Step-by-Step Instructions

In This Article:

Expert advice on how to replace or change a smoke detector battery, including a helpful diagram of a smoke detector’s main parts.

Nearly every type of smoke detector makes a chirping sound to let you know when it’s time to change the battery. Inevitably, that first chirp just happens to sound at about 3 AM, when you’re deep asleep.

Illustration of a finger pressing the red button on a ceiling-mounted smoke detector.
Test a smoke detector by simply pushing the test button.

If you would rather not risk being awakened by the chirp, you can beat it to the punch by proactively replacing the battery on a regular schedule.

Most detectors will operate about 6 months on a battery, so the strategy is to replace batteries twice a year. A good time to replace all of your smoke detectors’ batteries, because it serves as a twice-yearly reminder, is on the weekends when we set our clocks forward for daylight savings time and back to standard time.

Smoke detectors may be either battery powered or wired directly into a home’s electrical system. But nearly all smoke detectors, including those that run on household current, do contain a battery. Detectors that are hard-wired to the home’s electrical system use this battery to provide backup power in case a fire knocks out the house’s electrical power.

Both battery-operated and household-current smoke detectors sound the previously-mentioned beeping or chirping low-battery alarm. This alarm is different than the deafening, blaring fire alarm that occurs during a fire: It is a sporadic chirp or beep, not a constant blast.

Sometimes it can be tricky to figure out which smoke detector in your house is chirping. As a rule, the lower the battery gets, the more the detector chirps. So, once it starts to chirp, you either have to station yourself (and, possibly, other family members) near each detector and wait for the next chirp, or you have to let the battery grow weaker until the chirps sound frequently. Obviously, the second alternative is far from ideal because you risk the possibility of the detector ceasing to work. That’s why it makes sense to change all of the batteries semi-annually at a convenient time.

Step-by-Step Instructions

If you hear the beeping or chirping low-battery alarm, do not ignore it, and do not ever remove the battery without replacing it with a new one. Smoke detectors with fully-functional batteries are critical to the safety of your family and home. Sadly, news reports of tragic fires often point out that the home had smoke detectors but those detectors had been disabled.

In this video, Don gives a quick lesson on changing smoke detector batteries:


Homeowner hack: how often should you change smoke detectors? #hometips #smokedetectors #safety #tips

♬ original sound – Yelp

(Note: New lithium battery smoke detectors last up to 10 years. With these, the entire unit is disposable. If your home has this type of detector, you will need to replace the entire unit.)

Most conventional smoke detectors have a friction-fitting cover that hinges down or lifts off. With some, the entire body of the smoke detector clips onto a base that is attached to the ceiling or wall. To remove these, you typically give the body a counterclockwise twist.

Step by step, here’s how to change a smoke detector battery:

1 Remove the cover or body. Gently pry the cover open or unclip the body of the detector from its base with a slight twisting motion. Inside, you will find three main parts: the sensing chamber, a loud horn, and a battery (and in some cases, house voltage power source).

smoke detector diagram
Smoke Detector Diagram Don Vandervort, HomeTips © 1997 to 2023 | HomeTips


2 Replace the battery. Unclip the old battery from its holder. Most detectors utilize a 9-volt battery—use a brand new lithium 9-volt battery as a replacement. Be sure the male and female terminals are properly oriented and connect soundly with the base.


3 Close the cover or replace the body. Snap the cover shut or lock the body of the smoke detector back into its base.


4 Test the detector. Press the test button on the surface of the detector to make sure the battery is working. When the button is pressed, the detector should beep or chirp.


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About Don Vandervort
Don Vandervort has developed his expertise for more than 30 years as a remodeler and builder, Building Editor for Sunset Books, Senior Editor at Home Magazine, author of more than 30 home improvement books, and writer of countless magazine articles. He appeared for 3 seasons on HGTV’s “The Fix,” and served as MSN’s home expert for several years. Don founded HomeTips in 1996. Read more about Don Vandervort