The design of a 10cm×10cm flow cell for the soluble lead acid flow battery is described. A number of extended charge/discharge cycling experiments are presented to demonstrate the capability of the battery to cycle over lengthy periods and to identify the problems that limit the number of cycles that can be achieved. A charge efficiency below 100%, leading to a build up of deposits on both electrodes and a consequent drop in the concentration of Pb2+ in the electrolyte are found to limit cycle life.