Before you change anything, get hold of a replacement battery which is equal to what the manufacturer’s specification asks for.

If your system is monitored then place the account on ‘test’. This is to avoid a false dispatch. Then unplug the system’s transformer and make sure to be careful as it’s connected to a high voltage supply. If you’re unable to locate the transformer, then look for a pair of terminals labeled ‘AC’ on the panel’s schematic. Remove one wire from one of the terminals and make sure not to touch it to the circuit board or enclosure.

Disconnect the battery from the circuit board and then install your battery, plug your transformer back or reconnect the wire which you disconnected.

You may need to check your panel’s clock, if so, the instructions should be in your user manual. Also if you placed your account on ‘test’ then don’t forget to call and clear your account!