An electrochemical cell system and methods for controlling the system are provided that are operated to produce an amount of current based upon power draw. The cell utilizes a solution phase catholyte introduced into a cell containing a metallic anode and a catalytic surface. A cathodic species is introduced into the space between the anode and the surface as a liquid along with electrolyte and liquid caustic. The mixture of caustic, electrolyte and liquid catholyte is continuously recirculated through the space, and a portion of the recirculation stream is exhausted in order to control the concentration of reaction products in each cell. Controllable injection mechanisms are used to inject the liquids from storage sources based upon the monitored power draw. The control mechanism independently controls each injection mechanism to inject appropriate amounts of caustic, electrolyte and atholyte to achieve the desired concentrations.