Method of controlling a state-of-charge (soc) of a vehicle battery

Abstract

A system and method for controlling a state-of-charge (SOC) of a vehicle battery, such as a high-voltage battery used by a hybrid electric vehicle (HEV) for vehicle propulsion, so that the SOC is maintained within a desired SOC range that is temperature-dependent. In an exemplary embodiment, the system and method use a battery temperature prediction to determine a desired SOC range, and then control the amount of charge on the vehicle battery such that the SOC is maintained within the desired SOC range. As the battery temperature prediction goes lower (i.e., as it gets colder), the desired SOC range may need to be adjusted or shifted upwards in order to account for increased internal battery resistance and to ensure that the vehicle battery has enough power to start the vehicle. Similarly, as the battery temperature prediction goes higher (i.e., as it gets warmer), the desired SOC range may need to be adjusted or shifted downwards in order to reduce degradation effects and improve battery. The exemplary system and method control the SOC of the vehicle battery and may seek to optimize a number of different parameters, including battery life, battery performance and/or vehicle fuel economy.