Alpha Technologies Lomain Ni-Cd Pocket Plate Battery - Manual (Page 12)

745-680-B10-001 Rev. A 12
1.0 Introduction, continued
1.1 Theory of Operation, continued
Special seperation system
The oxygen created at the positive plate is absorbed by a special felt seperator and
prevented to escape from the distance between the plates. Displacement of electrolyte
by oxygen boubles occur within the seperator and reach the surface of the negative plate
causing the following reaction:
Chemically:
2Cd + O2+ 2H2O → 2Cd(OH)2
This reaction chemically discharges a certain amount of cadmium to cadmium
hydroxide. The current going through the battery recharges this material.
Electrochemically:
O2+ 2H2O+ 4e → 4OH
This reaction consumes the current directly; that is, hydrogen evolution at the
negative plate is prevented since the preferred reaction is oxygen recombination.
Special venting system
The battery cells are equipped with a low pressure flame arresting vent which operates as
a one way valve and allows to escape hydrogen and non-recombined oxygen and fixes the
internal pressure at 0.2 bar.
Porous disc
Pressure rubber
Plastic particles
Sealing ring
Fig. 3, Battery Vent
Fig. 4, Exploded view, Battery vent