Laboratory cells, utilizing sodium and chlorine as reactants, have been assembled and tested. They were shown to produce theoretical voltages over a temperature range of 825C to 1219C and were capable of being discharged at more than 20 amperes per square inch of electrode area. They were charged and discharged and exhibited electrochemical reversibility. Studies of protective coatings for cell container materials were made. A cell of more advanced design leading toward a prototype cell was engineered and assembled and tested. This work is evaluated in terms of practical feasibility of the Electrothermally Regenerative Transducer and a fuel cell battery based on the alkali metals and the halogens as reactants.