NOVELTY - A moles of oxy hydroxylated vanadium hydrate (OHV) formed from tetravalent vanadium solution is mixed with 5A-30A moles of sulfur, where A is molar amount of vanadium (V) in electrolyte. Mixture is heated, reduced, added with 1.7-3.5A moles of sulfuric acid (SA), and ratio of tri- and tetravalent vanadium compounds is adjusted. Mixture is then added with SA, water, and concentrations of V and sulfate are adjusted.    USE - As electrolyte for vanadium redox flow batteries.    ADVANTAGE - The method enables to form vanadium having reduced impurities, by processing generated combusted soot, by a simple method. The method enables to produce electrolyte containing tetravalent and trivalent vanadium in equivalent ratio.    DETAILED DESCRIPTION - Combusted soot containing tetravalent vanadium is suspended in water, and the pH of the resulting solution is adjusted to 1-3. The solution is reduced and filtered to obtain an aqueous solution containing tetravalent vanadium. The pH of the tetravalent vanadium containing aqueous solution is adjusted to 4.2-2.8 using ammonia or aqueous ammonia, and the precipitated oxy hydroxylated vanadium hydrate (OHVH) is filtered. If the number of moles of vanadium in the electrolyte is set to A, then A moles of OHVH hydrate is mixed with 5A-30A moles of sulfur. The resulting reaction mixture is heated to 380-445 degrees C, stirred and reduced to obtain mixture (M1). 1.7A-3.5 A moles of sulfuric acid having concentration of 4-10 moles/liter, is added to the mixture (M1) to dissolve vanadium compound heated and precipitated at 110-140 degrees C. The sulfur is removed from the resulting reaction mixture (M2) if desired by filtration.    The OHVH hydrate obtained is added to reaction mixture (M2), and trivalent and tetravalent vanadium compounds in the resulting solution (S1) are set to equimolar ratio. Sulfur is removed by filtration if desired from the solution (S1). The solution (S1) is added with sulfuric acid and water, and the concentration of vanadium and sulfate are adjusted to desired to value. The solution is then filtered to remove residuum to manufacture vanadium redox flow battery electrolyte.