Which Batteries Are Best for Smoke Alarms?

Part of our guide: Rechargeable vs Disposable Batteries: When Each Wins

By the BasketLab team · updated 27 July 2026 · how we rank

Smoke alarms are one of the few household gadgets where getting the battery wrong has consequences a good deal worse than an inconvenience. So let me save you the deliberating: this is not the place for your rechargeables, however green-minded you happen to be feeling. A standard alkaline or a lithium battery, every time. Here's the reasoning.

The recommendation, plainly

For a normal replaceable-battery alarm, fit a good-quality alkaline, a 9V or an AA depending on your model. Duracell, Energizer and GP all make ones that'll do the job for a year without any drama, and Amazon Basics alkalines are perfectly decent for the money. If you'd rather fit it and forget it, a non-rechargeable lithium battery lasts far longer, often up to ten years, which happens to match the lifespan of the alarm itself.

Whatever you choose, buy a name you actually recognise. A smoke alarm is the last place on earth to gamble on a mystery three-for-a-pound multipack from a bargain bin.

Why not rechargeables?

Rechargeable NiMH cells are brilliant in a games controller or a torch, and I'd cheerfully fill the house with GP or ALLMAX rechargeables for that sort of thing. A smoke alarm is different, for two reasons.

One is voltage. Rechargeables sit at around 1.2 volts rather than the 1.5 of an alkaline, and they hold that lower voltage dead flat right up until they fall off a cliff. An alkaline, by contrast, fades gradually, and that gentle fade is exactly what sets off the 3am low-battery chirp you know and love. A rechargeable can go from fine to flat with far less warning, and a smoke alarm depends on getting that warning.

The other is self-discharge. Rechargeables slowly leak charge just sitting there, even when nothing's drawing on them. A device you check twice a year, if you're honest, needs a battery that'll still be holding a useful charge eleven months from now. Alkalines and lithiums manage that easily. Standard rechargeables don't.

The bit that matters more than the brand

Honestly? The best battery in the world is useless in an alarm you never test. Press the test button once a month. It takes five seconds and it's the single most effective thing you can do here. Change the battery once a year as a matter of routine, not when it finally starts chirping at you, and pin it to a date you'll remember, like the clocks going back in autumn.

A couple of extras worth knowing. Sealed lithium alarms exist that never need a battery change at all; after their ten years you simply replace the whole unit, ladder and all. Smart alarms, such as Ring's, will ping your phone when they go off, which is genuinely handy if you're often out, though they still need power and the same battery logic applies. And a mains-wired alarm keeps a backup battery inside for exactly the moment the power fails, so don't ignore that either. Smoke alarms save lives, but only the ones that are actually working when it counts.