Figure shows the viscosity of the posolyte (left) and the negolyte (right) plotted versus the SoC for various total vanadium concentrations at T = 20 • C and c S = 4.07 M. Hereafter all results will be presented in terms of kinematic viscosity. As seen in the figure, both electrolytes exhibit the same behavior: the viscosity increases with vanadium concentration but decreases with SoC. The negolyte exhibits higher viscosities (5.82, mm 2 /s) compared to the posolyte (4.55, mm 2 /s), along with a more pronounced interaction between vanadium concentration and SoC, characterized by a nonlinear dependence that decreases for increasing values of c V . . The temperature is seen to have a significant impact on the viscosity of both electrolytes, specially at higher total vanadium concentrations. At c V = 0.915 M, the viscosity behaves almost linearly with SoC. The rise in sulfates concentration also contributes to increase the viscosity, but to a lesser extend than the vanadium concentration and temperature. As a general trend, the negolyte exhibits higher viscosity and greater sensitivity to parameter variations than the posolyte.