Battery State of Charge Estimation

Abstract

This chapter mainly introduces the definition of state of charge (SOC) and existing estimation methods, as well as various algorithms for SOC estimation. SOC is the remaining battery capacity and represents the percentage of the current remaining capacity. Estimating the SOC estimation of the lithium-ion battery accurately can make the lithium-ion battery pack safer when it is used, and it can also improve the performance of the batteries. However, the SOC interferes with various factors during the working process of the battery, which brings difficulties to the estimation of the SOC value. The main factors affecting the SOC are temperature, charge–discharge rate, self-discharge rate, and battery aging. These factors affect the accuracy of SOC estimation by using different equivalent circuit models and algorithms and could lead to different effects on the SOC estimation of batteries. Generally speaking, the more complex the equivalent model, the more accurate it is, the more complex its calculation is, and the higher its operating cost. Also, algorithms depend on their operating environment, and the adaptation of different batteries is different, so it is very important to select the appropriate models and algorithms for the lithium-ion battery.