IEC TS 61044:2021

IEC TS 61044 ®
Edition 1.0 2021-08
TECHNICAL
SPECIFICATION
Opportunity charging of lead-acid traction batteries
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IEC TS 61044 ®
Edition 1.0 2021-08
TECHNICAL
SPECIFICATION
Opportunity charging of lead-acid traction batteries

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.220.20; 29.220.99 ISBN 978-2-8322-1006-7

– 2 – IEC TS 61044:2021 © IEC 2021
CONTENTS
FOREWORD . 3
INTRODUCTION . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Planning the implementation of opportunity charging . 7
5 Operational procedures . 8
5.1 General . 8
5.2 Charging conditions . 8
5.3 Regular charges . 8
5.4 Ventilation. 9
5.5 Temperature . 9
5.6 Examples of discharge and charge profiles . 9
Bibliography . 12

Figure 1 – Examples of discharge and charge profiles of vented lead-acid batteries . 10
Figure 2 – Example of discharge and charge profiles of valve regulated lead-acid
batteries . 11

INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
OPPORTUNITY CHARGING OF LEAD-ACID
TRACTION BATTERIES
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
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
IEC TS 61044 has been prepared by IEC technical committee 21: Secondary cells and
batteries. It is a Technical Specification.
This first edition cancels and replaces the second edition of IEC TR 61044 published in 2002.
This edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) the recommended depth of discharge for opportunity charging has been adjusted;
b) a distinction is made between valve regulated lead-acid batteries (VRLA) and vented lead-
acid batteries.
– 4 – IEC TS 61044:2021 © IEC 2021
The text of this Technical Specification is based on the following documents:
Draft Report on voting
21/1081/DTS 21/1088/RVDTS
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 Technical Specification 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/standardsdev/publications.
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,
• replaced by a revised edition, or
• amended.
INTRODUCTION
Lead-acid traction batteries find a widespread application in industrial transportation vehicles
because of their particular properties of providing a reliable power supply source with a very
low environmental impact.
In such applications, both monitoring and power management by electronic means have made
great strides not only on the discharge side of the energy balance but during charging as well.
This progress permits refuelling, i.e., charging of a lead-acid traction battery in a well-
controlled manner during idle periods in the course of a working schedule.
As a result, the total capacity or ampere-hour output of the lead-acid battery increases per
working day substantially beyond the manufacturer's maximum recommended value.
However, such opportunity charging will provide improved capital efficiency only if adequate
precautions are taken to prevent premature deterioration of the state of the lead-acid traction
battery caused by such a practice.
This document is intended to present requirements, derived from the field experience of
battery manufacturers in general and from opportunity charging of lead-acid traction batteries
in particular, with the aim of preventing detrimental effects on batteries and industrial
equipment.
– 6 – IEC TS 61044:2021 © IEC 2021
OPPORTUNITY CHARGING OF LEAD-ACID
TRACTION BATTERIES
1 Scope
This document covers opportunity charging of lead-acid traction batteries, i.e., the use of idle
time during a working period to increase the state of charge (SoC) so as to extend the daily
working period of a lead-acid traction battery while at the same time avoiding an excessive
depth of discharge.
This document specifies requirements for the use of opportunity charging of lead-acid traction
batteries of vented and valve regulated types when the battery manufacturer has not provided
alternative specific operating procedures.
This document is only applicable for lead-acid traction batteries of vented and valve regulated
design for which the battery manufacturer has not provided specific operating procedures.
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 62485-3:2014, Safety requirements for secondary batteries and battery installations –
Part 3: Traction batteries
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
opportunity charging
use of periods of inactivity of a partially discharged battery to increase its state of charge
Note 1 to entry: Opportunity charging at a state of charge (SoC) of > 70 % is less effective and can result in a
significant increase of battery temperature and water loss.
3.2
regular charge
charge of a battery as specified by the manufacturer necessary to attain the state of maximum
storage of electric energy
3.3
self-compensating charger
device which supplies charge, monitors the state of charge, and terminates the charge of the
battery when the correct amount of electric charge has been supplied

Note 1 to entry: The control logic of the self-compensating charger will prevent overcharging if a fully charged
battery is connected to the charger.
3.4
vented lead-acid battery
secondary battery in which cells have a cover provided with an opening through which
products of electrolysis and evaporation are allowed to escape freely from the cell to the
atmosphere
[SOURCE: IEC 60050-482:2004, 482-05-14, modified – the term "vented cell" has been
replaced by "vented lead-acid battery" and the words "secondary cell having" have been
replaced by "secondary battery in which cells have".]
3.5
valve regulated lead-acid battery
VRLA
secondary battery in which cells are closed but have a valve which allows the escape of
...