Today, because of fossil energy crisis, the renewable energy becomes more significant. For example, the sun energy is used for generating electrical energy and the electrical vehicles are used for traortation. The challenge these energies are faced with, is non-permanent and limited generation or usage of them; the EVs need a equipment to storage electrical energy and generating electricity in the absence of sun is not possible. Therefore, it is necessary to use batteries for storing energy. The characteristics of batteries are different according to their types. Good conditions must be prepared to get appropriate operation and prevent of decreasing in batteries life time. The minimum or maximum allowed voltage is limited and these range must be considered. For reaching high voltages, the battery cells should be connected in series. The battery management system will check the SOC of each battery and if one of them have higher or lower voltage than limitation, charging or discharging procedure must be stopped. This will cause to use the capacity of batteries incompletely. Consequently, it is necessary to balance the SOC of battery cells with balancing circuits. Some of these circuits dissipate the energy of cells with higher SOC to reach a balanced state. Therefore, these circuits are not suitable for balancing applications, due to low efficiency. Some others, use the power electronic techniques to transfer the energy between batteries with higher and lower SOC. These circuits must have high efficiency to prevent losing stored energy and some other proper specifications such as: size, balancing speed, number of used semi-conductors, control procedure of main switch duty cycle, method of transferring energy between cells and soft switching. In this thesis, some battery cell balancing circuits are investigated and a new topology is introduced to improve the specification of these circuits. At first, some balancing circuits will analyze and their advantages and disadvantages will discuss. Then, proposed circuit will introduced based on forward converter, in which only one high frequency switch with soft-switching in turn off and turn on is used. Besides, no additional circuit is used to reset the magnetic core and the number of used elements, specially semi-conductors, are as less as possible. A controller is used to select the cell with lower voltage with an optimized algorithm. After that, the proposed circuit is analyzed theoretically and its performance is investigated. Also, a prototype of suggested circuit is made and the simulated and experimental results are compared. Keywords Battery, Cell Balancing, DC/DC Converters, Power Electronic Converters, Soft-Switching Techniques.