Joint SOC–SOP estimation method for lithium-ion batteries based on electro-thermal model and multi-parameter constraints

Accurate estimations of the state of charge (SOC) and the state of power (SOP) are required to ensure efficient and reliable utilization of Li-ion batteries. A new joint estimation method of SOC–SOP based on the electro-thermal model and multi-parameter constraints is proposed in this paper. The proposed method introduces temperature as one of the important constraints for SOP and considers the intrinsic relationship between SOC and SOP as well as the influence of voltage, temperature, and SOC on SOP estimation. First, an electro-thermal model is developed to describe the electric and thermal dynamic characteristics of a battery. Second, the battery SOC is accurately estimated by the unscented Kalman filter method. Then the state of power of the battery is predicted under the condition of multi-parameter constraints. Finally, experiments are conducted to verify the effectiveness of the proposed method. Simulation and experimental results show that this method has a high degree of estimation accuracy and is very simple to calculate. Under the DST condition, the maximum relative voltage error within the electro-thermal model is about 5%. The maximum estimation error of the peak discharge power does not exceed 5 W, and the overall average estimation error is about 1.2 W.