Fast Estimation of State of Charge for Lithium-Ion Battery

This paper proposes a fast measurement method to estimate the state of charge (SOC) of Li-ion battery based on AC impedance. The AC impedances of an 18650 lithium-ion battery related to various states of charge are measured firstly using a commercial AC impedance analyzer to form a database. Using the relationships between the state of charge and the AC impedance, the proposed method can obtain the battery state of charge quickly. To validate the accuracy of the proposed method, SOC 0%, 50%, and 100% are tested and compared in this paper. The results show that the error is 8.636%, 2.604%, and 0.6%, respectively.