This program is directed at the Research and Development of a high energy density electrically rechargeable Zinc-Air battery to serve as the external power supply for ventricular Assist Systems. To give the recipient of such systems maximum portability the external battery pack should store enough energy for 10 to 12 hours of operation. To have a portable battery pack of reasonable weight the battery system should be capable of approximately three times the energy density of the currently available Lead Acid or Nickel Cadmium batteries. The program is initially directed at the evaluation of a number of innovative components (Zinc Electrode, Air Electrode, Electrolyte, and Separator) for the Zinc Air System in small cell tests. Promising components will then be integrated into 5 to 10 ampere hour cells in a novel design for packaging into 12 volt power packs. The goal is a battery system that delivers greater than 110 Wh/Kg (50 Whr/lb) and has a life of 365 cycles (one year).