Evaluation of overcharge protection life in nickel cadmium cells with nonnylon separators

Abstract

Hydrogen gassing and the potential for cell rupture in aerospace nickel cadmium cells is directly related to loss of overcharge protection built into the cell during manufacturing. It is well known that cells having nylon separators contribute to this loss via a hydrolysis reaction of the nylon in the potassium hydroxide electrolyte environment in the cell. The hydrolysis reaction produces lower chain organics which are oxidized by the positive electrode and oxygen. Oxidation of the organics diminishes the overcharge protection. With introduction of the Super NiCd/sup TM/ and the Magnum/sup TM/ nickel cadmium cells the nylon hydrolysis reaction is eliminated, but any reducing agent in the cell such as nickel or an organic additive can contribute to loss of overcharge protection. The present effort describes analyses made to evaluate the extent of overcharge protection loss in cells which do not have nylon hydrolysis and quantifies the diminished amount of overcharge protection loss as a result of eliminating nylon from aerospace cells.