<p>The device has a generator which is driven by the engine and supplies an on-board network with at least one battery and a number of loads. A controller (10) receives information from the network and engine required to determine the control and/or regulation parameters for corresponding network and engine components. The controller performs power management and distributes power between the network and engine according to defined requirements and taking into account the condition that the desired network voltage (Us) lies within defined limits</p>
