Comparison of Methodologies for Estimating the State of Functionality in Lithium Batteries

Abstract

This study compares two methodologies for estimating the State of Function (SoF) of Lithium Iron Phosphate (LFP) batteries, widely used in electric vehicles. With the increasing adoption of these vehicles, accurate methods for calculating SoF are essential to ensure safety, efficiency, and longevity. The first approach, proposed by Lu et al. (2013), calculates SoF based on the battery’s ability to meet power demands, considering the residual voltage. The second, by Shen et al. (2018), estimates SoF based on the cell’s internal resistance, dynamically adjusting it according to the drained current and the cell’s internal condition. Both methodologies were evaluated in Matlab/Simulink, allowing for a detailed analysis of their advantages and limitations. The results show that while Lu’s approach is simpler, it may overestimate battery capacity in deep discharge scenarios. In contrast, Shen’s methodology provides a more accurate SoF estimate, especially under extreme conditions. This study contributes to the literature by providing a detailed comparison that can assist in optimizing battery management in electric vehicles.