Optimal Sizing of PCB Coils for Lithium-Ion Cell Dilation Measurement

Lithium-ion batteries are widely used, but accurate estimation of their state of charge and state of health is still an open issue. Integrating chemical and physical sensor data with electrical measurements can improve the estimation algorithms and foster the early detection of destructive failures. One-dimensional dilatometry systems based on the eddy currents principle represent low-cost and promising solutions to measure the dilation of the cells caused by charging operations and health degradation phenomena. These systems are based on a simple inductance-to-digital converter that measures the inductance of a PCB coil to evaluate the distance between the coil and a target. These devices require an accurate design since the coil sizing strongly influences the measurement accuracy. This work aims to optimize the design of the coil considering different parameters, notably the shape, the trace width, and the internal filling of the spiral.