Hey, you could salvage batteries from most people's throw aways... most times, like in stereos and CD players and such, people replace all the batteries, and it's usually not that they're all dead. Of course, these are also usually alkaline, and you'd need all kinds of adapters and pack holders to make different types of packs that wouldn't last very long, so maybe you could just use them for stuff around your house... making this post completely irrelevant to the topic of the thread!
OTOH - if you wanted to make a battery pack out of, say, AAA cells, you can get them from cordless phones for free. Break the packs open, there's 3 AAA cells in there, and they're Ni-MH usually. 1.2V ~2200mAH each.
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