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Simultaneous charging with the individual voltage-fed LLC resonant converters has the drawback of two-stage conversion losses and increased cost, volume, and control complexity. This work presents an isolated Quasi-Z-Source Inverter (QZSI) combined with an LLC resonant converter for a simultaneous charging system in a single-stage conversion at different voltage levels to overcome these issues. The dual tank resonant circuit (DTRC) design structure and required magnetizing inductance are detailed to achieve simultaneous charging. Moreover, the influence of the equivalent magnetizing inductance-to-inductance ratio on power sharing and efficiencies is analyzed. This analysis uses SiC MOSFETs with double-leg shoot-through PWM (DLST PWM) at the constant switching frequency. Simulations and experimental results are evaluated for the proposed converter with a prototype of $200 {W}$ on each HFT in the upper and lower circuits in the laboratory using the dSPACE1104 platform. This work has analyzed simultaneous charging at equal and unequal voltage levels. It offers a novel, efficient topology with simple control and a smaller size.