Load converter to stabilise voltage of the starter battery, which has to deliver high power for a short time, and the consumer battery, which has to deliver constant power at a lower level over an extended period. The converter is simply integrated into the existing cabling and increases the charge voltage to 14.2 V, thus guaranteeing optimum charging while in operation. A switch or an external control signal +D from a dynamo switches the converter on or off. Under and overvoltage in the range 8 to 16 V are equalized, preventing failure or interruption of the supply to the consumer battery.