Comparing VRLA Battery Specification Standards.
BS 6290 Part 4 1997 v IEC 60896 – 22 2004 -2
The document is intended to give the reader a better understanding of the difference between the major classifications of BS 6290 Part 4 (Lead-acid stationary cells and batteries – Part 4 Specification for classifying valve regulated types) and IEC 60896 – 22 (Stationary lead-acid batteries – Part 22: Valve regulated types – Requirements).
This document is not intended to comment on the specification classifications or make any judgement to the validity of tests or claims by manufacturers. The article is intended to draw attention to the different classifications and how the British Standard varies with the latest International Standard.
1) BS 6290 PART 4
When VRLA AGM types first became popular in the UK in the early 1980’s there was no standard covering these types. The first British Standard for VRLA AGM product was introduced in 1987. This was a fair attempt in making a comparison between VRLA AGM cells and High Performance Planté cells which dominated the UK stationary battery market at that time. However, it soon became evident that the specification did not cover many aspects that users were interested in and in some cases it was misleading. Over the following 10 years a revised Specification was drawn up and this was issued in 1997.
The 1997 version changed several requirements and introduced different classifications rather than one classification which covered many factors. It also clarified many issues including gas emission when in the overcharge float condition. Some changes to the specification were made because the 1987 version was difficult or in some cases impossible to meet without incurring considerable manufacturing cost. Some products under development at that time were intended to comply but would not because of idiosyncrasies within the specification wording. The 1997 version was a vast improvement. Significant introductions and clarifications to the Standard were; a) Safety Class, b) Performance Class, and c) Durability Class. The three classifications are discussed below.
a) Safety Class.
This is a reference to the flammability of containers, lids and covers and 3 classes are quoted i.e. FV0, FV1, and FV2. The highest level being FV0. To all intents and purposes FV0 means that the plastic will self extinguish. FV1 and FV2 are not as good as FV0 with respect to flame retardant level and may continue to burn even when the ignition source has been removed. There are 3 levels i.e. 1, 2, or 3. Product compliant with FV0 is referred to as level 1, FV1 to level 2 and FV2 to level 3.
b) Performance Class.
This is the compliance that the product has with respect to the published data. The manufacturer must state the compliance at seven different discharge rates as specified in the Standard. This section has 4 levels where the highest compliance is 1. In all cases, the product does not have to give 100% performance on the first discharge after a fully commissioning charge. In reality, this is very acceptable because although some cells may fall short of 100% compliance, in the vast majority of cases, the complete battery would easily exceed the claimed performance
c) Durability Class.
This part of the Standard refers to the life at elevated temperature and is more commonly referred to a “design Life”. However, it is not simply an accelerated test because several additional parameters are evaluated. This class has 5 levels where level 1 is the highest compliance and in terms of “design life” can be considered as 20 years. The “lowest” class is level 5 which equates to a design life of 4 years. In reality, we now know that the real life and design life are not the same and it is the view of the author of this article to consider a real life of 80% of the design life.
There are other tests within the Specification that the manufacturer must give answer to for the product tested. One of these is High Current Endurance and product is classified as “H” or “L”. Basically, the “H” indicates that the product is suitable for high current discharge applications such as switch tripping and closing or engine starting. The “L” classification signifies that the product is only suitable for low current applications such as discharge currents lower than the published 30 minute rate. The overall classification for a product having a safety class 1 with high current capability, performance class 2 and durability class 3, will have an overall classification of 1H23. A classification of 1L23 should not be considered as inferior. There are good commercial reasons for a product designed for low current applications. The product should not be considered as inferior. Similarly, product having a classification of 1L34 may still meet the specification required.
What we have to remember is that a product which is fully compliant with BS 6290 Part 4 1997 may have an overall classification of 3L45. This product has the lowest classification for flammability, it is only suitable for low current applications, the performance class could mean that when the product is assembled as a battery it may fail to meet the published performance and the design life is only rated as 4 years. However, it is a fully compliant product. Time moved on and in 2004, the IEC specification 60896 – 22 was published.
2) IEC 60896 – 22
IEC Standards are, as far as possible, an agreement for technical matters on an international basis. They are not “European Mainland” specifications and the UK organisations have a large input to the content. IEC 60896 looked very closely at BS 6290 Part 4 and has adopted many points plus additional requirements to make it more comprehensive. It does not have the same classification spectrum and as one example it refers to the Eurobat Guide for the design life which is not within the IEC 60896 Standard itself.
Making the comparison to the BS 6290 Part 4 specification, the following is applicable.
a) Safety Class.
The Eurobat document considers 4 “effective” classes whereas the BS has 3. The Eurobat refers to “standard” flammability for Vertical Flame of FV1, FV2 plus a lower specification of Horizontal Burn (HB). In addition to FV1, FV2 and HB the Eurobat Guide refers to a “High Premium flammability rating FV0”.
In conclusion: -
BS6290 Part 4: FV0, FV1 and FV2 Eurobat Guide: FV0, FV1, FV2 and HB.
b) Performance Class:
Tests carried out on a sample of 6 units as despatched from the factory must have at least 95% compliance with the rated performance. In effect, this means that every battery may fail to meet the rated performance when new. This needs to be put into perspective with the real world. We know that all lead-acid batteries will lose performance as they age. For VRLA product is it normally accepted that the end of life is when the product will not meet 80% of the rated value. Accordingly, batteries need to be oversized to allow for this end of life characteristic. It follows that if the battery can achieve 95% or more on first discharge then the installation is safe. Interestingly, it is reasonable to assume that all VRLA cell performance will increase by typically 5% during the first few years of float operation.
In conclusion: -
BS6290 Part 4: A complex list of different compliance levels at different rates. Eurobat Guide: Not less than 95% compliance at the test rates.
Note to avoid confusion: Planté batteries do not need to be oversized because they are deemed to have reached the end of life when they will not meet 100% of the published performance. They still have a real life of 25 years on float charge systems at 20°C.
c) Durability Class.
In the Eurobat Guide this is referred to as Design Life but the classifications are similar as below. Note: The BS quotes days on test before failure. The author has reclassified these to the nearest whole year to reflect years “design life”. For example, Durability Class 1 is >648 days which is corrected by multiplying by 11.36. This results in a calculated life of 7361 days i.e. 20.2 years.
In conclusion: -
BS6290 Part 4: >4 years, >8 years, >12 years, >16 years and >20 years Eurobat Guide: 3 – 5 years, 6 – 9 years, 10-12 years and 12 years and longer.
It is fair to say that neither “standard” is easy to understand. As such, the required battery specification from the user has to be clear and this must be documented to avoid confusion. It is entirely possible for the users required specification to call for every cell or monobloc to have not less than the published data on the first discharge. Under these circumstances it would be reasonable for the manufacturer to accept this after a commissioning charge, but this requirement may result in a premium price.
Many large users have their own requirements which may be a mixture of different standards. Reputable manufacturers will have no issues with this as a buying specification.
It would be irresponsible or foolhardy to simply request a battery that complies with IEC 60896 or to BS 6290 Part 4 without at qualifying the parameters as discussed above as a minimum. It has to be remembered that there are several classifications within the standards and these must be specified by the user.
Let the buyer beware and specify the requirements in detail.