Hydrobromic acid used as an electrolyte has been replaced with a far less toxic alkaline solution (1M KOH) and ferrocyanide. The higher pH is less corrosive, allowing the use of inexpensive polymer tanks. The increased electrical resistance in the membrane was compensated by increasing the voltage. The cell voltage was 1.2V. The cell's efficiency exceeded 99%, while round-trip efficiency measured 84%. The battery has an expected lifetime of at least 1,000 cycles. Its theoretic energy density was 19Wh/L. Ferrocyanide's chemically stability in high pH KOH solution without forming Fe(OH) or Fe(OH) needs to be verified before scale-up.