The invention relates to a method and an apparatus (1) for charging an energy storage (2) via a current generating device (3), comprising at least one control device (6), a burner (7) connected to a tank (11) for fuel supply, a charging device (4) connected to the energy storage (2), and a thermal element (8) whose one side is connected to the current generating device (3). To create such a method and such an apparatus (1), by means of which the capacity of an energy storage (2) of a vehicle (5) can be maintained for a longer period of time, it is provided for the second side of the thermal element (8) to be connected to a heat dissipating element (9) of a vehicle (5), and a monitoring unit (19) for the temperature of the heat dissipating element (9) is provided and connected to the control device (6) so that the current generating device (3) will be controllable to charge the energy storage (2) as a function of the temperature of the heat dissipating element (9).