IEC 62973-3:2024

Railway applications - Rolling stock - Batteries for auxiliary power supply systems - Part 3: Lead acid batteries

IEC 62973-3:2024 establishes the framework for the selection and operation of lead acid batteries of the VRLA type for auxiliary power supply systems on rolling stock of railways and complements IEC 62973-1, unless otherwise specified. This document provides guidance and links to standards for the required battery qualification tests procedures and safety measures to be implemented. In this document, the most appropriate clauses of these cited standards have been selected and adapted as needed to reflect the intended use of these batteries as auxiliary power sources on rolling stock of railways.
The battery-specific requirements for subcomponents of battery systems such as containers, charging controls, temperature probes, nameplates and similar are covered in this document as needed.
Charging systems are excluded from the scope of this document.

Applications ferroviaires - Matériel roulant - Batteries pour systèmes d'alimentation auxiliaire - Partie 3: Batteries au plomb

General Information

• Status: Published
• Publication Date: 09-Apr-2024
• ICS: 29.220.20 - Acid secondary cells and batteries
• ICS: 45.040 - Materials and components for railway engineering
• ICS: 45.060.01 - Railway rolling stock in general
• Technical Committee: TC 9 - Electrical equipment and systems for railways
• Drafting Committee: PT 62973-3 - TC 9/PT 62973-3
• Current Stage: PPUB - Publication issued
• Start Date: 10-Apr-2024
• Completion Date: 12-Apr-2024

Overview - IEC 62973-3:2024 (Lead acid batteries for rolling stock)

IEC 62973-3:2024 is the industry standard that defines the framework for selecting, qualifying and operating VRLA lead acid batteries used as auxiliary power supplies on railway rolling stock. It complements IEC 62973‑1 and adapts relevant clauses from existing battery and safety standards to the specific environmental, mechanical and electrical conditions encountered on trains. Charging systems themselves are excluded; the document focuses on battery cells/monoblocs, containers and related subcomponents.

Key topics and technical requirements

The standard provides prescriptive guidance and test references for safe, reliable battery use in rail applications, including:

• Battery types and definitions - VRLA (valve-regulated lead acid) cells, monoblocs, trays, crates and battery boxes.
• Environmental and mechanical requirements - operating temperature ranges, shock & vibration criteria, ventilation and installation orientations.
• System requirements - system voltage considerations, battery sizing inputs/outputs, and charge retention (self‑discharge) expectations.
• Charging and discharging performance - float/boost charge characteristics, temperature compensation, discharge profiles and compliance with energy demand/load profiles.
• Safety & protection - deep-discharge behavior, thermal considerations, fire protection and recommended safety measures.
• Subcomponent requirements - containers, charging controls, temperature probes, nameplates and marking/labeling rules.
• Electrical interface & markings - external connections, nameplate content and safety signs for battery boxes, trays and cells.
• Storage, transport and maintenance - handling instructions, storage conditions and routine maintenance guidance.
• Testing and qualification - type tests and routine tests including dielectric tests, load profile verification, shock & vibration, and electrical checks. Annexes provide test sequences, dielectric test parameters and a method to verify compliance with energy demand.

Practical applications and target users

IEC 62973-3:2024 is intended for professionals involved in design, procurement, installation, testing and operation of battery systems on railway vehicles:

• Rolling stock manufacturers and systems integrators specifying auxiliary power systems
• Battery manufacturers and test houses qualifying VRLA lead acid cells for rail use
• Railway operators and maintenance organizations defining lifecycle and safety procedures
• Certification bodies assessing compliance with railway electrical safety and performance requirements

Related standards and implementation notes

• Complements IEC 62973‑1 (general framework for railway battery systems).
• Selects and adapts clauses from established battery and safety standards (normative references listed in the document).
• Charging systems are explicitly excluded; refer to applicable charging-system standards when specifying chargers.

Keywords: IEC 62973-3:2024, railway batteries, VRLA lead acid batteries, rolling stock auxiliary power, battery qualification tests, battery sizing, railway battery safety.

Standards Content (Sample)

IEC 62973-3 ®
Edition 1.0 2024-04
INTERNATIONAL
STANDARD
Railway applications – Rolling stock – Batteries for auxiliary power supply
systems –
Part 3: Lead acid batteries
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IEC 62973-3 ®
Edition 1.0 2024-04
INTERNATIONAL
STANDARD
Railway applications – Rolling stock – Batteries for auxiliary power supply

systems –
Part 3: Lead acid batteries
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.220.20; 45.040 ISBN 978-2-8322-8567-1

– 2 – IEC 62973-3:2024 © IEC 2024
CONTENTS
FOREWORD . 5
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Abbreviated terms . 9
4 General requirements . 9
4.1 Definitions of components of a battery system . 9
4.2 Description of lead acid battery types . 10
4.2.1 General . 10
4.2.2 Lead acid batteries with valve-regulated cell design and immobilized
electrolyte . 11
4.3 Environmental conditions . 11
4.4 System requirements . 12
4.4.1 System voltage . 12
4.4.2 Charging requirements . 13
4.4.3 Discharging performances . 16
4.4.4 Charge retention(self-discharge) . 17
4.4.5 Requirements for battery sizing . 17
4.5 Safety and protection requirements . 18
4.5.1 General . 18
4.5.2 Deep discharge of batteries . 18
4.5.3 Temperature compensation during charging . 19
4.6 Fire protection . 19
4.7 Maintenance . 19
4.8 Charging characteristics . 19
5 Optional components of a battery system . 20
5.1 General . 20
5.2 Battery information system . 20
5.3 Battery heater . 20
5.4 Thermostat or cut-off switch . 20
6 Mechanical design of battery system . 21
6.1 General . 21
6.2 Interface mechanism . 21
6.3 Shock and vibration . 21
6.4 Ventilation of battery box . 21
7 Electrical interface . 22
7.1 General . 22
7.2 External electrical connections interface . 22
8 Markings. 22
8.1 Safety signs . 22
8.1.1 Outside the box . 22
8.1.2 Tray, crate or other places inside the box . 22
8.1.3 Cells and monoblocs . 23
8.2 Nameplate . 23
8.2.1 Battery box . 23

8.2.2 Nameplates on tray, crate or other nameplates inside the box . 23
9 Storage and transportation conditions . 23
9.1 Transportation . 23
9.2 Storage . 23
10 Testing . 24
10.1 General . 24
10.2 Type test . 24
10.2.1 General . 24
10.2.2 Tests for cells and monoblocs. 24
10.2.3 Dielectric test . 25
10.2.4 Load profile test . 25
10.2.5 Shock and vibration test . 25
10.3 Routine test . 26
10.3.1 General . 26
10.3.2 Visual checks . 26
10.3.3 Dielectric test . 26
10.3.4 Cell and monobloc voltages . 26
Annex A (informative) Declaration of test unit equivalence . 27
Annex B (normative) Dielectric test . 28
Annex C (normative) Compliance of battery with energy demand of load profile(s) . 29
C.1 General . 29
C.2 Battery sizing . 29
C.3 Compliance with energy demand of load profile . 29
C.3.1 General . 29
C.3.2 Test facility . 29
C.3.3 Test batteries . 29
C.3.4 Test procedures . 30
C.3.5 Energy demand compliance . 30
C.3.6 Test report . 30
Bibliography . 31

Figure 1 – Definition of single cells, monobloc, crate, tray and battery box . 10
Figure 2 – Example of the evolution of the voltage of a VRLA cell when discharged
with multiples of the 5 h rated current versus percentage of the 5 h rated capacity . 12
Figure 3 – Examples of current and voltage evolution during charge . 13
Figure 4 – Temperature versus voltage response graph for float charge operation . 15
Figure 5 – Temperature versus voltage response graph for boost charge operation . 16
Figure 6 – Examples of horizontal installation of VRLA cells and monoblocs . 21
Figure 7 – Typical schematic view of an electrical interface of a battery system . 22

Table 1 – Requirements for battery system charge operations . 13
Table 2 – Typical lead acid battery charge parameters . 14
Table 3 – Voltage and temperature reference levels for float charge operation . 15
Table 4 – Voltage and temperature reference levels for boost charge operation . 16
Table 5 – Input parameters required for the sizing of the battery to be provided by the

system integrator or end user . 17

– 4 – IEC 62973-3:2024 © IEC 2024
Table 6 – Output parameters provided at the conclusion of the sizing of the battery to
be provided by the battery system manufacturer . 18
Table 7 – Type tests for cells and monoblocs . 25
Table B.1 – Sequence for dielectric test . 28
Table B.2 – Voltages for dielectric test . 28

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
RAILWAY APPLICATIONS – ROLLING STOCK –
BATTERIES FOR AUXILIARY POWER SUPPLY SYSTEMS –

Part 3: Lead acid batteries
FOREWORD
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IEC 62973-3 has been prepared by IEC technical committee 9: Electrical equipment and
systems for railways. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
9/3041/FDIS 9/3066/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.

– 6 – IEC 62973-3:2024 © IEC 2024
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
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 webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
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RAILWAY APPLICATIONS – ROLLING STOCK –
BATTERIES FOR AUXILIARY POWER SUPPLY SYSTEMS –

Part 3: Lead acid batteries
1 Scope
This part of IEC 62973 establishes the framework for the electrical interfaces to the train, and
the sizing (e.g., capacity, cell number, to meet the requested load profile) and operation of lead
acid batteries of the VRLA type for auxiliary power supply systems on rolling stock of railways
and complements IEC 62973-1, unless otherwise specified.
This document provides guidance and links to standards for the required battery qualification
tests procedures and safety measures to be implemented.
The cited normative references for lead acid batteries provide multiple requirements and tests
applicable for their qualification.
In this document, the most appropriate clauses of these cited standards have been selected
and adapted as needed to reflect the intended use of these batteries as auxiliary power sources
on rolling stock of railways.
The battery-specific requirements for subcomponents of battery systems such as containers,
charging controls, temperature probes, nameplates and similar are covered in this document
as needed.
Charging systems are excluded from the scope of this document.
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 60896-21:2004, Stationary lead-acid batteries – Part 21: Valve regulated types – Methods
of test
IEC 60896-22:2004, Stationary lead-acid batteries – Part 22: Valve regulated types –
Requirements
IEC 61373:2010, Railway applications – Rolling stock equipment – Shock and vibration tests
IEC TS 61430, Secondary cells and batteries – Test methods for checking the performance of
devices designed for reducing explosion hazards – Lead-acid starter batteries
IEC TR 61431:2020, Guidelines for the use of monitor systems for lead-acid traction batteries
IEC 62485-2:2010, Safety requirements for secondary batteries and battery installations –
Part 2: Stationary batteries
– 8 – IEC 62973-3:2024 © IEC 2024
IEC 62498-1:2010, Railway applications – Environmental conditions for equipment – Part 1:
Equipment on board rolling stock
IEC 62973-1:2018, Railway applications – Rolling stock– Batteries for auxiliary power supply
systems – Part 1: General requirements
ISO/IEC 17025, General requirements for the competence of testing and calibration
laboratories
3 Terms, definitions and abbreviated terms
3.1 Terms and definitions
For the purposes of this document, the terms and definitions in IEC 62973-1:2018, and the
following 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
lead dioxide lead battery
lead acid battery
secondary battery with an aqueous electrolyte based on dilute sulphuric acid, a positive
electrode of lead dioxide and a negative electrode of lead
[SOURCE: IEC 60050-482:2004, 482-05-01, modified – Note has been deleted.]
3.1.2
battery information system
data collection system to provide optional additional information and guidance for battery
operation and maintenance
3.1.3
valve regulated lead acid battery
VRLA
secondary battery in which cells are closed but have a valve which allows the escape of gas if
the internal pressure exceeds a predetermined value
Note 1 to entry: The cell or battery cannot normally receive additions to the electrolyte.
[SOURCE: IEC 60050-482:2004, 482-05-15]
3.1.4
finite element analysis
FEA
numerical mathematical analysis method simulating the mechanical behaviour of an assembly
3.1.5
line replaceable unit
LRU
modular component of equipment designed to be replaced at an operating location whilst the
equipment remains in the operating environment

3.1.6
state of charge
SOC
level of charge in ampere hours of the battery relative to its rated
capacity in ampere hours and expressed in percentage points
Note 1 to entry: A term interrelated with SOC, is the term depth of discharge (DOD), i.e., the level of discharge in
ampere hours of the battery system when related to the same rated capacity in ampere hours and expressed in
percentage points and where, by convention, 0 % DOD equals to 100 % SOC and 100 % DOD equals to 0 % SOC.
Note 2 to entry: The real capacity of the battery may be different from the rated, i.e., declared capacity.
3.1.7
rated capacity
C
n
capacity value of a battery system determined under
specified conditions as per IEC 60896-21 and IEC 60896-22, and declared by the battery
manufacturer
3.1.8
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
3.2 Abbreviated terms
AC Alternating Current
AGM Absorbent Glass Mat
DC Direct Current
U Rated battery voltage
B
U Test voltage
T
4 General requirements
4.1 Definitions of components of a battery system
The main components of a lead acid battery and their interdependence are shown in Figure 1.

– 10 – IEC 62973-3:2024 © IEC 2024

Figure 1 – Definition of single cells, monobloc, 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. The designation LRU denotes its status of a line replaceable unit.
4.2 Description of lead acid battery types
4.2.1 General
A lead acid battery consists of an assembly of single cells or multiple-cell monoblocs. Each cell
contains stacks of several positive and negative plates that are separated by a separator,
immersed in electrolyte and connected through plate straps to the positive and negative
terminals. These extend to the outside of the cell or monobloc housing and serve as
interconnection points.
In the fully charged state the active material of the negative plate consists of lead and the active
material of the positive plate consists of lead dioxide.
In a discharged state the active material in both the positive and negative plates contain variable
amounts of the discharge reaction product, i.e., lead sulphate (PbSO ).
The electrolyte is dilute sulphuric acid (typically 40 % in weight), the density or concentration
of which depends on the specific cell design and state of charge.
As the electrolyte participates in the electro-chemical reactions, its density and concentration
are reduced during discharge in proportion of the ampere hours discharged.
4.2.2 Lead acid batteries with valve-regulated cell design and immobilized electrolyte
In the valve-regulated cell design the electrolyte is immobilized with a gelling agent (fumed SiO )
or with an AGM. This induces voids in the volume occupied by the electrolyte facilitating fast
gas transport and oxygen recombination.
The following cell types are in use on rolling stock.
Cell type a) built with either grid-type negative and positive plates or with grid-type negative
plates and tubular-type positive plates. The electrolyte is present in the form of a stiff gel.
Cell type b) built with grid-type negative and positive plates and with a limited amount of
electrolyte immobilized in an AGM.
An oxygen recombination reaction is operative in such cells and monoblocs reducing gassing
and electrolyte water loss.
The cells do not allow or require electrolyte level maintenance and can be operated in vertical
and horizontal position.
4.3 Environmental conditions
The system integrator or end user shall specify the ambient air temperature range in which the
battery is to be operated so that the most appropriate cell and monobloc design can be provided
by the battery manufacturer.
IEC 62498-1:2010 lists in Table 2 the appropriate inside vehicle compartment temperature
ranges identified as class T1 to TX.
Lead acid batteries can operate with proper safeguards in the temperature range from −25 °C
to +55 °C.
Operation outside this range impair service performance and life.
High battery temperatures accelerate battery ageing.
Low battery temperatures reduce actual available battery capacity.
It is recommended that not only the temperature level itself but also the cumulated duration at
a given temperature level shall be taken into consideration when battery life is to be anticipated.
Further environmental conditions to be taken in consideration are:
– Humidity: according to IEC 62498-1:2010
– Shock and vibration: according to IEC 61373:2010
– Altitude: according to IEC 62498-1:2010
Deviations may be agreed between end user and/or system integrator and cell/battery
manufacturer.
– 12 – IEC 62973-3:2024 © IEC 2024
4.4 System requirements
4.4.1 System voltage
The low voltage supply network has to allow operation of the connected equipment within the
minimum and maximum limits of the voltage range according to Table 1 of IEC 62973-1:2018.
The operation of the battery as power source shall occur within the agreed voltage limits
resulting from the resolved requirements of the battery manufacturer, system integrator and end
user.
The voltage during discharge of the battery system varies with elapsed time and current levels.
The actual cell design, state of charge (SOC), ageing, and ambient temperature additionally
influence this voltage. A discharge is terminated when a defined minimum battery system
voltage is reached as per Table 1 of IEC 62973-1:2018, taking into consideration for example
the voltage drop in connection cables.
To avoid excessive withdraw of capacity from the battery system and prevent a deep discharge
or polarity reversal of one or more cells in the battery system, the lower voltage limit has to be
taken into consideration for the battery sizing.
The typical evolution of cell voltage during a discharge is shown in Figure 2 as function of the
discharge current expressed in multiples of the rated 5 h current or I .
Figure 2 – Example of the evolution of the voltage of a VRLA cell when discharged with
multiples of the 5 h rated current versus percentage of the 5 h rated capacity
The evolution of charge current and charge voltage, during a constant-current-constant-voltage
(IU or CCCV) charge of a lead acid battery is shown in Figure 3.

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

Figure 3 – Examples of current and voltage evolution during charge
4.4.2 Charging requirements
The proper battery charging conditions are specified by the battery manufacturer and shall
follow Table 1. Table 2 provides some typical charging parameters to be considered for the
battery system.
Table 1 – Requirements for battery system charge operations
Activity Requirement
A regulated constant-current-constant-voltage charge with the
Float charge mode operation
capability of float voltage compensation according to the battery
system temperature shall be used
Boost charge mode operation (if
A regulated constant-current-constant-voltage charge with:
applicable)
a) the capability of boost voltage compensation according to the
battery temperature;
b) a boost charge activation trigger algorithm;
c) a boost charge duration limiter;
shall be used
Charge voltage control The actual float and boost voltage shall not deviate, in the constant
voltage phase, by more than 1 % from the set value
Battery voltage monitoring The voltage shall be measured with the voltage sensing leads placed
as close as possible to the positive and negative terminals of the
battery system
Charge current control The actual charge current shall not deviate, in the constant current
phase, by more than 1 % from the set value
Charge current ripple mitigation The AC ripple level of the charge current shall not exceed the values
recommended in IEC 62485-2:2010, Table 2
In no case shall the current ripple induce a discharge of the battery
Temperature compensation The temperature related correction factors of the float and boost
charge voltage shall be provided by the battery manufacturer and in
the format of Figure 4 and Figure 5 and Table 3 and Table 4
The correction factors shall be implemented in the charge control logic
Temperature monitoring The actual temperature of the cells and monoblocs shall be determined
with an appropriate sensor placed, with preference, directly on the
hottest cell or monobloc of the battery system
Data loss default action In case of a loss of battery voltage information, the charge of the
battery system shall be stopped
The above numerical values are of informative value only. Limit values are as indicated or as specified by the
agreement between the battery manufacturer, system integrator and end user.

– 14 – IEC 62973-3:2024 © IEC 2024
Table 2 – Typical lead acid battery charge parameters
Float charge conditions
Float voltage 2,15 V/cell to 2,30 V/cell at 25 °C for unlimited duration and corrected for battery
temperature
Temperature correction factor -0,003 V/K/cell to -0,005 V/K/cell
Boost charge conditions
Boost voltage 2,30 V/cell to 2,45 V/cell at 25 °C and corrected for battery temperature
Boost charge duration not to exceed 8 h
Temperature correction factor -0,003 V/K/cell to -0,005 V/K/cell
2 I maximum
Charging current
The above numerical values are of informative value only. The battery manufacturer specifies values applicable
to the battery in consideration.

The purpose of the temperature compensation of the float or boost voltage is to adjust the
amount of charge current flowing through the battery when the ambient temperature increases
or decreases.
This adjustment prevents not only battery overheating and excessive electrolyte water loss at
high temperatures, but also assures the achievement of faster full charge at low temperatures.
The cell or monobloc manufacturer shall provide the appropriate reference values for this
compensation at cell/monobloc level (slope).
The battery system manufacturer shall define the optimized number of cells/monoblocs to best
fit the voltage limits at train level as specified in Table 1 of IEC 62973-1:2018 as shown in
Figure 4 and Table 3, based on the actual battery system design .
Charging permanently with a voltage above or below the cell or monobloc manufacturer
specified limits cause accelerated ageing and a premature loss of capacity. A periodic charge
under boost charge conditions may be recommended by the battery manufacturer to assure an
equalisation of the individual cell voltages.
The battery system manufacturer shall also provide the value of the maximum battery
temperature above which all charge has to be terminated/inhibited.

Figure 4 – Temperature versus voltage response graph for float charge operation
Table 3 – Voltage and temperature reference levels for float charge operation
Reference U in T in °C of Slope of voltage compensation per K in 0,00X V/K deviation from
point V/cell the battery the 25 °C reference temperature
1 U T
1 1
2 U T (25 °C)
To be provided by the cell or monobloc manufacturer
2 2
3 U T
3 3
T and T are the result of set point (25 °C) and slope.
1 3
The temperature monitoring in Table 3 shall be according to Table 1.
A boost charge is carried out so as to speed up the full recharge of the battery or equalize
diverging cell capacities and voltages. As the boost voltage is significantly higher than the float
voltage, the danger of a resulting thermal runaway increases and a correction of the voltage as
function of battery temperature becomes even more imperative.
The cell or monobloc manufacturer shall provide the appropriate reference values for this
compensation at cell/monobloc level (slope).
The battery system manufacturer shall define the optimized number of cells/monoblocs to best
fit the voltage limits at train level as specified in Table 1 of IEC 62973-1:2018 as shown in
Figure 5 and Table 4, based on the actual battery design.
The battery manufacturer shall specify under which conditions a boost charge shall be initiated
and terminated.
– 16 – IEC 62973-3:2024 © IEC 2024

Figure 5 – Temperature versus voltage response graph for boost charge operation
Table 4 – Voltage and temperature reference levels for boost charge operation
Reference U in T in °C of Slope of voltage Conditions Minimum interval
point V/cell the battery compensation per K in specified for between two boost
0,00Y V/K deviation from initiating and charges as
the 25 °C reference terminating a boost specified in hours
temperature charge or events
4 U T
4 4
To be provided by To be provided by
To be provided by the cell
5 U T (25 °C)
the battery system the battery system
5 5
or monobloc manufacturer
manufacturer manufacturer
6 U T
6 6
T and T are the result of set point (25 °C) and slope.
4 6
The temperature monitoring in Table 4 shall be according to Table 1.
4.4.3 Discharging performances
4.4.3.1 General
The discharge requirement of the specified load profile(s) shall be met.
4.4.3.2 Load profile
The load profile reflects the actual current and/or power and/or resistive loads versus time
requirement of the auxiliary battery in rolling stock application. The load profile shall be
associated with an operating temperature range (maximum and minimum temperatures as
specified by the system integrator or end user, as per 4.4.5 of IEC 62973-1:2018) and system
voltage limits. Typical load profiles are shown in IEC 62973-1:2018 as examples only.
Such a load profile may incorporate requirements for extended discharge durations and low or
high temperature performance and others such as fulfillment level over service life.

The system integrator or end user shall provide these load profiles and associated conditions.
4.4.4 Charge retention(self-discharge)
Batteries lose capacity when stored in open circuit. This loss is quantified under normalized
conditions with the pertinent test clause in IEC 60896-21:2004.
The battery manufacturer shall provide guidance for the maximum possible duration of storage
in open circuit before a recharge, as specified for such a task, becomes necessary. The
influence of storage temperature shall be provided by the battery manufacturer.
4.4.5 Requirements for battery sizing
The selection of the battery, capable of meeting the energy demands as auxiliary power source
on rolling stock, i.e., its sizing shall be carried out by the battery system manufacturer.
The required parameters for sizing are listed in Table 5 and shall be provided by the system
integrator or end user.
Table 5 – Input parameters required for the sizing of the battery to be provided
by the system integrator or end user
Required parameters Information format
Load profile(s) Load expressed in A or W or Ω over time or combinations thereof
Relevant ambient air temperature range i.e., minimum and maximum battery
Ambient air temperature
system ambient temperature
Relevant voltage range according to the planned or present auxiliary power
supply system of the rolling stock
Operating voltage window
Possible voltage drops in connections and cables to and from the battery shall
not be overlooked
Required cycle capability Total number of discharges to be achieved with the most demanding load profile
Required service life in Service life in months based on required cycle capability and specified air
calendar months temperatures
Load expressed in A or W or Ω over time or combinations thereof
Extended discharge event
Number of events per year
Performance margins for future List of potential future performance level(s) amendments
loads
User-specific demands, Any additional information and specifications
conditions or constraints
All ancillary conditions shall be made available to the battery manufacturer as early and as
complete as possible, so as not to impair or delay the battery sizing activity.
At an appropriate stage of the battery sizing process, the battery manufacturer shall provide
feedback to the system integrator and/or end user on the actual sized battery by providing data
as per Table 6.
– 18 – IEC 62973-3:2024 © IEC 2024
Table 6 – Output parameters provided at the conclusion of the sizing
of the battery to be provided by the battery system manufacturer
Required parameters Information format
Voltage versus time curves or similar curves of the battery when a discharge
Load profile(s) with the load profile(s) is carried out at the upper and lower temperature limits of
the specified air temperature range
Confirmation of operability of the battery system within the minimum and
Ambient air temperature
maximum battery system ambient temperatures
Maximum and minimum voltage of the battery under the selected load profile and
operating temperature conditions
Float voltage value at 25 °C
Operating voltage window Temperature correction factor as per Table 3 and Figure 4
Boost voltage value at 25 °C
Temperature correction factor and operating conditions as per Table 4 and
Figure 5
Number of achievable discharges with a specified load profile when operated at
25 °C
Required cycle capability
Cycle capability derating when operated at the upper air temperature limit
Achievable service life in months when operated at 25 °C with a specified load
profile
Required service life in
calendar months
Service life derating when operated permanently at the upper air temperature
limit
Achievable extended discharge duration, in minutes at 25 °C, when the battery is
continued to be discharged, at the end of a regular load profile discharge, with
Extended discharge event
the specified power or current or resistive load of the specified extended-
duration load profile
Performance margins for Spare performance available under specified conditions
future loads
User-specific demands, Information as applicable
conditions or constraints
4.5 Safety and protection requirements
4.5.1 General
The battery crates, trays and boxes and connection hardware shall be stable against the action
of chemicals such as traces of battery electrolyte, hydraulic fluids, salt solutions and similar.
IEC 62498-1:2010 provides further guidance for the environmental conditions to be
encountered in railway applications.
The choice of the materials shall assure that no degradation of load-carrying or electrical
isolation properties occur.
See also 6.4 for ventilation of battery system box and vent plugs with flame barriers.
The proper qualification test shall be defined by mutual agreement between the battery
manufacturer, system integrator and/or end user.
4.5.2 Deep discharge of batteries
Lead acid batteries may experience deep discharge conditions in service on rolling stock when
an excessive amount of capacity is withdrawn or a specific low voltage is reached during a
discharge.
The battery manufacturer shall specify when a deep discharge occurred either in terms of:
a) of ampere-hours discharged in discharge events between two charges and referred t
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