Electric vehicles (EVs) are considered as trend and future of tools for transportation with the seemingly merits of zero pollution and zero fuel consumption theoretically. At present, one of the principal elements restricting EV development is the battery equalization issue. The differences in capacity between cells exist widely and may enlarge during charging and discharging process, which can reduce battery longevity as well as performance. To control the differences between cells, effective battery equalization method must be applied on the EV battery pack.

In this thesis, a design of active cell balancing circuit is proposed specific to low power EVs based on the design of a flyback transformer and a RCD clamping unit. Then another design is presented specific to high p...[ Read more ]

Electric vehicles (EVs) are considered as trend and future of tools for transportation with the seemingly merits of zero pollution and zero fuel consumption theoretically. At present, one of the principal elements restricting EV development is the battery equalization issue. The differences in capacity between cells exist widely and may enlarge during charging and discharging process, which can reduce battery longevity as well as performance. To control the differences between cells, effective battery equalization method must be applied on the EV battery pack.

In this thesis, a design of active cell balancing circuit is proposed specific to low power EVs based on the design of a flyback transformer and a RCD clamping unit. Then another design is presented specific to high power EVs which can achieve a higher balancing current on the strength of the design of a full bridge transformer and a current supplement unit. A circuit board is produced according to the design specific to low power EVs. Experiments are conducted to testify that the board can provide a default balancing current to the cell which needs to be balanced with a decent effect in reducing the differences between cells.