PNGV Equivalent Circuit Model and SOC Estimation Algorithm for Lithium Battery Pack Adopted in AGV Vehicle

Lithium battery is promising to power AGV vehicle. Given the inaccuracy of the state-of-charge (SOC) estimation, a partnership for a new generation of vehicle (PNGV) battery model is established, and an open-circuit voltage method is proposed in this paper. The model's parameters in different SOC state are calculated through the lithium battery's charge and discharge process; the internal resistance correction method and Kalman filter method are proposed separately on the basis of PNGV model. On that basis, the two methods are simulated and experimented to attain the open-circuit voltage and battery SOC. As indicated from the experimental results, the PNGV model is precise and able to describe the characterizations of battery in the discharge process. The accumulated error and inaccurate estimation of the initial value by the ampere-hour (or current integration) approach can be avoided through adopting the SOC estimations effectively. Additionally, the estimated SOC can be maintained highly accurate.