An electrical circuit for charging a secondary battery that comprises a dc-converter and an output connector that can be connected to the positive terminal of the secondary battery for applying a charging current to the secondary battery. The dc-converter has a voltage feedback connector for sensing a feedback voltage, wherein the dc-converter is adapted to regulate the output voltage by adjusting the output current at the output connector depending on the sensed feedback voltage and a feedback-sub-circuit connected to the output connector and to the voltage feedback connector of the dc-converter.