One of my smoke detectors was chirping and when I removed the 9V battery, I found it was hot. In fact, it was making a 'cooking' sound.

Was it the smoke detector causing the battery to cook itself or was it a defective battery?

  • I had a battery explode in one of my detectors. You got off lucky.
    – sww1235
    Mar 26, 2015 at 17:24

3 Answers 3


Wow- A smoke detector that could cause a fire..

It is very difficult to say

  • It could be a fault in the fire alarm- short circuit that caused the battery to heat up to a cooking point.

  • It could be a chemical fault in the battery where atmospheric pressure and chemical imbalances caused by some impurity during production caused the battery to heat up at a certain point of its life.

Either way

The safest option is to replace both and remove all doubt!

eg ever hear about the exploding iPods... :)

  • 2
    Now would be the time to buy the combo carbon monoxide & smoke detector that is required by code to go in houses. This site will tell your state require one, Smoke and Carbon Monoxide Alarms
    – lqlarry
    Nov 26, 2011 at 20:30

I just experienced the same problem. I discovered that I had installed the battery backwards. The smoke detector was chirping, so I removed battery (which was almost to hot to hold!), put another in out of same packet but in the correct orientation. No more chirping, and I have confirmed that the new battery is not overheating.

  • 1
    Have you confirmed that the detector is still working? If it drew enough current to cook ghd battery, it probably cooked the circuitry too.
    – keshlam
    Oct 28, 2015 at 18:41

I had this issue with a first alert BRK9120b that was 15 years old. After going through 2 or 3 batteries I changed the detector. All was fine until another detector in another bedroom started behaving the same way. At first thinking it was just the battery I changed it and the next day it was hot and dead again. I ordered 2 more detectors just to keep one hanging around as this seems to be a trend and I have 8 of these in my home. Fortunately after 15 years the detector hasn't changed all that much. The mounting holes are still the same but the bracket changed. It took an extra minute to change the bracket and the wire connector was still the same.

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