An integrated external controller/charger system for an implantable medical device is disclosed comprising an external controller/charger device with a Graphical User Interface (GUI) and first battery, and an external charging coil assembly coupleable to the external controller/charger device and including or associated with a second battery. The second battery is used to energize a charging coil in the external charging coil assembly, while the first battery is used to power other aspects of the system (data telemetry circuitry, control circuitry, the GUI, etc.). Because the second battery powers the relatively high-power charging function, the first battery in the external controller/charger device can be made smaller. Additionally, the second battery enables a suitable external controller device (e.g. a mobile device such as a cell phone) to provide charging functionality even if its first battery is otherwise inadequate.