IEC TR 61431:2020

IEC TR 61431 ®
Edition 2.0 2020-09
TECHNICAL
REPORT
Guidelines for the use of monitor systems for lead-acid traction batteries

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IEC TR 61431 ®
Edition 2.0 2020-09
TECHNICAL
REPORT
Guidelines for the use of monitor systems for lead-acid traction batteries

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 29.220.20 ISBN 978-2-8322-8854-2

– 2 – IEC TR 61431:2020  IEC 2020
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Desirable characteristics and features . 6
4.1 General . 6
4.2 Physical location of the monitoring device . 6
4.3 State of charge indication or "fuel gauge" . 7
4.4 Battery temperature information . 7
4.5 High battery temperature warning . 7
4.6 Low temperature warning . 7
4.7 Electrolyte level indication . 7
4.8 Electrolyte level maintenance log . 7
4.9 Uniformity of cell properties in a battery . 8
4.10 Battery commissioning date . 8
4.11 Battery configuration . 8
5 Evaluation and analysis . 8
5.1 State of charge indication or "fuel gauge" . 8
5.2 Battery temperature information . 8
5.3 Water consumption . 9
5.4 Uniformity of cell properties . 10
5.5 Electrolyte density . 10
5.6 Capacity throughput . 11
5.7 Battery age . 11
5.8 Battery data sheet . 11
5.9 Communication interfaces . 12
5.10 Ground faults . 12
5.11 Human factors . 12
6 Data monitoring – Recommended list of parameters to be monitored . 13
7 Analysis and evaluation of gathered battery data . 14
7.1 Data flow . 14
7.2 Prediction of residual operational life . 14
Annex A (informative) Example determination of the residual service life of lead-acid
traction batteries . 15
A.1 General . 15
A.2 Lost capacity due to stress factors . 15
A.2.1 Evaluation of the impact of a deep discharge . 15
A.2.2 Evaluation of impact of the battery temperature . 16
A.2.3 Evaluation of the impact of very high discharge currents. 17
A.2.4 Evaluation of the impact of the battery being in idle state . 17
A.2.5 Calculation of the residual capacity. 17
A.2.6 Residual number of cycles . 18

Figure 1 – Potential data flow in a monitor system . 14
Figure A.1 – Example of interrelation between discharge voltages and discharge
currents indicating a deep discharge condition . 16

Table 1 – Residence times and related temperature ranges . 9
Table 2 – Temperature warning levels . 9
Table 3 – Units and value resolution of measured characteristics . 13
Table A.1 – Derating factor due to ageing on standby and idling . 17

– 4 – IEC TR 61431:2020  IEC 2020
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
GUIDELINES FOR THE USE OF MONITOR SYSTEMS
FOR 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
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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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. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC TR 61431, which is a Technical Report, has been prepared by IEC technical
committee 21: Secondary cells and batteries.
This second edition cancels and replaces the first edition, published in 1995. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) The guidelines have been streamlined in terms of technical content and focussed for
automatic monitoring systems.
The text of this Technical Report is based on the following documents:
Enquiry draft Report on voting
21/1044/DTR 21/1053A/RVDTR
Full information on the voting for the approval of this Technical Report can be found in the
report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
– 6 – IEC TR 61431:2020  IEC 2020
GUIDELINES FOR THE USE OF MONITOR SYSTEMS
FOR LEAD-ACID TRACTION BATTERIES

1 Scope
This document is an informative document relating to aspects of automatic monitor systems
as utilized in lead-acid traction battery applications. It lists the characteristics and features
that need to be monitored and evaluated to properly assess the operative status of a traction
battery. Guidance concerning the accuracy and reliability of the generated information is also
provided.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
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
4 Desirable characteristics and features
4.1 General
This Clause 4 lists relevant characteristics and features, which, if measured or implemented,
would contribute information towards the assessment of the operational condition of a lead
acid traction battery. The characteristics are not listed in any order of priority.
The battery monitor system (BMOS) described in this document is a device solely collecting
and reporting data and should not be confused with a battery management system (BMS)
actively controlling the battery.
4.2 Physical location of the monitoring device
The device may be installed in one of the following locations:
a) directly on the battery,
b) on the charger,
c) on the vehicle.
Location a) is the preferred option as it provides continuous and continued monitoring. Option
b) and c) require additional methods to properly identify which battery is currently being
monitored. This requires a unique battery ID to be made available for battery recognition.
Such an ID could be stored for example on an RFID tag, a 2D QR code, NFC device or similar
information depositories.
If the device is directly integrated into the battery, the unique battery ID can be stored in the
device itself and the above-mentioned methods of battery identification are not needed.
4.3 State of charge indication or "fuel gauge"
The precise knowledge of the state of charge or driving range capability is a key functionality
of a monitor system. The device should allow these values to be displayed in a fuel gauge
manner with an acceptable error tolerance and without the necessity to undertake a capacity
test. Low state of charge or driving range should be indicated by an alarm signal.
4.4 Battery temperature information
Battery temperature is a crucial measuring parameter. The location of the temperature probe
should be selected so as to measure the electrolyte temperature of the hottest cell of the
battery.
When the battery is powering equipment operated for example in cold storage warehouses,
the probe should be preferably located at the coolest cell of the battery.
The actual value and its integration over service time are essential to predict discharge
capacities, adjust recharge conditions and predict battery lifetime.
4.5 High battery temperature warning
Temperatures in excess of 60 °C over a period of several hours can cause rapid degradation
of the battery. In batteries with valve regulated cells, such temperature levels may cause a
thermal runaway within a few hours leading to copious gas evolution and ultimate destruction
of the cells. A specific high temperature warning signal should be generated by the monitor
system to alert the operator.
4.6 Low temperature warning
Storage temperatures below −5 °C may cause electrolyte freezing in a discharged battery.
The monitor system should generate an adequate warning signal for information purposes
only.
4.7 Electrolyte level indication
In vented cells the correct filling level of the electrolyte is crucial to achieve service life. This
requires a periodic topping up of the electrolyte level with deionized or distilled water. The
actual electrolyte level is generally displayed visually on each cell with a floating device
integrated in the vent or watering plug. The electrolyte level of a selected cell, i.e. the pilot
cell, can be also transmitted via appropriate electrical circuits to the monitor system. Low
electrolyte levels should trigger a warning signal calling for inspection and, if confirmed, for
addition of water. It is however recommended that an additional visual inspection be carried
out periodically as floating level sensors may get stuck, erroneously indicating an adequate
filling level or causing an overfilling.
4.8 Electrolyte level maintenance log
The frequency of water additions and quantities needed increase as the vented battery ages.
Operating conditions and/or latent defects may further increase the need for maintenance.
The date of electrolyte level adjustments and, if accessible, the quantity of re-filled water
should therefore be recorded in a maintenance records section of the monitor system. This is
of particular relevance if an automatic watering system controlled by the charger is used. This
generally requires the monitoring system to be located in the charger or to be able to
communicate with the charger.
– 8 – IEC TR 61431:2020  IEC 2020
4.9 Uniformity of cell properties in a battery
A traction battery is an assembly of multiple 2 V single cells or 4 V, 6 V, or 12 V monoblocs.
The status of each individual cell contributes to the energy delivery capability, charge
acceptance and service life expectancy of the battery itself. Ideally the voltage of each cell of
the battery should be monitored continuously to detect present or developing anomalies.
These voltages should be measured and recorded, for example, at 1 min intervals and with a
10 mV resolution and displayed in such a way that absolute voltage levels, or the deviation
from the average cell voltage are displayed in a colour graduated way (green to orange to red
to blinking red) according to defined deviations or absolute values. This display should
replicate the layout of the cells in the battery so that the operator can by guided properly to
carry out further inspections or correlate cell property values with the location of local heat
sources, loose connectors, etc.
4.10 Battery commissioning date
In order to properly correlate and gauge the monitored battery characteristics and features,
the date of first use or commissioning should be made available to the monitor system and
embedded in the most appropriate way in the battery identification tag as per 4.2.
4.11 Battery configuration
In this document, and in particular in 5.4, it is assumed that the battery is configured by
connecting cells, monoblocs and batteries in series only and not in parallel.
5 Evaluation and analysis
5.1 State of charge indication or "fuel gauge"
The state of charge or SoC of a battery refers to the number of ampere hours discharged in
relation to a reference capacity value. This reference value may be the 5-hour rated capacity
value as declared by the manufacturer. However, this calculated value represents only a
simple "ampere hour" accounting-based state-of-charge (SoC) value, i.e.
= C − Q (Ah)
Q
est N dis
where
Q is the capacity estimated to be available for further discharge expressed in ampere
est
hours;
C is the rated capacity expressed in ampere hours;
N
Q is the capacity discharged expressed in ampere hours.
dis
This is a very simplified approach as the actual battery capacity may no longer relate to the
rated capacity value due to insufficient charging, ageing, te
...