Customer FAQs Discover answers to the most frequently asked questions from ADT customers with the click of a button. 1. How do I replace a smoke detector battery? When the batteries in your smoke detector need to be replaced, a “zone trouble” indicator will appear on your alarm keypad and/or a “sensor trouble” indicator will appear on your ADT Pulse app. You should replace the battery as soon as these indicators appear. The smoke detector requires (2) CR123A 3 volt batteries. Some models may only require (1) battery. These batteries can often be purchased at your local hardware, mass retailer or battery store. Before you replace the battery, put your system into test mode to prevent false alarms. Visit myadt.com and select “My Alarm” from the dashboard. Once you click “My Alarm”, a menu will appear. From the menu, select “System Management."Select “place system on test.” (Note: You can also call 800-ADT-ASAP to put your system into test mode.) To change the battery, simply twist the smoke detector in a counter clockwise direction. The mounting bracket will be only part that stays on the ceiling or wall. If you are having difficulties twisting it off, you might need to depress a small tab with a screwdriver on some models. Replace the battery, observing the proper polarity. Once you’ve changed your battery, line up the tabs or markings on the detector and mounting bracket and turn the smoke detector in a clockwise direction. Wiggle the detector to ensure that it is connected properly. The security system may need to be reset by entering your code into your system and hitting off twice. Remember to remove the system from “test mode.” Go to MyADT.com and click on “My Alarm."From the System Management option, select “Stop Test“ to remove the system from test mode and restore operations. Watch this video to learn more.