Changing the battery to your car alarm is an easy and economical do-it-yourself repair that can be completed in a matter of minutes. Depending on the make and model of your car and its alarm, your battery will be located in one of two places--either inside the small remote control that attaches to your key chain, or in the key itself.
Examine your car key or the alarm remote that attaches to your key chain. Locate the screws.
Unscrew the screws, using the micro Phillips screwdriver. These are very small screwdrivers that are commonly used for either glasses or computer repair.
Carefully set the screws aside and lift the "back" off your key or remote. The battery for your alarm will be silver and round, similar to those used in watches today.
Use the dime to carefully pry the battery from the housing. Once the battery is removed, you can bring it to the electronics department of any department store and the clerk there can match it for you. If you have the correct replacement battery on hand, slide it into place.
Replace the cover and screw the screws back into place. Test your new battery by trying your alarm.
