Every alarm system from Eclipse Security Systems comes with a backup battery already installed. This means that during power outages the alarm system will automatically switch to the backup battery. The battery will keep your alarm system powered for up to 48 hours, depending on how much you use the system during this time. After the main power comes back on, the alarm system will begin recharging the backup battery until it is at full power again. During this time the alarm system will report that the battery is low until fully charged.