Sensitivity of Impedance Parameters of Li-ion Batteries Under Different State of Health

Abstract

State of Health (SOH) estimation of lithium-ion battery is momentous for Battery Management Systems (BMS) in Electric Vehicle (EV). Nevertheless, one of the biggest challenges is which indicator can be used to describe the SOH considering external impact factors. In this paper, according to the accelerated testing results during the whole battery lifetime, the statistical-driven analysis method such as Path Analysis (PA) is adopted to reveal the sensitive relationship between capacity degradation and the fading law of internal impedance parameters identified from Equivalent Circuit Model (ECM). And the direct influence of each impedance parameter and indirect influence between them are analyzed, a new life indicator based on sensitive characteristic parameters is proposed, which can describe the capacity degradation characteristics of the battery as well as the power recession characteristics. Furthermore, to analysis the disturbance caused by the external factors such as environment temperature, more experiments are added and the compensating method is presented.