An advanced cell model for diagnosing faults in operation of Li-ion Polymer batteries

In this paper, an advanced cell model is proposed providing a better State of Health (SoH) determination for diagnosing faults during the operation of Li-ion Polymer batteries comparing to classical cell models. Li-ion polymer cell kinetic parameters were obtained by electrochemical impedance spectroscopy method and changes in these parameters were analyzed theoretically in cases of forced charging and discharging. It was observed that classical cell models were not sufficient enough to mimic the irreversible effects on Li-ion polymer cells caused by improper charging and discharging processes. Therefore cell equivalent circuit was improved and classified according to failure states. A new fuzzy logic based SoH evaluation method was developed from experimental results. This model provides means for better classification to define the irreversible changes that cells encounter in their lifetime.