THERMAL MANAGEMENT of Lithium-Ion Batteries

LT Christopher W. Fredrick, USN

Lithium-ion cells are the state of the art in portable power due to their superior energy and power capacities, long cycle life, and thermal stability. Used in a broad range of designs and form factors, this technology can be applied to an increasingly diverse range of military applications, including personal communications, reserve power, vehicle traction, and power for unmanned aerial and surface vehicles. Their benefits can be realized only with continuous use of an external battery management system (BMS) to maintain voltage, current and temperature within an acceptable window. The additional wiring to couple every cell within a large pack to the BMS adds to the weight and complexity of the power circuit, and places limitations in their use for maritime defense purposes. This thesis focuses on benchmarking the performance of thermal sensing devices planted inside a lithium-ion cell as part of a larger effort to investigate the use of wireless sensors in cell management. Experimental measures were performed to measure sensor accuracy and cell performance. First, several types of sensors were evaluated and the appropriate type for operation within a prismatic cell was selected. Then, the thermal response of the sensors was tested and analyzed. A sensor was then operated inside a cell undergoing a series of charge and discharge cycles. Their response, as well as the cell's potential and cycle current were recorded and analyzed. Thin-film thermistors were found to be the most suitable thermal sensing device to use within the cell. The thermistors responded rapidly, maintained good accuracy and measured even small temperature changes induced when cycling the cell. Operating a thermistor inside the cell did not impact charge or discharge performance.

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Jan 05, 2014

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