An LCC Based String-to-Cell Battery Equalizer with Simplified Constant Current Control

Abstract

Constant current equalization can effectively mitigate the inconsistency of battery strings in a fast manner. In this manuscript, a constant current string-to-cell battery equalizer with an open-loop current control is proposed. The equalization scheme is based on LCC multiresonant topology. It utilizes a common equalizer unit shared by each unbalanced cell to transfer energy from the entire string to a single cell. A constant balancing current is achieved with simple fixed-frequency open-loop control. The equalization speed is determined by the predesigned balancing current. Design considerations of the proposed equalizer are analyzed in detail, which ensure zero-voltage switching among all MOSFET s during the equalization process. An experimental platform to balance four lithium-ion battery cells is designed to verify the system performance. Experimental results validate the functionality and analysis of this equalizer. Compared with the conventional architecture, the proposed architecture exhibits a high efficiency, low components count, and obviously reduced control complexity.