Time-Domain Battery Impedance Identification under Piecewise Constant Current Excitation

This article shows how to model the voltage response of a battery excited by a piecewise constant current source. Modeling is done both by using a mathematical approach based on an orthonormal basis of functions and a fractional-order model, both identified in the time domain. The equivalent circuit model is based on the usage of the Mittag-Leffler function and on the proposal of a technique to ease the computational burden. The developed methods allow the reduction of the estimation times without approximating the exact solutions of the equivalent circuit model. Experimental results are aimed at validating both models. Outcomes obtained in the time-domain are compared with corresponding results obtained through electrochemical impedance spectroscopy (EIS) in the frequency-domain. Additional experimental results validate the approach using a standardized profile of discharge currents applied to an initially charged battery.