For the posolyte (right), the RMSE values remain close to those obtained with the entire spectrum, although they are slightly higher when using only two channels (Fig. and). The algorithm identifies optimal placements up to 800 nm, as the spectra signal of each specie vary. Notably, 440 nm appears as an optimal placement for identifying the absorbance of V V , which reaches its maximum at this lower wavelength (Fig. ). Moreover, this is the only region of the spectrum directly proportional to both the total vanadium concentration and the SoC, enabling a low RMSE with the addition of just one additional channel. This additional wavelength is placed around 760 nm, corresponding to the global maximum of the V IV spectrum. Subsequent optimal wavelengths are placed near local minima and maxima of V 2 O 3+ 3 , resulting in slightly lower RMSE values for SoC (Fig. ). For concentration (Fig. ), adding more wavelengths reduces the RMSE to values comparable to those obtained using the full spectrum, showing a more significant improvement than for the other RMSE metrics. As observed with the negolyte, equidistantly placed channels result again in higher RMSE values, particularly for the SoC, as the information about V V is concentrated at lower wavelengths.