Novel optical fiber-based method for spatially resolved temperature measurement and thermal anomaly detection in battery modules

Monitoring the thermal behavior of battery modules is critical for ensuring their safety and performance. This study investigates the application of distributed fiber optic sensors (FOS) for spatially resolved temperature measurements, comparing their effectiveness with conventional point-based temperature sensors commonly used in battery module monitoring. Validation of the fiber optic sensing data was performed using infrared thermography, which confirmed the capability of the fiber optics to detect localized thermal anomalies with high spatial precision. The study highlights the advantages of fiber optic sensors (FOS), including their minimal footprint and integration flexibility within battery modules, compared to traditional thermal monitoring methods and their placement. A specific focus was on identifying thermal anomalies caused by an intentionally aged cell integrated into a module. These anomalies, detected by the fiber optic system, were further analyzed and validated through computed tomography and post-mortem investigations, revealing defects in aged cells. We demonstrated that fiber optic sensing technology enabled the measurement of individual cell temperatures exceeding 80 ∘ C , while conventional temperature sensors, due to their application-oriented positioning, recorded temperatures below 40 ∘ C . Additionally, this method facilitated the identification of specific cells exhibiting significant capacity loss and thermal anomalies, attributed to severe lithium plating. The results in our test showed that using fiber optic sensors (FOS) for thermal monitoring enabled the detection of a thermal event earlier than conventional temperature sensors and even before the corresponding anomaly became electrically evident. The findings highlight that fiber optic sensors (FOS) provide a highly effective solution for advanced thermal monitoring, enabling the detection and characterization of thermal anomalies that are missed by conventional methods. The high sensitivity and spatial resolution of fiber optic sensing allow for the early identification of critical temperature changes, providing a significant advantage for thermal management. While not implemented in this study, integrating such a method into a BMS could enable real-time, predictive thermal management, allowing for earlier intervention in critical situations. This could help prevent thermal runaways, mitigate safety risks and enhance the operational reliability of next-generation battery systems. • Demonstration of spatial limitations of conventional temperature sensors during operation of battery modules. • Improved thermal anomaly detection with fiber optic sensors in battery modules. • Potential of fiber optic sensors for improved safety in large battery packs through spatially resolved temperature measurements.