Evaluation of Current-Mode Controller for Active Battery Cells Balancing With Peak Efficiency Operation

This article presents a current-mode controller for switched-inductor topology to achieve voltage balancing between battery cells or modules in a battery pack while operating at peak efficiency. The presented method yields several advantages and/or eliminates several drawbacks of the existing conventional fixed duty cycle scheme. Among these advantages: 1) the balancing current is well controlled instead of being a function of battery cells' voltages and system parasitic elements, which might result in exceeding the current ratings of the components, and 2) the balancing current reference is selected such that the balancing circuit operates at its maximum efficiency point and, therefore, yielding lower balancing power losses. This article also presents a battery balancing algorithm for utilization with the presented controller that achieves open circuit voltage balancing, which is a more accurate indicator of state-of-charge compared to terminal voltage. Experimental results obtained from a laboratory prototype of a three-cell battery pack are presented to evaluate the presented current control and balancing method under different modes of operation.