A charging system, comprising: - a switching converter comprising converter switches (1, 2) coupled to each other at a converter terminal, the switching converter for electrically coupling to a first electrical energy storage device, - a filter circuit comprising a series inductor having a first inductor terminal and a second inductor terminal, the second inductor terminal electrically coupled to the converter terminal, and a parallel capacitor having a first capacitor terminal electrically coupled to the first inductor terminal and a second capacitor terminal, - a first set of switches (20a, 20b) arranged for selectively electrically coupling, when switched on, the filter circuit with an alternating current voltage source, the alternating current voltage source for providing a time periodical voltage signal, - a coupling device for selectively electrically coupling a second electrical energy storage device to the filter circuit via at least the first inductor terminal, the coupling device comprising a detection device configured to detect a connection status of the coupling device and send, based on the status, a coupling signal indicating whether the second electrical energy storage device is connected to the coupling device, - a controller for controlling the first set of switches and the converter, configured to receive the coupling signal from the detection device, and based on the coupling signal, to switch on the switches (20a, 20b) of the first set and control the converter switches such that the time periodical voltage signal and the current through the series inductor are in phase, or to switch off the switches (20a, 20b) of the first set and control the converter switches (1, 2) for providing a current signal to the second electrical energy storage device for charging the second electrical energy storage device from the first electrical energy storage device. - a switching converter comprising converter switches (1, 2) coupled to each other at a converter terminal, the switching converter for electrically coupling to a first electrical energy storage device, - a filter circuit comprising a series inductor having a first inductor terminal and a second inductor terminal, the second inductor terminal electrically coupled to the converter terminal, and a parallel capacitor having a first capacitor terminal electrically coupled to the first inductor terminal and a second capacitor terminal, a series inductor having a first inductor terminal and a second inductor terminal, the second inductor terminal electrically coupled to the converter terminal, and a parallel capacitor having a first capacitor terminal electrically coupled to the first inductor terminal and a second capacitor terminal, - a first set of switches (20a, 20b) arranged for selectively electrically coupling, when switched on, the filter circuit with an alternating current voltage source, the alternating current voltage source for providing a time periodical voltage signal, - a coupling device for selectively electrically coupling a second electrical energy storage device to the filter circuit via at least the first inductor terminal, the coupling device comprising a detection device configured to detect a connection status of the coupling device and send, based on the status, a coupling signal indicating whether the second electrical energy storage device is connected to the coupling device, - a controller for controlling the first set of switches and the converter, configured to receive the coupling signal from the detection device, and based on the coupling signal, to switch on the switches (20a, 20b) of the first set and control the converter switches such that the time periodical voltage signal and the current through the series inductor are in phase, or to switch off the switches (20a, 20b) of the first set and control the converter switches (1, 2) for providing a current signal to the second electrical energy storage device for charging the second electrical energy storage device from the first electrical energy storage device. to receive the coupling signal from the detection device, and based on the coupling signal, to switch on the switches (20a, 20b) of the first set and control the converter switches such that the time periodical voltage signal and the current through the series inductor are in phase, or to switch off the switches (20a, 20b) of the first set and control the converter switches (1, 2) for providing a current signal to the second electrical energy storage device for charging the second electrical energy storage device from the first electrical energy storage device.