SoC Estimation of Lithium Ion Battery Using Combined Coulomb Counting and Fuzzy Logic Method

Abstract

The battery management system is becoming important due to the extending utilization of embedded devices equipped with rechargeable batteries that have higher power and energy density. Battery Energy Storage System (BESS) is used to store electrical energy on a large scale in power grid and electric vehicles. Lithium ion (Li-ion) battery is currently the most widely used form of energy storage. Parameters like State of Charge (SoC), ambient temperature, state of health etc determines the lifespan of a battery. SoC is a key factor which gives the rate of charge in the battery with respect to its total capacity. The direct measurement of SoC is not possible but it can be estimated by different methods. Coulomb counting method is the most widely used method to estimate SoC but the Coulomb-counting algorithm experiences aggregate mistakes due to the initial SOC. Coulomb counting and fuzzy logic method is combined here to estimate the SoC. Here a fuzzy logic method is used along with the CCM method to get optimal SoC value of the Li-ion battery. Simulation is done for the charging and discharging of Li-ion battery and the results are analyzed. Reliable operation and prolonged lifespan can be achieved through this technique. The new technique will help to establish more accurate and reliable results. Accurate SoC estimation save the battery from being deeply discharged and over-charged. Matlab simulink is the simulation tool used to establish the results.