A base station for passively recharging a battery in an implant without patient involvement is disclosed. The base station can be hand held or may comprise equipment configured to be placed at a fixed location, such as under a bed, on or next to a wall, etc. The base station can generate electric and magnetic fields (E- field and B-field) that couple with an antenna and a receiving coil within the implant to generate a charging current for charging the implant's battery. No handling or manipulation on part of the patient is necessary； the implant battery is passively charged whenever the patient is within range of either the magnetic or electric charging fields generated by base station. Charging using the B-field occurs when the IPG is at a relatively short distance from the base station, while charging using the E-field occurs at longer distances. Back telemetry from the implant can inform the base station whether B-field or E-field charging is indicated, and is preferred if possible for its ability to transfer higher amounts of power to the implant.
