How to Replace Alarm Batteries in Your Burglar Alarm System

Your burglar alarm is only as reliable as its power source. Whether you're a homeowner or an installer, knowing how and when to replace your alarm batteries is essential for keeping your property protected 24/7. A low battery can lead to false alarms, system malfunctions, or total failure when you need it most.

In this guide, we’ll show you exactly how to identify which batteries need replacing, how to do it safely, and which replacement parts to choose. Plus, we’ll link you to high-quality components available from West Midland Electrics (WME) to make maintenance quick and easy.

⚡ Why Alarm Batteries Matter

Burglar alarms rely on batteries in multiple components:

If any of these lose charge, your system could fail silently. Most modern alarms will notify you when a battery is low, either through a beeping control panel or a push notification from your smart alarm app.

🔹 Signs You Need to Replace Your Alarm Battery

Repeated beeping or LED flashing from the alarm panel
Notification in your smartphone app (e.g. Ajax)
External siren sounding randomly
Reduced sensitivity in motion detectors
Trouble arming/disarming the system

🔋 How Often Should You Replace Alarm Batteries?

Battery life depends on the device and usage, but general guidelines are:

Component	Typical Battery Life
Sensors	2–5 years
Control Panels	3–7 years
External Sirens	3–6 years

If your alarm system has been running for a few years without a battery change, it's time to check them.

🔧 Step-by-Step: Replacing Burglar Alarm Batteries

1. Disarm Your Alarm System

Always disarm the system before replacing any batteries to prevent tamper alarms or false alerts.

2. Locate the Device Needing a Battery Change

Your system or app should indicate which device has a low battery.

Check the control panel for error messages.
For smart systems like Ajax, the app will tell you the exact sensor.

3. Open the Device Housing

Use a screwdriver if required. Most alarm sensors and sirens have secure, snap-shut or screw-locked casings.

4. Remove the Old Battery

Note the orientation before removing. If there is any corrosion or debris, clean the compartment gently.

5. Insert the New Battery

Make sure to use the correct replacement battery. You can browse high-quality options in our Burglar and Intruder Alarm Battery Collection.

6. Test the Device

After installing the battery, test the device to confirm it’s working properly. Some alarms require you to acknowledge the change via the panel or app.

🔢 Choosing the Right Replacement Battery

Always match the battery model and voltage. Here are some popular types:

CR123A – common in wireless motion detectors
CR2 – used in compact sensors
12V sealed lead-acid – for control panels and bell boxes

Check your user manual or the existing battery label for details.

📢 Don’t Forget the Bell Box

Your external alarm bell box also has a battery that powers the siren if mains power is cut. These batteries are larger and typically last 3–6 years. Replacing them requires removing the box cover, ideally during daylight hours, when noise isn’t disruptive if it triggers.

🤔 FAQs: Alarm Battery Replacement

Q: Will my alarm go off when I change the battery?
If disarmed properly, it shouldn’t. Some systems may beep or flash as a warning.

Q: Can I change the battery myself?
Yes, for most systems - especially wireless models like Ajax. Always follow safety instructions.

Q: What if I change the battery but the error doesn’t clear?
Try rebooting the panel or sensor. If the problem persists, the sensor may need replacing.

Q: Where can I find compatible batteries?
Right here: Shop alarm batteries

🛍️ Related Products & Collections

Replacing your burglar alarm battery is a quick and essential job to ensure your system works when it matters most. Don’t wait for the warning beep or a triggered siren to remind you.

Visit WME for trusted, UK-stocked components including alarm batteries, sensors, and full security systems, delivered fast and at great trade prices.

Need help finding the right battery? Reach out to our team or check the product descriptions for full compatibility.