The disclosure relates to an electrical energy-supply device including several usage units, wherein each usage unit is adapted to generate or temporarily store electrical energy, and wherein a control means is adapted to control an exchange of power (E) between the energy-supply device and at least one device, The invention provides that the usage units of the energy-supply device are divided into strands and the usage units of each strand are connected to a series connection and the series connection is connected via a DC converter and at least one galvanically isolable switching unit is connected to a busbar arrangement.