In vehicles having a traction battery system, such as a hybrid electric vehicle (HEV), plug-in HEV (PHEV) or battery electric vehicle (BEV), vehicle controls evaluate a level of charge in the battery (state of charge (SOC)), and how much power the battery can provide (discharge) or receive (charge) in order to meet the driver demand and to optimize the energy usage (power limit). A battery may be represented by an equivalent circuit model (ECM) having battery ECM parameters (circuit elements) that represent battery characteristics. Battery parameters (such as SOC and power capability) calculations may be based on the battery ECM parameters.
A battery management system may calculate the SOC as a percentage of available charge as compared with a maximum charge capacity. One such method for calculating SOC is the ampere-hour integration method. A battery management system may, for example, calculate the battery power limit based on battery age, temperature, and SOC. The SOC and the battery power limits can then be provided to various other vehicle controls, for example, through a vehicle system controller (VSC) so that the information can be used by systems that may draw power from or provide power to the traction battery.