I have found that when a rechargeable battery is not accepting a good charge that it can be remade to almost full capacity by freezing it for several days. I don't know why. I just know that I have saved batteries for marine radios, computers, cordless drills digital cameras and cell phones this way. Discharge the battery before putting it in the freezer. If the battery is not removable, put the whole thing in the freezer. Plastic bags are a good idea to isolate the battery from its surroundings.