EN IEC 62984-3:2020

High-temperature secondary batteries - Part 3: Sodium-based batteries - Performance requirements and tests

IEC 62984-3:2020 specifies performance requirements and test procedures for high­-temperature batteries based on sodium for mobile and/or stationary use and whose rated voltage does not exceed 1 500 V. Sodium based batteries include sodium-sulphur batteries and sodium-nickel chloride batteries; both are high-temperature batteries and use a solid, sodium conducting electrolyte. Additional information on sodium-based batteries technology, their chemistries and construction are given in Annex B. This document does not cover aircraft batteries, covered by IEC 60952 (all parts), and batteries for the propulsion of electric road vehicles, covered by IEC 61982 (all parts).

Hochtemperatur-Sekundärbatterien – Teil 3: Natrium-basierte Batterien – Leistungsanforderungen und Prüfungen

Batteries d’accumulateurs à haute température - Partie 3: Batteries au sodium - Exigences et essais relatifs aux qualités de fonctionnement

L'IEC 62984-3:2020 spécifie les exigences relatives aux qualités de fonctionnement et les procédures d’essai relatives aux batteries au sodium à haute température pour usage mobile et/ou fixe et dont la tension assignée ne dépasse pas 1 500 V. Les batteries au sodium comprennent les batteries sodium-soufre et les batteries sodium chlorure de nickel; les deux types de batteries sont des batteries à haute température et utilisent un électrolyte conducteur solide au sodium. L’Annexe B donne des informations complémentaires sur la technologie des batteries au sodium, leurs caractéristiques chimiques et leur construction. Le présent document ne couvre pas les batteries d’aéronefs, couvertes par la série IEC 60952 (toutes les parties), et les batteries pour la propulsion des véhicules routiers électriques, couvertes par l’IEC 61982 (toutes les parties).

Visokotemperaturne sekundarne baterije - 3. del: Natrijeve baterije - Zahtevane lastnosti in preskusi

General Information

• Status: Published
• Publication Date: 28-May-2020
• ICS: 29.220.20 - Acid secondary cells and batteries
• Technical Committee: CLC/TC 21X - Secondary cells and batteries
• Drafting Committee: IEC/TC 21 - IEC_TC_21
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 29-May-2020
• Completion Date: 29-May-2020
• Ref Project: SIST EN IEC 62984-3:2020 - High Temperature secondary Batteries - Part 3: Sodium-based Batteries - Performance requirements and tests

Overview - EN IEC 62984-3:2020 (sodium-based batteries)

EN IEC 62984-3:2020 specifies performance requirements and test procedures for high‑temperature, sodium‑based secondary batteries (rated voltage ≤ 1 500 V) for mobile and/or stationary use. The standard covers sodium‑sulphur (Na‑S) and sodium‑nickel chloride (Na‑NiCl) battery technologies, both of which use a solid, sodium‑conducting electrolyte. It excludes aircraft batteries (IEC 60952) and traction batteries for road vehicles (IEC 61982).

Keywords: EN IEC 62984-3:2020, sodium-based batteries, high-temperature batteries, sodium-sulphur, sodium-nickel chloride, battery testing, performance requirements.

Key topics and technical requirements

• Scope and definitions: Battery construction, functionality, symbols and abbreviations specific to sodium‑based high‑temperature cells.
• Environmental (service) conditions: Normal and special service conditions for stationary and mobile installations, including temperature regimes.
• Electrical performance:
  • Nominal voltage and preferred values
  • Discharge and charge rate requirements (continuous, transient, boost)
  • Rated battery energy and capacity tests
  • Battery auxiliary energy consumption
  • Energy efficiency (η) and measurement
  • Long‑term endurance (LTE) metrics
• Thermal performance:
  • Warm‑up, cool‑down, standby and idle modes
  • Freeze‑thaw considerations and associated tests
• Test program:
  • Classification of tests: type tests, routine tests, special tests
  • Defined test methods: energy efficiency, auxiliary consumption, long‑term endurance, maximum continuous and transient discharge, boost charge, capacity/energy content, freeze‑thaw
• Marking & documentation: Data plate marking, instruction manual, test reports and standardized test report templates.
• Rules: Requirements for transportation, installation and maintenance for safe operation.

Practical applications - who uses this standard

• Battery manufacturers and module/system designers validating Na‑S and Na‑NiCl products.
• Test laboratories performing type, routine and special battery tests.
• System integrators and OEMs specifying high‑temperature battery performance for stationary energy storage or mobile non‑propulsion applications.
• Certification bodies and compliance engineers assessing conformity.
• Installers, maintenance teams and asset operators using the standard for safe transport, installation and lifecycle management.

Keywords: battery manufacturers, test laboratories, energy storage, sodium-based battery standard.

Related standards

• EN IEC 62984-1:2020 - General requirements for high‑temperature secondary batteries
• EN IEC 62984-2:2020 - Safety requirements and tests
• IEC 62902 - Marking symbols for battery chemistry
• Exclusions referenced: IEC 60952 (aircraft), IEC 61982 (vehicle propulsion)

This standard is essential for ensuring consistent performance testing and safe deployment of high‑temperature sodium‑based batteries across industrial and stationary energy storage applications.

Standards Content (Sample)

SLOVENSKI STANDARD
01-november-2020
Visokotemperaturne sekundarne baterije - 3. del: Natrijeve baterije - Zahtevane
lastnosti in preskusi
High Temperature secondary Batteries - Part 3: Sodium-based Batteries - Performance
requirements and tests
Batteries d'accumulateur à haute temperature - Partie 3: Prescriptions de performance et
essais
Ta slovenski standard je istoveten z: EN IEC 62984-3:2020
ICS:
29.220.20 Kislinski sekundarni členi in Acid secondary cells and
baterije batteries
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD EN IEC 62984-3

NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2020
ICS 29.220.20
English Version
High-temperature secondary batteries - Part 3: Sodium-based
batteries - Performance requirements and tests
(IEC 62984-3:2020)
Batteries d'accumulateurs à haute température - Partie 3: Hochtemperatur-Sekundärbatterien - Teil 3: Natrium-
Batteries au sodium - Exigences et essais relatifs aux basierte Batterien - Leistungsanforderungen und Prüfungen
qualités de fonctionnement (IEC 62984-3:2020)
(IEC 62984-3:2020)
This European Standard was approved by CENELEC on 2020-05-21. 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.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC
Management Centre or to any CENELEC member.
This European Standard exists 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,
Turkey and the United Kingdom.

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
© 2020 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62984-3:2020 E

European foreword
The text of document 21/1040/FDIS, future edition 1 of IEC 62984-3, prepared by IEC/TC 21
"Secondary cells and batteries" was submitted to the IEC-CENELEC parallel vote and approved by
CENELEC as EN IEC 62984-3:2020.
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2021-02-21
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2023-05-21
document have to be withdrawn
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.

Endorsement notice
The text of the International Standard IEC 62984-3:2020 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards
indicated:
IEC 60952 (series) NOTE Harmonized as EN 60952 (series)
IEC 61982 (series) NOTE Harmonized as EN 61982 (series)
IEC 62485-2 NOTE Harmonized as EN IEC 62485-2

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.cenelec.eu.
Publication Year Title EN/HD Year
IEC 62902 - Secondary cells and batteries - Marking EN IEC 62902 -
symbols for identification of their chemistry
IEC 62984-1 2020 High-temperature secondary batteries - Part 1: EN IEC 62984-1 2020
General requirements
IEC 62984-2 2020 High-temperature secondary batteries - Part 2: EN IEC 62984-2 2020
Safety requirements and tests
IEC 62984-3 ®
Edition 1.0 2020-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
High-temperature secondary batteries –

Part 3: Sodium-based batteries – Performance requirements and tests

Batteries d’accumulateurs à haute température –

Partie 3: Batteries au sodium – Exigences et essais relatifs aux qualités de

fonctionnement
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.220.20 ISBN 978-2-8322-8129-1

– 2 – IEC 62984-3:2020 © IEC:2020
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms, definitions, symbols and abbreviated terms . 6
3.1 Battery construction . 6
3.2 Battery functionality . 7
3.3 Symbols and abbreviated terms . 8
4 Environmental (service) conditions . 9
4.1 General . 9
4.2 Normal service conditions for stationary installations . 9
4.3 Special service conditions for stationary installations . 9
4.4 Normal service conditions for mobile installations (except propulsion). 9
4.5 Special service conditions for mobile installations (except propulsion) . 9
5 Performance requirements. 10
5.1 Electrical requirements . 10
5.1.1 Nominal voltage . 10
5.1.2 Discharge rate . 10
5.1.3 Charge rate . 11
5.1.4 Rated battery energy (W ) . 12
r
5.1.5 Battery auxiliary energy consumption . 12
5.1.6 Energy efficiency (η) . 12
5.1.7 Long term endurance (LTE) . 13
5.2 Thermal requirements . 13
5.2.1 General . 13
5.2.2 Warm-up . 13
5.2.3 Cool-down . 14
5.2.4 Standby mode . 14
5.2.5 Idle . 14
5.2.6 Freeze-thaw . 14
6 Performance test . 14
6.1 General . 14
6.1.1 Classification of tests . 14
6.1.2 Test object selection . 14
6.1.3 DUT initial conditions before tests . 15
6.1.4 Measuring equipment . 15
6.2 List of tests . 15
6.3 Type tests . 16
6.3.1 Battery auxiliary energy consumption test . 16
6.3.2 Energy efficiency test . 17
6.3.3 Long term endurance test . 17
6.3.4 Maximum continuous discharge rate test . 18
6.3.5 Maximum transient discharge rate test . 19
6.3.6 Boost charge rate test . 19
6.4 Routine tests. 20
6.4.1 Capacity / energy content combined test . 20
6.5 Special tests . 21

IEC 62984-3:2020 © IEC:2020 – 3 –
6.5.1 Freeze-thaw cycle test . 21
7 Markings. 22
7.1 General . 22
7.2 Data plate marking . 22
8 Rules for transportation, installation and maintenance . 23
8.1 Transportation . 23
8.2 Installation . 24
8.3 Maintenance . 24
9 Documentation . 24
9.1 Instruction manual . 24
9.2 Test report . 24
(informative) Standard template for report of test results and description of
the DUT – Report of type test . 25
A.1 Example 1 . 25
A.2 Example 2 . 27
(informative) Description of the technologies . 30
B.1 Sodium-sulphur battery . 30
B.1.1 Principle and features of sodium-sulphur batteries . 30
B.1.2 Structure of the sodium-sulphur battery . 30
B.2 Sodium-nickel battery . 32
B.2.1 Principle and features of the sodium-nickel cell . 32
B.2.2 Structure of sodium-nickel cell . 33
B.2.3 Battery design . 33
Bibliography . 34

Figure 1 – Transient discharge test . 19
Figure 2 – Example of capacity test . 21
Figure 3 – Markings for sodium-based batteries . 23
Figure 4 – Example of data plate . 23
Figure B.1 – Principle of the sodium-sulphur battery . 30
Figure B.2 – Cell structure . 31
Figure B.3 – Module structure . 31
Figure B.4 – Battery structure . 32
Figure B.5 – Overall cell reaction . 32
Figure B.6 – Schematic diagram of a sodium-nickel cell . 33

Table 1 – List of symbols and abbreviated terms . 9
Table 2 – Preferred values of battery nominal voltages . 10
Table 3 – Maximum allowed energy content loss after the test . 13
Table 4 – List of tests . 16

– 4 – IEC 62984-3:2020 © IEC:2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
HIGH-TEMPERATURE SECONDARY BATTERIES –

Part 3: Sodium-based batteries –
Performance requirements and tests

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 62984-3 has been prepared by IEC technical committee 21:
Secondary cells and batteries.
The text of this International Standard is based on the following documents:
FDIS Report on voting
21/1040/FDIS 21/1048/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 read in conjunction with IEC 62984-1:2020.

IEC 62984-3:2020 © IEC:2020 – 5 –
A list of all parts in the IEC 62984 series, published under the general title High­temperature
secondary batteries, 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 web site 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.

– 6 – IEC 62984-3:2020 © IEC:2020
HIGH-TEMPERATURE SECONDARY BATTERIES –

Part 3: Sodium-based batteries –
Performance requirements and tests

1 Scope
This part of IEC 62984 specifies performance requirements and test procedures for
high-temperature batteries based on sodium for mobile and/or stationary use and whose rated
voltage does not exceed 1 500 V.
Sodium based batteries include sodium-sulphur batteries and sodium-nickel chloride batteries;
both are high-temperature batteries and use a solid, sodium conducting electrolyte. Additional
information on sodium-based batteries technology, their chemistries and construction are given
in Annex B.
This document does not cover aircraft batteries, covered by IEC 60952 (all parts), and batteries
for the propulsion of electric road vehicles, covered by IEC 61982 (all parts).
NOTE High-temperature batteries are electrochemical systems whose cells' internal minimum operating
temperature is above 100 °C.
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 62902, Secondary cells and batteries – Marking symbols for identification of their chemistry
IEC 62984-1:2020, High­temperature secondary batteries – Part 1: General requirements
IEC 62984-2:2020, High­temperature secondary batteries – Part 2: Safety requirements and
tests
3 Terms, definitions, symbols and abbreviated terms
For the purposes of this document, the terms and definitions given in IEC 62984-1 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
3.1 Battery construction
Refer to IEC 62984-1:2020, 3.1.

IEC 62984-3:2020 © IEC:2020 – 7 –
3.2 Battery functionality
The definitions of IEC 62984-1:2020, 3.2 and the following apply:
3.2.16
residual capacity
capacity remaining in a cell or battery following a discharge, operation or storage under specific
test conditions
[SOURCE: IEC 60050-482:2004, 482-03-16]
3.2.17
discharge voltage
U
d
closed circuit voltage
DEPRECATED: on load voltage
voltage between the terminals of a cell or battery when being
discharged
[SOURCE: IEC 60050-482:2004, 482-03-28, modified – Added symbol, "closed circuit voltage"
changed to an admitted term, and term entry updated editorially.]
3.2.18
end-of-discharge voltage
final voltage
cut-off voltage
end-point voltage
specified voltage of a battery at which the battery discharge is terminated
[SOURCE: IEC 60050-482:2004, 482-03-30, modified – Synonyms given as admitted terms,
and term entry updated editorially.]
3.2.19
open-circuit voltage
voltage of a cell or battery when the discharge current is zero
[SOURCE: IEC 60050-482:2004, 482-03-32, modified – Updated editorially.]
3.2.20
battery endurance
numerically defined performance of a battery during a given test simulating specified conditions
of service
[SOURCE: IEC 60050-482:2004, 482-03-44]
3.2.21
cycling
set of operations that is carried out on a secondary cell or battery and is
repeated regularly in the same sequence
Note 1 to entry: In a secondary battery these operations may consist of a sequence of a discharge followed by a
charge or a charge followed by a discharge under specified conditions. This sequence may include rest periods.
[SOURCE: IEC 60050-482:2004, 482-05-28, modified – Updated editorially.]

– 8 – IEC 62984-3:2020 © IEC:2020
3.2.22
boost charge
accelerated charge applied at greater than normal values of electric currents or of voltages (for
a particular design) during a short time interval
[SOURCE: IEC 60050-482:2004, 482-05-37]
3.2.23
constant current charge
charge during which the electric current is maintained at a constant value regardless of the
battery voltage or temperature
[SOURCE: IEC 60050-482:2004, 482-05-38]
3.2.24
two step charge
charging method applied to a secondary battery using two levels of charge rate with feedback
control to initiate the changeover from a high to a low charge rate
[SOURCE: IEC 60050-482:2004, 482-05-48]
3.2.25
constant voltage charge
charge during which the voltage is maintained at a constant value regardless of charge current
or temperature
[SOURCE: IEC 60050-482:2004, 482-05-49]
3.2.26
energy efficiency
η
ratio of the electric energy provided from a secondary battery during discharge to the electric
energy supplied to the battery during the preceding charge
[SOURCE: IEC 60050-482:2004, 482-05-53, modified – The symbol has been added.]
3.2.27
warm-up
process of activation of the cells inside a high-temperature battery by the application of heat
from the ambient temperature up to their operating temperature
3.2.28
cool-down
process of inactivation of the cells inside a high-temperature battery due to their decrease of
temperature from the operating range down to a value where all the active material is inactivated
3.2.29
freeze-thaw cycle
cycle composed of a warm-up and a subsequent cool-down of a high-temperature battery
3.3 Symbols and abbreviated terms
The list of symbols and abbreviated terms, including some of those already defined in
IEC 62984-1:2020, is given in Table 1.

IEC 62984-3:2020 © IEC:2020 – 9 –
Table 1 – List of symbols and abbreviated terms
Symbol /
abbreviated Full term Reference
term
BMS Battery management system See IEC 62984-1:2020, 3.1.19
BSS Battery support system See IEC 62984-1:2020, 3.1.20
C
Rated capacity See IEC 62984-1:2020, 3.2.2
r
DUT Device under test
I
Nominal discharge rate
dn
I
Maximum continuous discharge rate
dMAX
I
Maximum transient discharge rate
dTR
I
Charge rate See IEC 62984-1:2020, 3.2.12
t
I
Nominal charge rate
tn
LTE Long term endurance
PCS Power conversion system
SOC State of charge See IEC 62984-1:2020, 3.2.13
U
Discharge voltage See 3.2.17
d
U
Nominal voltage See 3.2.8
n
W
Rated battery energy
r
η Energy efficiency See 3.2.26

4 Environmental (service) conditions
4.1 General
Refer to IEC 62984-1:2020, 4.1.
4.2 Normal service conditions for stationary installations
Refer to IEC 62984-1:2020, 4.2.
4.3 Special service conditions for stationary installations
Refer to IEC 62984-1:2020, 4.3.
4.4 Normal service conditions for mobile installations (except propulsion)
Refer to IEC 62984-1:2020, 4.4.
4.5 Special service conditions for mobile installations (except propulsion)
Refer to IEC 62984-1:2020, 4.5.

– 10 – IEC 62984-3:2020 © IEC:2020
5 Performance requirements
5.1 Electrical requirements
5.1.1 Nominal voltage
The preferred values of nominal voltages of high-temperature sodium-based batteries are given
in Table 2.
Table 2 – Preferred values of battery nominal voltages
Voltages in Volts DC
Electrochemical technology Nominal voltage values
Na-NiCl 48 110 220 400 600
Na-S 48 110 192 640 768
5.1.2 Discharge rate
5.1.2.1 General
The discharge of a sodium-sulphur battery or a sodium-nickel chloride battery is an exothermic
reaction. The total heat generated during discharge is the sum of the exothermic reaction heat
from the electrochemical reaction and the heat from the Joule effect due to the internal
resistance of the battery. Therefore, the temperature of cells inside the module tends to rise
during discharge. Thermal related issues are therefore one of the aspects to be considered
when defining the maximum discharge ratings, together with efficiency as a function of
discharge rate.
5.1.2.2 Nominal discharge rate (I )
dn
The nominal discharge rate is defined as the continuous discharge current over the rated
discharge duration of 8 h, on which sodium-based battery specifications are based, and this
value shall be reported in the rating plate. The nominal discharge rate of sodium-based
high-temperature batteries is expressed in accordance with the following formula:
C
r
I =
dn
n
where
I is the nominal discharge rate in amperes;
dn
C is the rated capacity in ampere⋅hours;
r
n is the rated discharge time in hours = 8 h.
5.1.2.3 Maximum continuous discharge rate (I )
dMAX
The maximum continuous discharge rate is defined as the maximum continuous current at which
the rated battery capacity can be discharged without exceeding the battery temperature limits.
This value shall be declared by the manufacturer and reported in the rating plate.
The maximum continuous discharge rate (I ) may be expressed in terms of power (watts)
dMAX
instead of current (amperes).
IEC 62984-3:2020 © IEC:2020 – 11 –
5.1.2.4 Maximum transient discharge rate (I )
dTR
It may however be possible, if additionally specified by the manufacturer, to exceed the
maximum discharge rate I for a short period before reaching thermal or other limits.
dMAX
The maximum transient discharge rate I is the maximum discharge current that the battery
dTR
can withstand for a definite time starting from specified conditions.
If a maximum transient discharge rate is declared by the manufacturer it shall be marked on the
rating plate with the corresponding transient discharge time.
It is allowed that the manufacturer declares the maximum transient discharge rating in terms of
discharge power instead of discharge current.
When I is specified, the value of the transient discharge time is at least 1 min.
dTR
The manufacturer may specify additional values of maximum transient discharge rate and time,
more suited for specific applications.
5.1.3 Charge rate
5.1.3.1 Reference charge process
The charging process of sodium-based high-temperature batteries involves a moderately
endothermic reaction, which generally mostly compensates for the heat generated by ohmic
losses due to the Joule effect, so that no temperature rise results.
The limitations in the charging process are therefore mainly of electrochemical nature and are
related to the respect of the safe operating limits of the cells. This is managed by the control
algorithms implemented within the BMS.
The reference charge process is declared by the manufacturer and described in the battery
documentation. It is the charge process on which the specification of the battery is based.
In the simplest case it is a two step charge process in which the first step is a constant current
or power charge and the second step is a constant voltage or reduced current charge.
The BMS shall manage the overall charging process in order to avoid stress or damage to the
battery.
5.1.3.2 Nominal charge rate (I )
tn
The nominal charge rate is the reference charge current defined by the manufacturer and
reported on the rating plate, that is used to charge the battery during the first step phase of the
reference charge process, on which all specifications of the battery are based. The nominal
charge rate of sodium-based high-temperature batteries is expressed in accordance with the
following formula:
C
r
I =
tn
n
where
I is the nominal charge rate in amperes;
tn
C is the rated capacity in ampere⋅hours;
r
n is the rated discharge time in hours = 8 h.

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5.1.3.3 Boost charge rate
It may be possible, if additionally specified by the manufacturer, to charge sodium-based
high-temperature batteries at a higher charging current during the first charging phase.
This is called a "boost charge".
The boost charge rate is the maximum charging current value that can be used to charge the
battery during the first step of the charging process without exceeding the safe operating
conditions of the cells inside the battery.
NOTE In this case, the state of charge achieved at the end of this first boosted charging phase will be lower than
that achieved at the end of the first phase of the reference charging process.
When the boost charge rate is declared by the manufacturer, it shall be reported in the rating
plate with the associated maximum SOC achievable after the boosted charge.
5.1.4 Rated battery energy (W )
r
The rated value of battery energy (see definition in IEC 62984-1:2020, 3.2.3) is usually
expressed in W∙h and shall be declared by the manufacturer and reported on the rating plate.
Battery energy is measured in reference conditions during a discharge at constant power.
5.1.5 Battery auxiliary energy consumption
The auxiliary energy consumption includes all electrical consumptions that do not contribute to
the charging of the electrochemical cell but are necessary for the correct and safe behaviour of
the battery such as, for example (with reference to IEC 62984-1:2020, Figure 1):
– BMS/BSS power supply;
– heating or cooling of cells;
– cooling of electronic circuits;
– supply of monitoring/communication circuits which are part of the battery.
Auxiliary energy consumption depends on various factors, including charge/discharge cycles
and environmental conditions. An evaluation of typical energy consumption in reference
conditions, representative of one typical application shall be given by the manufacturer and
measured according to the test procedure given in 6.3.1.
5.1.6 Energy efficiency (η)
Energy efficiency, η, as defined in 3.2.26, is defined as the ratio between W and W , where
out in
W is the net energy discharged (i.e. the difference between discharged energy and the
out
auxiliary (BMS/BMU/BSS) energy consumption during the discharge phase), and W is the total
in
charged energy (i.e. the sum of the charged energy and the auxiliary (BMS/BMU/BSS) energy
consumption during the charge phase), according to following formula:
WW−
W
discharge aux,discharge
out
η
WW + W
in charge aux,charge
The energy efficiency of sodium-based high-temperature batteries is mainly affected by the
energy consumption of auxiliary circuits, whose major contribution is the energy spent to keep
cells within their operating temperature range.
NOTE For this reason, the energy efficiency of a sodium-based high-temperature battery is higher with short
standby periods.
==
IEC 62984-3:2020 © IEC:2020 – 13 –
To get a realistic evaluation of the energy efficiency, the standard test procedure given in 6.3.2
shall be used. This test procedure depicts a realistic application. It may not be consistent with
all of the possible applications, but it makes the test reproducible, letting users compare
batteries from different vendors with the same testing conditions.
The energy efficiency, measured according to the test procedure given in 6.3.2, shall be
declared by the manufacturer.
5.1.7 Long term endurance (LTE)
Long term endurance is the ability of a battery to retain its initial energy content over a specified
lifetime in terms of time or number of charge/discharge cycles.
A sodium-based high-temperature battery shall not decrease its energy content by more than
the values described in Table 3, where two classes of performance, LTE class 3 and LTE
class 5, are defined according to the allowed energy content loss.
Table 3 – Maximum allowed energy content loss after the test
Battery type LTE class
Energy content loss (α)
3 ≤ 3,0 %
All
5 ≤ 5,0 %
The relevant test procedure and assessment criteria for the long term endurance test are given
in 6.3.3.
5.2 Thermal requirements
5.2.1 General
Sodium-based high-temperature batteries are based on an electrochemical process that
operates correctly in a given temperature range, well above the normal ambient temperature.
As a result, the internal parts of the battery cells shall constantly be kept at the correct working
temperature to achieve the specified battery performance. Additional information on
sodium-based batteries technology, their chemistries and construction are given in Annex B.
The temperature profile during warming-up and cooling-down of active materials of a battery
(contained in the battery cells) shall carefully follow the profile specified by the manufacturer in
order to avoid cell damage or incorrect behaviour. This task is normally performed automatically
by the battery BMS without intervention by the user, however the battery is not operational until
it is within the specified internal temperature range.
The battery BMS shall automatically perform, without user intervention, the management and
control of the internal battery temperature in order to prevent the possibility of battery damage
due to human error. In particular, the BMS shall prevent battery charge or discharge outside its
internal operating temperature range. This has to be ensured also in the case of a loss of power
supply to the BMS.
The manufacturer shall declare the minimum number of freeze-thaw (warm-up and cool-down)
cycles that the battery can withstand during the whole battery lifecycle. This value shall be
reported in the battery datasheet and rating plate.
5.2.2 Warm-up
The BMS shall automatically manage the warm-up phase according to the manufacturer-
specified temperature profile. The BMS shall also prevent the user from altering the temperature
profile; this is in order to prevent battery damage and/or possible incorrect battery behaviour.

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The BMS shall prevent the battery from being charged or discharged during warm-up phase.
5.2.3 Cool-down
The BMS shall automatically manage the cool-down phase according to the manufacturer-
specified temperature profile. The BMS shall also prevent the user from manually altering the
temperature profile in order to prevent battery damage or possible incorrect battery behaviour.
The BMS shall prevent the battery from being charged or discharged during the cool-down
phase and when the battery is cool.
5.2.4 Standby mode
In standby mode, the battery is fully operational and may enter any state of charge or discharge.
The BMS shall automatically keep the internal battery temperature within the manufacturer-
specified range when the battery is in the standby mode.
5.2.5 Idle
When in this mode the battery does not exchange energy with the external circuit (e.g. it is
disconnected), so it cannot charge or discharge.
The BMS, in this mode, shall be able to (at the choice of the user) either drive the battery into
a cool-down process or make use of the stored energy to keep the battery within the operating
temperature range. In both cases the BMS shall operate fully automatically.
5.2.6 Freeze-thaw
A cycle composed of a complete cool-down and a new warm-up to the operating temperature
is also called freeze-thaw (cycle).
Sodium-based high-temperature batteries are not intended to be freeze-thaw cycled often, and
are optimized to steadily keep their internal operating temperature. This minimizes thermal
stresses. However, cooling down the battery may be necessary, for example, in case of periodic
maintenance. For this reason, the manufacturer may optionally declare the granted number of
freeze-thaw cycles that the battery can withstand during its lifetime. This is demonstrated by
the relevant test procedure described in 6.5.1.
6 Performance test
6.1 General
6.1.1 Classification of tests
Refer to IEC 62984-1:2020, 6.1.1.
6.1.2 Test object selection
6.1.2.1 Device under test (DUT) for type tests
Refer to IEC 62984-1:2020, 6.1.2.1.
6.1.2.2 DUT for routine tests
Refer to IEC 62984-1:2020, 6.1.2.2.

IEC 62984-3:2020 © IEC:2020 – 15 –
6.1.2.3 DUT for special test
Refer to IEC 62984-1:2020, 6.1.2.3.
6.1.2.4 DUT for site test
Refer to IEC 62984-1:2020, 6.1.2.4.
6.1.3 DUT initial conditions before tests
6.1.3.1 Internal temperature
Refer to IEC 62984-1:2020, 6.1.3.1.
6.1.3.2 Charge condition before tests
Refer to IEC 62984-1:2020, 6.1.3.2.
6.1.4 Measuring equipment
6.1.4.1 Voltage measurements
Refer to IEC 62984-1:2020, 6.1.4.1.
6.1.4.2 Current measurements
Refer to IEC 62984-1:2020, 6.1.4.2.
6.1.4.3 Temperature measurements
Refer to IEC 62984-1:2020, 6.1.4.3.
6.1.4.4 Humidity measurement
Refer to IEC 62984-1:2020, 6.1.4.4.
6.1.4.5 Time measurements
Refer to IEC 62984-1:2020, 6.1.4.5
6.1.4.6 Power measurements
Refer to IEC 62984-1:2020, 6.1.4.6.
6.2 List of tests
The list of tests is given in Table 4.
In order to allow long duration tests to be carried out in parallel with other tests, it is permitted
to use three different specimens for the type tests program, as outlined in Table 4.

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Table 4 – List of tests
Specimen
Category No. Test name Subclause
1 2 3
Capacity / energy content
Routine tests 1 6.4.1 X X X
combined test
Battery auxiliary energy
2 6.3.1 X
consumption test
3 Energy efficiency test 6.3.2 X
Maximum continuous discharge
4 6.3.4 X
rate test
Type tests
Maximum transient discharge
5 6.3.5 X
rate test
6 Boost charge rate test 6.3.6 X
7 Long term endurance test 6.3.3 X
Special tests 8 Freeze-thaw cycle test 6.5.1  X

The sequence of type tests is not mandatory. However, before any type test or special test
sequence, the test specimen has to be submitted to the routine test.
6.3 Type tests
6.3.1 Battery auxiliary energy consumption test
The test duration is 18 h and will result in the evaluation of the typical daily energy consumption
of auxiliary circuits.
NOTE 1 It is important to extend the test duration to 18 h because power consumption varies during charge,
discharge or standby states so it is necessary to average the measurement over a suitable time span.
Before the test, the battery shall be charged to 100 % SOC according to the charging procedure
declared by the manufacturer.
The conditions of the battery at the beginning of the test are the following:
– The battery is charged to 100 % SOC.
– The internal temperature shall be at the upper limit of the hysteresis of the temperature
control (in case of on/off control) or at the set point temperature (in case of proportional
tempe
...