Emergency lighting battery replacement

[Tom Sutton]

I am trying to find out if there is legislation for how long between emergency lighting battery replacement or is it just a case of if they work they work if they don't replace regardless of age of battery.

I received the above enquiry today and up to now I haven’t purchased the appropriate BS and still relying on the local reference library so I am unable to be confident on the reply. However could one of you could experts give me the benefit of your expertise?

[chris.]

Would need to double check, but I think both fire alarms and emergency lighting use the same rule of 4 years regardless of the current condition

[Galeon]

And central battery units with wet cells would be different.

[Richr]

I have always thought it is down to the manufactuers data sheet

[Graeme]

replace when testing dictates. Self contained fittings with Nic-cad can gave a span of a minimum 4-7 years.

[kurnal]

I usually recommend replacement when they fail on test and find that once the fittings are more than a couple of years old you can reckon on 20% replacement every year.

[Davo]

TW

A quick look in BS5266 does not reveal anything about battery life
As usual, the manufacturer is best placed to know, but if you have carried out the proper testing then 4 years seems about right, as you can only discharge recharge so many times before rechargable batteries deteriorate

hope this helps

davo

[Wiz]

The biggest problem with ni-cad batteries (most commonly used in self-contained emergency light fittings) is something called the memory effect.

The 'memory effect' is where the battery is regularly discharged by a small amount only, and then recharged. If you do this too often, when you want the battery to give a deep discharge, it won't be able to do it. It has 'memorised' how it was previously used and only expects to replicate that!

It is far better (for battery life) to give an emergency light fewer but longer tests, than many short duration tests.

Another problem is that poor quality ni-cad batteries that are subject to high temperatures are likely to have a short duration life. The high temperatures may be present in a luminaire from electrical components used in the control circuitry.

If you ever have to replace batteries in a self-contained emergency lighting fitting always use 'high-temperature' versions. Please note with cheaper quality fittings it is normally more cost-effective to replace the whole fitting than just the batteries (taking into account all costs against the fact that a new fitting has all new components which are guaranteed for at least year). I would say that if a replacement fitting will cost less than £25 then it is not worth just replacing the batteries.

In my opinion, a good quality ni-cad battery used in an emergency lighting luminaires normally has a typical life of about 5 years and depending on the factors mentioned above.

[Davo]

TW

found this on ICEL website

http://www.icel.co.uk/media/technical/ICEL1010.pdf


regards

davo

[Tom Sutton]

Thanks davo I also found that document but doesn’t answer the question on replacing batteries.

I assume if it’s a central battery system then the lead acid batteries would be subjected to a specific test and if any fail, then you would need to be replaced. For self contained units using Ni Cad batteries they would have a duration test and if they did not remain operational for the required time they would fail the test. The two most likely causes would be the charging unit or the battery and if it’s the battery then change it or follow Wiz’s advice. This full discharge would also help to eradicate the memory problem. I would think stationary lead acid batteries have quite a long life but Ni cad batteries have about 3 to 5 years.

I cannot find anywhere that recommends batteries should be replaced at a set interval therefore its all subject to test and replace when necessary.

Thanks to all of you and I am sorry if I labour the point but I do not wish to pass on duff info.

[Wiz]

Wet lead acid batteries used in emergency lighting systems generally have a very long life if properly looked after. Much depends on their quality but 10 years should be expected as a minimum and up to 30 years for top quality set. They are very cost-effective if looked after.

Unfortunately, they are rarely properly looked after and therefore often last nowhere as long as their expected life. So if you have to replace them after only a few years due to poor maintenance, they work out very expensive indeed. Far better to have do no maintenance on SLA and change them every 4 years. Obviously, you can also pay a bit more for your SLA batteries and get ones with a planned 10 year life (but no good for fire alarms where the recommendations ask for a 4 year replacement cycle no matter their condition).

The wet lead acid batteries need to have their electrolyte topped up on a regular basis and testing includes measuring the specific gtavity of the electrolyte.

The normal chemical process of the wet lead acid battery charging causes some of plate material to become detached and fall to the bottom of the battery housing. This process speeds up if the electrolyte level is too low or the battery is overcharged for some reason. these deposits will eventually become so deep they will 'short out' the bottom of the plates and ruin the battery.

Wet lead acid battery capacity can be tested using a known load of approx. C/5 to C/20 over a shortish period of time (30-60 minutes) and measuring the battery terminal voltage with this load.

[chris.]

Have to say thinking about it, i know of a site where the wet cells were installed at about 1988 in a fire alarm main battery unit - the batteries were religously looked after by the onsite maintenance untill early 2007 (so around 19 years being looked after by the clients own maintenance) always being topped up, load tested and kept terminals clean and tidy with not a single problem

A company came to service it instead in 2007, and at the end of last year, the levels were low, corrosion had taken place and 2 of them split.. Just shows how bit of care and attention makes such a big difference.   Though there is a limit to what a alarm company can do if they only attend site every 3-6 months, when the batteries sometimes need a check much more frequently.

Now they have a new battery charger with SLA batteries.. cant ever imagine those batteries working in 20 years time regardless of how much care they are given.

[Galeon]

We quoted to rip a cb unit with wet cells and didn't get the job , however we were called out to by the housing trust  a few weeks later after the company who had undercut us , had done their funky stuff.
I had to cut the battery supply first then power off the 240v as the planks had left the wet charger in and installed sla batteries.
The housing manager face turned white as I told him to stand outside in the corridor , while we shut it down.
The batteries were fit to explode , the mind boggles.
We then got the job to put it right.

[Tom Sutton]

Now they have a new battery charger with SLA batteries.. cant ever imagine those batteries working in 20 years time regardless of how much care they are given.

Five years tops or sooner according to http://www.actmeters.com/manuals/Testing%20SLA%20Batteries.pdf and check out item 14.

[Wiz]

Now they have a new battery charger with SLA batteries.. cant ever imagine those batteries working in 20 years time regardless of how much care they are given.

Five years tops or sooner according to http://www.actmeters.com/manuals/Testing%20SLA%20Batteries.pdf and check out item 14.

I'm sure ACT are only talking about the basic SLA batteries normally used in fire alarm and intruder alarm panels

There are a number of manufacturers who make a 10 year life SLA battery.Primarily intended for emergency lighting CBUs. Could be used in Fire alarms but might be automatically thrown out after four years even if they are good - Although BS 5839 part 1 recommends using batteries of a type having a life of at least four years under normal working conditions, most service engineers take this to mean that all batteries should be replaced after 4 years no matter their condition