Comparison on cell balancing methods for energy storage applications

Abstract

Background: Unbalanced cells in the battery caused by differences in cell compounds and initial charge capacities may reduce its capacity and exert on a bad influence on its safety and lifetime. Methods: This paper introduces comparisons on the different cell balancing methods for energy storage applications. This study first categorizes cell balancing circuits as passive or active cell balancing methods based on the usage of resistors. Then, this paper investigates the advantages and disadvantages of these passive and active cell balancing methods. The investigated passive cell balancing methodologies include a fixed shunting resistor circuit and a switching shunting resistor circuit. In addition, the studied active cell balancing methods in this paper include cell balancers using capacitor, inductor/transformer, or DC-DC converter. Findings: Based on the comparison results of this study, a passive cell balancer is easy to implement although it requires long balancing time and has low cell balancing energy efficiency because of a thermal loss from a resistor. This passive cell balancer is a suitable technique for portable tools and low-power systems. On the other hand, an active balancing method has higher energy transmission efficiency and shorter balancing time than a passive cell balancer although it requires complex control algorithms and high cost for fabricating the balancing circuit. Applications: By comparing the advantages and disadvantages of these cell balancing methods, this paper presents a guide for selecting a proper cell balancing method for energy storage applications.