A Fiber Bragg Grating sensor-based approach for extended operational monitoring of Lithium-Ion battery in residential renewable energy system

Lithium-ion batteries (LiBs) are widely recognized for their high energy density, long cycle life, and favourable electrochemical performance, making them a fundamental technology for applications such as electric transportation, renewable energy integration, and grid-scale energy storage. In renewable residential systems, they store excess energy from solar panels or wind turbines, ensuring stable power supply. However, their safe operation is fundamental, as they are susceptible to thermal runaway and mechanical deformation, which can lead to severe failures. Monitoring temperature and strain is essential to ensure battery safety. This study presents a novel approach for continuous and prolonged safety monitoring of LiBs using Fiber Bragg Grating (FBG) sensors, which offer high metrological qualities and the ability to measure temperature and strain simultaneously. Residual strains and changes in the baseline temperature may indeed be the cause of unexpected issues and therefore be considered as warning parameters. An automated system was developed to operate in remote control to charge/discharge the battery according to desired protocols. Eight FBG sensors were mounted on a polymer lithium-ion (POLI) battery shell. Four FBGs were pre-tensioned and glued to measure cell’s temperature and deformation, while the other four were applied only with heat-conducting paste to capture temperature variations. Repeated charge–discharge cycles at different rates (0.5ℂ and 1ℂ) were performed on a lithium-ion system. FBG sensors revealed higher mechanical deformations along the x-direction (∼152 μɛ) than along the y-direction (∼42 μɛ). A 24-hour domestic grid scenario was then simulated for 4 consecutive repetitions, replicating typical household power demand with integrated renewable energy. Results showed a progressive reduction of the maximum strain values over the cycles, suggesting a stable mechanical behaviour of the POLI cells under the investigated operating conditions. FBG sensors are effective in detecting both strain and temperature variations, indicating that also mechanical deformations could potentially be used to improve state-of-charge (SoC) estimation