This work presents a simple control and design approach for parallel resonant converters (PRC) for battery charger applications in renewable energy sources (RES). The proposed method particularly aims to operate the PRC in accordance with the Constant-Current Constant-Voltage (CC-CV) Charging Method, which is frequently applied for various battery types. In contrast to traditional resonant converter applications, the method offers to operate the PRC at two different constant frequencies for the CC and CV charging phases. Thus, neither conventional frequency control nor phase shift control is needed and the PRC can operate in open-loop configuration. Compared to the conventional frequency controlled resonant converters, the method facilitates the design and implementation of the charger circuit, reduces required components and costs. Moreover the design of filter configuration is also simplified. The basic control principles and design steps are explained in detail. Finally, experimental results for the proposed method are given, which confirms the validity of the proposed approach.