The invention concerns a method for controlling a direct voltage source with a first direct voltage source (2) and a voltage monitoring device (24), which monitors an output voltage of the first direct voltage source (2) and acts upon a control device (31), the control device (31) controlling the working state of the first direct voltage source (2). Further, the invention concerns a voltage supply device (22) with which the method can be used. In this connection it is endeavored to reduce the risk of an increase in voltage in a circuit with several direct voltage sources. For this purpose, a second direct voltage source (3) produces a voltage change at the voltage monitoring device (24).