Abstract: The invention concerns a charger (CU) for batteries (A) in an electrical mobile device (MU), wherein a power oscillator (OSZ) produces an alternating magnetic field with the primary part (W.sub.PRI) of an inductive coupler, for the inductive transmission of charging power. By alternatingly receiving power for charging the batteries (A), the mobile device (MU) which is coupled to the charger (CU), charges the entire inductive coupler via its secondary coupler part (W.sub.SEC). The charger (CU) contains detection means (SEL, AMP, RE and FE-DEM) which generate at least one control signal (S.sub.C 1, S.sub.C 2) when the inductive load of the coupler is periodically changed in order to switch the power level, which is inductively transmitted by the charger (CU) to the mobile device (MU), from a low average value in the stand-by mode to a higher average value for the charging operation.

Abstract: A device for charging batteries is comprised of a mobile electrical device MD and a charging unit CU and inductively transmits electrical power by means of a alternating magnetic field from at least one primary winding W1, W2 to at least one secondary winding W3, W4 in the mobile device MD. According to the invention, the alternating magnetic field is generated by a self-oscillating push-pull oscillator which contains switches Q1, Q2 that are reciprocally connected with positive feedback and in each push-pull branch, contains a resonance circuit with the effective inductance of at least one primary winding W1 or W2 and with a circuit capacitance C1, C3 or C2, C4, wherein the primary windings W1 and W2 in the charging unit CU are disposed spatially separate from each other so that each generates a magnetic alternating field in a different spatial region and the secondary windings W3, W4 in the mobile device are disposed so that each spatial region is equally loaded.