An external charger for an implantable medical device (IMD) is disclosed including a three- axis magnetic field sensor at the center of a primary charging coil. The sensor first senses a magnetic charging field produced by the coil with no IMD present (vector A). The sensor then senses the field in useful operation when such field is being provided to the IMD (vector B). From these vectors, a vector C is calculated representing the magnetic field reflected from the IMD. Vector C can be used to determine a vector D, representing the position of the IMD in physical space relative to the external charger. Information comprising one or more volumes can be stored in the external charger, and compared with vector D to determine whether charger-to-IMD positioning will provide an adequate amount of power to the IMD, and/or to provide an indication of charger-to-IMD alignment.
