Modeling active cell balancing of lithium-ion bat-teries in MATLAB/Simulink

Problem. The article is devoted to the study of active balancing of lithium-ion battery cells. Active balancing of lithium-ion battery cells is crucial for ensuring high efficiency, durability and reliability of electric vehicles. By monitoring the state of charge, voltage and temperature of each cell, BMS helps to avoid overcharging and deep discharge, which can lead to safety problems and shorten the battery life. Optimal management and balancing of lithium-ion electric vehicle batteries ensures that each cell receives the optimal amount of energy, which maximizes the efficient and safe use of electrical energy. Balancing of lithium-ion electric vehicle batteries becomes important for better and more efficient use of electric vehicles. Considering the significant contribution of cell balancing to the BMS battery management system, the study provides a detailed overview of battery balancing methods and demonstrates an example of balancing based on the built model of active balancing of lithium-ion battery cells in MATLAB/Simulink. Simulations of active balancing of lithium-ion battery cells demonstrate improved efficiency of SOC and voltage control. Goal. The goal is to simulate active balancing of lithium-ion battery cells. Active balancing improves the safety, durability and efficiency of electric vehicle batteries.Methodology. The research methodology is based on the use of an interactive tool (software) for modeling, simulation and analysis of dynamic systems MATLAB/Simulink. The results. The results of the simulation of active balancing of two lithium-ion batteries without an external source of electrical energy demonstrate that, when balancing batteries with initial states of charge SOC1=90% and SOC2=68%, their state of charge equalization occurs after 24 s of simulation at the level of SOC1=SOC2=74.08% and does not change its value in the future. The results of the simulation of active balancing of two lithium-ion batteries with an external source of electrical energy demonstrate that, when balancing batteries with initial states of charge SOC1=90% and SOC2=68%, their state of charge equalization occurs after approximately 12.9 s of simulation at the level of SOC1=SOC2=86.2%. After that, the state of charge of both batteries continues to increase equally. After 40 s of simulation, the state of charge of the two batteries was equal to SOC1=SOC2=93.84%. Comparison of the results of modeling active balancing of two lithium-ion batteries without an external source of electric energy and with an external source of electric energy demonstrates that when using an external source of electric energy, the balancing time of the batteries is reduced by almost 2 times (from 24 s to 12.9 s), while the batteries have a significantly greater SOC convergence (SOC1=SOC2=86.2% instead of SOC1=SOC2=74.08%). Originality. An active balancing model using a switched capacitor for two lithium-ion batteries with a nominal voltage of 3.7 V and a nominal capacity of 5.4 A·h was built in MATLAB/Simulink in two operating modes: without an external source of electric energy and with an external source. Practical value. Balancing an electric vehicle battery is a necessary and critical process that is performed to improve safety, durability, and long-term performance. It ensures that all batteries are charged evenly, which increases safety, extends battery life, and improves performance. Such research is crucial for improving the efficiency of electric vehicles and promoting environmental sustainability.