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Alarm System Batteries

Alarm system batteries come in many varieties, depending on the type of system they are used in. The most common main panel types are 12-volt batteries in either 4- or 7-amp/hour capacities (12v, 4ah battery and 12v, 7ah battery)

You’ll know you need a new battery when the system keypads begin beeping, and display a “low battery” message or a “trouble” light on the keypads.

If your system is beeping and you're not sure how to stop it, see "My Alarm Keeps Beeping - What Can I Do?".

If you have a burglar alarm monitoring service, you will also have gotten a call from the central monitoring station alerting you to the problem.

Learn more about home alarm system monitoring.

Here I’ll list some of the many different types of security system batteries out there, and how you can deal with them when they have problems. If you don’t want to handle this yourself, your alarm dealer will be happy to take care of it for you.


If your alarm system is monitored, be sure to call the central station to put the system on “Test” before working on it

Some home alarm companies allow only their own technicians to work on their systems, so check with your alarm representative before attempting any service work yourself

Alarm System Batteries
for the Main Panel

  1. Remove the connectors from the battery terminals by pulling gently and rocking the clip from side to side.
  2. Take the battery with you to a local supplier of alarm system batteries. This ensures that you get the correct security alarm battery. If you’re shopping online, make sure the battery is listed for home alarm use; this will ensure that you get the correct terminal width of 3/16”.
  3. Install the new battery, making sure to connect the red cable to the red “positive” terminal, and the black cable to the black “negative” terminal.
  4. Allow 24-48 hours for the plug-in transformer to fully trickle charge the new battery. Once it has, the low battery indication will clear from the keypads.

Helpful Tip:

If your home alarm battery is a smaller 12-volt, 4-AH sealed lead acid battery, consider replacing it with the larger 12V, 7-AH unit

The cost difference is minimal, but alarm panels will run longer on the 7AH batteries

Just measure the space available in your alarm system panel enclosure before buying the new battery

I always recommend marking the installation date on all new batteries, just for reference. Use a Sharpie or other permanent marker. This may not show up too well on a black battery case, so just write on a piece of masking tape.

For more details on how to do this, see this page on alarm battery replacement.

Wireless “All-In-One”
Alarm System Batteries

These panels often use a rechargeable battery pack rather than a sealed lead-acid battery. It’s best to order this type of alarm system battery by the make and model of panel, since the connector must match the panel exactly.

  1. To access the battery, open the case according to the manufacturer’s instructions. Many are like a clamshell, and the two halves can be popped open by pressing some tabs. See an example of this on an Ademco Lynx system.
  2. Unplug the old battery and remove it from the panel.
  3. Install the new unit and plug it into the connector. Mark the date on the battery pack where it will be visible.
  4. Close up the panel, and allow up to 48 hours for the low battery message to clear.

Smoke Alarm Battery Replacement

You’ll need to verify what kind of smoke detectors you have. There are 3 main types:

  • Battery operated smoke alarms that are stand-alone, and do not connect to 110-volt house wiring or an alarm system
  • 110-volt smokes that connect to house electrical wiring. These have a standby battery strictly as a backup during a power outage.
  • Low-voltage smoke detectors that do connect to an alarm system, either through low-voltage wiring or wirelessly.

Replacing Smoke Alarm Batteries

For the first 2 types, remove the detector from its base plate and open the battery compartment.

Remove the old battery. Insert the new battery, making sure it makes contact with the terminals inside.

Close the compartment and re-attach the smoke to its baseplate.

Many smoke detectors use common 9v alkaline batteries you probably have on hand.

The 3rd type of smoke detector could be one of 2 designs: Hardwired or wireless.

Hardwired smoke detectors are powered by the main alarm panel through the wiring, and have no battery inside them.

If you have a wireless smoke detector, you’ll need to first put your alarm system on “Test” if it’s monitored by a central station. Then you can proceed to change the battery as usual.

Many brands of wireless smoke detector use the popular CR123 lithium alarm system batteries.

For more information on smoke alarms, see these pages:

First Alert Smoke Detectors

Kidde Smoke Detectors

System Sensor Smoke Detectors

Smoke Detector Problems and How to Solve Them

Alarm System Batteries for Wireless Sensors and Other Transmitters

Wireless transmitters come in many different varieties, including wireless keyfobs, pendants, and door and window sensors. Check each type of transmitter you have to see which batteries you’ll need.

In the past, wireless home security alarm batteries included 9-volt, “AA”, and “AAA” alkaline batteries.

Newer systems have moved to the higher performance lithium batteries. Within this type there are many “button” or “wafer” cells, including:


…and there are others.

Replacing a Wireless Home Security System Battery

  1. Open the case or cover of the wireless sensor/transmitter. Some cases simply unsnap using a coin or small screwdriver at a corner or along an edge. Others have a cover or shell that can be released by squeezing a button or tab on one end.
  2. Identify the battery, and install a fresh one.
  3. Re-assemble the transmitter, and clear the keypad of any tamper messages if needed.
  4. Test the sensor. An easy way to do this is to first set the “chime” feature at the keypad. Then, open and close the door or window to trip the transmitter a time or two.

If the plastic cases on your transmitters are brittle from heat or age they may break when you remove them.

Replacement cases are available for many brands of wireless security sensors including Ademco. Search for cases by brand name and model number found on the transmitter base.

Wireless Keypad Batteries

Many wireless keypads use one of the standard alkaline batteries previously mentioned. You can usually swap these out with fresh batteries and begin using the device again.

A few wireless keypads have a battery that is factory-soldered onto the circuit board. This kind must be sent to the manufacturer for battery replacement. If the maker is no longer in business or parts are unavailable, your choices are limited:

  1. Find a local battery shop that can do the replacement
  2. Replace the battery yourself
  3. Replace the entire system

In most cases, your money is better spent on a new system, rather than on trying to resuscitate a failing wireless keypad. Even if you do get the keypad working, the rest of the equipment has already taken a lot of wear. Best to get a new one, and enjoy some of the many modern features available now.

Even after all your efforts, you may decide that your system is beyond reasonable repair. If this happens, find out what a new system will cost by getting a few Free Home Security Systems Quotes from companies in your area.

These can help you decide whether to pull the plug on the old system, install a new system yourself, or step aside and let a professional security company do the work.

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