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How to Change a Smoke Detector Battery

Expert advice on replacing or changing a smoke detector battery, including a helpful diagram of a smoke detector’s main parts.

how to test smoke detector

Test a smoke detector by simply pushing the test button.

Instead of waiting for a smoke detector to jolt you out of bed in the middle of the night with the loud chirping or beeping sound it makes when the batteries begin to die, beat it to the punch by replacing the battery twice a year on a regularly-scheduled basis. 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 beep, not a constant blast.

change a smoke detector battery©Don Vandervort, HomeTips

The Basic Parts Inside a Smoke Detector

Step-by-Step Instructions

If you hear the beeping or chirping low-battery alarm, do not ignore it; change the battery immediately. 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.

(Note: New lithium battery models last up to 10 years; 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:

1Remove 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).


2Replace 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.


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


4Test 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.

Join the Conversation

  • Joshua Gerlach

    I had the same issue and was getting really upset. As an electrical engineer I really wanted to fix this. I tried several different batteries, including approved models, with same result. I measured the voltages of each and they ranged from 9.22 – 9.68 VDC. What didn’t make sense is I replaced batteries on units that weren’t chirping and then they started after putting the new batteries in. I thought I should be able to put the old battery back and it would be fine again right? Wrong! It continued chirping and was driving me nuts. I thought maybe the electrical prongs inside we’re going to making good contact, so I pried them out further. Still not working. I finally prayed “God help me please.” Shortly after I noticed a spring beside the battery that gets pushed down when a battery is inserted and the lid is closed. I thought “Hmm, I wonder if that is part of a circuit tied to the battery?” So I tore off a piece of paper and wrapped it around the battery to make the battery slightly thicker and put more pressure on the spring. I inserted the battery and closed the door. I noticed a red light flash once when closing the door, which I didn’t recall seeing before. I reinstalled and waited for the chirp to happen again. It didn’t happen so I tried this same method on two others. It worked on 3 of 3. “Thank you God!” Can’t say it will work for everyone else, but it’s worth a try. Hope this helps save a few hairs for others out there.

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