Fire System Battery Capacity Calculation

Fire safety systems require a secondary power source (typically batteries) to ensure the operation of the system in the event of primary power (mains) failure. Over the decades, the requirements for battery capacity have evolved and changed in Australian Standard AS 1670.1, AS 1670.4, AS 2220.2 and AS2293.1.

Russ Porteous
CEO, Firewize
09 Jun, 2021

The primary power source for a fire detection and alarm system (incorporating where applicable an occupant warning system), emergency warning systems (including sound and intercom systems for emergency purposes) and emergency light and exit sign systems in buildings is 240VAC mains power.

These systems also incorporate a secondary (reserve) power source such as a self contained battery or central battery system (in the case of some emergency light and exit sign systems).

These type of batteries are called stationary batteries and are manufactured to comply with Australian Standard / New Zealand Standard AS/NZS 4029.2, which is derived from IEC 60896-2.

Battery Capacity Calculations AS1670 AS2220 AS2293

Battery Capacity Calculation

When calculating required battery capacity, an additional allowance shall be made for an expected degradation of capacity over the useful live of the battery. This applies as follows to the following systems as follows;

  • 125% of the required capacity for a fire detection and alarm system;
  • 125% of the required capacity for an emergency warning system;
  • 133% of the required capacity for emergency light and exit light systems.