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A laboratory-scale cell was constructed to test the performance of V (II)/V (III) and V (IV)/V (V) half-cells in an all-vanadium redox battery. Graphite plates were used as electrodes, and the membrane was manufactured from a sulfonated polyehylene anion-selective material. The average charging efficiency of the cell was over 90 percent. Stability tests on the reduced and oxidized electrolytes, measured over the temperature range of-5 C to 60 C, showed no accelerated decomposition at high temperatures and no crystallization at the lower temperatures. After prolonged usage, however, a slow deterioration of the positive electrode and the membrane was observed.