This paper addresses a dual active bridge isolated DC-DC converter into a cascaded battery energy storage system (BESS) with an additional benefit of medium frequency galvanic isolation. The topology, named as multi-level cascaded medium frequency isolated cascaded power conversion system, is presented in the beginning of this paper to improve the performance of cascaded BESS. Its working principles, including DAB and cascaded H-bridge PWM converter, are described as a guidance for designing the whole system. Moreover, a downscaled prototype is constructed in the laboratory, and the experimental results obtained from the prototype are provided and discussed in purpose of validating the feasibility of multi-level cascaded medium frequency isolated power conversion system (MFIPCS).