How to Change an Alarm Battery

Updated February 21, 2017

House alarms, including smoke detectors, carbon monoxide alarms and burglar alarms, add a sense of security to your home. However, all of these helpful security tools are only effective if you keep the batteries fresh and functional.

Ideally, batteries in your house alarms should be changed twice a year. Many people change the batteries when the clocks are set forward in the spring and back in the fall, using the regular event as an easy way to remember this important maintenance task. The alarm will beep to let you know when the battery is running low, but it is better to keep the batteries fresh and change them before they are low enough to set off the notification. No matter when you decide to change the batteries, be sure to do it regularly to ensure your family's safety.

Determine the battery type. In order to change the battery, you must be sure you have the right type of replacement battery. Most smoke detectors use 9-volt batteries, and carbon monoxide detectors tend to use four AA batteries. A security alarm might use a specialised battery that you must acquire from the manufacturer or the alarm maintenance company. In some cases, you might even have to let the alarm company do regular battery changes on your security system, in which case you should mark your calendar to remember to call them within the recommended time frame. If you don't know what type of battery your alarm takes, open the alarm to look inside. In some cases, a screwdriver might be necessary for this step.

Clean the inside of the alarm. This is particularly applicable for smoke alarms. In a smoke alarm, dust or dirt inside the alarm can float through the sensor, causing it to go off. A quick dusting to the interior of the alarm can help prevent this. If any corrosion has leaked into the inside of the alarm from the old batteries, clean it thoroughly. If corrosion is particularly pervasive, it might be time to buy a new alarm.

Place the battery according to instructions. Alarms come with instructional flyers that provide directions for changing the batteries. If you have any doubts about which direction the batteries should go in, consult the diagrams in the instructions. Most alarms will provide a chart on the battery compartment itself showing which direction the plus and minus ends of the batteries should lie. Install the batteries and replace the battery cover.

Test the alarm. Before declaring the task complete, check to be sure the alarm works. Most home alarms have a test button that, when depressed, will set off the alarm for a short time. You might want to muffle the alarm with a towel at this point so that the loud sound of the alarm is less disruptive. Once you've tested the alarm and are certain it works with the new batteries, your job is done.


In most cases, you will require an alarm key or special code to open a home security system. This key is available from the alarm manufacturer or maintenance company. In addition to changing the alarm batteries twice a year at minimum, it is also a good idea to test the alarm once a month to be sure it is still working properly.


Always check instructions for security alarms. If your alarm is under warranty, changing the battery on your own could possibly void the warranty. If your smoke alarm is more than 10 years old, it should be replaced.

Things You'll Need

  • Appropriate new battery or batteries
  • Instructions for changing the battery
  • Screwdriver, if necessary
  • A towel or blanket to mute the alarm
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About the Author

Katriena Knights is an experienced author of fiction and nonfiction, including several novels and novellas and numerous articles and website content. She currently works for wiseGeek, Internet Brands and Page1 Solutions in addition to Demand Studios. She has a bachelor's degree in English literature and also works as a professional editor. Her interests and knowledge are wide and varied.