Analytical Charged Capacity Expression of Lithium-Ion Battery for SOH Estimation Based on Constant Current Charging Curves

Abstract

Accurate evaluation of the state of health (SOH) plays an important role in battery management systems. The incremental capacity (IC) analysis method is applied to analyze battery aging mechanisms and estimate SOH. The charged capacity can be obtained by integration of the IC curve. To obtain the analytical charged capacity expression based on the IC curve, the fitting results of the IC curve by Gaussian functions and Lorentz functions are compared. The comparison results show that the Lorentz functions are more suitable than Gaussian functions on fitting IC curve and estimating charged capacity because of its relatively simpler integration form. Therefore, the analytical charged capacity equation is proposed by the integration of the Lorentz functions. The experimental results demonstrate that the capacity estimation error is lower than 1.5%.