Most cheap AA battery chargers charge two batteries at a time. Many devices use 1 or 3 AA batteries, meaning it's difficult to make sure you've always got two compatible batteries in the charger.
My fairly limited understanding of chargers is that they trickle feed energy into the batteries until the voltage in the circuit increases to a threshold, indicating that the batteries are charged. So it seems to me that I could short one of the two battery holders, and put the battery in the other one, such that the battery charges twice as fast.
Is this possible? If so, how can I figure out if it will change too fast and damage the battery? If not, is there any reasonably reliable way of charging a handful of single AAs, given only a cheap double AA charger? (I would prefer not to damage the charger, but don't mind modifying it, if necessary). Also, most of these batteries are NiMH, but there are a couple of lithium batteries, and there might be a NiCad or two as well.