[dragontamer]

Don't leave them in the charger! You precharge and then store for a year+. Modern NiMHs only need topping off once per year or less.

So you have two piles. Good charged NiMHs and uncharged depleted NiMHs. While(uncharged.size() >= 2) put them in charger.

Then once per year, do a refresh charge on all the NiMHs. Easy-peasy.

[amelius]

So now you have two piles, you come back after a year and then have to figure out which is which. All of this because someone wanted to save a few cents on the implementation of a charger.

[dragontamer]

The pile with 0 or 1 batteries in it is the one of partially charged batteries.

The pile with 2 or more batteries is the full set of fresh batteries.

Alternatively, buy a Battery Daddy and put +side up when it's charged, and -side up when it's uncharged.

Like the problems you are talking about really aren't that hard to deal with.