A Solar Power-Assisted Battery Balancing System for Electric Vehicles

This paper proposes a solar power-assisted electric vehicle battery balancing system. There are three operation modes of the system: solar-balancing, storage-balancing, and charge balancing. The solar-balancing mode charges the battery module with the lowest state of charge (SOC) using the solar power during vehicle driving; the charge-balancing mode is operated when the vehicle is parked and being charged by the conventional charger. Under this mode, the balancing circuit discharges the battery module with the highest SOC by transferring the energy to an additional storage cell while the solar panel also charges the storage cell independently at the same time if solar power is available. When the solar power is low, the storage-balancing mode will be selected to charge the battery module with the lowest SOC using energy stored in the storage cell. This system eliminates the energy loss that would otherwise happen in conventional active and passive balancing schemes by equalizing the battery using solar/stored energy in the storage cell. A 48-V battery pack with four 12-V battery modules system is simulated and tested. A prototype system is developed to prove the concept. The simulation and experimental results verify that the proposed system not only achieves the same balancing performance as conventional balancing circuits, but also effectively increases the overall usable battery energy by 2.1%–3.3% every 13.2 km.