Size minimum new battery capacity
Standby Battery Calculator
Combine standby and alarm loads with ageing and alarm-current derating.
Method context
BS 5839-1:2025 Annex E / 24.3.5
The implementation follows the current Swift calculator in the Fire Regs Pro project. It is an estimate for revision and preliminary checking.
Check before use: Confirm the current standard, project specification, manufacturer data, environmental derating and actual site measurements. A browser result is not a design certificate.