Your Guide to Buying Replacement Alarm Batteries Online

Behind almost every security keypad, fire alarm panel, access-controlled door and automatic gate is the same kind of battery: a small, sealed lead acid (SLA/AGM) backup battery that takes over when the power goes out. Most of that equipment runs on one of just three sizes: 12V 4.5 to 5Ah, 12V 7Ah, or 6V 1.3Ah. If you know which size you have, finding a replacement is quick, no matter which brand of panel it sits in. This guide explains the three sizes, how to decode the part number on your old battery, what changes for commercial fire alarm systems, and how to swap a battery safely.

AJC® makes replacement SLA/AGM batteries for more than 1,000 alarm, fire, access control and gate models. Browse AJC alarm batteries to find your match.

Why Does the Backup Battery Matter So Much?

A hardwired alarm system runs on household power, and the backup battery keeps it armed and communicating if the power fails or is cut. Some wireless systems run on their battery full time. Alarm companies are good at installation and monitoring, but battery upkeep usually falls to the owner, and an old or drained battery is a common cause of low-battery chirps, trouble codes and false alarms. Worse, it can leave the system unable to work during an outage, which is when it's needed most.

The Three Battery Sizes Behind Most Alarm Systems

AJC® alarm batteries use maintenance-free AGM construction, so you never add water or acid, and they ship sealed, charged and ready to install. They are UL Recognized Components and carry a 12-month warranty with 30-day returns.

How Do You Know What Battery to Get?

Start with the label on the battery you're replacing. It will show a model number plus the specs you need to match. Our example below is a CA1240.

Decode the part number

Many SLA part numbers follow the same pattern: a brand prefix, then the voltage, then the capacity. CA1240 reads as a 12V battery rated 4.0Ah. UB1270 and SB1270 both read as 12V 7Ah. Batteries labelled 4Ah, 4.5Ah and 5Ah are typically built in the same case size, so a 5Ah battery is a common drop-in upgrade for a 4Ah original.

Match the voltage exactly

A 12V panel needs a 12V battery, and a 6V panel needs a 6V battery. Using the wrong voltage can stop the system from working or damage its charging circuit.

Match or exceed the capacity

Amp-hours (Ah) measure how much energy a battery stores, not how much current it delivers. A higher Ah rating means longer backup time from the same voltage. If a larger-capacity battery fits the cabinet and your equipment's manual allows it, it's a safe upgrade. A lower Ah rating will work but shortens backup time.

Match the terminal

F1 spade terminals are 0.187 in wide and F2 terminals are 0.250 in wide. 12V 7Ah batteries come with either terminal depending on the equipment, so check the old battery before you order.

To find a match, go to ajcbattery.com and search for the number on your old battery, in this case "CA1240". You can also search by the make and model of your panel.

Do Fire Alarm and Commercial Systems Need Anything Different?

Commercial fire alarm control panels use the same 12V SLA sizes, but the rules around them are stricter.

• Standby time is set by code. NFPA 72 requires a fire alarm system's batteries to run it for 24 hours in standby without building power, then operate all devices in alarm for 5 minutes (15 minutes for voice evacuation systems).
• Many panels use batteries in pairs. A lot of commercial fire alarm panels run on 24 volts, using two identical 12V batteries wired in series. Replace both batteries at the same time with the same size and capacity.
• Batteries must be dated. NFPA 72 requires storage batteries to be marked with their month and year of manufacture, which inspectors check during routine testing.
• Use a qualified technician. Fire alarm battery replacement is normally done by a licensed fire alarm service provider and recorded in the system's inspection and testing records.

Facility managers, installers and service companies buying in volume can set up an account through our wholesale battery program, which offers volume pricing, Net 30 terms and purchase order support.

Should You Do It Yourself or Go Through the Alarm Company?

For a home or small business alarm you own, replacing the battery yourself is usually the simplest option. A service visit from your alarm company can carry a fee, and the battery they supply often costs more as well. An AJC® 12V 4.5Ah alarm battery is $17.39 and a 12V 7Ah is $19.39 at the time of writing. Call your alarm company instead if your contract covers batteries, if you lease the equipment, or if the panel is hard to reach safely.

How Do You Switch the Batteries?

The exact method for switching batteries varies by system, but most wired panels follow the same steps. Always follow your manufacturer's instructions where they differ.

1. Put the system in test mode. If the alarm is monitored, call the monitoring company and ask them to place the account on test so a tamper or low-battery signal doesn't trigger a dispatch. Many panels also have a test mode you can set from the keypad.

2. Disarm the system and find the control panel. It's usually a metal cabinet in a basement, closet or utility room. Leave AC power connected so the panel keeps its programming.

3. Note the wiring. Open the cabinet and take a photo of the battery connections. The red lead goes to the positive (+) terminal and the black lead to the negative (−) terminal.

4. Disconnect black first, then red. Pull on the connectors, not the wires, and keep the bare leads from touching each other or the metal cabinet.

5. Connect the new battery: red first, then black. Push each connector fully onto its terminal and set the battery back in place.

6. Close up, test and take the system off test. Run a battery test from the keypad if your panel has one. A low-battery trouble can take several hours to a day to clear while the new battery charges. Then call the monitoring company to restore normal monitoring.

How Often Should You Replace Your Alarm System Battery?

Plan on replacing an SLA alarm battery every 3 to 5 years. Heat, frequent power outages and deep discharges shorten that, so replace it sooner if the panel shows a low-battery trouble that won't clear, or if the battery is swollen, cracked or leaking. A simple habit helps: write the installation month and year on the new battery with a permanent marker so you always know its age. For more maintenance and testing tips, read our alarm system replacement battery tips.

What Should You Do With the Old Battery?

Don't put a used SLA battery in the trash. Lead acid batteries are recyclable and are accepted at battery retailers, auto parts stores and local recycling centers. Tape the terminals before you drop it off. See our battery recycling page for details, then browse our replacement alarm batteries to find your match.