MANUALLY ACTIVATED SILVER-ZINC BATTERIES
In 1951 Eagle-Picher initiated a program which led to the development of a series of cell designs of various sizes designated as the “A” line of cells. These have since been standardized into cells offering a wide range of capabilities. Each of these cell sizes offers low and high rate capabilities in both primary and secondary designs. Modifications of these designs have been used in practically all space and missile development programs. Nearly all launch and primary storage energy for the manned space flights has been supplied by Eagle-Picher batteries. The silver-zinc system is desirable for these applications due to its high energy to weight and volume ratios, and extremely high reliability.
The design of a manually activated silver-zinc system is intended to provide a battery having maximum energy with minimum weight and volume which can be stored for a period of time and then readied for use by the manual introduction of electrolyte. The principle components are the electrodes, the separator system, the cell housing and the electrolyte. The advantage of the single cell housing is that a wide range of designs can be obtained by the tailoring of individual components to satisfy any configuration requirement. The chemical elements used include a porous silver plate oxidized to the divalent state coupled with a specially prepared sponge zinc plate. The electrolyte employed is a solution of potassium hydroxide in water.
Practically any material capable of restraining the cells and enduring the dynamic environments can be utilized to house the number of cells required for the intended use. The most popular are stainless steel, titanium and fiberglass. Containers can be fabricated and welded, molded or machined depending on need.
For use in extremely cold environments, thermostat-controlled heater systems are employed. These can be designed to heat the battery to a temperature compatible with the voltage level desired. Depending on the application, voltage can be supplied to the heater from either an external source or from the battery.
This system is capable of undergoing extreme conditions of shock, acceleration, vibration and is operable at all altitudes and is especially adaptable for airborne equipment, missiles and spacecraft.
Secondary batteries produced by Eagle-Picher have been used in applications ranging from long-life service applications to manned space flights. Each is manufactured under exacting specifications to insure that the capabilities are compatible with requirements. Cycle life, depending on design requirements and discharge depths, has been demonstrated in excess of 500 cycles. These batteries, as in the primary system, are also rated as low and high rate systems. Extended wet life over the primary system is accomplished through the use of multiple wraps of semipermeable membrane separator between the positive and negative electrodes. The secondary series can be manufactured either dry-charged or dry-uncharged. The high rate secondary batteries may be discharged at sufficiently high rates to expend their energy in 15 minutes. The low rate units provide best efficiencies at rates of four hours or greater. As with the primary batteries, voltage regulation at any discharge rate is good, and with moderate temperature control, storage in the dry condition is practical for up to five years.