Originally Posted by PR_Tom

ok, I would take a pencil eraser and clean off the metal charge contacts as good as possible. If the base has those pointy contacts, the very tips will sometimes get a tiny speck of crud on there, preventing a good charge connection. Also in general, if it's a Ni-cd battery pack, try to run it form a full charge, to a full discharge everytime, else the per-charge life decreases pretty quickly.