The battery in your ADT motion detector usually needs changing every 12 to 24 months, depending on the model and how often the detector triggers

Most ADT motion detectors use standard AA or 9-volt batteries that you can buy at any drugstore or supermarket. The exact steps depend on whether you have a wireless detector (battery-powered) or a hardwired detector (which may have a backup battery). Wireless detectors are far more common in home systems, and changing the battery takes about two minutes once you know where it sits.

Your ADT system will usually alert you when a battery is running low — you'll see a low-battery message on your keypad or receive a notification on your phone through the ADT mobile app. Some systems send an email or text instead. Don't ignore this alert, because a dead battery means that detector stops working, even though your system may still show it as armed.

Key Takeaways

  • Wireless ADT motion detectors typically use AA batteries, while some older models use 9-volt batteries; check your detector's label or your system paperwork to confirm which type yours needs.
  • You can change the battery yourself without calling ADT — open the detector's cover, note which way the old battery sits, remove it, and slide in the new one the same way.
  • Your ADT keypad or mobile app will show a low-battery warning before the battery dies completely, giving you time to replace it before the detector stops working.
  • After you insert the new battery, close the cover firmly and wait 30 seconds for the detector to reconnect to your system; if the low-battery alert doesn't clear within a few minutes, the battery may not be making good contact.

Locate your motion detector and identify the battery type

Motion detectors are usually mounted on a wall or corner at about six to eight feet high, angled downward to cover the room. Look for a small label on the back or inside the battery compartment that lists the battery type — it will say "AA" or "9V" or show a picture of the battery. If you can't find a label, check your ADT paperwork or the original box the detector came in.

If you're not sure which detector is low on battery, your ADT keypad will tell you. Press the menu button and look for a "Sensors" or "System Status" option — it should list which device has the low-battery warning. Some systems also show this information in the ADT mobile app under "System Health" or "Alerts."

Open the detector and remove the old battery

Most wireless ADT motion detectors have a cover that slides or pops off. Look for a small seam or slot on the edge of the detector. If it slides, gently push or pull in the direction the seam runs — usually downward or to one side. If it pops, use your fingernail or a plastic tool (not a metal screwdriver, which can damage the electronics) to gently pry the edge until the cover releases.

Once the cover is open, you'll see the battery sitting in a plastic holder. Note which direction it's facing — the positive end (marked with a + sign) should be pointing toward one end of the holder. Gently pull or slide the battery out. If it's stuck, wiggle it slightly rather than forcing it, which can damage the contacts inside.

Insert the new battery in the same direction

Take your new battery — AA or 9V, depending on your detector — and slide it into the holder the same way the old one was facing. You should hear or feel a small click when it seats properly. Don't force it; if it doesn't slide in smoothly, flip it around and try the other direction.

Make sure the battery is fully inserted and sitting flat in the holder. A battery that's only partially seated won't make good contact with the metal terminals, and your detector will either not work or show a low-battery warning even though the battery is new.

Close the cover and wait for the system to recognize the change

Slide or snap the cover back into place until it sits flush with the detector body. You should hear a click or feel it seat firmly. Don't overtighten it — the cover should close smoothly without needing force.

After you close the cover, wait 30 to 60 seconds. Your motion detector needs time to reconnect to your ADT system and report that the battery has been replaced. During this time, the detector may blink a light or make a small beeping sound — this is normal. Check your ADT keypad or mobile app after a minute or two; the low-battery alert should disappear.

What to do if the low-battery alert doesn't clear

If the alert is still showing after five minutes, the battery may not be making good contact with the terminals inside the detector. Open the cover again and remove the battery. Wipe both the battery and the metal contacts inside the holder with a clean, dry cloth to remove any dust or corrosion. Reinsert the battery and close the cover, then wait another minute.

If the alert still doesn't clear, the battery itself may be defective — this happens occasionally with new batteries. Try a different battery from a different package or brand. If a second new battery also doesn't work, the detector's internal contacts may be damaged, and you'll need to contact ADT to have the detector replaced.

Hardwired detectors with backup batteries

If your motion detector is hardwired (connected to your home's electrical wiring rather than battery-powered), it may still have a backup battery inside for when the power goes out. These backup batteries are usually 9-volt or AA batteries, and they're changed the same way as wireless detectors — open the cover, note the direction, remove the old battery, and insert the new one.

Hardwired detectors don't rely on the backup battery for normal operation, so a low-battery alert on a hardwired detector is less urgent than on a wireless one. However, you should still replace it within a few weeks so the backup is ready if your power goes out. If you're not sure whether your detector is hardwired or wireless, look for wires running into it; wireless detectors have no wires.

Frequently Asked Questions

How often do I need to change the battery?

Most ADT motion detectors need a new battery every 12 to 24 months, depending on how often the detector triggers and the brand of battery you use. Your system will alert you when the battery is low, so you don't have to guess. Some detectors last longer if they're in low-traffic areas and trigger less often.

Can I use rechargeable batteries in my motion detector?

Rechargeable batteries (NiMH) work in most ADT motion detectors, but they tend to drain faster than alkaline batteries and may trigger low-battery alerts more often. Alkaline batteries (the standard kind you buy at the store) are usually more reliable for motion detectors. Check your detector's label to see if it specifies which type to use.

What happens if the battery dies while I'm away?

If a motion detector's battery dies completely, that detector stops working and won't trigger an alarm if motion is detected in that area. However, your other detectors and door/window sensors will still work. ADT sends a low-battery alert to your keypad and app before the battery dies, so you have time to replace it before you leave home.

Do I need to disarm my system before changing the battery?

You don't have to disarm your system to change a battery, but it's a good idea to do so to avoid accidentally triggering an alarm while you're working on the detector. Simply enter your code on the keypad to disarm, change the battery, and then re-arm when you're done.

Why is my motion detector still showing low battery after I changed it?

The most common reason is that the battery isn't making good contact with the metal terminals inside the detector. Remove the battery, wipe both the battery and the contacts with a clean, dry cloth, and reinsert it firmly. If that doesn't work, try a different new battery — the first one may have been defective.