prEN IEC 62973-2:2025

SLOVENSKI STANDARD
01-december-2025
Železniške naprave - Vozna sredstva - Baterije za pomožne močnostne napajalne
sisteme - 2. del: Nikelj-kadmij (NiCd) baterije
Railway applications - Rolling stock - Batteries for auxiliary power supply systems - Part
2: Nickel Cadmium (NiCd) batteries
Bahnanwendungen - Fahrzeuge - Batterien für Bordnetzversorgungssysteme – Teil 2:
Nickel-Cadmium-Batterien (NiCd-Batterien)
Applications ferroviaires - Matériel roulant - Batteries pour systèmes d'alimentation
auxiliaire - Partie 2: Batteries au Nickel Cadmium (NiCd)
Ta slovenski standard je istoveten z: prEN IEC 62973-2:2025
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 62973-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2025
ICS 45.060.01; 29.220.99 -
English Version
Railway applications - Rolling stock - Batteries for auxiliary
power supply systems - Part 2: Nickel Cadmium (NiCd) batteries
(IEC 62973-2:2020)
Applications ferroviaires - Matériel roulant - Batteries pour Bahnanwendungen - Fahrzeuge - Batterien für
systèmes d'alimentation auxiliaire - Partie 2: Batteries au Bordnetzversorgungssysteme - Teil 2: Nickel-Cadmium-
Nickel Cadmium (NiCd) Batterien (NiCd-Batterien)
(IEC 62973-2:2020) (IEC 62973-2:2020)
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 62973-2:2020 (9/2585/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: 81174 Ref. No. prEN IEC 62973-2:2025 E

European foreword
This document (prEN IEC 62973-2:2025) consists of the text of IEC 62973-2:2020 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)
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 60623 2017 Secondary cells and batteries containing EN 60623 2017
alkaline or other non-acid electrolytes -
Vented nickel-cadmium prismatic
rechargeable single cells
IEC 61373 2010 Railway applications - Rolling stock EN 61373 2010
equipment - Shock and vibration tests
IEC 62259 2003 Secondary cells and batteries containing EN 62259 2004
alkaline or other non-acid electrolytes -
Nickel-cadmium prismatic secondary single
cells with partial gas recombination
IEC 62485-2 2010 Safety requirements for secondary EN IEC 62485-2 2018
batteries and battery installations - Part 2:
Stationary batteries
IEC 62973-1 2018 Railway applications - Rolling stock - EN IEC 62973-1 —
Batteries for auxiliary power supply
systems - Part 1: General Requirements

Under preparation. Stage at the time of publication: prEN IEC 62973-1:2025.
IEC 62973-2 ®
Edition 1.0 2020-05
INTERNATIONAL
STANDARD
colour
inside
Railway applications – Rolling stock – Batteries for auxiliary power supply

systems –
Part 2: Nickel Cadmium (NiCd) batteries

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 45.060.01; 29.220.99 ISBN 978-2-8322-8234-2

– 2 – IEC 62973-2:2020 © IEC 2020
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions and abbreviated terms . 9
3.1 Terms and definitions . 9
3.2 Abbreviated terms . 11
4 General requirements . 12
4.1 Definitions of components of a battery system, refer to Figure 1 (images are
examples) . 12
4.2 Definitions of NiCd battery type . 12
4.2.1 General . 12
4.2.2 Sintered/PBE plate/electrode technology . 13
4.2.3 Sintered/sintered plate/electrode technology . 13
4.2.4 Fiber plate/electrode technology . 13
4.2.5 Pocket plate/electrode technology . 13
4.3 Environmental conditions . 13
4.4 System requirements . 13
4.4.1 System voltage . 13
4.4.2 Charging requirements . 15
4.4.3 Discharging requirements . 17
4.4.4 Charge retention (self-discharge) . 18
4.4.5 Requirements for battery capacity sizing. 18
4.5 Safety and protection requirements . 19
4.5.1 General . 19
4.5.2 Deep discharge of batteries . 19
4.5.3 Temperature compensation during charging . 20
4.6 Fire protection . 20
4.7 Maintenance . 20
4.8 Charging characteristics . 20
4.9 Optional additional components to battery system . 20
4.9.1 General . 20
4.9.2 Battery information system . 21
4.9.3 Battery heater . 21
4.9.4 Thermostat or cut-off switch. 21
5 Mechanical design of battery system . 21
5.1 General . 21
5.2 Interface mechanism . 21
5.3 Location of battery system on the vehicle . 21
5.4 Accessibility to the battery . 22
5.5 Shock and vibration . 22
5.6 Ventilation of battery box . 22
5.7 Water filling system . 22
6 Electrical interface . 22
6.1 General . 22
6.2 External electrical connections interface . 23

IEC 62973-2:2020 © IEC 2020 – 3 –
7 Markings. 23
7.1 Safety signs . 23
7.1.1 Outside the box . 23
7.1.2 Tray, crate or other places inside the box . 23
7.1.3 Cells or monobloc batteries . 23
7.2 Nameplate . 24
7.2.1 Battery box . 24
7.2.2 Nameplates on tray, crate or other nameplates inside the box . 24
7.2.3 Cells or monoblocs . 24
8 Storage and transportation conditions . 24
8.1 Transportation . 24
8.2 Storage of batteries . 24
9 Testing . 25
9.1 General . 25
9.2 Type test . 25
9.2.1 General . 25
9.2.2 Parameter measurement tolerances . 26
9.2.3 Electrical characteristic tests . 26
9.2.4 Dielectric test . 26
9.2.5 Load profile test . 26
9.2.6 Shock and vibration test . 26
9.3 Routine test . 27
9.3.1 General . 27
9.3.2 Visual checks . 27
9.3.3 Dielectric test . 27
9.3.4 Electrical characteristics tests . 27
Annex A (informative) Examples of typical load profiles . 28
A.1 General . 28
A.2 Example of load profile – High speed train (Figure A.1) . 28
A.3 Example of load profile – Regional train/ EMU (Figure A.2) . 29
Annex B (normative) NiCd load profile verification . 30
B.1 General . 30
B.2 General methodology . 30
B.3 Battery sizing documentation . 31
B.4 Operational verification (load profile test) . 31
B.5 Test report . 32
Annex C (informative) Declaration of cell model range representative of the testing . 33
C.1 Electrical performance declaration . 33
C.2 Shock and vibration declaration . 33
Bibliography . 34

Figure 1 – Definition of NiCd cell(s), monobloc battery, crate, tray, and box . 12
Figure 2 – Example of a NiCd cell discharge curve at various constant discharge
currents based on percentage of capacity . 14
Figure 3 – Example of a NiCd cell charge curves . 15
Figure 4 – Typical NiCd battery charging characteristics . 17
Figure 5 – Typical schematic of an electrical interface of a battery system . 23

– 4 – IEC 62973-2:2020 © IEC 2020
Figure A.1 – Example of load profile for high speed train (without starting up segment) . 28
Figure A.2 – Example of load profile for regional train/ EMU (without starting up
segment) . 29

Table 1 – Requirements of the charging characteristics . 15
Table 2 – Typical NiCd battery charging characteristics . 16
Table 3 – Parameters and responsibility for battery capacity sizing . 19
Table 4 – Type test and routine test . 25

IEC 62973-2:2020 © IEC 2020 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RAILWAY APPLICATIONS – ROLLING STOCK –
BATTERIES FOR AUXILIARY POWER SUPPLY SYSTEMS –

Part 2: Nickel Cadmium (NiCd) 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 62973-2 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
9/2585/FDIS 9/2594/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.

– 6 – IEC 62973-2:2020 © IEC 2020
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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
IEC 62973-2:2020 © IEC 2020 – 7 –
INTRODUCTION
This document considers the requirements for vented or partial recombination Nickel
Cadmium (NiCd) batteries following IEC 62973-1:2018.
In this document the interface with a LVPS or charger is specified and the LVPS or charger
itself is out of scope.
– 8 – IEC 62973-2:2020 © IEC 2020
RAILWAY APPLICATIONS – ROLLING STOCK –
BATTERIES FOR AUXILIARY POWER SUPPLY SYSTEMS –

Part 2: Nickel Cadmium (NiCd) batteries

1 Scope
This part of IEC 62973 applies to NiCd rechargeable batteries for auxiliary power supply
systems used on railway vehicles. It is an extension of IEC 62973-1:2018 which specifies
common requirements for all battery technologies of other parts of IEC 62973. Unless
otherwise specified, the requirements of IEC 62973-1:2018 apply.
Battery systems described in this document are used in conjunction with charging systems
onboard rolling stock, as described in IEC 62973-1:2018. Charging systems (e.g. LVPS,
converters, etc.) are excluded from the scope of this document.
This document also specifies the design, operation parameters, safety recommendations,
routine and type tests, as well as marking and designation.
This document is used in addition to IEC 60623:2017 or IEC 62259:2003 for NiCd Cells.
Specific requirements on subcomponents within the battery systems are covered in this
document, e.g. temperature measurement components.
When there is an existing IEC standard specifying additional test conditions and requirements
for NiCd batteries used in specific railway applications and which conflicts with this document,
the latter takes precedence.
The main objective of this document is to achieve standardization of the electrical interfaces
by considering NiCd battery parameters to allow for calculating the NiCd battery capacity
required for a specific load profile.
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 60623:2017, Secondary cells and batteries containing alkaline or other non-acid
electrolytes – Vented nickel-cadmium prismatic rechargeable single cells
IEC 61373:2010, Railway applications – Rolling stock equipment – Shock and vibration test
IEC 62259:2003, Secondary cells and batteries containing alkaline or other non-acid
electrolytes – Nickel cadmium prismatic secondary single cells with partial gas recombination

IEC 62973-2:2020 © IEC 2020 – 9 –
IEC 62485-2:2010, Safety requirements for secondary batteries and battery installations –
Part 2: Stationary batteries
IEC 62973-1:2018, Railway applications Rolling stock – Batteries for auxiliary power supply
systems – Part 1: General requirements
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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
battery crate
container with frame walls for holding several cells or batteries
Note 1 to entry: Refer to 4.1 and Clause 5.
[SOURCE: IEC 60050-482:2004/AMD1:2016, 482-05-10, modified – Note 1 to entry has been
added.]
3.1.2
battery tray
container with a base and walls for holding several cells or batteries
Note 1 to entry: Refer to 4.1 and Clause 5.
[SOURCE: IEC 60050-482:2004/AMD1:2016, 482-02-35, modified – Note 1 to entry has been
added.]
3.1.3
cell
basic functional unit of NiCd battery, 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
[SOURCE: IEC 60050-482:2004/AMD1:2016, 482-01-01, modified – Note has been deleted
and the specific use “of NiCd battery" has been added.]
3.1.4
monobloc battery
battery with multiple separate but electrically connected cell compartments each of which is
designed to house an assembly of electrodes, electrolyte, terminals or interconnections and
possible separators
Note 1 to entry: The cells in a monobloc battery can be connected in series or in parallel.
[SOURCE: IEC 60050-482:2004, 482-02-17]

– 10 – IEC 62973-2:2020 © IEC 2020
3.1.5
nickel cadmium battery
secondary battery with an alkaline electrolyte, a positive electrode containing nickel oxide and
a negative electrode of cadmium
[SOURCE: IEC 60050-482:2004/AMD1:2016, 482-05-02, modified – A synonym has been
removed.]
3.1.6
rated capacity,
C
n
capacity value of a battery determined under IEC 60623:2017 specified conditions and
declared by the battery manufacturer
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.
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.
3.1.9
ageing factor,
quantitative factor expressing the degradation in the ability of the battery, due to usage, to
deliver electrical energy under specified operating conditions such as, but not limited to,
operating ambient temperature, cycling considering depth of discharge (DOD), and
maintenance practices
3.1.10
nickel cadmium battery information system
electronic system collecting and analyzing battery data to provide additional information, i.e.
information not necessary for battery operation
Note 1 to entry: Additional information can be information about e.g. condition-based maintenance.
3.1.11
battery system
battery
system that includes battery tray(s), battery crate(s), monobloc(s), electrical components
and/or equipment and associated electromechanical components and connections
3.1.12
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.

IEC 62973-2:2020 © IEC 2020 – 11 –
3.1.13
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.
3.1.14
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.
3.2 Abbreviated terms
AC Alternating Current
C Capacity at the n-hour rate
n
CCCV Constant Current Constant Voltage
DC Direct Current
DOD Depth Of Discharge
EMU Electrical Multiple Unit
FEA Finite Element Analysis
LVPS Low Voltage Power Supply
NiCd Nickel Cadmium
PBE Plastic Bonded Electrode
SOC State Of Charge
– 12 – IEC 62973-2:2020 © IEC 2020
4 General requirements
4.1 Definitions of components of a battery system, refer to Figure 1
(images are examples)
Figure 1 – Definition of NiCd cell(s), monobloc battery, crate, tray, and box
Some batteries may not include all the above components, e.g. single cells may be installed
in a tray without crates.
4.2 Definitions of NiCd battery type
4.2.1 General
A battery consists of several cells or monoblocs, and/or assembled in trays, crates, and then
assembled in a battery box. Internally, each cell has plate stacks consisting of several
positive and negative plates that are separated by a single or multilayer separator. These are
held by a supporting structure which in turn are connected to positive and negative terminals
that extend to the outside of the cell container.
The positive active material is nickel hydroxide, and the negative active material is cadmium-
hydroxide.
IEC 62973-2:2020 © IEC 2020 – 13 –
The plate stacks are surrounded by alkaline electrolyte, an aqueous solution mainly of
potassium hydroxide (KOH), and distilled or deionized water. The electrolyte does not
participate in the electrochemical reaction, which takes place in the cell, but only acts as an
ion-carrying medium with its specific gravity remaining fairly constant allowing for large
electrolyte reserves to be used. The electrolyte does not chemically change or degrade due to
charge/ discharge cycles.
Due to NiCd electrochemistry technology, some abuse conditions can be tolerated at the cell
level, e.g. overcharging will cause water electrolysis, but only water is consumed. Since there
is no chemical change or degradation of electrolyte, it is not necessary to add complex control
systems to handle such cases.
4.2.2 Sintered/PBE plate/electrode technology
The sintered positive plate/ electrode is obtained by chemical impregnation of nickel
hydroxide into a porous nickel sinter coated thin steel strip that is previously perforated and
nickel-plated.
The negative plastic bonded electrode (PBE) is obtained by the coating of slurry consisting of
cadmium oxide mixed with a plastic binder onto a nickel-plated thin perforated steel strip.
4.2.3 Sintered/sintered plate/electrode technology
The sintered positive and negative plate/electrode is obtained by chemical impregnation of
nickel hydroxide and cadmium oxide into a porous nickel sinter coated thin steel strip that is
previously perforated and nickel-plated.
4.2.4 Fiber plate/electrode technology
Both the positive and negative plates/electrodes consist of non-woven fibers of nickel or
nickel-plated plastic fibers of high porosity.
4.2.5 Pocket plate/electrode technology
Both the positive and negative plates/electrodes consist of several flat, perforated metal
pockets made from perforated steel strips linked together encapsulating the active materials.
4.3 Environmental conditions
NiCd cells/ batteries can perform at extreme temperatures: below –25 °C or above +40 °C.
Especially when at one extreme temperature is specified, deviations for the opposite extreme
temperature may be agreed between end user and/ or system integrator and cell/ battery
manufacturer.
4.4 System requirements
4.4.1 System voltage
The charging voltage for the NiCd battery is dependent on the number of cells, temperature,
and its plate/electrode technology.
Although the nominal battery voltage is set by Table 1 of IEC 62973-1:2018, the number of
cells can vary due to the cell charging requirements by their plate/electrode technology.

– 14 – IEC 62973-2:2020 © IEC 2020
Due to higher cell charging voltage required by the fiber or pocket plate technology, a lower
number of cells can be used in series with a higher capacity. While due to lower charging
voltage of sintered/PBE or sintered/sintered plate technology, more cells can be used in
series with a lower capacity. Less cells with a higher capacity or more cells with lower
capacity would provide similar energy.
The optimised number of cells in a NiCd battery calculated by the battery manufacturer shall
allow to operate between the minimum and maximum equipment operating voltage range
considering the operating conditions and battery load profile. Then the operational battery
charging voltage at 20 °C shall be set considering the calculated number of cells and
individual cell charging characteristics. Refer to Table 2.
The NiCd battery nominal voltages and the discharge voltages are different. Figure 2 shows
typical discharges of a NiCd cell at different constant discharging currents (shown in multiples
of C or multiples of I , C and I are related, e.g. 0,2 C is equivalent to I ) that vary by
n n n n 5 5
battery discharge rate designation (e.g. L, M, H per IEC 60623:2017). This discharge curve
(discharge voltages relative to discharge capacities based on constant current discharges)
shall be available at different temperatures.

Figure 2 – Example of a NiCd cell discharge curve at various constant
discharge currents based on percentage of capacity
The following example, a) in Figure 3 shows a typical charge of a NiCd cell at constant
charging current at 0,2 C (equivalent to I ) for the initial phase followed by b) in Figure 3
5 5
constant charging voltage for the last phase depending on the NiCd battery type
plate/electrode technology. Charging curves shall be available from battery manufacturers.
Typically, the charging function is performed by the LVPS or charger in a low voltage system
architecture.
IEC 62973-2:2020 © IEC 2020 – 15 –

a) Example of charge b) Example of charge
current rate curve voltage curve

NOTE The positive sign of current in a) in Figure 3 shows the charging condition. When the charge and discharge
currents are combined in the same curve, the charge current is depicted with a negative sign opposite to the sign
in the load profile as described in Annex A.
Figure 3 – Example of a NiCd cell charge curves
4.4.2 Charging requirements
The required battery charging characteristics and the optimum charging method are specified
according to Table 1 and Table 2 respectively.
Table 1 – Requirements of the charging characteristics
Requirements Characteristics
Normal condition Float charge by LVPS or charger with temperature compensation.
Charging method Depending on NiCd battery type plate/electrode technology. Refer to Table 2.
Steady state control The charge voltage tolerance refers to the voltage demand according to the ideal
tolerance of the battery charging characteristic of the battery.
charge voltage output at the
In case of temperature compensation ± 1,5 % or lower tolerance.
charging system
Without temperature compensation ± 1 % or lower tolerance.
Charging voltage ripple ≤ 5 % (according to IEC 60077-1 but with disconnected battery).
Charging current ripple The battery charging current shall be DC, as any superimposed AC component in
the charging current can lead to a temperature increase of the battery. The AC
content in the charging current shall not exceed values as per IEC 62485-2:2010.
Temperature compensation Temperature compensation as required by the NiCd battery type plate/electrode
technology. Refer to Table 2.
Detection of temperature Signal from sensor on battery or battery compartment, detection inside battery
charging system.
The float and boost charge concept in Table 2 are illustrated in Figure 4.

– 16 – IEC 62973-2:2020 © IEC 2020
Table 2 – Typical NiCd battery charging characteristics
NiCd battery charging characteristics Float charging Boost charge at Remarks
voltage at 20 °C 20 °C
Basic data for Charging voltage at 1,40 V/ cell 1,60 V/ cell See points ① and ② on
charging (Note 1) 20 °C (Note 2) (Note 2) Figure 4
Mandatory, change NA 45°C See point ③ on Figure 4
from boost to float
The switch point from
charging
boost to float charge is
based on parameters
such as temperature,
current and/or time
Temperature Typical case with a -3 mV/ cell/ °C -3 mV/ cell/ °C See Figure 4
correction single value (Note 3) (Note 3)
Switching set Mandatory stop Up to 70 °C maximum See point ④ on Figure 4
points charging of battery
(all charge
modes) Standard, from boost NA The switch point Current measurement
to float charging from boost to float necessary as well as
charge is based on temperature and/or time
parameters such
as temperature,
current and/or time
(Note 4)
Standard, from float The switch point NA Current measurement
to boost charging from float to boost necessary as well as
charge is based on temperature and/or time
parameters such
as temperature,
current and/or time
(Note 4)
NOTE 1 When single level charging is used, the boost charge voltage = the float charge voltage.
NOTE 2 The values of the charging voltages for the different charge modes are indicative values. The
manufacturer can choose different values for reaching a certain state of charge depending on the NiCd
technology. Those values are clearly indicated in the cell documentation and available upon request from the cell
manufacturer. The voltage tolerance is taken at maximum ±1 %.
NOTE 3 A temperature compensation is necessary, a typical value is of -0,003 V/°C/cell. In case the numerical
value is adjusted for some type of cells specified as CCCV, it is clearly indicated in the cell manufacturer‘s
documentation and in the approval documents. It is possible to have 3 values;
• one for temperatures lower than or equal to T , (T ≤ 45 °C, e.g. T = 20 °C)
1 1 1
• one for temperature higher than T , and lower than or equal 45 °C, and
• one for temperature higher than 45 °C.
NOTE 4 The charging current can vary depending on the designed charging current value as indicated on the
documentation provided by the manufacturer for the cell.
NOTE 5 Point ⑤ in Figure 4 corresponds to the maximum charging voltage at the equipment as expressed in
Table 1 of IEC 62973-1:2018.
IEC 62973-2:2020 © IEC 2020 – 17 –

NOTE The location of the temperature sensor is agreed between the end user and battery manufacturer. Refer to
4.5.3.
Figure 4 – Typical NiCd battery charging characteristics
The charging voltage of the battery shall be limited to the maximum voltage at the equipment
in Table 1 of IEC 62973-1:2018. The temperature compensation voltage control should be
limited to these values considering the charging cell voltage values in Table 2 multiplied by
the number of cells in series for the battery.
The typical charging voltages per cell for most applications are shown in Table 2 with
temperature compensation voltage control. Higher or lower values, within the above limits,
can be selected depending on sizing and application parameters (e.g. in Japan for
sintered/PBE, a single level float charge voltage of 1,43 V/cell without temperature
compensation voltage control charging is typical).
In some cases, in agreement between the end user and manufacturer, the temperature
compensation voltage control charging may not be required. This information shall be agreed
upon prior to calculating the battery capacity required for a specific load profile. In such a
case, the battery temperature sensor may be omitted. It is the responsibility of the battery
manufacturer to calculate the additional battery capacity needed to consider the non-
temperature compensated charging regime. In case of extreme low temperature, a heater can
be added to limit the additional capacity needed. Then the temperature activation point of the
heater shall be agreed prior to battery capacity calculation.
4.4.3 Discharging requirements
4.4.3.1
...