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Planning Instruction 66571758GB0 Fire Detection 34

8.5 Battery backup calculation

The formula for calculating the required battery capacity is:

(L1 x T1 + L2 x T2) x 1.25 [Ah]
where
L1 = standby current in amperes
T1 = standby time in hours
L2 = alarm current in amperes
T2 = alarm time in hours
1.25 = compensation for ageing

The requirements for standby time and alarm time varies in various countries, but if no national requirements exist,
it is recommended to use T1 = 72 hours and T2 = 0.5 hours.

Note! The standby time may be reduced to 30 h under conditions that ensure repair of a broken power
supply and/or main supply within 24 h. Refer to EN54 part 14.

Note! A 51 Ah battery requires 2 A charging current to be recharged according to EN54 part 4 (80% within
24 h and 100% within an additional 48 h).

Note! National and/or local regulations may require different standby, alarm and recharging times.

Note! Use the system capacity calculation tool.

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Schneider Electric Pelco Finland Oy Kalkkipellontie 6, 02650 Espoo, Finland Telephone: +358 10 446 511 Fax: +358 10 446 5103 www.pelco.com/nordic
Document Number 66571758GB0 49 2011