Microcontroller Based Pack to Cell Active Cell Balancing for Battery Management System (BMS) Using Dc-Dc Fly-Back Converter

Battery Management System (BMS) is an important part of an electric vehicle. In a battery pack, a large number of battery cells are used. The quality and performance of each cell are not always equal. They are different from others in many cases. In this situation cell balancing procedures are applied to balance the imbalanced cells. Imbalanced cells are very harmful to a battery pack. Passive cell balancing and Active cell balancing are two cell balancing methods that are being used to balance the cell. Between these two methods, active cell balancing is more efficient because less energy is wasted through this method. In this paper, a pack to cell active cell balancing technique has been proposed by using a DC-DC converter and microcontroller. Here the cell voltage is being used as measurement parameter to balance the cells in the battery pack. A fly-back converter is used as a DC-DC converter and an Arduino Nano as a controller. N-type MOSFET is used as a switch for switching the flow path. To verify the proposed technique a prototype of a series connected three Li-ion cells battery pack has been designed. The method was being applied in three conditions such as, relaxation mode, charging mode and discharging mode. The data was collected during three modes with 5 minute gap. This method takes about 30 minutes to balance the cells during relaxation and charging mode. But in discharging mode it takes less than 25 minutes to balance the cells. The proposed method is mostly effective for high-amperage cells. This method takes less time to balance the cells and is mostly effective during discharging conditions.