A new direct current internal resistance and state of charge relationship for the Li-ion battery pulse power estimation

The conventional test to obtain the direct current internal resistance (DCIR) has only experimented with a duration time of 5 seconds in the discharge region[3]~[5]. To obtain the DCIR, the duration time, Deltat and the region condition are important for the hybrid electric vehicle (HEV). In this paper, a new measurement method to obtain a direct current internal resistance (DCIR) is proposed. The proposed approach is performed during 10 seconds in the charge and discharge regions in order to obtain the new relationship between the DCIR and the state of charge (SOC). Thus, this obtained data can be used to estimate the battery pulse power using the previous SOC algorithm, extended Kalman filter (EKF)[6], which includes the DCIR-SOC relationship. The experiments are achieved using a fresh 1.3 Ah 18650 type Li-ion battery at 25degC.