Fast Charging Circuit for NiCd Battery Used in Implant Electronic Systems

A fast charging circuit for NiCd battery used in implant electronic systems is described. The circuit utilized the techniques of 1) sensing the internal gas pressure and temperature rise by sensing of the battery terminal voltage, and 2) setting the maximum charging current according to the concept of charge retention capacity, >95 percent after 100 cycles, of the battery. Experimental results show that a B-20 cell can be fully charged in 20 minutes instead of 14 hours.