A direct, non-invasive method for measuring the SoC in VRFBs is through Ultraviolet-Visible (UV-Vis) absorbance spectroscopy. UV-Vis spectroscopy has been widely explored in the literature for studying the chemistry of vanadium electrolytes as well as for measuring the SoC. Early investigations, such as those by Blanc et al. , laid the groundwork for understanding the complex chemistry of the posolyte, along with subsequent contributions by other groups . The method has been applied both offline and online to determine the state of charge (SOC) of vanadium electrolytes . Most of these works employ calibration procedures based on empirical models, which makes them prone to measurement drifts. More recently, Loktionov et al. proposed a disruptive approach based on the spectral deconvolution method, searching for the individual absorbance contribution of each vanadium compound. Building on their method, we further refined, simplified and extended the deconvolution method to a wider range of concentrations, confirming its strength and robustness in measuring the total vanadium concentration and SoC independently .