Stéphane Raël

A methodology to assess the State of Health of lithium-ion batteries based on the battery's parameters and a Fuzzy Logic System

This paper presents a methodology used to assess the State of Health (SOH) of lithium-ion batteries. This methodology can be readily embedded in all battery management devices including the electronics for electric vehicles. The smart estimation method is based on a Fuzzy Logic System (FLS) and two calculated batterys parameters. Therefore it enhances the SOH value based primarily on both the calendar and the cycling life. The FLS is constructed by using only the temperature and the absolute value of the current that the battery sustains. Finally, through the experiments, obtained results for both a new and an aged battery demonstrate the accuracy of the methodology and how it can improve the batterys lifespan.

Impedance measurements combined with the fuzzy logic methodology to assess the SOC and SOH of lithium-ion cells

This paper describes experimental results aiming at analyzing lithium-ion batteries performances with aging, for different state of charge and temperatures. The results are provided from electrochemical impedance spectroscopy (EIS) measurements on new and aged cells. A climatic test chamber is used during experiments to simulate the conditions of the temperature. Experimental data are plotted over a broad spectrum of frequencies on Nyquist diagrams. We will also inspect the impact of the presence of a DC current during the EIS measurement. Finally, obtained results will be processed in a way to be used in a fuzzy logic system (FLS), to assess either the state of charge (SOC) or the state of health (SOH) of cells.