IEC TS 62257-8-1:2007

IEC/TS 62257-8-1 ®
Edition 1.0 2007-06
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for small renewable energy and hybrid systems for rural
electrification –
Part 8-1: Selection of batteries and battery management systems for stand-alone
electrification systems – Specific case of automotive flooded lead-acid batteries
available in developping countries

IEC/TS 62257-8-1:2007(E)
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IEC/TS 62257-8-1 ®
Edition 1.0 2007-06
TECHNICAL
SPECIFICATION
colour
inside
Recommendations for small renewable energy and hybrid systems for rural
electrification –
Part 8-1: Selection of batteries and battery management systems for stand-alone
electrification systems – Specific case of automotive flooded lead-acid batteries
available in developping countries

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
T
ICS 27.160; 27.180 ISBN 2-8318-9189-2

– 2 – TS 62257-8-1 © IEC:2007(E)

CONTENTS
FOREWORD.3

INTRODUCTION.5

1 Scope.6

2 Normative references .6

3 Terms and definitions .6

4 Batteries and battery management system selection .9

4.1 Batteries technical characteristics .9
4.1.1 Battery cases .9
4.1.2 Battery terminals .9
4.1.3 Electrolyte .9
4.2 Comparative tests .10
4.2.1 Evaluation of the charge and discharge current for testing (I ).10
test
4.2.2 Test 1: Battery endurance test.10
4.2.3 Test 2: Endurance test for battery+BMS .15
4.2.4 Test 3: Battery storability test .17
5 Documentation .18
6 Installation rules .19
6.1 Packing and shipping .19
6.2 Environment .19
6.3 Battery accommodation, housing.20
6.3.1 Provision against electrolyte hazard .20
6.3.2 Prevention of short circuits and protection from other effects of
electric current .21
6.3.3 Battery enclosures.21
6.4 Final inspection .22
6.5 Safety .22
6.5.1 Safety provisions .22
6.5.2 Safety Information .22
6.6 Administrative formalities .23
6.7 Recycling .23

Figure 1 – Test 1 phases .11
Figure 2 – Phase A battery endurance test .12
Figure 3 – Phase B battery endurance test .13
Figure 4 – Test 2 phases .15
Figure 5 – Phase C battery-BMS endurance test.16
Figure 6 – Test 3 phases .17
Figure 7 – Phase D storability test .18
Figure 8 – Marking for spillage prevention .19

Table 1 – Testing procedure .10
Table 2 – Evaluation of charge and discharge current (I ).10
test
Table 3 – Voltage regulation variation with temperature (examples).11

TS 62257-8-1 © IEC:2007(E) – 3 –

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY AND

HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 8-1: Selection of batteries and battery management

systems for stand-alone electrification systems –

Specific case of automotive flooded lead-acid batteries

available in developing countries

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,
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2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
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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.
The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a technical
specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC 62257-8-1, which is a technical specification, has been prepared by IEC technical
committee 82: Solar photovoltaic energy systems.

– 4 – TS 62257-8-1 © IEC:2007(E)

This document is based on IEC/PAS 62111 (1999); it cancels and replaces the relevant parts

of IEC/PAS 62111.
This part of IEC 62257 is to be used in conjunction with the IEC 62257 series.

It is also to be used with future parts of this series as and when they are published.

The text of this technical specification is based on the following documents:

Enquiry draft Report on voting

82/457/DTS 82/476/RVC
Full information on the voting for the approval of this technical specification can be found in
the report on voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• transformed into an International Standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

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 publication using a colour printer.

TS 62257-8-1 © IEC:2007(E) – 5 –

INTRODUCTION
The IEC 62257 series of documents intends to provide to different players involved in rural

electrification projects (such as project implementers, project contractors, project supervisors,

installers, etc.) documents for the setting up of renewable energy and hybrid systems with a.c.

voltage below 500 V, d.c. voltage below 750 V and power below 100 kVA.

These documents are recommendations:

• to choose the right system for the right place;

• to design the system;
• to operate and maintain the system.
These documents are focused only on rural electrification concentrating on but not specific to
developing countries. They must not be considered as all inclusive to rural electrification. The
documents try to promote the use of renewable energies in rural electrification; they do not
deal with clean mechanisms developments at this time (CO emission, carbon credit, etc.).
Further developments in this field could be introduced in future steps.
This consistent set of documents is best considered as a whole with different parts
corresponding to items for safety, sustainability of systems and at the lowest life cycle cost as
possible. One of the main objectives is to provide the minimum sufficient requirements,
relevant to the field of application that is: small renewable energy and hybrid off-grid systems.
For rural electrification project using PV systems, it is recommended to use solar batteries
defined in IEC 61427.
Nevertheless in many situations, it is a fact that most of the rural electrification projects are
implemented using locally made automotive flooded lead–acid batteries. But these products
are not designed for photovoltaic systems application. There is presently no test to
discriminate, in a panel of models of such batteries, which one could provide the best service
as close as possible to the requirement of the General Specification as a storage application
for small PV individual electrification systems (see IEC 62257-2) in an economically viable
way.
The purpose of Part 8-1 of IEC 62257 is to propose tests for automotive lead acid batteries
and batteries management systems used in small PV Individual Electrification Systems
This document and the others in the IEC 62257 series are only guidance and so cannot be
international standards. Additionally, their subject is still under technical development and so
they shall be published as Technical Specifications.

NOTE The IEC 62257 series of Technical Specifications is based on IEC/PAS 62111 (1999-07) and is developed
in accordance with the PAS procedure.

– 6 – TS 62257-8-1 © IEC:2007(E)

RECOMMENDATIONS FOR SMALL RENEWABLE ENERGY AND

HYBRID SYSTEMS FOR RURAL ELECTRIFICATION –

Part 8-1: Selection of batteries and battery management

systems for stand-alone electrification systems –

Specific case of automotive flooded lead-acid batteries

available in developing countries

1 Scope
This Technical Specification proposes simple, cheap, comparative tests in order to
discriminate easily, in a panel of automotive flooded lead-acid batteries the most acceptable
model for PV Individual Electrification Systems.
It could be particularly useful for project implementers to test in laboratories of developing
countries, the capability of locally made car or truck batteries to be used for their project.
Furthermore battery testing specifications usually need too costly and too much sophisticated
test equipment to be applied in developing countries laboratories.
The tests provided in this document allow to assess batteries performances according to the
general specification of the project (see IEC 62257-2) and batteries associated with their
Battery Management System (BMS) in a short time and with common technical means. They
can be performed locally, as close as possible to the real site operating conditions.
The document provides also regulations and installation conditions to be complied with in
order to ensure the life and proper operation of the installations as well as the safety of
people living in proximity to the installation.
This document is not a type approval standard. It is a technical specification to be used as
guidelines and does not replace any existing IEC standard on batteries.
2 Normative references
The following referenced documents are indispensable for the application 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, International Electrotechnical Vocabulary (IEV) – Part 482: Primary and
secondary cells and batteries
IEC 61427, Secondary cells and batteries for photovoltaic energy systems (PVES) – General
requirements and methods of test
IEC 62257 (all parts), Recommendations for small renewable energy and hybrid systems for
rural electrification
3 Terms and definitions
For the purposes of this document, the terms and definitions for secondary cells and batteries
given in IEC 60050-482 and the following apply.

TS 62257-8-1 © IEC:2007(E) – 7 –

3.1
electrochemical cell or battery

electrochemical system capable of storing in chemical form the electric energy received and

which can give it back by conversion

3.2
secondary cell
cell which is designed to be electrically recharged

NOTE The recharge is accomplished by way of a reversible chemical reaction.

[IEV 482-01-03]
3.3
storage battery (secondary battery)
two or more secondary cells connected together and used as a source of electric energy
3.4
lead-acid battery
storage battery in which the electrodes are made mainly from lead and the electrolyte is a
sulphuric acid solution
3.5
terminal (pole)
conductive part provided for the connection of a cell or battery to external conductors
3.6
density
commonly considered as the volumic mass, in kg / dm
NOTE Density is also defined as a dimensionless magnitude expressing the ratio of the electrolyte mass to the
water mass occupying the same volume at 4°C.
3.7
electrolyte
liquid or solid substance containing mobile ions which render it ionically conductive
NOTE The electrolyte may be liquid, solid or a gel.
[IEV 482-02-29]
3.8
dry charged battery
state of delivery of some types of secondary battery where the cells contain no electrolyte and
the plates are dry and in a charged state
[IEV 482-05-30]
3.9
self-discharge
phenomenon by which a cell or battery loses energy in other ways than by discharge into and
external circuit
[IEV 482-03-27]
3.10
observed battery capacity
quantity of electricity or electrical charge that a battery in high state of charge can deliver
under the proposed test conditions. In practice, battery capacity is expressed in Ampere-
hours(Ah)
– 8 – TS 62257-8-1 © IEC:2007(E)

3.11
nominal capacity
suitable approximate quantity of electricity, used to identify the capacity of a cell or a battery

NOTE This value is usually expressed in Ampere-hours (Ah).

3.12
rated capacity (of a cell or a battery)

quantity of electricity, declared by the manufacturer, which a cell or a battery can deliver

under specified conditions after a full charge

NOTE 1 The rated capacity shown on the battery label is given for a discharge period which depends on the
technology used in the battery.

NOTE 2 The capacity of a battery is higher when it is discharged slowly. For example, variations are in the order
of 10 % to 20 % between a capacity measured over 5 hours and a capacity measured over 100 hours.
3.13
short-circuit current
maximum current given by a battery into a circuit of a very low resistance compared with that
of the battery, under specified conditions
3.14
charge rate
electric current at which a secondary cell or battery is charged
NOTE The charge rate is expressed as the reference current I = C /n where C is the rated capacity declared by
t r r
the manufacturer and n is the time base in hours for which the rated capacity is declared.

[IEV 482-05-45]
3.15
ambient temperature
temperature of the medium in the immediate vicinity of a battery
3.16
gassing of a cell
evolution of a gas resulting from electrolysis of the water in the electrolyte of a cell
[IEV 482-05-51]
3.17
constant current charge
charge during which the electric current is maintained at a constant value regardless of the
battery voltage or temperature

[IEV 482-05-38]
3.18
initial charge
commissioning charge given to a new battery to bring it to the fully charged state
3.19
cycling (of a cell or battery)
set of operations that is carried out on a secondary cell or battery and is repeated regularly in
the same sequence
NOTE In a secondary battery these operations may consist of a sequence of a discharge followed by a charge of
a charge followed by a discharge under specified conditions. This sequence may include rest periods.
[IEV 482-05-28]
TS 62257-8-1 © IEC:2007(E) – 9 –

3.20
commissioning
final checking of installation and operation of a battery on site.

3.21
BMS
battery management system (or battery charge/discharge controller)

4 Batteries and battery management system selection

4.1 Battery technical characteristics
4.1.1 Battery cases
Battery cases shall be made of suitable materials capable of withstanding impacts and shocks
and resistant to acid.
4.1.2 Battery terminals
Terminals shall be protected against accidental short circuits. Positive and negative polarities
shall be identified.
4.1.3 Electrolyte
The electrolyte for lead acid batteries is prepared from special sulphuric acid for storage
batteries. It shall be colorless, odorless and free of all insoluble material deposits. As there is
no standard for such an electrolyte, impurity levels shall follow the battery manufacturer
requirements.
The electrolyte level checking interval varies depending on:
• the type of battery;
• the temperature;
• the use;
• the regulation algorithms of the charge controller;
• the battery age;
• the quality of distilled water;
• the PV resource.
The service interval would be determined by the above parameters and electrolyte reservoir
size which is a specification of the specific battery used. Care should be used to ensure that
the service interval is within the capability of the maintenance organization.
The batteries shall be designed in order to be able to check the electrolyte levels and to add
distilled water.
NOTE 1 Faradic water consumption for vented batteries:
when a battery reaches its fully state of charge, water electrolysis occurs according to the Faraday’s Law.
Under standard conditions:
3 3
1 Ah decomposes H O into 0,42 dm H + 0,21 dm O
2 2 2
Decomposition of 1 cm (1 g) H O requires 3 Ah
An estimation of water consumption of a battery is given by
Battery H2O (g) consumption = (X Ah charged – Y Ah discharged) × number of cells in battery / 3.

– 10 – TS 62257-8-1 © IEC:2007(E)

NOTE 2 The number of cells for a 12 V lead acid battery is 6.

4.2 Comparative tests
The proposed comparative tests are designed to discriminate the most appropriate batteries

taking in consideration the techno economic context of the project.

These comparative tests include a sequence of three tests as indicated in Table 1.

IMPORTANT: All the batteries shall be tested simultaneously in order to ensure that they are

tested in the same conditions (insulation, temperature, etc.).

Table 1 – Testing procedure
Test 2: the couple battery-BMS is selected with another
endurance test
Test 1: most durable batteries are first selected with a
battery endurance test
See 4.2.3
See 4.2.2 Test 3: in parallel to test 2, the selected batteries are
subjected to a storability test
See 4.2.4
The installation rules for batteries provided in Clause 6 are also applicable to test installations.
4.2.1 Evaluation of the charge and discharge current for testing (I )
test
Automotive lead acid batteries are typically rated at C .
The proposed test uses a C I . The C capacity of any battery may be obtained from its
10 test 10
manufacturer.
If not, Table 2 gives an assessment of the C I value for a 100 Ah C battery.
10 test 20
Table 2 – Evaluation of charge and discharge current (I )
test
Nominal Evaluation of Value of I
test
C capacity C capacity
(C × 0,1)
20 10
(Ah) (Ah)
(A)
100 87 8,7
For anot
...