Abstract: A system for charging a rechargeable battery of a portable unit in a rack includes a detection circuit which detects the presence of the unit in the rack. The system has circuitry for transferring of energy from a supply circuit of the rack via a charging circuit of the unit to the battery. The transfer circuit is formed by an induction path which comprises a coil of the rack and a coil of the unit. The unit has a transmission circuit which, after placement of the unit in the rack, transmits a message via a wireless path, for example the induction path, to a control circuit of the rack, the control circuit being connected to the supply circuit. If the rack does not receive, or does not satisfactorily receive, a message expected upon placement of the unit in the rack, the control circuit controls the supply circuit so as to make the supply circuit select a higher transfer rate than normal for the purpose of transferring energy to the battery via the induction path.