One of my pet peeves is the prevalence of devices powered by odd numbers of standard batteries (AA, AAA). Since I try to avoid using disposable cells and all of the chargers that I've so far owned charge cells in pairs, this means that it is almost impossible to get the odd cell to the same state of discharge as any other. Therefore it is impossible to charge said odd cells without damaging one of the pair.
I'd like to create a simple device that could safely bring any two rechargeable cells to the same level of discharge. I presume that other than mechanical and wiring bits, all that would be needed would be resistors and diodes. But, being an electrical retard, I'm not quite sure... not at all sure, really, where to begin.
My immediate focus is on LSD NiMH cells; but discussions that are applicable to other chemistries are more than welcome.