Recent component technology innovations will be combined with new materials available to significantly improve the energy density and cycle life of sealed rechargeable nickel-zinc prismatic batteries. The zinc electrode has long been recognized as having a high energy density, but the nickel-zinc system has been limited in life by separators which require electrolyte concentrations which are not optimum for electrode performance because of solubility and replating of zinc to form treeing (and consequent shorting) and shape change. The objective of the proposed program is to demonstrate the feasibility of the battery with improvements in separator, electrolyte concentration, and positive active material density, to reach goals of performance which will provide a battery of cells which conveniently fit in a belt or vest and can provide sufficient energy for ventricular assist.