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Fire Alarm Battery Calculator
Size the standby battery for a fire alarm panel from its quiescent and alarm current, using the AS 1670.1 style calculation.
Fire Alarm Battery Calculator
Size the standby battery for a fire alarm panel from its quiescent and alarm current, using the AS 1670.1 style calculation.
The panel plus every loop device and module at rest, from the datasheets or the panel's own loop calculation.
Everything drawing in alarm: panel, devices, sounders, strobes and relays.
Normally 24 hours; check the standard and the fire engineer's brief for the site.
Normally 30 minutes.
Allows for a battery giving less at a high discharge rate. Use the battery maker's figure if you have it.
Results
Standby load: 8.40 Ah
Alarm load (derated): 1.58 Ah
Capacity needed (x 1.25 for ageing): 12.47 Ah
Battery size: 17 Ah
A planning figure using the calculation commonly applied under AS 1670.1: 1.25 x (standby current x standby hours + derating x alarm current x alarm hours). Fire systems must be designed and certified by an accredited fire practitioner, using the current standard and the panel maker's battery calculation. On a 24 V panel the size is for each of the two 12 V batteries in series. Keep batteries between 15 and 30°C, or apply the maker's temperature correction.
How it works
Capacity = 1.25 x (quiescent current x standby hours + derating factor x alarm current x alarm hours). 1.25 allows for the battery ageing; the derating factor allows for it giving less at a high discharge rate. The suggestion is the next common sealed lead-acid size up.
Good to know. These calculators use the formulas and standards the industry works to, so they give you a sound first answer for planning and quoting. They can't see your site, though, so treat the result as a guide rather than the final word: check it against the manufacturer's datasheets, the relevant Australian Standard and, for fire and life-safety systems, the designer's own calculation before you buy or install. We provide them free as a guide and can't take responsibility for decisions made on the result alone. Want a second opinion? Our team is happy to check your figures.
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