A system control unit for controlling a charging system that is intended for charging an electrical energy storage device, comprising an electric generator; an internal combustion engine that is mechanically connected with the electric generator; a generator controller for controlling the electric generator; an engine controller for controlling the internal combustion engine; and a transmitting device for transmission of messages, whereby the engine controller is connected with the generator controller by way of the transmitting device, and whereby the engine controller is operable in that a message containing information about an operating state of the internal combustion engine can be produced and said message can be sent to the generator controller via the transmitting device.