Patent ID: 7741805

Claim:
Method for managing electric power flow of an electric power storage device adapted to provide power through an electric circuit including an electric machine to crank an internal combustion engine, the method comprising: cranking the engine during a first engine cranking event; after cranking the engine during the first engine cranking event, continually updating an available power from the electric power storage device to crank the engine during a second engine cranking event subsequent to the first engine cranking event based on an initial estimate of an internal resistance of the electric power storage device computed as a function of an open circuit voltage of the electric power storage device, a resistance of the electric circuit, and a minimum voltage of the electric power storage device corresponding to the first engine cranking event; determining a power threshold required to crank the engine during the second engine cranking event as a function of a lowest ambient temperature corresponding to a predetermined number of engine cranking events preceding the second engine cranking event; and if the available power is less than the power threshold, taking remedial measures including at least one of reducing power flow out of the electric power storage device and increasing power flow to the electric power storage device.