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Battery size


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Hi, could some on tell me who to work out the size of a battery needed to back up the system for 12 and then 24hrs.

 

We've just taken over a national trust site and they require 24hrs back up though out the whole system. 

 

Thanks

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Hi, could some on tell me how to work out the size (Ah) of a 12v battery needed to back up the system for 12hrs and then 24hrs.

 

We've just taken over a national trust site and they require 24hrs back up thoughout the whole system. 

 

Thanks

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I recall it as 15 minute activation not 30 minutes. Seen as the bell timer would be 15 minutes the alarm current after 15 minutes will be different on an SAB.

Was sure the standard says something along the lines of "12 (24) hours standby including one full activation"?

Still useful chart tho, not a bad thing to be overspec standby capacity wise.

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  • 3 months later...
On 20/05/2019 at 22:34, sixwheeledbeast said:

I recall it as 15 minute activation not 30 minutes. Seen as the bell timer would be 15 minutes the alarm current after 15 minutes will be different on an SAB.

Was sure the standard says something along the lines of "12 (24) hours standby including one full activation"?

Still useful chart tho, not a bad thing to be overspec standby capacity wise.

30 mins for fire alarms. 

 

15 mins intruder. 

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Cmin=1.25(T1xI1+T2xI2x1.75) which is the calculation in BS 5839-6:2019 which is easier in my view as I hate doing division. the T2 is 0.5 which is the same as dividing by 2 .

T1 = 24hours 

l1 = quiescent load 

T2 = 30 minutes in alarm

l2 = alarm load

1.75 = derating factor

Peter Robinson

Freelance

M:07889038650

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