Simultaneous temperature and strain monitoring of lithium-ion battery modules using fiber Bragg grating arrays

Lithium-ion batteries are subjected to coupled electrical, thermal, and mechanical stresses during operation, which may lead to significant safety risks. Conventional battery management systems, typically operating at the module level, have difficulty achieving simultaneous cell-level monitoring of multiple physical parameters. To address this limitation, this study develops a fiber Bragg grating-array-based thermo-mechanical monitoring system for a 16-cell lithium iron phosphate battery module. A customized substrate and an optimized grating-array layout are designed to enable simultaneous temperature and strain sensing as well as dual-parameter decoupling. Charge–discharge experiments are conducted at four charging rates (0.6C, 0.5C, 0.4C, and 0.3C) to investigate the thermo-mechanical evolution of the battery module during operation. The results show that, during charging, the maximum temperature changes are 11.0°C, 9.0°C, 8.0°C, and 6.5°C, respectively, while the corresponding maximum strain changes are 300, 275, 250, and 225 µε. During discharging, the maximum temperature change is 7.0°C and the maximum strain change is 150 µε. Comparative measurements with thermistors and resistance strain gauges show good agreement between the proposed fiber Bragg grating array and the reference sensors. The proposed method provides a feasible strategy for module-level simultaneous temperature–strain monitoring and dual-parameter decoupling, with practical significance for battery safety management and early warning.