Design and Performance Analysis of Active and Passive Cell Balancing for Lithium-Ion Batteries

Abstract

Electric Vehicles (EV) are growing areas of research since the demand for clean transportation is ever-increasing. Batteries form an integral part of EVs. Battery Management systems (BMS) need to support many features, including charge balancing to improve battery life and longevity. Among passive cell balancing and active cell balancing, the latter provides better battery life and efficiency. Among different active and passive cell balancing techniques, popular techniques like Flyback transformer-based active cell balancing and switched capacitor-based active cell balancing are used. These methods are not only easy to implement but also provide good performance. These balancing circuits are integrated with non-ideal RC models of a lithium-ion battery. The bleed resistor-based passive cell balancing took more than 16000 seconds to reach a 0.01V difference for capacitors with 5F capacitance, whereas the switched capacitor design is estimated to take 500 seconds. The multi-winding flyback active cell balancing system reached a 2% difference in SOC in 1800 seconds. There was a visible increase in time taken for balancing the cells using multi-winding active cell balancing as the cell temperature increased. A 2.32% increase in the time taken for balancing the cells was observed when cell temperature increased from 293K to 313K.