If your ADT security alarm system is displaying "Low Battery" you may need to replace your battery. Also, you may want to consider replacing your backup battery if it is more than three years old. The average life of an alarm system battery is from three to five years. Your security system backup battery is designed to run your system for six to eight hours in case of a power outage. Additionally, the battery is designed to protect your home if an intruder cuts your power to disable your alarm system.
Call ADT at 1-800-ADT-ASAP (1-800-232-2727) and tell them you want to place your system in "test" mode for one hour. When your system is in the test mode, ADT still receives all of the alarms produced by your system but they will not respond to the alarms. They will ask you for your name, address, and security password.
Disconnect the power from your alarm system main control panel (usually located in the master bedroom closet, basement, or laundry room). If there is a retaining screw on the power supply plug remove it, then unplug your system.
Open the control panel box with your key (if applicable) or a screwdriver.
Disconnect the battery black and red leads. If it is difficult to disconnect the terminals from the battery, rotate the battery so you can push the terminals off the battery with a screwdriver.
Remove the battery from the control panel box, place the new battery in, and connect the terminals. Make sure you connect the red lead to the battery terminal which is marked with the red indicator and the black lead to the black battery terminal (the alarm siren may make a chirp sound when you connect the battery--this is normal). Mark the date on your battery for future reference.
Close the control panel box, plug in the power supply, call ADT and tell them to take your system off test mode.