Real time battery power capability estimation

Accurate battery power capability estimation is a key to battery life and performance in electric and hybrid vehicles. If power capability is predicted to be higher than actual, battery life is reduced and there is potential for vehicle shutdown. If power capability is predicted lower than actual, the customer may experience slower acceleration, lower top speed, and reduced usable electric drive range. In this paper an approach is proposed to estimate lithium-ion battery charge and discharge power capabilities online. First a simplified Randles circuit model is used to represent a battery cell. Then an Extended Kalman Filter (EKF) is constructed to estimate the model parameters and voltage across the RC network. Algorithms to calculate the charge and discharge power capabilities are presented. Both desktop simulation and pack level vehicle data are shown to support the correctness and accuracy of the proposed algorithms.