An energy store (14a) has at least three energy storage sections (u, v, w) and at least two switching elements. Each energy storage sections (u, v, w) has multiple energy storage modules and each energy storage module has at least one energy storage element that receives and stores energy from an energy source (12). The energy store (14a) is connected to a first coil (50) so that a voltage induced in the first coil (50) is used to charge the energy storage elements. The energy store (14a) is matched to properties of the voltage provided by the first coil (50) by switching the switching elements. As a result, the energy storage modules of an energy storage section (u, v, w) are connected in parallel and/or in series with one another and/or at least one energy storage module of at least one energy storage section (u, v, w) is bypassed.