Patent ID: 7489113

Claim:
An energy storage system for a motor vehicle, comprising: an electric machine configured for operation at least as a generator, for generating a generator current; a vehicle electrical system battery connected in parallel to the electric machine; a capacitor unit connected in parallel to the electric machine; and a controller configured such that the battery is charged with a maximum battery charging current, if the vehicle is in a boost or braking operating mode, and in all other operating modes, the battery is charged by a battery charging current that is adjusted as a function of a state of charge of the battery, wherein the controller is configured to adjust discharging of the battery such that a pre-defined minimum battery charging current flows through the battery, if the state of charge of the battery exceeds a pre-defined first charge threshold value; the controller is configured to adjust charging of the battery such that a pre-defined maximum battery charging current flows through the battery, if the state of charge of the battery falls below a pre-defined second charge threshold value; and the controller is configured to regulate the generator current such that a predetermined minimum charging current flows through the battery, if the state of charge of the battery is equivalent to a predetermined state of charge.