuitry
[SOURCE: IEC 62973-1:2018, 3.1.9, modified – “temperature sensor” has been replaced with
“PTC”.]
– 8 – IEC 62973-4:2021 © IEC 2021
3.1.6
rated capacity
C < at the 5 h rate >
capacity value of a battery determined under specified conditions and declared by the battery
manufacturer
Note 1 to entry: In this document, rated capacity is at the 5 h rate; C .
[SOURCE: IEC 60050-482:2004, 482-03-15, modified – Abbreviation and Note 1 to entry have
been added.]
3.1.7
state of charge
SOC
remaining capacity to be discharged, normally expressed as a percentage of the full battery
rated capacity as expressed in relevant standards
Note 1 to entry: Practical definitions of SOC are dependent upon chosen technologies.
[SOURCE: IEC 62973-1:2018, 3.1.6]
3.1.8
depth of discharge
DOD
capacity removed from a battery during discharge in relation to its full rated capacity
expressed as a percentage
Note 1 to entry: It is the complement of SOC.
Note 2 to entry: As one increases, the other decreases by the same amount.
Note 3 to entry: Practical definitions of DOD are dependent upon chosen technologies.
[SOURCE: IEC 62973-1:2018, 3.1.7]
3.1.9
end user
organization which operates the battery system
Note 1 to entry: The end user is normally an organization which operates the vehicle equipped with the battery
system, unless the responsibility is delegated to a main contractor or consultant.
[SOURCE: IEC 62973-1:2018, 3.1.11]
3.1.10
system integrator
organization which has the technical responsibility of the complete battery system and
charging system
Note 1 to entry: The system integrator can be the end user or the train manufacturer, or none of them.
[SOURCE: IEC 62973-1:2018, 3.1.12]
3.1.11
manufacturer,
organization which has the technical responsibility for its scope of supply
Note 1 to entry: The manufacturer can be the train builder or the system integrator of a battery system, a cell
manufacturer, etc. If necessary to explicitly distinguish, “train manufacturer”, “battery system manufacturer” or “cell
manufacturer” is expressed.
[SOURCE: IEC 62973-1:2018, 3.1.13]

IEC 62973-4:2021 © IEC 2021 – 9 –
3.2 Abbreviated terms
AC Alternating Current
C Capacity at the 5-h rate
DC Direct Current
DOD Depth of Discharge
LRU Line Replaceable Unit
Ni-MH battery Nickel-Metal Hydride battery
OCV Open Circuit Voltage
SOC State of Charge
4 General requirements
4.1 Definitions of components of a battery system (images are examples)
Figure 1 shows the definition of cell(s), battery module, crate, tray and battery box.

Figure 1 –Definition of cell(s), battery module, crate, tray and battery box
Some batteries may not include all of the above components, e.g. single cells may be
installed in a tray without crates.

– 10 – IEC 62973-4:2021 © IEC 2021
4.2 Definition of battery type
4.2.1 General
A battery consists of a number of cells or battery modules and/or assembled in trays, crates,
and then assembled in a battery box.
A cell consists of positive and negative plates, electrolyte, metal container and sealing cap.
Positive and negative terminals, which are apart by a separator, are housed and sealed in the
metal container with a sealing cap.
The sealing cap consists of a positive terminal, a pressure release valve and an insulator
which are insulated to a negative part that forms a container. The container wears an
insulating envelope.
The positive active material is nickel hydroxide, and the negative active material is hydrogen
absorbed nickel-alloy.
The electrodes are surrounded by electrolyte, an aqueous solution mainly of potassium
hydroxide (KOH), and distilled or deionized water. The electrolyte does not chemically change
or degrade due to charge/discharge cycles.
4.2.2 Cell designation
Sealed nickel-metal hydride cells shall be designated by a letter L, M, H or X which signifies:
– low rate of discharge (L);
– medium rate of discharge (M);
– high rate of discharge (H);
– very high rate of discharge (X).
NOTE
...