prEN IEC 61951-2:2026

Sekundärzellen und -batterien mit alkalischen oder anderen nichtsäurehaltigen Elektrolyten - Tragbare wiederaufladbare gasdichte Zellen und Batterien - Teil 2: Nickel-Metallhydrid

Accumulateurs alcalins et autres accumulateurs à électrolyte non-acide - Accumulateurs étanches pour applications portables - Partie 2: Nickel-métal hydrure

Sekundarni členi in baterije z alkalnimi ali drugimi nekislinskimi elektroliti - Sekundarni zatesnjeni členi in baterije za prenosne naprave - 2. del: Nikelj-kovinski hidrid

General Information

• Status: Not Published
• Publication Date: 04-Oct-2027
• ICS: 29.220.30 - Alkaline secondary cells and batteries
• Technical Committee: CLC/TC 21X - Secondary cells and batteries
• Current Stage: 4060 - Enquiry results established and sent to TC, SR, BTTF - Enquiry
• Start Date: 05-Jun-2026
• Completion Date: 05-Jun-2026
• Ref Project: oSIST prEN IEC 61951-2:2026 - Secondary cells and batteries containing alkaline or other non acid electrolytes - Secondary sealed cells and batteries for portable applications - Part 2: Nickel-metal hydride

Relations

• Revises: EN 61951-2:2017 - Secondary cells and batteries containing alkaline or other non acid electrolytes - Secondary sealed cells and batteries for portable applications - Part 2: Nickel-metal hydride
• Effective Date: 31-Oct-2023
• Revises: EN 61951-2:2017/A1:2022 - Secondary cells and batteries containing alkaline or other non-acid electrolytes - Secondary sealed cells and batteries for portable applications - Part 2: Nickel-metal hydride
• Effective Date: 31-Oct-2023

Overview

prEN IEC 61951-2:2026 is an important international standard from CLC and IEC for secondary sealed cells and batteries containing alkaline or other non-acid electrolytes, with a specific focus on nickel-metal hydride (NiMH) cells and batteries for portable applications. These sealed rechargeable batteries are widely used in consumer electronics, power tools, electric mobility devices, and various portable equipment, owing to their balance of energy density, safety, and environmental benefits.

This standard defines requirements for the designation, marking, dimensions, performance, and safety of NiMH batteries in various configurations, including small prismatic, cylindrical, and button cells. It aims to ensure interoperability, reliability, and safety in the broad market of portable rechargeable power sources.

Key Topics

• Designation and Marking: Clear rules for naming, marking, and identifying NiMH cells and batteries, including codes for shape, performance characteristics, and special features such as high recovery or low self-discharge.
• Product Types: Covers small prismatic cells, cylindrical cells (dimensionally interchangeable with standard primary cells), and button cells.
• Dimensional Standards: Defines maximum allowable sizes for each cell type to support compatibility in device integration.
• Electrical Performance: Establishes methods for testing rated capacity, discharge performance, endurance in cycles, and charge retention under various conditions, including temperature extremes.
• Safety Requirements: Outlines essential safety considerations and test procedures to minimize risks such as overheating, leakage, or failure during charge/discharge cycles and storage.
• Compliance and Type Approval: Provides guidance on type approval and batch acceptance testing, ensuring manufacturing consistency and regulatory compliance.

Applications

Nickel-metal hydride batteries are integral to a broad range of portable electronic devices due to their rechargeable nature and reliability. Common applications addressed by this standard include:

• Consumer Electronics: Such as remote controllers, flashlights, toys, and electric toothbrushes, where standardized battery dimensions and performance support seamless device design.
• Power Tools: Including hand-held equipment and light-duty machinery requiring robust and cyclical rechargeable batteries.
• Personal Mobility Devices: Like mobility scooters and e-bikes that are not required to be registered for road use, leveraging the safety and endurance benchmarks set by this standard.
• Fixed Installations: Emergency lighting and in-vehicle accessories, where consistent battery performance ensures safety and operational continuity.

By adhering to the specifications of prEN IEC 61951-2:2026, manufacturers and designers can ensure that NiMH batteries deliver reliable energy storage, safe operation, and interchangeability across various international markets.

Related Standards

For comprehensive assurance of quality and compatibility, the following related international standards are referenced within prEN IEC 61951-2:2026:

• IEC 60086-2: Physical and electrical specifications for primary batteries, which aids in ensuring interchangeability with rechargeable versions.
• IEC 61959: Mechanical testing methods for sealed portable secondary cells and batteries.
• IEC 62133-1: Safety requirements for portable sealed secondary cells and batteries, with a focus on nickel-based rechargeable systems.
• IEC 62902: Marking symbols for batteries to identify cell chemistries.
• IEC 60050-482: Terminology and vocabulary standards for primary and secondary cells and batteries.

These standards work together to support the safe design, identification, and use of NiMH batteries across a wide spectrum of industries and applications, aligning with international quality and safety expectations.

---

Keywords: nickel-metal hydride batteries, NiMH, secondary cells, portable battery standard, battery safety requirements, battery marking, battery designation, IEC 61951-2, rechargeable battery standard, CLC battery standard, battery performance, alkaline battery standard.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2026
Sekundarni členi in baterije z alkalnimi ali drugimi nekislinskimi elektroliti -
Sekundarni zatesnjeni členi in baterije za prenosne naprave - 2. del: Nikelj-
kovinski hidrid
Secondary cells and batteries containing alkaline or other non acid electrolytes -
Secondary sealed cells and batteries for portable applications - Part 2: Nickel-metal
hydride
Sekundärzellen und -batterien mit alkalischen oder anderen nichtsäurehaltigen
Elektrolyten - Tragbare wiederaufladbare gasdichte Zellen und Batterien - Teil 2: Nickel-
Metallhydrid
Accumulateurs alcalins et autres accumulateurs à électrolyte non-acide - Accumulateurs
étanches pour applications portables - Partie 2: Nickel-métal hydrure
Ta slovenski standard je istoveten z: prEN IEC 61951-2:2026
ICS:
29.220.30 Alkalni sekundarni členi in Alkaline secondary cells and
baterije batteries
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

21A/967/CDV
COMMITTEE DRAFT FOR VOTE (CDV)
PROJECT NUMBER:
IEC 61951-2 ED5
DATE OF CIRCULATION: CLOSING DATE FOR VOTING:
2026-03-13 2026-06-05
SUPERSEDES DOCUMENTS:
21A/922/CD, 21A/951A/CC
IEC SC 21A : SECONDARY CELLS AND BATTERIES CONTAINING ALKALINE OR OTHER NON-ACID ELECTROLYTES
SECRETARIAT: SECRETARY:
France Mr Jean-Marie Bodet
OF INTEREST TO THE FOLLOWING COMMITTEES: HORIZONTAL FUNCTION(S):

TC 35
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 cells and batteries containing alkaline or other non acid electrolytes – Secondary sealed cells and
batteries for portable applications – Part 2: Nickel-metal hydride

PROPOSED STABILITY DATE: 2027
NOTE FROM TC/SC OFFICERS:
The compilation of comments has been analyzed and solved by the project team. The resolved comments have been
presented during IEC SC21A WG2 Hybrid Meeting held in Washington on 2025-10-29, approved by the members of
the WG2 and distributed to NCs.
The revised draft (clean document) for CDV is proposed to be onboarded on Online Standard Development (OSD).
electronic file, to make a copy and to print out the content for the sole purpose of preparing National Committee positions.
You may not copy or "mirror" the file or printed version of the document, or any part of it, for any other purpose without
permission in writing from IEC.

IEC CDV 61951-2 © IEC 2026
Link to Committee Draft for Vote (CDV) online document:
Click here
How to access
This link leads you to the Online Standards Development (OSD) platform for National Mirror Committee’s
(NMC) comments. The project draft may be found further down this document.

Resource materials
We recommend NCs to review the available materials to better understand the member commenting on
the OSD platform.
This includes the:
• OSD NC roles overview
• How to add and submit comments to the IEC

Contact
Should you require any assistance, please contact the IEC IT Helpdesk.
ii
IEC CDV 61951-2 © IEC 2026
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Parameter measurement tolerances . 9
5 Cell and battery designation and marking . 10
5.1 Cell and battery designation . 10
5.1.1 Small prismatic cells and cylindrical cells . 10
5.1.2 Button cells. 11
5.1.3 Batteries . 12
5.2 Cell or battery termination . 12
5.3 Marking . 12
5.3.1 Small prismatic cells and cylindrical cells . 12
5.3.2 Button cells. 13
5.3.3 Batteries . 13
5.4 Exemption of wording. 13
6 Dimensions. 13
6.1 Small prismatic cells and cylindrical cells . 13
6.1.1 General . 13
6.1.2 Small prismatic cells . 14
6.1.3 Cylindrical cells . 15
6.2 Button cells . 19
6.3 9 V type nickel-metal hydride batteries . 19
7 Electrical tests . 21
7.1 General . 21
7.2 Charging procedure for test purposes . 21
7.2.1 Charging procedure for cell. 21
7.2.2 Charging procedure for battery . 21
7.3 Discharge performance . 21
7.3.1 General . 21
7.3.2 Discharge performance at 20 °C . 22
7.3.3 Discharge performance at 0 °C . 23
7.3.4 Discharge performance for R cylindrical cells (rapid charge cells) . 24
7.4 Charge (capacity) retention . 24
7.5 Endurance . 25
7.5.1 Endurance in cycles. 25
7.5.2 Permanent charge endurance . 28
7.6 Charge acceptance at constant voltage . 32
7.7 Overcharge . 32
7.7.1 Small prismatic, L, M, H, X, LS or MS cylindrical, and button cells . 32
7.7.2 LT/LU, MT/MU or HT/HU cylindrical cells . 33
7.7.3 J cylindrical cells . 33
7.7.4 JT cylindrical cells . 33
7.7.5 R cylindrical cells (rapid charge cells) . 34
7.8 Surface temperature limitation device operation (for S cell only) . 34
IEC CDV 61951-2 © IEC 2026
7.9 Storage . 34
7.9.1 Button cells or batteries, small prismatic cells or batteries, cylindrical
cells or batteries . 34
7.9.2 High recovery type button cells or batteries, small prismatic cells or
batteries, cylindrical cells or batteries (F type) . 36
7.10 Charge acceptance at +55 °C for LT, MT or HT cylindrical cells . 37
7.11 Trickle charge acceptance for JT cylindrical cells . 38
7.12 Internal resistance . 38
7.12.1 General . 38
7.12.2 Measurement of the internal AC resistance (Impedance) . 39
7.12.3 Measurement of the internal DC resistance . 39
8 Mechanical tests . 40
9 Safety requirements . 40
10 Type approval and batch acceptance . 40
10.1 General . 40
10.2 Type approval . 40
10.2.1 Type approval for small prismatic cells and button cells . 40
10.2.2 Type approval for cylindrical cells . 43
10.2.3 Type approval for batteries . 47
10.3 Batch acceptance . 47
Bibliography . 49

Figure 1 – Jacketed cylindrical cells . 14
Figure 2 – Jacketed small prismatic cells . 14
Figure 3 – Jacketed cells dimensionally interchangeable with primary cells . 17
Figure 4 – Button cells . 19
Figure 5 – Jacketed 9 V type nickel-metal hybride batteries . 20

Table 1 – Dimensions of jacketed small prismatic cells . 15
Table 2 – Dimensions of jacketed cylindrical cells dimensionally interchangeable with
primary cells . 15
Table 3 – An example of dimensions of jacketed cylindrical cells not dimensionally
interchangeable with primary cells . 17
Table 4 – Dimensions of button cells. 19
Table 5 – Dimensions of jacketed 9 V type nickel-metal hydride batteries . 21
Table 6 – Discharge performance at 20 °C for small prismatic cells and cylindrical cells . 22
Table 7 – Discharge performance at 20 °C for button cells . 22
Table 8 – Discharge performance at 20 °C for batteries . 23
Table 9 – Rated capacity (mAh) compliance test (example) . 23
Table 10 – Discharge performance at 0 °C for small prismatic cells and cylindrical cells . 24
Table 11 – Discharge performance at 0 °C for button cells . 24
Table 12 – Endurance in cycles for small prismatic, button and cylindrical cells not
dimensionally interchangeable with primary cells . 25
Table 13 – Endurance in cycles for H or X cells . 26
Table 14 – Endurance in cycles for X cells . 26
Table 15 – Endurance in cycles for HR or XR cells . 26
IEC CDV 61951-2 © IEC 2026
Table 16 – Endurance in cycles for cylindrical cells dimensionally interchangeable with
primary cells . 27
Table 17 – Permanent charge endurance for L, M, J, H or X cells . 28
Table 18 – Permanent charge endurance for LT, MT or HT cells . 29
Table 19 – Permanent charge endurance for LU, MU or HU cells . 31
Table 20 – Overcharge for LT/LU, MT/MU, or HT/HU cylindrical cells at 0 °C . 33
Table 21 – Capacity deterioration due to storage period for cells or batteries . 36
Table 22 – Capacity deterioration due to storage period for cells or batteries (high
recovery type) . 37
Table 23 – Charge and discharge at +55 °C . 37
Table 24 – Trickle charge acceptance for JT cylindrical cells . 38
Table 25 – Constant discharge currents used for measurement of DC resistance . 40
Table 26 – Sequence of tests for type approval for small prismatic cells . 40
Table 27 – Sequence of tests for type approval for small prismatic cells (high recovery
type) . 41
Table 28 – Sequence of tests for type approval for button cells . 42
Table 29 – Sequence of tests for type approval for button cells (high recovery type) . 42
Table 30 – Sequence of tests for type approval for cylindrical cells . 43
Table 31 – Sequence of tests for type approval for cylindrical cells (high recovery type) . 44
Table 32 – Sequence of tests for type approval for cylindrical cells (Not assume
permanent charge usage) . 45
Table 33 – Sequence of tests for type approval for cylindrical cells (high recovery type
and not assume permanent charge usage) . 46
Table 34 – Sequence of tests for type approval for batteries . 47
Table 35 – Sequence of tests for type approval for batteries (high recovery type) . 47
Table 36 – Recommended test sequence for batch acceptance . 48

IEC CDV 61951-2 © IEC 2026
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
Secondary cells and batteries
containing alkaline or other non acid electrolytes –
Secondary sealed cells and batteries for portable applications –
Part 2: Nickel-metal hydride
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) 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
IEC CDV 61951-2 © IEC 2026
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
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 61951-2 has been prepared by subcommittee 21A: Secondary cells and batteries
containing alkaline or other non-acid electrolytes, of IEC technical committee 21: Secondary
cells and batteries. It is an International Standard.
This fifth edition cancels and replaces the fourth edition published in 2017 and its amendment
1 published in 2022. This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) addition of application examples as performance reference test in scope;
b) addition of manufacture period indication options;
c) revision of dimensions of jacketed cylindrical cells dimensionally interchangeable with
primary cells (ϕP: reference value);
d) revision of charge endurance test objects (7.5.2.1);
e) revision of type approval test table (10.2) which harmonized with revision of charge
endurance test objects.
The text of this International Standard is based on the following documents:
Draft Report on voting
21A/XX/FDIS 21A/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 [change
language if necessary].
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 of the IEC 61951 series can be found, under the general title Secondary cells
and batteries containing alkaline or other non-acid electrolytes - Secondary sealed cells and
batteries for portable applications, 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 61951-2 © IEC 2026
INTRODUCTION
Note from IEC: The following items were listed in the bibliography but not cited in the text.
Please find a suitable place to cite them to justify their inclusion in the bibliography:
IEC 60051 (all parts), Direct acting indicating analogue electrical measuring instruments and
their accessoriesIEC 60051 (all parts) [1]
IEC 60086 (all parts), Primary batteriesIEC 60086 (all parts) [2]
IEC 60485, Digital electronic d.c. voltmeters and d.c. electronic analogue-to-digital
convertorsIEC 60485 [3]
IEC CDV 61951-2 © IEC 2026
1 Scope
This part of IEC 61951 specifies marking, designation, dimensions, tests and requirements for
secondary sealed nickel-metal hydride small prismatic, cylindrical and button cells and batteries
which are conveniently hand-carried, suitable use for portable applications.
Examples of portable applications are remote controllers, flashlights, toys, electric toothbrush,
power tools and similar equipment.
This standard also covers portable cells and batteries for the following applications as a
performance reference standard (specific standards or regulations take precedence):
a) Fixed application: in-vehicle accessories, emergency lights and similar equipment, and
b) Personal mobility application: mobility scooters or electric bicycles that are not required to
be registered for use on the road, and similar equipment.
NOTE The cell is not limited to specific products indicated in examples, if there is agreement between supplier and
purchaser.
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 60050-482:2004, International Electrotechnical Vocabulary (IEV) - Part 482: Primary and
secondary cells and batteries
IEC 60086-2, Primary batteries - Part 2: Physical and electrical specifications
IEC 61959, Secondary cells and batteries containing alkaline or other non-acid electrolytes -
Mechanical tests for sealed portable secondary cells and batteries
IEC 62133-1, Secondary cells and batteries containing alkaline or other non-acid electrolytes -
Safety requirements for portable sealed secondary cells and for batteries made from them, for
use in portable applications - Part 1: Nickel systems
IEC 62902, Secondary cells and batteries - Marking symbols for identification of their chemistry
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-482:2004 and
the following apply.
ISO and IEC maintain terminology databases for use in standardization at the following
addresses:
– IEC Electropedia: available at https://www.electropedia.org/
– ISO Online browsing platform: available at https://www.iso.org/obp
3.1
nominal voltage
suitable approximate value of the voltage used to designate or identify a cell or a battery
Note 1 to entry: The nominal voltage of a sealed nickel-metal hydride rechargeable single cell is 1,2 V.
IEC CDV 61951-2 © IEC 2026
Note 2 to entry: The nominal voltage of a battery of n series connected cells is equal to n times the nominal voltage
of a single cell.
[SOURCE: IEC 60050-482:2004, 482-03-31, modified - Addition of Notes 1 and 2 to entry.]
3.2
rated capacity
capacity value of a cell or battery determined under specified conditions and declared by the
manufacturer
Note 1 to entry: The rated capacity is the quantity of electricity C Ah (ampere-hours) declared by the manufacturer
which a single cell can deliver during a 5 h period when charging, storing and discharging under the conditions
specified in 7.3.2.
Note 2 to entry: The capacity of a battery is the quantity of electricity C Ah (ampere-hours) declared by the
manufacturer which a battery can deliver during a 5 h period, when charged, stored and discharged under the
procedure described in 7.3.2.
[SOURCE: IEC 60050-482:2004, 482-03-15, modified - Addition of Notes 1 and 2 to entry.]
3.3
small prismatic cell
cell in the form of a rectangular parallelepiped whose width and thickness dimensions are not
more than 25 mm
3.4
cylindrical cell
cell of circular cross-section in which the overall height is equal to, or greater than the overall
diameter
3.5
button cell
cell of circular cross-section in which the overall height is less than the overall diameter
3.6
nickel-metal hydride cell
cell containing a nickel hydroxide compound for the positive electrode, a hydrogen absorbing
alloy for the negative electrode, and potassium hydroxide or other alkaline solution as
electrolyte
Note 1 to entry: Positive electrodes are isolated from negative electrodes by a separator
3.7
nickel-metal hydride battery
assembly of secondary cell(s) as a source of electrical energy characterized by its voltage, size,
terminal arrangement, capacity and rate capability
3.8
sealed cell
cell which remains closed and does not release either gas or liquid when operated within the
limits of charge and temperature specified by the manufacturer
Note 1 to entry: The cell is equipped with a safety device to prevent dangerously high internal pressure.
Note 2 to entry: The cell does not require addition to the electrolyte and is designed to operate during its life in its
original sealed state.
Note 3 to entry: The nickel-metal hydride cell, however, may release gas towards the end of its life due to the
accumulation of hydrogen in the cell.
[SOURCE: IEC 60050-482:2004, 482-05-17, modified - The existing note has been developed
into Notes 1, 2 and 3 to entry.]
IEC CDV 61951-2 © IEC 2026
3.9
surface temperature limited cell
cell which performs a function that prevents the temperature increase from a certain standard
point even at the moment of an abnormal occurrence such as short circuit of cell
3.10
high recovery type cell or battery
cell or battery which has lower "permanent capacity loss" than normal type after storage
Note 1 to entry: It is defined as "high recovery type" in 7.10.2, Table 22.
3.11
low self-discharge type cell
cell which is able to retain higher charge capacity than normal type after storage by reducing
self-discharge
Note 1 to entry: It is defined as "low self-discharge type" in 7.4.
3.12
9 V type nickel-metal hydride battery
nickel-metal hydride battery which is interchangeable with 9 V primary batteries and is
composed of cylindrical cells, small prismatic cells or button cells
3.13
trickle charge
method of charge applied to a battery wherein the state of charge is maintained by a continuous,
long term, regulated small electric current
Note 1 to entry: The trickle charge compensates self-discharge effects and maintains the battery in an
approximately fully charged state.
Note 2 to entry: The trickle charge is not suitable for cells and batteries that are designed with overcharge
protection.
Note 3 to entry: The trickle charge is performed with the cell or battery disconnected from the load.
[SOURCE: IEC 60050-482:2004, 482-05-17, modified - Replace secondary battery type not
suitable for trickle charge to cells and batteries that are designed with overcharge protection.
and add Note 3 to entry.]
4 Parameter measurement tolerances
The overall accuracy of controlled or measured values, relative to the specified or actual values,
shall be within the following tolerances:
a) ±1 % for voltage;
b) ±1 % for current;
c) ±1 % for capacity;
d) ±2 °C for temperature;
e) ±0,1 % for time;
f) ±0,1 mm for dimensions;
g) ±5 % for humidity.
These tolerances comprise the combined accuracy of the measuring instruments, the
measurement techniques used and all other sources of error in the test procedure.
The details of the instrumentation used shall be provided in each report of results.
IEC CDV 61951-2 © IEC 2026
5 Cell and battery designation and marking
5.1 Cell and battery designation
5.1.1 Small prismatic cells and cylindrical cells
5.1.1.1 General
Sealed nickel-metal hydride small prismatic rechargeable single cells and cylindrical
rechargeable single cells shall be designated according to discharge rate characteristics by a
letter L, M, J, H or X which signifies:
– low rate of discharge (L);
– medium rate of discharge (M);
– medium high rate of discharge (J);
– high rate of discharge (H);
– very high rate of discharge (X).
NOTE 1 These cells are typically but not exclusively used for the following discharge rates:
– L up to 0,5 I A;
t
– M up to 3,5 I A;
t
– J up to 5,0 I A;
t
– H up to 7,0 I A;
t
– X over 7,0 I A.
t
NOTE 2 These currents are expressed as multiples of I A, where I A = C Ah/1 h (see IEC 61434 [4]).
t t 5
When a cell is intended for permanent charge at elevated temperatures, typically higher than
40 °C, a letter "T" is placed after the letter L, M, J, H or X.
When a cell is intended for permanent charge at elevated temperatures, typically higher than
50 °C, a letter "U" is placed after the letter L, M, J, H or X.
When a cell is intended for surface temperature limitation under an abnormal situation, a letter
"S" is placed after the letter L or M.
When a cell is intended for rapid charge, typically at 1,0 I A, a letter "R" is placed after the
t
letter L, M, J, H or X.
When a cell or battery is intended as a high recovery type, a letter "F" is placed after the letter
L, M, J, H or X.
When a cell is intended as a low self-discharge cell, a letter "I" is placed after the letter L, M, J,
H or X.
5.1.1.2 Small prismatic cells
Sealed nickel-metal hydride small prismatic rechargeable single cells shall be designated by
the letters "HF" followed by a letter L, M, J, H or X, and where applicable, followed by a letter
T, U, R, F and/or I, followed by three groups of figures, each group being separated by a solidus,
as follows:
a) The two figures to the left of the first solidus shall indicate the maximum width specified for
the cell, expressed in millimetres, rounded up to the next whole number.
b) The two figures in the middle shall indicate the maximum thickness specified for the cell,
expressed in millimetres, rounded up to the next whole number.
IEC CDV 61951-2 © IEC 2026
c) The two figures to the right of the second solidus shall indicate the maximum height specified
for the cell, expressed in millimetres, rounded up to the next whole number.
EXAMPLE HFLF 18/07/49 designation identifies a small prismatic cell of low discharge rate capability, high recovery
type with a maximum width of 18 mm, a maximum thickness of 7 mm and a maximum height of 49 mm.
5.1.1.3 Cylindrical cells
Sealed nickel-metal hydride cylindrical rechargeable single cells shall be designated by the
letters "HR" followed by a letter L, M, J, H or X, and where applicable, followed by a letter T, U,
S, R, F and/or I, followed by two groups of figures, each group being separated by a solidus,
as follows:
a) The two figures to the left of the solidus shall indicate the maximum diameter specified for
the cell, expressed in millimetres, rounded up to the next whole number.
b) The two figures to the right of the solidus shall indicate the maximum height specified for
the cell, expressed in millimetres, rounded up to the next whole number.
EXAMPLE 1 HRLF 33/62 designation identifies a cylindrical cell of low discharge rate capability, high recovery type
with a maximum diameter of 33 mm and a maximum height of 61,5 mm.
EXAMPLE 2 HRLTF 33/62 designation identifies a cylindrical cell of low discharge rate capability, intended for
permanent charge at elevated temperatures, typically higher than 40 °C, high recovery type, with a maximum
diameter of 33 mm and a maximum height of 61,5 mm.
EXAMPLE 3 HRXRFI 23/43 designation identifies a cylindrical cell of very high discharge rate capability, intended
for rapid charge typically at 1,0 I A, high recovery type, low self-discharge type with a maximum diameter of 23 mm
t
and a maximum height of 43 mm.
For cells dimensionally interchangeable with primary cells, the following single or double figures
following the letter L or M, J, H or X, and where applicable, following the letter T, U, S, R, F
and/or I may indicate:
– 20- Size D;
– 14- Size C;
– 6- Size AA;
– 03- Size AAA.
NOTE Unless a discharge rate type L, M, J, H, or X is specified in the designation, cells dimensionally
interchangeable with primary cells correspond to M type
For the purpose of this explanation, an example is given below.
EXAMPLE 4 HRMRFI03 designation identifies a sealed nickel-metal hydride cylindrical rechargeable single cell, of
medium discharge rate capability, also intended for rapid charge typically at 1,0 I A, high recovery type and low self-
t
discharge type, dimensionally interchangeable with primary cell and whose type designation is AAA.
When a manufacturer designs a cell with dimensions and tolerances which make it
interchangeable with a primary cell, the designations in Table 2 shall also be marked on the
cell.
5.1.2 Button cells
Sealed nickel-metal hydride button rechargeable single cells shall be designated by the letters
"HB" followed by, if designated, letter F and/or letter I, followed by two groups of figures, each
group being separated by a solidus, as follows:
a) The three figures to the left of the solidus shall indicate the maximum diameter specified for
the cell, expressed in tenths of millimetres, rounded up to the next whole number.
b) The three figures to the right of the solidus shall indicate the maximum height specified for
the cell, expressed in tenths of millimetres, rounded up to the next whole number.
EXAMPLE HBFI 116/054 designation identifies a button cell, intended as a high recovery type, low self -discharge
type, with a maximum diameter of 11,6 mm and a maximum height of 5,4 mm.
IEC CDV 61951-2 © IEC 2026
5.1.3 Batteries
Sealed nickel-metal hydride rechargeable batteries shall be designated with the following form:
𝑁1 𝑠𝑖𝑛𝑔𝑙𝑒𝑐𝑒𝑙𝑙𝑑𝑒𝑠𝑖𝑔𝑛𝑎𝑡𝑖𝑜𝑛−𝑁2 (1)
where
N1 is the number of series connected cells greater than or equal to 2 in the battery;
N2 is the number of parallel connected cells greater than or equal to 2 in the battery.
N1 and/or N2 is not shown if its value is 1.
Sealed nickel-metal hydride battery designation will be identified based on single cells within
the series and not the battery as a whole.
– Small prismatic cells in battery
EXAMPLE 1 2HFLF 18/07/49 designation identifies a small prismatic cell of low discharge rate capability, high
recovery type with a maximum width of 18 mm, a maximum thickness of 7 mm and a maximum height of 49 mm with
two series connected cells.
– Cylindrical cells in battery
EXAMPLE 2 3HRLF 33/62 designation identifies a cylindrical cell of low discharge rate capability, high recovery
type with a maximum diameter of 33 mm and a maximum height of 61,5 mm with three series connected cells.
EXAMPLE 3 4HRLTF 33/62 designation identifies a cylindrical cell of low discharge rate capability, intended for
permanent charge at elevated temperatures, typically higher than 40 °C, high recovery type, with a maximum
diameter of 33 mm and a maximum height of 61,5 mm with four series connected cells.
EXAMPLE 4 HRXRFI 23/43 -2 designation identifies a cylindrical cell of very high discharge rate capability, intended
for rapid charge typically at 1.0 I A, high recovery type, low self-discharge type with a maximum diameter of 23 mm
t
and a maximum height of 43 mm with two parallel connected cells.
– Cells interchangeable with primary cells in batteries
EXAMPLE 5 HRMRFI03-3 designation identifies a sealed nickel-metal hydride cylindrical rechargeable single cell,
of medium discharge rate capability, also intended for rapid charge typically at 1.0 I A, high recovery type and low
t
self-discharge type, dimensionally interchangeable with primary cell whose type designation is AAA with three
parallel connected cells.
– Button cells in battery
EXAMPLE 6 HB 116/054-3 designation identifies a button cell, with a maximum diameter of 11,6 mm and a maximum
height of 5,4 mm with three parallel connected cells.
5.2 Cell or battery termination
This standard does not specify cell or battery termination.
5.3 Marking
5.3.1 Small prismatic cells and cylindrical cells
Each jacketed cell supplied without connections shall carry durable markings giving the
following minimum information:
– sealed rechargeable nickel-metal hydride, nickel-metal hydride or Ni-MH;
– rated capacity;
– nominal voltage;
– polarity (+ and -);
– date of manufacture (which may be in code);
IEC CDV 61951-2 © IEC 2026
– name, identification or registered trademark of manufacturer or supplier;
– mark for promoting useful use of cell resources.
NOTE 1 This mark is applied where a recycling programme is available.
NOTE 2 In general, sealed nickel-cadmium rechargeable single cells with connection tabs need no labels if they
form an integral part of a battery, in which case, the battery itself is marked with the above information.
NOTE 3 If manufacturer and purchaser agree to omit date indication from date of manufacture, they can indicate
year and month or week of manufacture on the cell. The method of indicating the manufacturing period may be
determined by the agreement. The first date rule of month or week is based on ISO 8601.
5.3.2 Button cells
Each button cell supplied without connection shall carry durable markings giving the following
minimum information:
– designation as specified in 5.1;
– polarity (+ and -);
– date of manufacture (which may be in code);
– name, identification or registered trademark of manufacturer or supplier.
NOTE If manufacturer and purchaser agree to omit date indication from date of manufacture, they can indicate year
and month or week of manufacture on the cell. The method of indicating the manufacturing period may be determined
by the agreement. The first date rule of month or week is based on ISO 8601.
5.3.3 Batteries
Each battery shall carry durable markings giving the following minimum information:
– sealed rechargeable nickel-metal hydride battery, nickel-metal hydride battery, or Ni-MH;
– rated capacity;
– nominal voltage;
– date of manufacture (which may be in code);
– marking symbols (identification of the chemistry according to IEC 62902).
NOTE If manufacturer and purchaser agree to omit date indication from date of manufacture, they can indicate year
and month or week of manufacture on the battery. The method of indicating the manufacturing period may be
determined by the agreement. The first date rule of month or week is based on ISO 8601.
5.4 Exemption of wording
Each cell or battery shall include minimum information on the label as specified in 5.3.1 to 5.3.3.
Therefore, additional information such as safety cautions should be included in the form of a
manual not on the cell or battery label.
In addition, cells or batteries encased in soft or hard plastic with the safety cautions printed on
the outside, should not include caution details on the cell or battery label.
6 Dimensions
6.1 Small prismatic cells and cylindrical cells
6.1.1 General
Figure 1 and Figure 2 show the shape of the jacketed cells.
IEC CDV 61951-2 © IEC 2026
Figure 1 – Jacketed cylindrical cells

Figure 2 – Jacketed small prismatic cells
6.1.2 Small prismatic cells
Table 1 shows the dimensions for jacketed small prismatic cells.
IEC CDV 61951-2 © IEC 2026
Table 1 – Dimensions o
...