The present invention relates to a motor vehicle that is equipped with an electrical door closing mechanism, a radio-based signal receiver and a control unit, wherein the door closing mechanism can be actuated after receiving and verifying an access authorization code by electrical signals that are generated by a control unit. The motor vehicle possesses an electrical charging apparatus accessible from the outside so that a signal generator that is provided to generate the access code can be charged from the electrical system of the motor vehicle in the event of an insufficient charge. Furthermore, the invention describes a method for charging a signal generator that can be executed using the device according to the invention.