Ultralife Batteries

Searched batteries: Duracell MN1604, Goldpeak 1604P mayors, Energizer 522, Eveready 216, 522, or 122 Ultralife U9VL.

Try Home Depot!
Walmart could, but Home Depot finally!

Well, for starters, you need to buy new smoke alarms if they are over 2 years. It is useful to have new sensors just in case your old broken and you do not know about them. To buy the batteries, try to SST or even an electronics store like Fry's or Best Buy

Ebay would be best if the type is very weird, you more often or not may pay with a mandate that you look at a post office or grocery store. They cost 1.00 most places and whatever amount you want to be for. These are cashed by banks.

It is wise to replace all your firealarms w / new every three to ten years.