A single-metal redox flow battery employing bis(acetylacetone)ethylenediamine cobalt(II) as the active species and tetrabutylammonium hexafluorophosphate as the supporting electrolyte with acetonitrile as the solvent has been examined. Cyclic voltammetry is used to measure the electrode kinetics of the anodic and cathodic reactions. Three redox couples are observed in the stable potential window, these electrode reactions are quasi-reversible and together yield a cell potential of 2.0 V. The disproportion reactions of active species are controlled by the diffusion coefficient. The effect of the environmental factors, such as temperature, oxygen and water, has been tested in the experiment. The charge–discharge characteristics of this system are evaluated in an H-type glass cell. The coulombic efficiencies 90.24% and 87.88% in cycle 5 and cycle 8 are obtained, respectively, with 1 mA charge 0.5 mA discharge current.