For what it's worth there's a fellow locally who rebuilds batteries that won't hold a charge. He says that it's normally one or two cells in the pack that go bad. He disassembles the battery packs, tests the individual cells and takes good cells from one pack to replace bad cells in another. Sounds like a lot of work to me but he seems to like the result.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.