Camcorder Battery won't charge

Battery charging light will not come on when plugged in but will play back and rewind tapes. Only used it a few times and stopped using it when the battery would no longer charge. Also tried buying a new battery to see if the old one had worn out and it still does not work. I have had my battery and transformer checked both are working fine. No explanation has been given but they have offered to fix it for a price.