A mobile data storage device is configured in the manner of a data storage card, or a data storage stick. The mobile data storage device can include at least one electrical coil (7), and energy storage (6), a data storage (1), at least one interface unit (3), and at least one permanent magnet (8). The at least one interface unit (3) is configured for the output or the receiving of data that is stored, or that can be stored, in the data storage (1). The energy storage (6) can be inductively charged by a magnetic alternating field, which can be generated by displacing the at least one permanent magnet (8) in a region of the electrical coil (7). At least one of the at least one interface unit (3) is electrically coupled to the energy storage for the energy supply thereof.