Techniques for charging a battery within an implantable component (implant) of an implantable medical device system. A multi-loop external charging device includes a plurality of coil/loop antennas that are each configured to emit a magnetic field that is received by an implantable coil of the implantable component. At least one characteristic (e.g., phases, amplitudes, etc.) of the emitted magnetic fields are varied relative to one another over time.