Lithium-Ion Battery Charging Control Using a Coupled Electro-Thermal Model and Model Predictive Control

This paper presents a novel application of model predictive control (MPC) to the problem of managing lithiumion cell performance using a highly accurate low-order electrothermal equivalent circuit model and is experimentally validated via laboratory experiments. The proposed method uses MPC to ensure compliance with cell-level operational limits and has the potential to extend lifetime by mitigating certain mechanisms of cell degradation leading to capacity fade. A five-state electrothermal model is developed, characterized and validated. Implementation employs an extended nonlinear Kalman filter for state estimation and MPC for controlling charge/discharge current. The complete method is experimentally validated using a 26650 cylindrical format lithium-iron phosphate (LFP) cell. The new method: (i) develops a fully coupled electro-thermal model of cell dynamics; (ii) incorporates a dynamic hysteresis model to improve accuracy; (iii) employs a nonlinear Kalman filter for accurate state estimation to inform the MPC algorithm; and (iv) utilizes a modified form of MPC which correctly models direct feed-through behavior to characterize ohmic resistance.