How to Change a Backup Battery in a Smoke Alarm

Updated February 21, 2017

A study by the National Fire Protection Association reports that over three-quarters of all fire related deaths happened at home. Furthermore, the study reports that over half of those deaths occurred in buildings without smoke detectors. Given these startling findings, it is crucial to have a smoke detector in all residential dwellings. In new construction, smoke detectors are required in order to gain an occupancy permit. These new detectors are so state of the art, they are hard-wired into the home's electrical system. However, even though they generally have an ongoing power supply, it is critical to change the backup battery on a regular basis.

Place a step ladder on firm footing under the detector. Climb up high enough to reach your smoke detector.

Remove the detector cover. If the cover is hinged to the rest of the unit, there should be some sort of button to push. If the cover can be completely removed, often it will rotate off the base of the detector.

Find the old battery, remove it from its housing in the detector case and gently pull it from the battery terminals.

Examine the new battery and determine which side is positive and which is negative. Line up the top of the new battery with the correct end of the terminal cover.

Use gentle pressure to snap the battery into the terminal cover. Return the battery to the correct area in the smoke detector unit.

Replace the smoke detector lid. Determine if the unit is operating correctly by running an alarm test. Find the test button on the outside of the detector. Push the button; if the battery is in correctly and the detector is in proper working order, the unit should emit a very loud beep when the button is pushed in.


Remember to change your batteries at least twice a year. In areas of the United States that observe daylight savings time, change the battery when the clocks are switched forward and back to help yourself remember. Many detectors emit a warning beep if the battery is running low. Most detectors use a 9-volt battery.


Don't pull the battery too hard or you could pull wires out of the detector and ruin the unit. Do not rely solely on the warning beep in your detector, as this is not foolproof.

Things You'll Need

  • Battery
  • Step ladder
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About the Author

Shelly Schumacher has a diverse writing background that includes work in print as well as electronic publications. She has been writing for over 18 years and enjoys working with a variety of different clients on both writing projects and as a marketing and public relations consultant. Schumacher holds a Bachelor of Science in journalism from the University of Wisconsin.