9-Volt Batteries - Part 1 : The Tear Down - Battery No.1 thru No. 5

[user 30299]

Over the years the current drain for smoke detectors has become better. If the manufacturer has supplied the battery with it and it doesn't say in the instructions that the battery supplied is for testing only and should be replaced with a fresh one on installation, then fine for that one. But check what YOUR smoke detector says IS the correct battery.ó
You can now get ones with a 10 year sealed for life of detector battery. So you never have to replace the battery for the life of the detector. 3M make them. Anyway, use the recommended battery or better. Don't use heavy-duty zinc carbon unless it says you can.
But to answer your other question. Zinc carbon batteries have a shorter shelf life than Alkaline so make sure it's fresh. That's trickier

Or just buy the 10-year, sealed for life detectors, and stop worrying for 10 years
.

All the smoke detectors in my home have a "Low Battery Feature". It's a pretty standard feature these days.
They start "chirping" about every minute to tell you the battery voltage is low.

Nice feature, except when it starts chirping at 1:00 AM. You have no choice but to change the battery!
Battery removal without immediate replacement is bad karma . . . . lol