Locate the main security panel box. This is usually a metal box located in a secure area, such as a basement crawl space or closet.
Open the main security panel box. Find the security system transformer (which resembles an AC adapter and the backup battery). The backup battery is usually a 12-volt battery; it is a black box with red and black wires leading into it.
Unplug the transformer. Remove the leads from the backup battery.