A non-aqueous vanadium acetylacetonate redox flow battery with different organic solvents and tetrabutylammonium hexafluorophosphate has been investigated. Cyclic voltammograms show three redox couples in 1,3-dioxolane, tetrahydrofuran, acetylacetone and two redox couples in dimethyl sulfoxide. Cell potentials between 2.21 and 2.61V are measured, depending on the solvent used. Impedance Spectroscopy has been used to determine rate limiting step in the non-aqueous redox flow battery. Experiments in a charge-discharge test cell yielded coulombic and energy efficiencies of 85.9-98.5% and 26.6-43.6%, respectively. (C) 2013 Elsevier Ltd. All rights reserved.