DIY Alarm System Battery Replacement

Sealed lead-acid battery


Your alarm system battery supplies backup power to operate your system during a power outage. Most alarm panels operate on 12-volts, and use one of a few different sizes of sealed lead-acid battery. These batteries are produced under names like Casil, Panasonic, and EnerSys Genesis (formerly Yuasa).

After 3-5 years of service, a security alarm battery will be down to approximately 80% or less of its original rated capacity. This means it may not be able to run the system for very long in case of a power failure.



How to Know If You Need a New Battery

The first sign of alarm battery failure is usually a beeping keypad. The beeping or chirping will often occur at the same time every day (or night). This is because many panels do their automatic battery test every 24 hours. Less commonly, a low battery condition can cause false alarms at random times of the day or night.

Almost all alarm panels will also display a keypad trouble light to indicate a problem. Keypads with LCD displays will print out “low batt” or something similar. Keypads with LED’s may need you to press a button or two for the lights to show the trouble condition.

You can find out how to read the system trouble codes from your alarm users’ manual. If you don’t have a manual for you’re alarm system, free downloads are available for many systems at PanelGuides.com.



Should I Replace My Own Battery?

Luckily, replacing a burglar alarm battery isn’t difficult, and can be done easily by most homeowners. This can save you the cost of a service call, and maybe a buck or two on the price of the replacement battery.

See "Replacing the Alarm System Battery" further down this page.

You may "inherit" an existing alarm system when you buy a house. For some ways to keep these systems running, see these pages:

Tips on maintaining older Brinks Home Security Systems.

DSC 832 Tips and Advice for Older Systems.

If you want to be on the safe side, simply replace your home alarm system battery every year or two. Skip down this page to “Replacing the Alarm System Battery”.

Burglar alarm battery replacement is one of the most basic home security systems DIY projects, and is easy to do. The battery must be changed every few years anyway, so it pays to learn how.

Doing routine battery changes requires no tools, other than possibly a key to open the alarm panel box. Then you can be confidant that your alarm system battery will be able to do its job whenever called upon.

If you’re a little more ambitious and/or thrifty, you can test your home alarm battery, and only replace it if necessary. This can save you some money, versus blindly replacing it at intervals. If you go this route, you’ll need a digital multimeter, or DMM to measure the battery voltage. The DMM I used here is a $3.00 special from Harbor Freight (Yes, I said 3 dollars!). As you can see, you don’t need a fancy one.

By the way, the alarm panel shown in this example is the very popular DSC Power 832. Although it has been discontinued, you may still "inherit" a perfectly functional one when buying a house.

You’ll also have to disconnect the low voltage transformer. This can be done either by unplugging it from the wall outlet, or by disconnecting a wire on the alarm panel circuit board. Doing this requires a screwdriver.

Be sure to check with your alarm company first, if you have a monitored alarm system. Many companies prefer that their customers don’t perform any service on their system. If you’re under contract with a company, working on the system yourself could void your warrantee.


Free Home Security Systems Quotes from BuyerZone.com






12-Volt, 4 AH

This is probably the most commonly used alarm system battery of all time. It's small enough to fit in any standard-size alarm panel, and provides enough power to run most basic systems for a few to several hours. Different manufacturers list this size battery with various amp-hour ratings of 4, 4.5, or 5, but they're all the same capacity. As long as the voltage matches the old battery, you're good to go. Battery terminals come in two widths: F1 terminals are 3/16" wide, while F2 terminals are 1/4" wide. Most alarm panels use the narrower F1 terminals. As long as the battery you buy is listed for alarm use, it will have the correct width terminals. See details on a Casil Genuine CA1240 12V 4Ah SLA Alarm Battery.




12-Volt, 7 AH

This battery will often fit in panels designed originally for the smaller 4-amp-hour unit, and will give longer run time in case of a power outage. Like the smaller battery, manufacturers sometimes label this battery as having a capacity of 7, 7.5, or even 8 amp-hours. This is just marketing hype; they're all going to give you the same amount of back-up power. As with the 4 amp-hour units, look for batteries listed for alarm system use. They will then have the correct 3/16-inch wide terminals. See more about a 12 Volt 7 Amp Hour Alarm Battery.




Battery Packs

Battery packs are chosen to fit many all-in-one type alarm panels. One of the most common is the Ademco/Honeywell Lynx system. Like some other all-in-ones, the Lynx is primarily a wireless system, and doesn't have to power keypads, motion detectors, or any other peripheral devices. This means that it only needs enough stand-by battery power to run it's internal radio receiver, main circuit board, and the sounder. Unlike the larger 4- and 7-amp-hour batteries above, battery packs are not "generic". Make sure the replacement pack you buy is specifically stated to be for use with your brand and model of alarm system. This will assure that you get the correct voltage, capacity, and connector style to fit your panel. View a Backup Battery for an Ademco Lynx System.

Are There Other Alarm Batteries?

The batteries above will cover the vast majority of alarm panels around today, but there have been many different systems produced. You may have an older system requiring a different size or style of battery, or one taking a special type of battery connector.

To find a battery for this type of system, find the make and model number first. This is usually located inside the lid, but can sometimes be found on the main board, on the bottom of the enclosure, or some other location.

Use the model number and brand name to narrow down the search for your battery. Click here to find other Alarm Batteries at Amazon.com.








Burglar alarm battery in panel


Testing a Home Alarm panel battery


How to Test an Alarm System Battery

Open the alarm system panel box, and locate the battery. Most panels just have the battery sitting on the bottom of the “can”. If there is a date written on the battery, and it’s at least 5 years old, replace the battery.

If there’s no date written on it, continue with testing. Position the battery so that you have access to the terminals on the top. This usually means laying the battery on its side.



Home alarm system battery terminals

Disconnect AC power by unplugging the low voltage transformer, if possible. If you can’t easily reach the transformer (or if you don’t know where it is), you’ll need to disconnect one of its wires inside the panel.



Low voltage transformer


The circuit board will have at least one row of screw terminals. At one end or the other, look for 2 screws marked “AC”, “Trans(former)”, or “XFMR”. Loosen one of these 2 screws, and pull the wire free. Be careful not to let the wire touch anything, or you could fry the transformer. By the way, don’t be concerned about electric shock, since the transformer only puts out around 18 volts.



Plug-in transformer terminals in panel

Set your DMM to measure “DC Volts”, within the range of 12 volts. Touch a probe to each battery terminal, and check the voltage reading. You’ll notice the voltage dropping, hopefully not too rapidly. A good battery will drop steadily for a few minutes, then level off and even begin climbing slightly. If yours behaves this way, and stays above 12 volts, the battery is good.



Security alarm battery voltage

If after 5 minutes or so the voltage continues to drop, or if it ever goes below 12 volts, the battery should be replaced.



How to Replace an Alarm System Battery

If the battery fails the test, reconnect transformer power so the system will run when you take out the battery.

Remove the connectors from the battery terminals. They are the quick-connect spade type, and simply pull-off and push-on. Take the unit to a battery store, where they will sell you a replacement battery of the same size.

Note that the new battery must have the same rated voltage as the old one. The amp-hour rating should be the same or higher.

Label the new battery with the date, for future reference. If you use a black Sharpie, it won’t show up well if the battery casing is also black. In that case, add a short piece of masking tape, and write on that.



DIY alarm system battery replacement

Install the new alarm system battery, making very sure to match the positive and negative terminals to the correct wires: red to red, and black to black.

Using your multimeter, check the battery voltage. It should climb slowly but steadily, as the alarm panel’s charging circuit does its job. If the voltage doesn’t increase after 5 minutes or so, check the AC power connections again. If they are good, you may have a blown transformer.

To check the plug-in transformer, set your DMM to the “AC Volts” position, and touch a probe to each AC terminal on the circuit board. You should see 16-18 volts or so. If not, you’ll need a new transformer. These are available online, or you can get a comparable unit from Radio Shack or other electronics supplier.



Testing a plug-in transformer

Replacement is done by simply swapping out the old transformer for the new one. Unlike the battery, AC connections aren’t polarity-sensitive. There is no “positive” or “negative”, as the leads are interchangeable.



Extech Digital MultiMeter






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