A Multifunctional Battery Equalizer Based on LLC Converter

Lithium‐ion batteries have many merits: being easily recyclable, having a high energy density, and having a longer usable life. But the voltage‐inconsistency problem will decrease the maximum usable capacity of a battery string and may induce a safety event. Hence, battery equalizers are important for the safe operation of a battery string. However, most battery equalizers solely focus on equalization. This means single circuit functionality. To deal with the problem, an integrated, inductor‐inductor‐capacitor‐converter (LLCC)‐based equalizer is proposed in this work. The proposed equalizer utilizes only two switch components to equalize the voltages of battery cells while also enabling controllable output of battery‐string energy; additionally, all switch components in the equalizer operate in a zero‐voltage‐switching state, which reduces switching losses. Finally, a prototype of the equalizer was built, and steady and dynamic experiments were also done using the prototype. The results demonstrate the multi‐functionality and feasibility of the proposed equalizer.