Inductive Low-cost System to Measure the Volume Variation of Prismatic Lithium-ion Cells

Battery use is continuously on the rise for several applications as proven by the rapid growth of electric vehicles market. The development of more accurate battery control and estimation algorithms is an essential requirement to enhance battery performance. Sensor fusion techniques promise to improve control and estimation algorithms by combining the currently used electric and thermal measured data with physical and chemical ones. In particular, the cell volume variation appears to be connected to both State of Charge and State of Health. In this work, an inductive sensor, based on eddy currents, is used to develop a low-cost system to measure the volume variation of prismatic lithium-ion cells. The developed system consists of a cell holder structure, similar to the one used in commercial batteries, equipped with eddy current sensors. The system is applied to both fresh and aged cells. The obtained results prove that the proposed measurement system is able to track the cell expansions due to both the thermal and State of Charge variations. Furthermore, the volume variations found are comparable to literature experiments, in which expensive laboratory equipment is used.