Exogenous Kalman Filter for State-of-Charge Estimation in Lithium-Ion Batteries

This paper presents State-of-Charge (SoC) estimation of lithium-ion batteries using eXogenous Kalman filter (XKF). The state-space equation for the lithium-ion battery is obtained from the equivalent circuit model (ECM). It has linear process equations and a nonlinear output voltage equation. The estimation is done using a cascade of nonlinear observer and a linearized Kalman filter. The method is tested using experimental data of a lithium-ion-phosphate (LiFePO₄) battery under dynamic stress test (DST) and federal urban driving schedule (FUDS). The results are compared with existing Kalman filters.