Systems, devices, and methods for powering and/or controlling electrically- powered devices. A power supply system is operable to provide a voltage across at the active and the counter electrode assemblies of a transdermal delivery device. The system includes a power source and a magnetic coupling element for securing the power supply system to the electrically powered device. Power may be transferred inductively or through direct electrical connection between the power supply system and the electrically powered device. Coupling means are provided on the power supply systems and the electrically powered device for ensuring correct mechanical and electrical coupling.