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Lukmon Otunubi thesis (REVISED 05-20-2024).pdf (1.87 MB)

DESIGN AND IMPLEMENTATION OF AN ACTIVE CELL BALANCING OF A LITHIUM IRON PHOSPHATE (LIFEPO4) BATTERY MODULE

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posted on 2024-06-21, 14:25 authored by Lukmon Ayodele OtunubiLukmon Ayodele Otunubi

Batteries have become essential for a wide range of applications in the field of energy storage and electrification, from portable gadgets to electric cars and renewable energy systems. But effectiveness, performance, and lifespan of a battery pack are closely related to each of the individual cells of which it is composed. The phenomenon of cell voltage imbalance, which can result in a variety of problems ranging from decreased capacity and efficiency to safety concerns and premature failure, poses a significant challenge in managing battery systems.

Therefore, battery cell balancing plays a crucial role in improving the overall performance of battery packs. To guarantee uniform charge and discharge characteristics, balancing is the process of equalizing the charge of individual cells inside a battery pack. Battery cell balancing seeks to prolong the operational life of packs, improve the efficiency of its energy use, and ensure the safety of the overall system.

The methods used for battery cell balancing encompass a wide range of approaches, from passive methods that release extra energy as heat, to active methods that move energy across cells. The particular battery chemistry, application requirements, and required level of balancing precision are only a few examples of the variables that influence the choice of balancing technique.

Lithium Iron Phosphate (LiFePO4) rechargeable batteries are widely used by electric utility companies in battery storage applications. Battery cells are combined to form a battery module. Each module is constantly monitored with sensors and controlled by a Battery Management System (BMS). The BMS performs balancing of the cells. Each cell in the battery stack is monitored to maintain a healthy battery state of charge (SoC). The motivation for this work is to develop an active balancing system to replace a passive system currently being performed manually on an existing battery storage system consisting of LiFePO4 cells. An active cell balancer was designed using the LT8584 active cell balancer, which is based on a flyback DC-DC converter design. An LTspice simulation of the design was created for a single cell. It demonstrates critical parameters of the flyback converter cycle time. A PCB board, designed using KiCAD, was implemented. It is anticipated that the proposed design could be used to restore the health of SoC of faulty modules in lieu of removing and replacing them with a new module, resulting in potential cost savings. The proposed design is scalable in that it could be used for n number of cells in a battery module consisting of LiFePO4 battery cells.

History

Degree Type

  • Master of Science in Electrical and Computer Engineering

Department

  • Electrical and Computer Engineering

Campus location

  • Fort Wayne

Advisor/Supervisor/Committee Chair

ELIZABETH A.THOMPSON

Additional Committee Member 2

CLAUDIO FREITAS

Additional Committee Member 3

OMONOWO D. MOMOH