Thanks for scaring up a drill! That's something I've really missed when piecing things together from wood.
I presume these are NiCad battery packs? If so, then the official charger is probably not very "smart", and simply charges at a controlled current. This is the kind where you are supposed to remember to remove the battery after "about 8 hours" for best results.
If so, we could easily do much better with a timer-controlled arduino-based charger. I'm picturing a small LCD readout of how long the battery has been charging and how long it will continue to charge. After any battery has been in the charger for about 8 hours, it cuts off (or down) the charge current. Otherwise I'm sure the batteries on the charger will be left there for days and weeks on end due to the realities of a group work environment.
The main thing to be researched would be what an appropriate voltage and current is to safely charge the packs, and for how long.