Motor vehicle with hybrid drive

1. Motor vehicle, with a hybrid drive device having an internal combustion engine, at least one electric machine at least one electric energy storage mechanism; a fuel cell system for generating electric power, wherein the fuel cell system is an auxiliary power source for delivering a lower power than the internal combustion engine; a control unit controls the operation of the fuel cell system to operate continuously in a predetermined operating range or at a predetermined operating point of a high efficiency, with the power the fuel cell system delivers being supplied at least to one power consuming device and any excess power of the fuel cell system being supplied to at least one additional power consuming device as required to maintain high fuel cell system efficiency.

2. Motor vehicle as claimed in claim 1 , wherein the excess power of the fuel cell system is supplied at least partially into the at least one energy storage mechanism so that the latter functions as the additional power consuming device.

3. Motor vehicle as claimed in claim 1 , wherein the excess power can be at least partially supplied to the at least one electric machine as driving power, so that the electric machine serves as the additional power consuming device.

4. Motor vehicle as claimed in claim 1 , wherein at least some of the excess power of the fuel cell system can be supplied at least partially to the at least one electric machine and the at least one energy storage mechanism as a function of at least one operating criterion so that at least one of these devices serve as the additional power consuming devices.

5. Motor vehicle as claimed in claim 4 , wherein the at least one operating criteria include a drive power demand of the motor vehicle, charge status and maximum charge capacity of the at least one electric energy storage mechanism.

6. Motor vehicle according to claim 1 , wherein the fuel cell system maximum deliverable power is approximately equal to the maximum power demand of the vehicle electric system and of at least one secondary unit which does not deliver any driving power.

7. Motor vehicle as claimed in claim 6 , wherein the at least one secondary unit an air conditioning system, interior heating, seat heating, cigarette lighter, radio, television, navigation system, data processing system, ice chest, refrigerator, window opener, door opener, sunroof opener, convertible top opener, trunk opener, vehicle steering, vehicle brake system, vehicle interior lighting, vehicle exterior lighting, telecommunications system, compressor, oil pump, water pump, gasoline pump, tool unit, a cable winch, vehicle lift or street sweeper brush.

8. Motor vehicle as claimed in claim 1 , wherein the predetermined operating range or operating point is at or near the maximum efficiency of the fuel cell system.

9. Method for operating a motor vehicle with a hybrid drive device having an internal combustion engine, at least one electric machine, a fuel cell system for generating electric power which delivers a lower power than the internal combustion engine, and at least one electric power storage mechanism, comprising the steps of

activating the fuel cell system;

operating the fuel cell system continuously in an operating range or at an operating point of high efficiency;

supplying at least a portion of the power generated by the fuel cell system to at least one power consuming device;

supplying any excess power generated by the fuel cell system to at least one other power consuming device in order to maintain a power demand on the fuel cell system corresponding to high efficiency operating range or operating point.

10. Method as claimed in claim 9 , wherein the excess power of the fuel cell system is stored at least partially in one of the at least one energy storage mechanisms.

11. Method as claimed in claim 9 , wherein the predetermined operating range or operating point is at or near the maximum efficiency of the fuel cell system.