Distributed temperature measurement in lithium-ion battery modules using time-domain reflectometry

As electric vehicles (EVs) continue to gain widespread adoption, the safety of lithium-ion battery systems has become a critical concern. Thermal runaway events and battery failure are increasingly reported, underscoring the importance of reliable temperature monitoring. However, due to market driven constraints on cost, weight and space, current battery systems often rely on limited temperature detection, which limits the reliability of diagnosis. This study introduces a method for real-time, distributed temperature measurement using time-domain reflectometry (TDR) along a single cable sensor. An innovative correlation technique is developed to relate the TDR measured reflection parameter to local temperature along the cable. The approach is experimentally validated inside a battery module composed of 18650 cells, demonstrating its ability to detect and localize hot spots. The method identifies a defective cell within a 30-cell module, even when cells are spaced by 5 mm. Compared with optical-fiber-based solutions, the proposed technique offers a low-cost, robust and easily integrable alternative for enhancing battery safety and thermal monitoring. • Time-domain reflectometry enables distributed temperature sensing in battery modules. • Thermal mapping in lithium-ion module • Method allows detection of thermal anomalies during cycling.