Low-cost optical multi-wavelength sensor for accurate real-time state-of-charge monitoring in vanadium flow batteries

We presents a novel, low-cost optical sensor for accurate real-time monitoring of state of charge (SoC) and total vanadium concentration in vanadium flow batteries. Using only six discrete wavelengths, the sensor achieves precision comparable to full-spectrum methods while significantly reducing equipment costs and complexity. A general deconvolution method is used to measure both the SoC and the total vanadium concentration in both the posolyte and negolyte, with calibration covering concentrations from 1.2 to 1.8 M. We achieve an overall accuracy of 2.4% for the SoC and 70 mM for the total vanadium concentration. Additionally, an optimization study is proposed to determine the optimal number and placement of spectral channels, providing a basis for designing tailored optical sensors for vanadium electrolytes.