Replacing your alarm battery can be a DIY project if you're comfortable with wiring and you're a bit patient. Learn how to replace your alarm system battery: How To Replace An Alarm System Battery
Your alarm battery is a crucial component to the alarm system since it provides backup power in case your AC mains power fails. Each time the power goes out, the battery automatically kicks in to provide power to the alarm. But this also takes a toll and eventually the alarm battery needs to be replaced. Typically they last anywhere from 1-3 years but that depends on the quality of the battery charging circuit, the battery itself, how often kicks in, and whether power is restored before the battery is completely discharged.
When you replace your security system battery, pay attention to the size, voltage, capacity (AH rating) and terminal type. Most standard alarms use 12V batteries, ranging from 4AH to 8AH batteries. Larger batteries allow your alarm system to run longer when power fails. An alarm battery typically has an F1 187 fast on tab which is 0.187" or 4.75mm wide.