Abstract: A secondary battery, such as a nickel-hydrogen (NiH.sub.2) cell, has a first and a second cell stack, each cantilevered from opposite sides of a weld ring. The weld ring is located at the approximate center or middle of a pressure vessel composed of two half sections which are welded to opposite sides of the weld ring. The cell stacks are essentially unsupported at their outer ends. Electrical current carriers are received in longitudinal channels formed on opposite sides of an axially located cell stack support member, on which the cell elements are captured. Cantilever mounting of two cell stacks from a central weld ring is found to improve the integrating and durability of the cell. It also increases the eneregy capacity of the battery through the ability to add more cells through the use of axially longer pressure vessels, increasing the capacity of the battery. Location of the weld ring between the pair of cell stacks improves heat transfer between the cells and the pressure vessel during discharge.

Abstract: A metal-hydrogen cell is disclosed in which the durability of the battery is substantially increased and the system mass and volume are reduced. A plate stack within the casing is compressed by a spring which is supported from the casing without support from the terminals. The spring support is external to the cell stack; that is, it does not pass through the stack. Optionally, terminals are positioned at non-axial positions on the casing, extending outwardly from each domed end of the casing at axially offset positions on the domed ends so that the terminals do not extend beyond the length and diameter of the casing. This contributes to the reduction in the effective size of the cell.

Abstract: A metal-gas electrochemical cell is disclosed wherein electrolyte is progressively supplied from a reservoir into the electrode or cell stack as needed, so as to maintain each stack component with adequate electrolyte, as the plates "grow" and absorb electrolyte with repeated cycling. The reservoir preferably is a compressible bladder positioned between one end of the plate stack and a retaining plate. As the plate stack "grows" with repeated cycling, the bladder is slowly compressed, forcing electrolyte from the bladder through an electrolyte distribution tube located within the plate stack. One end of the electrolyte distribution tube is fixed to an end plate of the plate stack and the second end of the distribution tube may be connected to a Belleville washer or other spring which acts through the distribution tube to compress the plate stack. The elasticity of the spring permits the stack to expand as the electrodes grow.