prEN IEC 62660-1:2026

• Status: Not Published
• Publication Date: 02-Mar-2028
• ICS: 29.220.20 - Acid secondary cells and batteries
• ICS: 43.120 - Electric road vehicles
• Technical Committee: CLC/TC 21X - Secondary cells and batteries
• Current Stage: 4020 - Enquiry circulated - Enquiry
• Start Date: 25-Sep-2026
• Due Date: 30-Jun-2027
• Completion Date: 25-Sep-2026
• Ref Project: oSIST prEN IEC 62660-1:2026 - Secondary lithium-ion cells for the propulsion of electric road vehicles - Part 1: Performance testing

• Revises: EN IEC 62660-1:2019 - Secondary lithium-ion cells for the propulsion of electric road vehicles - Part 1: Performance testing
• Effective Date: 27-Jan-2026

SLOVENSKI STANDARD
01-november-2026
Sekundarni litij-ionski členi za pogon električnih cestnih vozil - 1. del: Preskušanje
zmogljivosti
Secondary lithium-ion cells for the propulsion of electric road vehicles - Part 1:
Performance testing
Lithium-Ionen-Sekundärzellen für den Antrieb von Elektrostraßenfahrzeugen - Teil 1:
Prüfung des Leistungsverhaltens
Eléments d'accumulateurs lithium-ion pour la propulsion des véhicules routiers
électriques - Partie 1: Essais de performance
Ta slovenski standard je istoveten z: prEN IEC 62660-1:2026
ICS:
29.220.20 Kislinski sekundarni členi in Acid secondary cells and
baterije batteries
43.120 Električna cestna vozila Electric road vehicles
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

21/1311/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 62660-1 ED3
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-09-25 2026-12-18
SUPERSEDES DOCUMENTS:
21/1281/CD, 21/1296A/CC
IEC TC 21 : SECONDARY CELLS AND BATTERIES
SECRETARIAT: SECRETARY:
France Mr Yves BOUDOU
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):

TC 69,ISO/IEC JTC 1/SC 25
ASPECTS CONCERNED:
SUBMITTED FOR CENELEC PARALLEL VOTING NOT SUBMITTED FOR CENELEC PARALLEL VOTING
Attention IEC-CENELEC parallel voting
The attention of IEC National Committees, members of
CENELEC, is drawn to the fact that this Committee Draft
for Vote (CDV) is submitted for parallel voting.
The CENELEC members are invited to vote through the
CENELEC online voting system.
This document is still under study and subject to change. It should not be used for reference purposes.
Recipients of this document are invited to submit, with their comments, notification of any relevant patent rights of
which they are aware and to provide supporting documentation.
Recipients of this document are invited to submit, with their comments, notification of any relevant “In Some
Countries” clauses to be included should this proposal proceed. Recipients are reminded that the CDV stage is
the final stage for submitting ISC clauses. (SEE AC/22/2007 OR NEW GUIDANCE DOC).

TITLE:
Secondary lithium-ion cells for the propulsion of electric road vehicles - Part 1: Performance
testing
PROPOSED STABILITY DATE: 2030
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IEC CDV 62660-1 © IEC 2026
CONTENTS
CONTENTS . 1
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Test conditions . 8
4.1 General . 8
4.2 Measuring instruments . 8
4.2.1 Range of measuring devices . 8
4.2.2 Voltage measurement . 8
4.2.3 Current measurement . 8
4.2.4 Temperature measurements . 8
4.2.5 Other measurements . 9
4.3 Tolerance . 9
4.4 Thermal stabilization . 9
5 Dimension measurement . 9
6 Mass measurement . 11
7 Electrical measurement . 11
7.1 General . 11
7.2 General charge conditions . 11
7.3 Capacity . 11
7.4 SOC adjustment . 12
7.5 Power . 12
7.5.1 General . 12
7.5.2 Test method . 12
7.5.3 Calculation of power density . 13
7.5.4 Calculation of regenerative power density. 14
7.6 Energy . 15
7.6.1 General . 15
7.6.2 Test method . 15
7.6.3 Calculation of energy density . 15
7.7 Storage test . 16
7.7.1 General . 16
7.7.2 Charge retention test . 16
7.7.3 Storage life test . 17
7.8 Cycle life test . 17
7.8.1 General . 17
7.8.2 BEV cycle test . 18
7.8.3 HEV cycle test . 22
7.9 Energy efficiency test . 25
7.9.1 General . 25
7.9.2 Common tests for BEV and HEV applications . 25
7.9.3 Test for cells of BEV application . 27
7.9.4 Energy efficiency calculation for cells of HEV application. 28
Annex A (informative) Selective test conditions . 30
IEC CDV 62660-1 © IEC 2026
Annex B (informative) Cycle life test sequence . 32
Annex C (informative) Current-voltage characteristic test . 35
C.1 General . 35
C.2 Test method . 35
Bibliography . 37

Figure 1 – Example of temperature measurement of cell . 9
Figure 2 – Examples of maximum dimensions of cell . 10
Figure 3 – Dynamic discharge profile A for BEV cycle test . 20
Figure 4 – Dynamic discharge profile B for BEV cycle test . 21
Figure 5 – Discharge-rich profile for HEV cycle test . 23
Figure 6 – Charge-rich profile for HEV cycle test . 24
Figure 7 – Typical SOC swing by combination of two profiles for HEV cycle test . 25
Figure B.1 – Test sequence of BEV cycle test . 32
Figure B.2 – Concept of BEV cycle test. 33
Figure C.1 – Test order of the current-voltage characteristic test . 36

Table 1 – Discharge conditions . 11
Table 2 – SOC and temperature condition for power test . 12
Table 3 – Dynamic discharge profile A for BEV cycle test . 19
Table 4 – Dynamic discharge profile B for BEV cycle test . 20
Table 5 – Discharge-rich profile for HEV cycle test . 23
Table 6 – Charge-rich profile for HEV cycle test . 24
Table A.1 – Capacity test conditions . 30
Table A.2 – Power test conditions . 30
Table A.3 – Cycle life test conditions . 30
Table A.4 – Conditions for energy efficiency test for BEV application . 31
Table B.1 – Test sequence of HEV cycle test . 33
Table C.1 – Charge and discharge current for the current-voltage characteristic test . 35

IEC CDV 62660-1 © IEC 2026
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Secondary lithium-ion cells for the propulsion of electric road vehicles -
Part 1: Performance testing
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 corres ponding 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) IEC draws attention to the possibility that the implementation of this document may involve
the use of (a) patent(s). IEC takes no position concerning the evidence, validity or applicability
of any claimed patent rights in respect thereof. As of the date of publication of this document,
IEC [had/had not] received notice of (a) patent(s), which may be required to implement this
document. However, implementers are cautioned that this may not represent the latest
IEC CDV 62660-1 © IEC 2026
information, which may be obtained from the patent database available at https://patents.iec.ch.
IEC shall not be held responsible for identifying any or all such patent rights.
IEC 62660-1 has been prepared by IEC technical committee 21: Secondary cells and batteries.
It is an International Standard.
This third edition cancels and replaces the first edition published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) The purpose of each test has been added.
b) The power test has been revised for clarification, and an informative part of the current -
voltage characteristic test has been moved to the new Annex C.
The text of this International Standard is based on the following documents:
Draft Report on voting
21/XX/FDIS 21/XX/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.
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 the parts in the IEC 62660 series, published under the general title Secondary
lithium-ion cells for the propulsion of electric road vehicles, 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.
IEC CDV 62660-1 © IEC 2026
INTRODUCTION
The commercialization of electric road vehicles including battery, hybrid and plug -in hybrid
electric vehicles has been accelerated in the global market, responding to the global concerns
on CO reduction and energy security. This, in turn, has led to rapidly increasing demand for
high-power and high-energy-density traction batteries. Lithium-ion batteries are estimated to be
one of the most promising secondary batteries for the propulsion of electric vehicles. In the light
of the rapid spread of hybrid electric vehicles and the emergence of battery and plug -in hybrid
electric vehicles, a standard method for testing performance requirements of lithium -ion
batteries is indispensable for securing a basic level of performance and obtaining essential data
for the design of vehicle systems and battery packs.
This document specifies performance testing for automobile traction lithium-ion cells that
basically differ from the other cells including those for portable and stationary applications
specified by other IEC standards. For automobile application, it is important to note the usage
specificity; i.e. the design diversity of automobile battery packs and systems, and specific
requirements for cells and batteries corresponding to each of such designs. Based on these
facts, the purpose of this document is to provide a basic test methodology with general
versatility, which serves a function in common primary testing of lithium-ion cells to be used in
a variety of battery systems.
This document is associated with ISO 12405-4:2018 [1] .
IEC 62660-2:2018 [2] specifies the reliability and abuse testing for lithium-ion cells for electric
vehicle application.
IEC 62660-3:2022 [3] specifies the safety requirements of lithium-ion cells for electric vehicle
application.
IEC CDV 62660-1 © IEC 2026
1 Scope
This part of IEC 62660 specifies performance and life testing of secondary lithium-ion cells used
for propulsion of electric vehicles including battery electric vehicles (BEV) and hybrid electric
vehicles (HEV).
This document specifies the test procedures to obtain the essential characteristics of lithium -
ion cells for vehicle propulsion applications regarding capacity, power density, energy density,
storage life and cycle life.
This document provides the standard test procedures and conditions for testing basic
performance characteristics of lithium-ion cells for vehicle propulsion applications, which are
indispensable for securing a basic level of performance and obtaining essen tial data on cells
for various designs of battery systems and battery packs.
NOTE 1 Based on the agreement between the cell manufacturer and the customer, specific test conditions can be
selected in addition to the conditions specified in this document. Selective test conditions are described in Annex A.
NOTE 2 The test specification for lithium-ion battery packs and systems is defined in ISO 12405-4:2018 [1].
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies.
For undated references, the latest edition of the referenced document (including any
amendments) applies.
ISO/TR 8713:2019, Electrically propelled road vehicles — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/TR 8713:2019 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 electric vehicle
BEV
electric vehicle with only a traction battery as power source for vehicle propulsion
3.2
cell block
group of cells connected together in parallel configuration with or without protective devices
(e.g. fuse or positive temperature coefficient resistor (PTC)) and not yet fitted with its final
housing, terminal arrangement or electronic control device
3.3
hybrid electric vehicle
HEV
vehicle with both a rechargeable energy storage system and a fuelled power source for
propulsion
IEC CDV 62660-1 © IEC 2026
3.4
rated capacity
C
n
capacity value of a cell in ampere hours (Ah) determined under specified conditions and
declared by the cell manufacturer
Note 1 to entry: The subscript n in C is the time base in hours (h). In this document, n = 3 for BEV application and
n
n = 1 for HEV application unless otherwise specified.
Note 2 to entry: Term and definition based on IEC 60050-482:2004, 482-03-15.
3.5
I
t
reference test current in amperes (A) which is expressed as
𝐼 =𝐶 /1
t 𝑛
Note 1 to entry: 1 has a dimension of time in hours (h).
Note 2 to entry: See IEC 61434:1996 [4], clause 2.
3.6
room temperature
temperature of 25 °C ± 2 K
3.7
secondary lithium-ion cell
cell
secondary single cell whose electric energy is derived from the insertion and extraction
reactions of lithium ions between negative electrode and positive electrode
Note 1 to entry: A secondary lithium-ion cell is a manufactured unit providing a source of electric energy by direct
conversion of chemical energy.The cell consists of electrodes, electrolyte, container, terminals, and, if any,
separators. The electrode can be monopolar or bipolar; the current collector of the former has active material of
single polarity and the latter has positive and negative electrode active materials. [The electrolyte includes an ionic
conductive liquid, or a mixture of liquid and solid.] The cell is designed to be charged electrically.
Note 2 to entry: Where the term "cell" is used alone in this document, it refers to a secondary lithium -ion cell".
3.8
state of charge
SOC
quantity of [electricity] stored in a cell expressed as a percentage of rated capacity charge
retention ability of a cell to retain capacity on open circuit under specified conditions of storage
3.9
pouch cell
cell having the shape of a parallelepiped whose faces are rectangular and with a prismatic
flexible laminate film case
3.10
prismatic cell
cell having the shape of a parallelepiped whose faces are rectangular and with a prismatic hard
case
[SOURCE: IEC 60050-482:2004, 482-02-38, modified − The word "cell" has been added to the
term, "qualifies a cell or a battery" has been replaced with "cell" in the definition, and "and with
a prismatic hard case housing" has been added.]
IEC CDV 62660-1 © IEC 2026
4 Test conditions
4.1 General
Unless otherwise stated in this document, cells shall be tested at room temperature. For the
purposes of this document, room temperature is 25 °C ± 2 K.
The details of the instrumentation used shall be provided in any report of results.
Test and measurement shall be conducted with caution to prevent a short circuit.
Cell blocks can be tested as an alternative to cells in accordance with the agreement between
the cell manufacturer and the customer.
Concerning the cell for plug-in hybrid electric vehicles (PHEV), the cell manufacturer can select
either the test condition of BEV application or of HEV application.
NOTE Test and measurement can be conducted under fixing condition recommended by the cell manufacturer.
4.2 Measuring instruments
4.2.1 Range of measuring devices
The instruments used shall enable the values of voltage, current and temperature to be
measured. The range of these instruments and measuring methods shall be chosen so as to
ensure the accuracy specified for each test.
For analogue instruments, this implies that the readings shall be taken in the last third of the
graduated scale.
Any other measuring instruments may be used provided they give an equivalent accuracy.
4.2.2 Voltage measurement
The resistance of the voltmeters used shall be at least 1 MΩ/V.
4.2.3 Current measurement
The entire assembly of ammeter, shunt and leads shall be of an accuracy class of 0,5 or better.
4.2.4 Temperature measurements
The cell temperature shall be measured by use of a surface temperature measuring device
capable of an equivalent scale definition and accuracy of calibration as specified in 4.2.1. The
temperature shall be measured at a location which most closely reflects the cell temperature.
The temperature may be measured at additional appropriate locations, if necessary.
The examples for temperature measurement are shown in Figure 1. The instructions for
temperature measurement specified by the cell manufacturer shall be followed.
IEC CDV 62660-1 © IEC 2026
Figure 1 – Example of temperature measurement of cell
4.2.5 Other measurements
Other values may be measured by use of a measuring device, provided that it complies with
4.3.
4.3 Tolerance
The overall accuracy of controlled or measured values, relative to the specified or actual values,
shall be within the following tolerances:
a) ±0,1 % for voltage;
b) ±1 % for current;
c) ±2 K for temperature;
d) ±0,1 % for time;
e) ±0,1 % for mass;
f) ±0,1 % for dimensions.
These tolerances comprise the combined accuracy of the measuring instruments, the
measurement technique used, and all other sources of error in the test procedure.
4.4 Thermal stabilization
For the stablization of cell temperature, the cell shall be soaked to a specified ambient
temperature for a minimum of 12 h. This period may be reduced if thermal stabilization is
reached. Thermal stabilization is considered to be reached if after one interval of 1 h, the
change of cell temperature is lower than 1 K.
5 Dimension measurement
The maximum dimension of the total width, thickness or diameter, and height of a cell shall be
measured at room temperature up to three significant figures in accordance with the tolerances
in 4.3.
Examples of maximum dimensions are shown in Figure 2 a) to Figure 2 f).
IEC CDV 62660-1 © IEC 2026
a) Cylindrical cell (1) b) Cylindrical cell (2)

c) Prismatic cell (1) d) Prismatic cell (2)

e) Prismatic cell with laminate film case (1) f) Prismatic cell with laminate film case (2)
Key
A total width
B total thickness
C diameter
D total height (including terminals)
E total height (excluding terminals)
Figure 2 – Examples of maximum dimensions of cell
NOTE Prismatic cells are provided with either a rigid metal case or flexible laminate film case. A prismatic cell with
laminate film case is usually called a pouch cell.
IEC CDV 62660-1 © IEC 2026
The volume of a prismatic cell is given by the product of its total height excluding terminals,
total width, and total thickness, and that of a cylindrical cell is given by the product of the cross
section of the cylinder and its total height excluding terminals.
6 Mass measurement
The mass of a cell is measured at room temperature up to three significant figures in accordance
with the tolerances in 4.3.
7 Electrical measurement
7.1 General
During each test, voltage, current and temperature shall be recorded.
Before each test, the cell temperature shall be stabilized at room temperature according to 4.4,
unless otherwise specified.
The ambient temperature shall be the room temperature unless otherwise specified.
7.2 General charge conditions
Unless otherwise stated in this document, prior to electrical measurement test, the cell shall be
charged as follows.
Prior to charging, the cell shall be discharged at room temperature at a constant current
described in Table 1 down to an end-of-discharge voltage specified by the cell manufacturer.
Then, the cell shall be charged at room temperature according to the charging method declared
by the cell manufacturer.
7.3 Capacity
The capacity of a cell shall be measured in accordance with the following phases.
Phase 1 - The cell shall be charged in accordance with 7.2.
After recharge, the cell temperature shall be stabilized in accordance with 4.4.
Phase 2 - The cell shall be discharged at specified temperature at a constant current I (A) to
t
the end-of-discharge voltage that is provided by the cell manufacturer. The discharge current
and cell temperatures indicated in Table 1 shall be used.
In addition to Table 1, specific test conditions may be selected based on the agreement between
the cell manufacturer and the customer. Selective test conditions are shown in Table A.1.
Table 1 – Discharge conditions
Cell temperature Discharge current
°C A
BEV application HEV application
1/3 I 1 I
t t
IEC CDV 62660-1 © IEC 2026
Phase 3 - Measure the discharge duration until the specified end-of-discharge voltage is
reached. Calculate the capacity of cell expressed in Ah up to three significant figures, by
multiplying the discharge current (A) with the discharge duration (h).
7.4 SOC adjustment
The test cells shall be charged as specified below, unless otherwise specified. The SOC
adjustment is the procedure to be followed for preparing cells to the various SOCs for the tests
in this document.
Phase 1 - The cell shall be charged in accordance with 7.2.
Phase 2 - The cell shall be left at rest at room temperature in accordance with 4.4.
Phase 3 - The cell shall be discharged at a constant current according to Table 1 for (100 −
n)/100 × 3 h for BEV application and (100 − n)/100 × 1 h for HEV application, where n is SOC
(%) to be adjusted for each test.
7.5 Power
7.5.1 General
This test is intended to determine the power characteristics of a cell under the representative
usage conditions of BEV and HEV applications.
Based on the current-voltage characteristic test in 7.5.2, the power density and regenerative
power density of a cell shall be calculated according to 7.5.3 and 7.5.4, respectively.
The power density and regenerative power density shall be calculated and reported for each
combination of SOC and temperature in 7.5.2.
7.5.2 Test method
The test shall be carried out in accordance with the following procedure.
a) Mass measurement
Mass of the cell shall be measured as specified in Clause 6.
b) Dimension measurement
Dimensions of the cell shall be measured as specified in Clause 5.
c) SOC and temperature adjustment
The test in 7.5.2, list item d) shall be conducted under each combination of SOC and cell
temperature at the test commencement as specified in Table 2, according to the procedure
specified by the cell manufacturer.
SOC shall be adjusted according to 7.4.
Table 2 – SOC and temperature condition for power test
SOC Cell temperature
% °C
20 25
50 −20 0 25 45
80 25
NOTE Selective test conditions are shown in Table A.2.
d) Current-voltage characteristics test
IEC CDV 62660-1 © IEC 2026
Discharge the cell for 10 s at the maximum current for discharge specified by the cell
manufacturer (I ), and measure the voltage at the end of the 10 s pulse (U ).
dmax d
Charge the cell for 10 s at the maximum current for charge specified by the cell manufacturer
(I ), and measure the voltage at the end of the 10 s pulse (U ).
cmax c
The values of I and I change depending on SOC, test temperature and charge or
dmax cmax
discharge state.
The charge and discharge limits of current and voltage at low temperature specified by the
cell manufacturer should be taken into account.
In case that I and I are not available, the value may be obtained according to the test
dmax cmax
in Annex C.
7.5.3 Calculation of power density
7.5.3.1 Power calculation
The power shall be calculated according to Formula (1) and is rounded to three significant
figures.
𝑃 =𝑈 ×𝐼 (1)
d d dmax
where
P is the power (W);
d
U is the measured voltage at the end of the 10 s pulse of I discharge (V);
d dmax
I is the maximum discharge current which is specified by the cell manufacturer (A).
dmax
If P is an estimated value, this shall be stated.
d
7.5.3.2 Power density per unit mass
Mass power density shall be calculated from Formula (2), and is rounded to three significant
figures.
𝑃
d
(2)
𝜌 =
pd
𝑚
where
ρ is the power density (W/kg);
pd
P is the power (W);
d
m is the mass of the cell (kg).
7.5.3.3 Power density per unit volume
Volumetric power density shall be calculated from Formula (3), and is rounded to three
significant figures.
𝑃
d
(3)
𝜌 =
pvlm
𝑉
IEC CDV 62660-1 © IEC 2026
where
ρ is the volumetric power density (W/l);
pvlm
P is the power (W);
d
V is the volume of the cell (l).
7.5.4 Calculation of regenerative power density
7.5.4.1 Regenerative power
Regenerative power shall be calculated according to Formula (4) and is rounded to three
significant figures.
𝑃 =𝑈 ×𝐼 (4)
c c cmax
where
P is the regenerative power (W);
c
U is the measured voltage at the end of the 10 s pulse of I charge (V);
c cmax
I is the maximum charge current specified by the cell manufacturer (A).
cmax
If P is an estimated value, this shall be stated.
c
7.5.4.2 Regenerative power density per unit mass
Regenerative power density per unit mass shall be calculated from Formula (5) and is rounded
to three significant figures.
𝑃
c
(5)
𝜌 =
pc
𝑚
where
ρ is the regenerative power density (W/kg);
pc
P is the regenerative power (W);
c
m is the mass of the cell (kg).
7.5.4.3 Regenerative power density per unit volume
Volumetric regenerative power density shall be calculated from Formula (6) and is rounded to
three significant figures.
𝑃
c
(6)
𝜌 =
pvlmc
𝑉
where
ρ is the volumetric regenerative power density (W/l);
pvlmc
P is the regenerative power (W);
c
V is the volume of the cell (l).
IEC CDV 62660-1 © IEC 2026
7.6 Energy
7.6.1 General
This test is intended to determine the energy density that can be derived from a cell under the
representative usage conditions of BEV and HEV applications.
Based on the test in 7.6.2, the energy density of a cell shall be calculated according to 7.6.3.
7.6.2 Test method
Mass energy density (Wh/kg) and volumetric energy density (Wh/l) of cells in a certain current
discharge of 1/3 I (A) for BEV application and 1  I (A) for HEV application shall be determined
t t
according to the following procedure.
a) Mass measurement
Mass of the cell shall be measured as specified in Clause 6.
b) Dimension measurement
Dimensions of the cell shall be measured as specified in Clause 5.
c) Capacity measurement
Capacity of the cell shall be determined in accordance with 7.3 at room temperature.
d) Average voltage calculation
The value of the average voltage during discharging in the above capacity test shall be
obtained by integrating the discharge voltage over time and dividing the result by the
discharge duration. The average voltage is calculated in a simple manner using th e following
method: Discharge voltages U , U , …, U are noted every 5 s from the time the discharging
1 2 n
starts and voltages that cut off the end-of-discharge voltage in less than 5 s are discarded.
The average voltage U is then calculated in a simplified manner using Formula (7) up to
avr
three significant figures by rounding off the result.
𝑈 +𝑈 +⋯+𝑈
1 2 𝑛
𝑈 = (7)
avr
𝑛
7.6.3 Calculation of energy density
7.6.3.1 Energy density per unit mass
The mass energy density shall be calculated using Formula (8) and Formula (9) up to three
significant figures by rounding off the result.
𝑊 =𝐶 𝑈 (8)
ed d avr
where
W
is the electric energy of the cell at room temperature (Wh) when discharged under
ed
specified conditions;
C
is the discharge capacity (Ah) at 1/3  I (A) for BEV or 1  I (A) for HEV;
d
t t
U
is the average voltage during discharging (V).
avr
𝑊
ed
(9)
𝜌 =
ed
𝑚
IEC CDV 62660-1 © IEC 2026
where
ρ is the mass energy density (Wh/kg);
ed
W
is the electric energy of the cell at room temperature (Wh) when discharged under
ed
specified conditions;
m
is the mass of the cell (kg).
7.6.3.2 Energy density per unit volume
The volumetric energy density shall be calculated using Formula (10) up to three significant
figures by rounding off the result.
𝑊
ed
(10)
𝜌 =
evlmd
𝑉
where
ρ is the volumetric energy density (Wh/l);
evlmd
W
is the electric energy of the cell at room temperature (Wh) when discharged under
ed
specified conditions;
V
is the volume of the cell (l).
7.7 Storage test
7.7.1 General
This test is intended to determine the capacity retaining characteristics of a cell under storage
or non-use, and is composed of the charge retention test in 7.7.2 and the storage life test in
7.7.3.
7.7.2 Charge retention test
This test is intended to determine the charge retention characteristics of a cell under storage
including transportation.
The charge retention characteristics of the cell at a 50 % SOC shall be determined according
to the following procedure.
Phase 1 - The cell shall be charged in accordance with 7.2.
Phase 2 - The cell shall be discharged to 50 % SOC in accordance with the method specified
in 7.4. Then, the cell shall be stabilized at room temperature for 1 h.
NOTE The SOC value can be changed according to the agreement between the customer and the cell manufacturer.
Phase 3 - Discharge the cell to the end-of-discharge voltage at a discharge current of 1/3  I (A)
t
for BEV application and 1  I (A) for HEV application and at room temperature. This discharge
t
capacity is C .
b
Phase 4 - Repeat phases 1 and 2 one time.
Phase 5 - The cell shall be stored for 28 days at an ambient temperature of 45 °C.
Phase 6 - After phase 5, the cell shall be stabilized at room temperature according to 4.4. Then,
discharge the cell at a constant current of 1/3  I (A) for BEV application and 1  I (A) for HEV
t t
IEC CDV 62660-1 © IEC 2026
application until the end-of-discharge voltage, and then measure the capacity of cell. This
discharge capacity is C .
r
Charge retention ratio shall be calculated according to Formula (11).
𝐶
r
𝑅= ×100 (11)
𝐶
b
where
R
is the charge retention ratio (%);
C
is the capacity of the cell after storage (Ah);
r
C
is the capacity of the cell before storage (Ah).
b
7.7.3 Storage life test
This test is intended to determine the degradation characteristics of a cell under the storage or
non-use of BEV and HEV applications.
The storage life of a cell shall be determined according to the following procedure.
Phase 1 - Determine the capacity, power density and regenerative power density of the cell in
accordance with 7.2, 7.3 and 7.5.
Phase 2 - Adjust the SOC of the cell to 100 % for BEV application, and to 50 % for HEV
application in accordance with 7.4. The cell shall then be stored for 42 days at an ambient
temperature of 45 °C.
Phase 3 - Following the storage of phase 2, the cell shall be stablized at room temperature
according to 4.4 and discharged at a constant current of 1/3  I (A) for BEV application and 1 I
t t
(A) for HEV application, down to the end-of-discharge voltage specified by the cell
manufacturer. Then, measure the capacity of the cell. This discharge capacity is the retained
capacity (Ah). The power density and regenerative power density shall also be measured.
Phase 4 - Repeat phase 2 and phase 3 for three times.
The capacity, power density, regenerative power density and retained capacity measured in
phase 1 and phase 3 shall be reported.
If the cell is stored at room temperature during the test for rest such as for test timing
adjustment, the total time of such rest shall be reported.
NOTE An ambient temperature higher than 45°C can be selected based on the agreement between the cell
manufacturer and the customer.
7.8 Cycle life test
7.8.1 General
This test is intended to determine the degradation characteristics of the cell by charge and
discharge cycles representing the normal usage conditions of BEV and HEV applications.
The cycle life performance of a cell for BEV application and HEV application shall be determined
according to the tests in 7.8.2 and 7.8.3.
The test sequence is shown in Annex B.
IEC CDV 62660-1 © IEC 2026
NOTE Selective test conditions are shown in Table A.3.
7.8.2 BEV cycle test
7.8.2.1 Measurement of initial performance
Before the charge and discharge cycle test, measure the capacity, dynamic discharge capacity,
and power as the initial performance of the cell.
– Capacity
The capacity shall be measured as specified in 7.3 at 25 °C.
– Dynamic discharge capacity C
D
The dynamic discharge capacity C shall be measured at 25 °C and 45 °C.
D
The dynamic discharge capacity is defined by the time integrated value of charge and
discharge current confirmed by the following test: Discharge the fully charged cell
repeatedly by the dynamic discharge profile A specified in Table 3 and Figure 3 until the
voltage reaches the lower limit specified by the cell manufacturer.
– Power
The power shall be measured as specified in 7.5 at 25 °C and 50 % SOC.
7.8.2.2 Charge and discharge cycle
The charge and discharge cycle test shall be performed as follows.
a) At the start of the test, cell temperature shall be 45 °C. The ambient temperature shall be
45 °C.
b) Test phases
The procedure from phase 1
...