Comparative Performance Analysis on Passive and Active Balancing of Lithium-Ion Battery Cells

In high-power battery applications, rechargeable batteries play a significant role. To satisfy the requirements of energy and power it is necessary to build a battery pack with numerous cells connected in either series or parallel combination. Each battery has slightly different capacity due to the manufacturing tolerances, environmental conditions, chemical and electrical characteristics of individual cells, such as open circuit voltage (OCV), internal impedance across cells, battery charge and discharge rate and external temperature gradients in a typical pack. After multiple charging and discharge cycles, the battery cells or modules appear to get out of balance in terms of uneven voltage across the pack. The variation in voltage appears to increase over period as some batteries charge and discharge faster and others charge and discharge more slowly. This greatly decreases the available battery pack capacity and also contributes to premature cell failure. Hence for series connected battery packs, balancing is required to maximise the operating range, increase life of battery, enhance battery protection, performance and reliability. This paper explains about different architectures used for balancing of cells along with the comparative analysis. Simulation results for passive balancing with switched shunting resistor and active balancing using flyback converter circuit is discussed.