Marine Engine Q & A- Electrical-Nickel-Cadmium Battery Plates

Plates
The active materials for nickel-cadmium cells are improved by additions of other substances. Positive plates carry a paste made up initially of nickel hydroxide with a small percentage of other hydroxides to improve capacity and 20% graphite for better conductivity. The material is brought to the charged state by passing a current through it, which changes the nickel hydroxide to hydrated nickel oxide NiO(OH). Performance of cadmium in the negative plates is improved by addition of 25% iron plus small quantities of nickel and graphite.
Active materials may be held in pocket or sintered plates former are made up from nickel plated mild steel strip shaped to form an enclosing pocket The pockets are interlocked at their crimped edges and held in a frame. Electrolyte reaches the active materials through perforations in the pockets.
Sintered plates are produced by heating (to 900°C) powdered nickel which has been mixed with a gas-forming powder and pressed into a grid or perforated plate. The process forms a plate which is 75% porous. Active materials are introduced into these voids