Combined data driven and online impedance measurement-based lithium-ion battery state of health estimation for electric vehicle battery management systems

Impedance measurement-based lithium-ion battery state of health (SOH) estimation technique is the most accurate technique compared to the model-based and data-driven techniques. Typically, electrochemical impedance spectroscopy (EIS) is used to measure the impedance of the lithium-ion battery. However, installing EIS in an on-board battery management system (BMS) for online estimation of SOH is impractical in terms of complexity, cost, and increased weight of BMS. Aiming to provide a solution, a single frequency impedance measurement-based technique is proposed for precise estimation of battery SOH during charging without implementing EIS in electric vehicle BMS. Aim is to estimate battery SOH using battery charger. A Series of laboratory experiments are conducted to collect EIS data at different states of charge and temperatures. After critical analysis of the data, 30% SOC and 1 Hz frequency is considered for measuring the impedance during the charging period for SOH estimation. The proposed SOH estimation technique is highly accurate for all practical purposes BMS while at the same time it is convenient, simple, cost-effective, and does not require any historical usage data.