Empirical law for lithium ion state of charge estimation for EV application

Implementation of a robust and reliable method for the on-board estimation of the batteries state of charge is a sensible point for the electric vehicles development. This work presents an empirical law for lithium ion battery SOC estimation. For this purpose, the experimental activity performed on two commercial lithium ion battery cells of different sizes is presented. Then an empirical function characterizing the variation trends of Li-ion battery SOC is proposed. The objective is to estimate the SOC based on two top-level control parameters, such as the applied load power and the battery temperature.