A method of managing a battery system using a battery management system. The method includes receiving, measured characteristics of one or more battery cells from one or more sensors, receiving, estimated parameters of the battery cells, estimating, one or more states of the battery cells by applying a battery model based on the measured characteristics and the estimated parameters of the battery cells, updating, at least a portion of the estimated parameters based at least in part on the estimation of the states of the battery cells by applying two or more separate battery models, updating, the one or more states of the battery cells based at least in part on the updated estimated parameters of the battery cells, and regulating charging or discharging of the battery based on the updated estimation of the states of the battery cells.