Empirical performance modelling of a lithium-ion battery of a solar car

Abstract

The aim of the work is to ascertain a solar car battery performance. The student engineering team of Peter the Great Petersburg Polytechnic University designs the car. Parameters as terminal voltage, operating current, power losses and efficiency are determined depending on battery state of charge (SOC) and operating power. For electrochemical transient modelling, an equivalent RC-circuit is included based on Thevenin battery model. It is assumed in the model that internal resistance, open circuit voltage and the RC-circuit voltage drop depends only on the SOC. Experimental data was obtained from the LG INR18650 MJ1 battery discharge curves. Modelling was performed for SOC values in the range of 0.17 to 0.95 since the terminal voltage dependence on SOC is nearly linear there. The proposed model is sufficient for state of charge estimating and battery performance determination.