Unused AA batteries do eventually go bad and all batteries including the AA batteries have an expiration date.
The AA battery may still work after the expiration date but it will not have as much charge and will not last as long as a new battery.
Most AA batteries as well as AAA and C and D cell batteries will last up to 10 years unused and 9 V batteries last up to 5 years unused.
A battery is a chemical product which produces electricity by chemical reactions at its inside.
When the battery has passed the recommended usage period, the components that make up the battery will deteriorate, leading to performance degradation.
That is why there is an expiry date on the battery.
This loss of capacity (aging) in batteries is irreversible.
As the battery loses capacity, the length of time it will power the product (run time) decreases.
Lithium-Ion batteries continue to slowly discharge (self-discharge) when not in use or while in storage.
Routinely check the battery's charge status.
AA batteries start off with 1.5 volts of energy, but the voltage goes down as the batteries are used up.
Once the batteries dip below 1.35 volts, they appear to be dead, even though they still have a lot of juice left.
The best way to store batteries is to do the following.
Keep them in their original packaging. Did you just buy a new pack of batteries and would you like to unbox them immediately?
Separate old and new batteries.
Store them at room temperature or below.
Keep them away from metal objects.
Be sure to control the humidity.