A system is disclosed for controlling the charging of a rechargeable battery in an implanted human tissue stimulator by means of an external power source. Included in the stimulator are battery protection devices designed to sense the state of charge of the battery and limit the charging currrent amplitude...http://www.google.ca/patents/US4082097?utm_source=gb-gplus-sharePatent US4082097 - Multimode recharging system for living tissue stimulators
