BATTERY APPARATUS AND METHOD FOR ESTIMATING RESISTANCE STATE

A processor of a battery apparatus estimates an internal resistance of a battery at a reference temperature based on a measured voltage of the battery, a measured current of the battery, an open circuit voltage of the battery, and a measured temperature of the battery, and estimates a resistance state of the battery based on the estimated internal resistance and a beginning of life (BOL) resistance at the reference temperature when the battery is in a BOL state.