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HarrisTweed  
#1 Posted : 12 May 2019 02:55:01(UTC)
Rank: New forum user
HarrisTweed

I’m new to the forum so apologies if my post is not posted in the right place.

I work in a low risk small office (25 people) and feel 3 hour discharge is excessive.

Few points
- it would take no more than 30mins to exit.
- surely discharging the full 3 hours and then having to wait 24 hours for the battery to recharge is not practical
- running 1 hour tests would be more practical for my environment?
- can I have a Risk Assessment that documents the need for 3 hours excessive?


Can anyone give me some pointers?

Thanks
Jason
Messey  
#2 Posted : 12 May 2019 17:40:16(UTC)
Rank: Forum user
Messey

Jason, you are right: it seems ludicrous to require a 3 hour battery test when the building can be evacuated in minutes.

But the 3 hour test is all to do with maintaining battery life and nothing to do with evacuation times. 

I am not a battery expert, but my understanding is that modern batteries can lose duration if they are not almost completely discharged regularly - in this case annually 

So discharging a standard 3-hour EL battery for 1 hour obviously only completes a 33% discharge nowhere near enough to maintain the batteries resilience.  Over the the maximum duration of the battery will diminish to dangerous levels. Lets not forget here, these are critical bits of the building’s infrastructure so need to be pretty damn resilient 

I am sure this more knowledgable about batteries will come on here and provide more details or maybe perhaps argue against my understanding. 

But like you, I always question everything and to be told “BS 5266 says you must” isn't enough. The battery life rationale was what I was told by a very experienced engineer, so its good enough for me!

By the way, if you program the annual test for Fridays, the EL batteries will have the weekend to charge up - assuming your operation is usual office hours

thanks 2 users thanked Messey for this useful post.
SNS on 12/05/2019(UTC), HarrisTweed on 01/07/2019(UTC)
andrewjb1  
#3 Posted : 13 May 2019 11:59:28(UTC)
Rank: Forum user
andrewjb1

When i have looked into it before, some of the older emergency lights had a shorter battery life and the manuafacurer only recomend a one hour test so it can come down to what the manufacturer recomends. 

Even if there is no sleeping / residential on site the emergency lights may be needed for longer as they may be needed for searching the building and to allow for recharging as menstioned in 'Messey's' post.

thanks 1 user thanked andrewjb1 for this useful post.
HarrisTweed on 01/07/2019(UTC)
Hsquared14  
#4 Posted : 13 May 2019 12:23:03(UTC)
Rank: Super forum user
Hsquared14

Messey has pretty well stolen my thunder on that question.  So I will just confirm his main points:

  • Evacuation time is nothing to do with it
  • Battery discharge test is a requirement of British Standards for EL installations
  • Discharge periods depend on the type of system and type of battery but a good rule of thumb is that your emergency lighting should give you 3 hours of light with an absolute minimum of 1 hour for evacuation
  • EML kicks in when the main lights fail not just in a fire or in other situations where you might need to evacuate
  • Batteries recharge by a trickle charge from the mains so you don't have to wait 24 hours for it to recharge ie you don't have to stay out of the building until the batteries have recharged.   Partial charging will give you enough time coverage (1hr) for evacuation.  But if it bothers you then do it on Friday afternoon or Saturday morning then it has the weekend to recharge and of course the standard says that it should be done while the building is unoccupied so that will work out quite well.  Otherwise put a simple back up in place, I've seen good quality torches in some places like hospitals.
  • Read this - it should help you understand the whys and hows a bit.   https://www.firesafe.org.uk/emergency-lighting/
thanks 1 user thanked Hsquared14 for this useful post.
HarrisTweed on 01/07/2019(UTC)
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