If you are like me, you probably have a *lot* of batteries.  Particularly on location with a couple of strobes.  You’ve got a bucket full of AAs, and maybe 3 or 4 batteries for your SLR.  All well and good up until you start changing batteries in the field.  Maybe it’s just me, but once I start swapping batteries, when I get home it they are generally all jumbled up and I have no idea which are still charged, which are dead and which may have been partially used, but still need a “top off”.   To solve this I came up with a rather simple solution – when I charge my batteries, as they are charged I put a rubber band around them.  This serves two purposes – 1) it keeps each set of AAs together in a nice neat group of 4, but more importantly it “marks” them.  Since I obviously have to take the rubber band off before using the battery, at the end of the day, I know that any battery with no band has at least been used, and the ones still banded are fresh.  Then I simply charge the loose ones and re-band them.  Works with both AAs and SLR batteries, quick and easy.