Joint Estimation of SOC and Operating Voltage of Vehicle 12V Lithium-ion Battery

Vehicle 12V lithium-ion battery is mainly used for automotive startup and low-voltage system power supply, and accurately estimate its state of charge (SOC) and operating voltage in time is essential to vehicle safety. For this, a joint estimation method for SOC and operating voltage of on-board 12V lithium-ion battery is proposed based on the second-order RC equivalent circuit model combined with the vehicle pre-charge conditions. In additional, the adaptive forgetting factor recursive least squares (AFFRLS) method is adopted to obtain circuit parameters, subsequently, double extended Kalman filter (DEKF) algorithm used to achieve SOC online estimation of 12V lithium-ion battery. Furthermore, combined with characteristic current curve under charging failure scenario, strategy for predicting the operating voltage of 12V lithium-ion battery is also proposed. Finally, a 12V 44Ah lithium-ion battery is selected to carry out the validation as proof of concept. The experimental results show that in the temperature range of 0 ℃ ~40 ℃ , the proposed joint estimation method has a maximum error of 1.6% in the SOC estimation and the accuracy of the operating voltage prediction is controlled within ±0.3%.