Motor vehicle electrical system and method for operating a motor vehicle electrical system

摘要

#CMT# #/CMT# The network (1) has an electrical energy storage unit (2) assigned to a starter (S). A shift element (8) is arranged between the energy storage unit and a generator (G). Another shift element (10) is arranged between another electrical energy storage unit (3) and the generator, where the electrical energy storage units comprise high charging voltage and low charging voltage respectively. A step-down converter (11) is arranged parallel to the shift elements of the energy storage unit at the low charging voltage. A diode (9) is arranged parallel to the former shift element. #CMT# : #/CMT# The electrical energy storage units are designed as a lead acid battery and a lithium-ion battery respectively. The shift elements are designed as relays or as power semiconductor switches. An independent claim is also included for a method for operating a motor car onboard network. #CMT#USE : #/CMT# Motor car onboard network. #CMT#ADVANTAGE : #/CMT# The electrical energy storage units are designed as the lead acid battery and the lithium-ion battery respectively, thus optimizing efficient, cost-effective and space-saving electrical energy storage units. The internal resistance of the energy storage unit is selected such that the energy storage unit can provide sufficient power to ensure a cold-start ability of the starter. The motor car onboard network is manufactured in a flexible and cost-effective manner. The difference between open-circuit voltages of the energy storage units is smaller than a flux voltage of the diode such that a permanent current flow can be prevented. #CMT#DESCRIPTION OF DRAWINGS : #/CMT# The drawing shows a circuit diagram of a motor car onboard network. G : Generator S : Starter 1 : Motor car onboard network 2, 3 : Electrical energy storage units 8, 10 : Shift elements 9 : Diode 11 : Step-down converter.