Low-Cost Inductive Sensor and Fixture Kit for Measuring Battery Cell Thickness Under Constant Pressure

Abstract

This study investigates the application of inductive proximity sensors for accurately measuring battery expansion. Previous research has obtained high accuracy sensing using strain gauges, displacement sensors, and load cells, but has been limited by sensor cost. A proximity sensor based on changes in mutual inductance with a metal target sensor benefits from low cost, high accuracy, simple design, and ease of installation, calibration, and measurement; all allowing for better scalability for testing many cells simultaneously. Initial testing demonstrated that the inductance sensor readings were linearly proportional to displacement at multiple cycling temperatures. Further tests were conducted comparing the performance of the inductance sensor with highly accurate displacement sensors (1µm at $2000). Our sensor demonstrates a 3.2 µm maximum error at less than $20 cost, highlighting the cost-effectiveness of the proposed sensor. Thus, the proposed sensing platform will enable low-cost, high throughput testing of cell expansion.