A Novel On-Board Electrochemical Impedance Spectroscopy System for Real-Time Battery Impedance Estimation

This paper proposes a real-time electrochemical impedance spectroscopy (EIS) technique, that can provide high accurate estimation of the impedance of each Li-ion cell of a battery (BT) stack, even for less than mOhm. Thus, the suggested EIS technique can be used in high demanding applications, such as nearly zero-energy buildings, microgrids and electric vehicles. This is attained, because a smooth cell excitation current is utilized that is provided by the proper control of the gate-source of each cells parallel-connected MOSFET and thus, effective harmonic analysis can be accomplished. Since the circuit topology of the EIS is implemented without requiring expensive electronic equipment, it is affordable to be applied in the BT system of any application. The proposed EIS system can cooperate with a BT cell equalization (BCE) system that utilizes the same MOSFET control scheme to provide the excitation current. Thus, a combined EIS-BCE system is developed that can be used to improve the performance of a Li-ion BT management system (BMS). The accuracy of the EIS technique and its high performance by operating within a combined EIS-BCE system are experimentally validated.