With a standby load of , an alarm load of and a standby period of hours with an additonal 30 minutes in alarm condition, you will need batteries or larger.

Actual value returned by calculation :

Whoa there tiger... That calculation returned a calculation of ?

You must have entered the Quiescent & Alarm loads in wrong.

Please try again. Remember, the figures need to be entered in milliamps.

If you have entered the figures correctly then please speak with the manufacturers of the equipment because a seperate power supply may be required.

Fire Alarm Battery Calculator

Calculate The Correct Size Batteries For Your Fire Alarm System.

Installing the correct size of batteries in a fire alarm panel is crucial for reliable performance and continued operation during a power cut.

To check if you have the right batteries, enter your Quiescent and Alarm load figures, along with the standby period and actual battery sizes you have installed in the fields above then click 'Calculate'. Your results will be available for download in PDF format.

Batteries installed in a fire panel must be able to fully recharge within 24 hours. If the required batteries are too large for the fire panel enclosure, the panel's charger may not be powerful enough to charge them at the required rate. In this case, we recommend contacting your fire panel manufacturer for guidance. Any other power supply unit (PSU) used for critical path signaling, such as dual comm units or other signaling equipment, should also have the same standby period as the fire panel.

The fire panel should indicate any faults in critical path equipment and power supplies used for sounder circuits or dual comm units, among others, until the faults have been rectified

Additionally, any other power supply unit (PSU) used for critical path signaling, such as dualcomm units or other signaling equipment, should have the same standby period as the fire panel.

This tool and all other automatically generated documentation are provided 'as is' for your personal use and at your own risk.

Please note that this is an automated tool, and Fire and Security Engineers (Fase) will not accept responsibility for any incorrect usage, incorrect calculations returned by the tool, or any damage caused by the usage of this tool at any part of the test procedure

This tool performs the standard battery calculation detailed in Annex D of BS5839-1:2017 for life safety systems. Please note that this tool does not provide calculations for property category systems.

Please read your specification carefully, sometimes variations of this calculation are required.

To comply to BS5839, your own calculations should be carried out & recorded.

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Fire and Security Engineers

Fire Alarm System Design, Installation, Commissioning & Compliance Services


12 Lincoln Close,






01925 500254

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