Patent ID: 7657438

Claim:
A method for controlling a vehicular electric system having a plurality of power sources that supplies power to an onboard electrical load and an onboard battery, wherein the plurality of power sources includes at least one of a generator driven by an engine of a vehicle, a regenerative braking system, and an external source, the vehicular electric system including a power supply control device that controls power distribution from each of the power supplies, the battery having a storage capacity of a plurality of hypothetical energy units, the method comprising: storing, by the power supply control device, a cost of generation for each unit of charge stored in the battery; obtaining, by the power supply control device, information that includes, for each power source, a power generation cost that is an amount corresponding to fuel consumption for generating unit electrical power by the power source, the information further including information on an energy cost of the onboard battery based on charge and discharge histories of the onboard battery, the charge and discharge histories of the onboard battery including, for each unit of charge stored in the battery, the generation cost of the unit of charge; determining a current cost of the battery from the costs of generation corresponding to the units of charge stored in the battery; determining an amount of power that needs to be supplied; calculating, by the power supply control device, a quota for power distribution for each of the power sources and the batten from the power generation costs of the power sources and the current cost of the battery; and adjusting a power supply distribution of the plurality of power sources, a receiving power rate of the onboard electrical load, and one of a power supply distribution of the onboard battery and a receiving power rate of the onboard battery to reduce a consumed power cost, wherein the adjusting is based on the information and performed by prioritizing a power supply from one of the plurality of power sources which has a lowest power generation cost of the plurality of power sources.