Abstract

Extending the lifetime of the battery system of the Electric Vehicles will affect the economic feasibility of the vehicle. Connecting the battery cells in series raise the problem of imbalance voltages of the cells caused by Difference of internal resistance, imbalanced SoC, gradients of ambient temperature of the battery pack during charging and discharging.
The commercial solution for this problem is shunting the cell with extra charge to a dissipative resistor and gets rid of the extra charge as heat.
This thesis proposes the use of Serial Resonant Switched Capacitor Converter for battery Cell Voltage equalization, which allows the extra charge to be transferred to other cell instead of dissipated it as heat. The thesis can be divided into five parts: the first part is introduction to the lithium-ion battery system, estimation of the State of Charge and battery modeling; the second part is a review for the switching topologies that used for battery cell equalization; the third part is the modes of operation of the proposed converter, modeling and simulation. And also introducing the new concept of controlled switching which allow the use of current sharing technique to reduce the equalization time. The fourth part is building the prototype circuit and allows the microcontroller to tune the circuit to achieve the zero current switching and the last part is the conclusion and the future work