INVESTIGATION OF CELL BALANCING TECHNIQUES IN ELECTRIC VEHICLE BATTERY PACKS

Abstract

A problem with electric vehicle battery packs is that cells are not always equal, as their capacity, internal resistance, temperature, and battery pack state-of-charge can be different and lead to a loss of energy in the battery, to faster cell degradation, or to safety issues. This paper compares the performance of several cell balancing techniques for electric vehicle battery packs for standard charging and discharging conditions. The time, energy efficiency, state of charge equalization, thermal behavior, power loss, and overall pack performance of all three types of balancing (passive, active capacitor, and active inductor) were compared. The results show that the most convenient and least costly solution is passive balancing, although it is the most energy-consuming solution with the longest voltage equalization time. The active balancing methods not only decreased thermal losses but also increased the efficiency of the balancing. The inductor-based technique has been found to be the fastest to equalize and the least deviated final state of charge, while the capacitor-based technique has been found to provide a good balance between the complexity of the circuit, equalization time, and efficiency. The balanced battery packs also had less loss of available capacity, little voltage drop, and even better temperature uniformity during use. Enhancements have been made to help improve the reliability of packs and prevent overcharging and deep-discharging. The results indicate that the battery capacity, balancing time requirement, battery cost, circuit complexity, and thermal load are all important parameters to consider when choosing a balancing strategy. Overall, in applications where energy efficiency, service life, and operational safety are of primary concern, as in high-capacity electric vehicle battery packs, active balancing is more suitable.