An improved external charger for charging the battery within or providing power to an implantable medical device is disclosed. The improved external charger includes circuitry for detecting the temperature of the external charger and for controlling charging to prevent exceeding a maximum temperature. The external charger in some embodiments includes a user interface for allowing a patient to set the external charger's maximum temperature. The user interface can be used to select either constant maximum temperatures, or can allow the user to choose from a number of stored charging programs, which programs can control the maximum temperature to vary over time. Alternatively, a charging program in the external charger can vary the maximum temperature set point automatically. By controlling the maximum temperature of the external charger during charging in these manners, the time needed to charge can be minimized while still ensuring a temperature that is comfortable for that patient.