AUTOMATICALLY ACTIVATED SILVER-ZINC BATTERIES
Development of the automatically, or remote, activated silver-zinc battery at Eagle-Picher was initiated in the early 1950’s. The early systems developed were simple single section batteries with one voltage output. Today Eagle-Picher is producing highly reliable complex systems comprised of as many as fourteen different voltage outputs for the missile industry. The Couples Department of Eagle-Picher Industries has produced in excess of five million five hundred thousand (5,500,000) batteries encompassing over six hundred fifty (650) different configurations. The Couples Department maintains a flexible engineering, production and administration staff to ensure proper design, development, qualification, production and delivery to meet the requirements of the applicable program.
The basic design of the automatically activated, silver-zinc battery utilizes a gas generator, tubular electrolyte reservoir, manifold, battery block, sump, vent system and heater system where applicable. Detailed
descriptions of these components and their contribution to the overall operation of the battery are contained in the following paragraphs.
The means of moving the electrolyte reservoir to the battery block is provided by the gas generator. The gas generator consists of an igniter and a rapid burning propellant. The igniter and propellant are sealed by a frangible diaphragm to prevent contamination. Normally an electrical signal ignites a match which in turn ignites the propellant. As the propellant burns a gas pressure is generated which bursts the frangible diaphragm. Alternate methods of ignition are available; these include mechanical release of a firing pin, pneumatic or hydraulic pressure, and inertial devices. Eagle-Picher manufactures its own gas generators.
The electrolyte reservoir provides the means of storing the electrolyte (potassium hydroxide) for long periods of time (5 years and longer) with no contamination prior to use. The reservoir consists of copper or stainless steel tubing shaped to fit around or along the battery block. The reservoir utilizes two (2) frangible diaphragms at each end of the reservoir. Upon application of gas pressure at the generator side of the reservoir, the frangible diaphragms burst resulting in a hydraulic pressure at the manifold side of the reservoir. Sufficient hydraulic pressure results in the bursting of the output diaphragms and entry of the electrolyte into the manifold. The pressure generated by the gas generator is sufficient to sweep the reservoir free of electrolyte.
The means of proper distribution of electrolyte to each cell in the battery block is provided by the manifold. The manifold is designed to channel excess electrolyte to the sump system along with the gases produced by the gas generator.
The housing which contains the cell arrangement is referred to as the battery block. The block contains spacers for isolation of cells and is designed to accommodate the shape-dictated configuration pattern. The number of cells required for each block is dictated by the voltage requirements. The cell is designed to meet the current and time profile of the individual specification. The cell assembly consists of silver-oxide positive plates and zinc negative plates. The requirements for temperature, activation time and activated stand time govern the type of material used to separate and isolate the positive and negative plates. The material generally used for the battery block is plexiglass. Eagle-Picher manufactures each battery block.
The vent system provides the means of releasing internal pressures generated at activation and during late stages of battery discharge and blocks entry of outside atmosphere prior to activation. The vent system consists of a one-way relief valve and an external vent tube. The relief valve allows the battery block to operate at a nominal pressure.
A thermostatically controlled heater system is normally incorporated in the battery when the specification requires cold battery operation. The heater system consists of thermostats located properly to ensure proper internal temperature, and heater of sufficient wattage to bring the battery to optimum temperature within the allotted time. Basic heaters consist of resistance wire wound around the electrolyte reservoir.