Accurate Surface Temperature Monitoring of Lithium-Ion Batteries

Accurate measurement of lithium-ion cell surface temperature is crucial for battery performance analysis, thermal safety, and precise modelling. Temperature sensors must produce accurate and reproducible measurements for these purposes, including guaranteeing that the response time of safety operations is as short as possible. However, established literature has shown that thermocouple sensors, such as the common K and T-Type, show significant temperature measurement variations due to electromagnetic interference, affecting battery model reliability. This study investigates these discrepancies by measuring the surface temperature of a discharging 21700-model cylindrical lithium-ion cell using various thermocouples, thermistors, and digital sensors. Additionally, a magnetic field sensor assesses the impact of electromagnetic interference on thermocouple accuracy during cell discharging. Empirical results reveal that sensors with smaller measurement junctions display superior thermal responses compared to larger sensors, highlighting the importance of sensor size and electromagnetic effects on measurement accuracy. A simulation of heat transfer from the cell to attached thermocouples verifies these results.