State of charge Kalman filter estimator for automotive batteries

A state of charge estimator for rechargeable batteries that operate under variable and repetitive charging and discharging conditions is proposed. The estimator is based on a state-space dynamic model of the battery which is obtained by modelling the kinetic of reactions and the diffusion phenomena. By using the terminal current and voltage measurements, an extended Kalman filter estimates the concentrations of the main chemical species which are averaged on the thickness of the active material in order to obtain the state of charge of the battery. The estimator is tested on experimental data derived from typical operating conditions of Nickel–Metal Hydride batteries used in automotive hybrid vehicles.