Reconfigurable Power Circuits to Series or Parallel for Energy-Balanced Multicell Battery Pack

Multicell battery pack has the cells connected in series and parallel for fast charging and heavy load with low conduction loss. Thus, cell balancing control is required to maximize the utilization of the battery pack. The previous studies on cell balancing have used dedicated cell balancing circuits, including magnetic components and multiple capacitors. Instead of using additional passive components, this article proposes reconfigurable power circuits that only consist of power switches. With the merits of being reconfigurable into series or parallel in a multicell battery pack, the proposed circuits perform active cell balancing with a load capacitor and a load current for low cost and high system density. These features are essential for low-power applications with multiple cells, such as drones, wireless speakers, electronic point-of-sale, and mobile devices, which require compact system size. The operational principle, balancing features, and loss models of the proposed circuits are shown with a comprehensive analysis. A prototype board has been built to evaluate the performance of the proposed circuits with the experimental results. It is shown that the proposed circuits have a peak efficiency of 95.3% with 12 V, 1 A charging and 3.7 V, 0.4 A load.