Wireless power transfer has been introduced as a proper replacement for conventional cable power transfer systems recently. With the developments of the electric transportation, transferring power wirelessly has been found to introduce several advantages in charging Lithium-Ion batteries. Among different configurations of wireless power transfer, Series Parallel structure is found to be more interesting in high power applications, because of its high voltage gain. This paper investigates almost consistent output voltage of a wireless power transfer system with fixed switching frequency which fits Lithium-Ion battery charging profiles. Moreover, ZVS operation of the switches in rated power is guaranteed in order to avoid MOSFETs switching losses. A method for selecting the compensation capacitors is introduced. Simulation and experimental results are used to verify the theory.