An ADT home security alarm is equipped with a 12-volt backup battery that powers the system in the event of an electrical outage. ADT alarms will produce an audible chirp and a light will glow on the main control panel when the battery is beginning to fail. Replacing the backup battery before it goes bad will keep the alarm system operating properly 24 hours a day. The job takes less than half an hour with a few steps.
Notify the ADT service provider that you are changing the backup battery. The call number is on the base unit of the ADT security system. Failing to call ADT when the alarm system is disabled may trigger an alert and bring a visit from the police.
Disconnect the system from the power supply, or turn off the circuit breaker if the system is wired into the house.
Disconnect the cables from the backup battery--positive first, then negative--using a wrench to remove the cable clamps from the C-shaped battery posts. Use a spray lubricant to loosen the battery cables, if necessary.
Clean the battery cable clamps with a piece of steel wool, concentrating on the parts that connect directly to the battery post. This is good preventive maintenance against corrosion.
Attach the replacement battery by connecting the negative batty cable to the negative post, then the positive cable to the positive post.
Turn on the power at the circuit breaker.
Dispose of the old battery properly.