hello there I hope you will be able to help. My whole fire alarm career I have been told and carried out battery calculations with the understanding the end result is per battery for eg if the formulae came out at 6.1ah I would supply 2x 7ah batteries is this correct? Or is it an overall calculation for total of both batteries so 2x 3.2ah batts. I have just started at a new company that are just starting on fire and have been questioned on this.
many thanks
Jamie

I am not a fire alarm engineer but looking at BS 5839 Part 1 AMD 2013 it appears to say, you do your battery calculation and the result upgraded to the next available size, ie 6.1 Ah would be 7Ah as in your example. This is the total of the standby capacity you require 2 X 3.2Ah batts or 1 X 7Ah batt, in your previous method you would be doubling the capacity and I cannot find any reference to that. I would suggest you log on to www.firealarmengineers.com/ and post there as they will be able to give you much better advice than me.

It has occurred to me a situation where you would require two batteries would be when the batteries are 12V and the system is 24V and you would need to connect them in series.

Check out http://firealarmengineers.com/forum/showthread.php?tid=7281&highlight=calculate