SIST EN 60993:2003 (HD 585 S1:1991)

• Abstract:

  Applies to electrolytes and their components when used in vented nickel-cadmium cells.

• Status: Published
• Publication Date: 31-Mar-2003
• ICS: 29.220.30 - Alkaline secondary cells and batteries
• Technical Committee: ISCB - Secondary cells and batteries
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Apr-2003
• Due Date: 01-Apr-2003
• Completion Date: 01-Apr-2003
• Ref Project: EN 60993:2002 - Electrolyte for vented nickel-cadmium cells

• Replaces: SIST HD 585 S1:1997 - Electrolyte for vented nickel-cadmium cells
• Effective Date: 06-May-2014
• Referred By: SIST EN IEC 61204-7:2018 - Low-voltage switch mode power supplies - Part 7: Safety requirements (IEC 61204-7:2016)
• Effective Date: 03-Feb-2026
• Referred By: SIST EN IEC 62485-1:2018 - Safety requirements for secondary batteries and battery installations - Part 1: General safety information
• Effective Date: 03-Feb-2026

SIST EN 60993:2003 (HD 585 S1:1991) is the Slovenian standard published by SIST for electrolyte for vented nickel-cadmium cells. It specifies the composition, purity and properties of the electrolyte and of the materials used to prepare it, especially when the manufacturer has not given specific instructions. The document is meant for people preparing, checking or using electrolyte for vented nickel-cadmium cells.

What does SIST EN 60993:2003 (HD 585 S1:1991) specify?

SIST EN 60993:2003 (HD 585 S1:1991) applies to electrolytes and their components for vented nickel-cadmium cells. It covers electrolyte used for filling new cells, refilling cells when the electrolyte must be changed, and topping up with water during service when no manufacturer instructions are available.

The document is organized into clauses on scope, object, definitions, preparation, requirements for filling and replacement electrolytes, and physical and chemical requirements. It also has two informative appendices.

Annex	What it covers
Appendix A	Analytical methods and reference standards for determining impurities in potassium hydroxide
Appendix B	Relationships between electrolyte density, KOH content, temperature, and LiOH content

What are the key requirements of SIST EN 60993:2003 (HD 585 S1:1991)?

The standard focuses on keeping the electrolyte composition controlled, clean and measurable. In practice, that means checking the raw materials, preparing the electrolyte carefully, and monitoring density and carbonate during service.

• Clause 4 states that electrolyte is prepared either by diluting commercial potassium hydroxide (KOH) solution with purified water or by dissolving solid KOH in purified water. This matters because the starting materials set the quality of the finished electrolyte.
• Clause 4 also warns that solid KOH must be added to water, not the other way around, and that steel or plastic vessels, preferably polyethylene, should be used. This is a handling and safety point as well as a quality point.
• Clause 4.1 sets minimum KOH content for solid and liquid KOH and limits impurities such as zinc, copper, chloride, iron, lead, calcium, magnesium, carbonate, sodium, aluminium, sulphate, nitrate and silica. For buyers and quality staff, this is the acceptance check for the alkali used to make electrolyte.
• Clause 4.2 sets water requirements: clear and colourless appearance, pH limits, conductivity limits, total dissolved solids, and impurity limits. This matters because topping-up water directly affects electrolyte purity and cell life.
• Clause 4.3 sets the requirements for solid lithium hydroxide (LiOH) used as an additive, including minimum LiOH content and impurity limits. This is relevant when the battery maker specifies LiOH in the electrolyte.
• Clause 5 says filling and replacement electrolytes shall be clear and free from solids, and their composition and density shall follow the manufacturer’s instructions. If the electrolyte is made from solids, the water used must meet Clause 4.2, and impurity limits in Table 4 apply.
• Clause 6.1 says electrolyte density in service is influenced by carbonate build-up, gassing, state of charge, evaporation and uptake into active materials. Clause 6.2 explains that density outside the manufacturer’s values is corrected by removing electrolyte and adding water or strong electrolyte, or by changing the electrolyte completely.
• Clause 6.3 says that, if the ingredients and filling electrolyte meet the specified requirements, the user normally needs to check only density and carbonate. If the manufacturer gives no instructions, the maximum carbonate level is 75 000 mg/dm3, and the sample must be filtered before analysis.

What terms does SIST EN 60993:2003 (HD 585 S1:1991) define?

• Critical impurity - an impurity that harms cell operation and causes irreversible degradation.
• Major impurity - an impurity that reduces performance and/or cell life.
• Minor impurity - an impurity that has no effect on cell life or performance.
• Filling electrolyte - the electrolyte used to fill new vented nickel-cadmium cells before service.
• Operating electrolyte - the electrolyte in use in a cell, changed by water addition, carbon dioxide absorption and transfer of impurities from cell parts.
• Replacement electrolyte - the electrolyte used to refill cells when the operating electrolyte exceeds impurity limits.
• KOH - potassium hydroxide, the main alkaline component used to prepare the electrolyte.
• LiOH - lithium hydroxide, a possible additive used when the manufacturer specifies it.

Who uses SIST EN 60993:2003 (HD 585 S1:1991)?

SIST EN 60993:2003 (HD 585 S1:1991) is used by battery manufacturers, laboratory staff, quality control teams and users who maintain vented nickel-cadmium cells. It is relevant for electrolyte preparation, incoming inspection of KOH, water and LiOH, and for checking density and carbonate during service.

What changed in SIST EN 60993:2003 (HD 585 S1:1991) from the previous edition?

SIST EN 60993:2003 supersedes HD 585 S1:1991. The endorsement notice states that the text of IEC 60993:1989 was approved as a European Standard without modification.

Which standards are used with SIST EN 60993:2003 (HD 585 S1:1991)?

Appendix A refers to these standards for analytical work on potassium hydroxide and related reagents:

• ISO 990 - assay of potassium hydroxide for industrial use
• ISO 993 - sulphate content in potassium hydroxide
• ISO 994 - iron content in potassium hydroxide
• ISO 995 - silica content in potassium hydroxide
• ISO 1550 - sodium content in potassium hydroxide
• ISO 2466 - sampling and preparation of test solution
• ISO 2900 - carbon dioxide content in potassium hydroxide
• ISO 3177 - chloride content in potassium hydroxide
• ISO 3194 - sulphur compounds in potassium hydroxide
• ISO 3698 - calcium and magnesium contents in potassium hydroxide
• ISO 6353/1 and ISO 6353/2 - general test methods and specifications for reagents for chemical analysis

What does the SIST EN 60993:2003 (HD 585 S1:1991) document contain?

Clause 4 gives preparation guidance for electrolyte and quality limits for KOH, water and LiOH. Clause 5 covers the practical requirements for filling and replacement electrolytes, including clarity, freedom from solids and impurity limits. Clause 6 explains how density behaves in service, how to correct density outside the specified range, and how carbonate control is handled. Appendix A lists analytical methods for impurity testing, and Appendix B gives density relationships used to interpret electrolyte strength and temperature effects.

SLOVENSKI SIST EN 60993:2003 (HD 585
S1:1991)
STANDARD
april 2003
Electrolyte for vented nickel-cadmium cells
ICS 29.220.30 Referenčna številka
SIST EN 60993:2003 (HD 585
S1:1991)(en)
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

EUROPEAN STANDARD EN 60993
NORME EUROPÉENNE
EUROPÄISCHE NORM July 2002
ICS 29.220.30 Supersedes HD 585 S1:1991
English version
Electrolyte for vented nickel-cadmium cells
(IEC 60993:1989)
Electrolyte pour éléments Elektrolyt für geschlossene
ouverts au nickel-cadmium wiederaufladbare Nickel-Cadmium-Zellen
(CEI 60993:1989) (IEC 60993:1989)
This European Standard was approved by CENELEC on 2002-07-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60993:2002 E
Foreword
The text of the International Standard IEC 60993:1989, prepared by SC 21A, Secondary cells and
batteries containing alkaline or other non-acid electrolytes, of IEC TC 21, Secondary cells and
batteries, was approved by CENELEC as HD 585 S1 on 1991-02-01.
This Harmonization Document was submitted to the formal vote for conversion into a European
Standard and was approved by CENELEC as EN 60993 on 2002-07-01.
The following date was fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2003-07-01
Annexes designated "informative" are given for information only.
In this standard, annexes A and B are informative.
__________
Endorsement notice
The text of the International Standard IEC 60993:1989 was approved by CENELEC as a European
Standard without any modification.
__________
NORME
CEI
INTERNATIONALE
IEC
INTERNATIONAL
Première édition
STAN DARD
First edition
1989-07
Electrolyte pour
éléments ouverts
au nickel-cadmium
Electrolyte for vented
nickel-cadmium cells
© IEC 1989 Droits de reproduction réservés
— Copyright - all rights reserved
Aucune partie de cette publication ne peut être reproduite ni
No part of this publication may be reproduced or utilized in
utilisée sous quelque forme que ce soit et par aucun
any form or by any means, electronic or mechanical,
procédé, électronique ou mécanique, y compris la photo-
including photocopying and microfilm, without permission in
copie et les microfilms, sans l'accord écrit de l'éditeur.
writing from the publisher.
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I EC 993 © 3
CONTENTS
Page
FOREWORD 5
PREFACE 5
Clause
1. Scope 7
2. Object 7
3. Definitions 7
3.1 Classification of impurities
3.2 Filling electrolyte
3.3 Operating electrolyte
3.4 Replacement electrolyte 9
4. Preparation of the electrolyte 9
4.1 Requirements of potassium hydroxide (KOH), solid and
liquid, supplied for preparation of electrolytes 9
4.2 Requirements of water used for topping up and preparation
of electrolytes
4.3 Requirements of solid lithium hydroxide (LiOH, H 2O) used
as an additive for preparation of electrolytes 15
5. Requirements 15
for filling and replacement electrolytes
6. Physical and chemical requirements of electrolyte 17
6.1 Density of electrolyte 17
6.2 Minimum and maximum values of electrolyte densities 19
6.3 Purity of the electrolyte 19
APPENDIX A - (informative) 21
APPENDIX B - (informative) 23

993©IEC —5
INTERNATIONAL ELECTROTECHNICAL
COMMISSION
ELECTROLYTE FOR VENTED NICKEL-CADMIUM CELLS
FOREWORD
1)
The formal decisions or agreements of the IEC on technical matters,
prepared by Technical Committees on which all the National Committees
having a special interest therein are represented, express, as nearly
as possible, an international consensus of opinion on the subjects
dealt with.
2)
They have the form of recommendations for international use and they
are accepted by the National Committees in that sense.
3)
In order to promote international unification, the IEC expresses the
wish that all National Committees should adopt the text of the IEC
recommendation for their national rules in so far as national con-
ditions will permit. Any divergence between the IEC recommendation and
the corresponding national rules should, as far as possible, be clearly
indicated in the latter.
PREFACE
This standard has been prepared by Sub-Committee 21A: Alkaline secon-
dary cells and batteries, of IEC Technical Committee No. 21: Secondary
cells and batteries.
The text of this standard is based upon the following documents:
Six Months' Rule
Report on Voting
21A(CO)58
21A(CO)64
Full information on the voting for the approval of this standard can be
found in the Voting Report indicated in the above table.

993 IEC — 7 —
©
ELECTROLYTE FOR VENTED NICKEL-CADMIUM CELLS
1 Scope
This standard applies to electrolytes and their components when used
in vented nickel-cadmium cells.
These electrolytes are used:
- for filling cells supplied without filling electrolyte, and/or
-
for refilling cells if change of electrolyte is required, and/or
if the operating electrolyte needs to be topped up with water
provided no specific recommendations from the manufacturer are
available.
2. Object
The object of this standard is to define the composition, purity and
properties of electrolytes and their components for use in vented
nickel-cadmium cells and requirements for them in the absence of
specific recommendations from the manufacturer.
3. Definitions
For the purpose of this standard, the following definitions apply.
3.1 Classification of impurities
Impurities are classified according to their effect on cell life and
performance as far as the values given in the following tables are
exceeded.
-
Critical: impurities which have a detrimental effect on cell
operation and performance characteristics and which
result in an irreversible degradation of the cell;
- Major: impurities which reduce either performance character-
istics and/or life of the cell;

- Minor:
impurities which have no effect on cell life and/or
performance characteristics.
993 C©IEC
3.2 Filling electrolyte
Electrolyte used for the filling of new vented nickel-cadmium cells
prior to service.
3.3
Operating electrolyte
Electrolyte in use in vented nickel-cadmium cells. It will differ in
composition from the filling and replacement electrolyte by the addition
of water, absorption of carbon dioxide from the air and the transfer of
impurities from the internal components of the cell.
3.4 Replacement electrolyte
Electrolyte used to refill vented nickel-cadmium cells when the
operating electrolyte exceeds the impurity limits.
4. Preparation of the electrolyte
The electrolyte is prepared by dilution of a commercially available
potassium hydroxide solution of a higher concentration with purified
water or by dissolving solid potassium hydroxide in purified water.
If required, additives, for instance lithium hydroxide, should be
added according to the manufacturer's instructions.
Note.- Extreme caution should be exercised when dissolving solid
potassium hydroxide in water: considerable heat is generated
during the solution process.
It is essential that solid potassium hydroxide should always be
added to water; never add water to solid potassium hydroxide.
The inst
...