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4466 EXTERNAL POWER SUPPLY - FIRE ALARM SOLUTIONS TECHNICAL DESCRIPTION
4.4.1.
BATTERY BACKUP TIME
Find out the required battery backup time, according to national regulations / customer demands, in normal state and in alarm state.
Calculate the battery capacity required in normal state (QN) and the battery capacity required in alarm state (QA) respectively QN.
QN (Ah) = ITN (A) x battery backup time in normal state (h)
QA (Ah) = ITA (A) x battery backup time in alarm state (h)
The total battery capacity Q = QN + QA (Ah)
The battery voltage at the end of a discharging period is not the same as at the start. Round up the calculated capacity and add at
least 20% margin at room temperature (~20˚C) and up to 40% in cold premises, as a safety margin. The following tables show the
relation between current consumption (I) and backup time.
I (A)
4
3
2
1.5
1.0
0.8
0.6
0.4
0.2
The values in the table above are calculated and give only a rough idea of the back-up time.
Backup time (hours:min) @ 20˚C without any margin
Built-in 7.2 Ah batteries.
1:0
1:30
2:30
3:30
6:30
9:0
12:0
18:0
36:0
9
External 42 Ah batteries
10:30
14:00
21:00
28:00
42:00
52:30
70:00
105:00
210:00
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