Okay, one of my 10 #smokedetectors started its low #battery alarm tonight. They always start beeping during the night, don't they?.

Should I continue to buy cheap 9V blocks at the local discounter or switch to rechargeable batteries instead (edit: for the environment)?

Non-rechargeable: Duracell industrial (1,35€) lasted 3½ years. Cheap batteries (50 Cents) lasted 2 years.

The rechargeable ones (~5€) do seem to provide just 8,4V and store only ~300-650mAh. Charging via USB cable or proprietary charger. I'm afraid they don't last more than a year and replacing them frequently is tedious.

Do you have experience with that?