Design and Simulation of an On-Board Integrated Charger using Cell Bypass Balancing Circuit for Electric Vehicles

This paper presents the design of an onboard integrated charger using cascaded converters and cell bypass balancing circuit for lithium-ion battery packs. Lithium-ion based serially connected battery cells experience imbalance in operation while charging and discharging. This limits the effective capacity utilization of the battery pack. Among all the active balancing circuits, cell/module bypass reconfiguration is considered to be quite efficient and fast, but introduces surge currents and reduces the system efficiency. This may also damage the components connected and reduce the battery life. In this paper we propose a modified circuit topology to overcome this problem. Simulations are carried out for 14 series connected cells each with nominal voltage of 3.7 V and capacity of 40Ahr. The results indicate considerable scope of application of the proposed approach for on-board electric vehicle applications.