My DSLR, like most, uses a proprietary lithium-ion battery pack. I've got four batteries that have been used quite a lot. Only two of them can be reliably charged and used for any significant length of time.
Is there any way to revive a battery with diminished capacity? I realize that eventually, they do wear out forever. But is there a possibility that some sort of reconditioning would extend their useful life?
Failing that, is there any way to turn the old batteries over for recycling, and to get a recycling credit towards the purchase of a new one?