Automatic Voltage Distortion Compensation for Improved State Estimation Accuracy in Battery Management Systems with Continuous Cell Balancing

In battery systems, the electrical connections between the voltage nodes and battery management system are typically implemented with a single wire per node to limit the system cost, resulting in limited voltage sampling frequency and reduced effective balancing power rating. An augmented equivalent circuit model for Lithium-ion battery packs is proposed that incorporates the parasitic cell connection resistance and improves the state-of-charge and available power estimation accuracy during continuous cell balancing. A new cell connection resistance extraction technique is introduced that leverages an existing isolated Čuk converter designed for active cell balancing. Simulation results estimate a potential elimination of 6.7% state-of-charge estimation drift per hour, when cell balancing is active. The wire resistance extraction technique is demonstrated experimentally in a 4kWh custom liquid-cooled battery module with a prototype battery management system.