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This paper presents the analysis and design procedure of a voltage equalizer, which consists of a boost full-bridge input cell and a symmetrical voltage multiplier (SVM). The batteries under different initial voltage conditions can be charged to a desired uniform voltage level by the proposed voltage equalizer. The fundamental operation principle of the voltage equalizer is described, and a dc equivalent resistance model is derived to analyze the charging and equalization behaviors. The design procedure based on analytical models is presented to give the optimal parameter configuration for the voltage equalizer to reduce voltage imbalance among the batteries and improve the power conversion efficiency. The model of the equivalent resistance is verified by simulation study of an equivalent circuit. A 10-W prototype for 3 series-connected energy storage modules was built and tested with voltage imbalance. Experimental results confirm the validity of the design method, and demonstrate that the proposed voltage equalizer can achieve a good voltage equalization with a standard deviation reduced to a few millivolts. [ABSTRACT FROM AUTHOR]