Experimental Characterization and Development of a SoC/SoH Estimator for a LiFePO4 Battery Cell

This paper presents the results of experimental characterization of an automotive LiFePO4 battery cell for the purpose of building of a control-oriented battery equivalent electrical circuit model suitable for designing a combined state-of-charge (SoC) and state-of-health (SoH) estimator. The SoC/SoH estimator design has been based on the time-series representation of the battery model utilized within the extended Kalman filter (EKF) parameter estimator, with SoC reconstruction based on the known open-circuit voltage vs. discharged charge curve. In order to provide a consistent SoC estimate during low-excitation intervals, EKF-based estimation has been combined with a Coulomb (charge) counting approach. The effectiveness of the proposed SoC/SoH estimator has been verified by means of computer simulations on the developed battery model for different battery operating regimes.