Vented nickel-cadmium cells

The international standards IEC60623, 60896 and 60993 are useful references for vented lead-acid and nickel-cadmium cells. 

Fig. 13.1 Cell balance for vented and sealed nickel cadmium cells. It is important to avoid hydrogen gas evolution in the sealed cell...

Vented sintered-plate nickel-cadmium cells, in the discharged state, consist of flat positive nickel hydroxide and negative cadmium hydroxide plates, separated by materials that act as a gas barrier and electrical separator. The electrolyte, normally a 31% potassium hydroxide solution completely covers the plates and separators for this reason vented cells are referred to as flooded cells. ... 

FIGURE 27.1 Constant-current charge voltage of vented sintered-plate nickel-cadmium cell, C/10 charge rate. 

A variety of plate formulations are used in vented, sintered nickel-cadmium cells produced by different manufacturers. The plates differ according to the nature of the substrate, method of sintering, impregnation process, formation and termination techniques. The predominate plate fabrication process used for vented sintered plate over the years has been described by Heischer." There are several reviews on electrode fabrication processes that have been used in flooded vented cells. ... 

The service life (discharge time) of the vented sintered-plate nickel-cadmium cell, normalized to unit weight (kilogram) and size (liter) at various discharge rates at 25°C, is approximated in Figs. 27.12 and 27.13. 

Typical Vented Sintered-Plate Nickel-Cadmium Cells... 

A listing of several typical vented sintered-plate nickel-cadmium cells is given in Table 27.3. The 14-, 22-, and 36-Ah sizes are those typically employed in aircraft batteries. Other cells are available in sizes up to about 350 Ah. The larger cells are generally constructed in steel containers rather than the plastic containers now used for the aircraft-size cells. 

The construction of this cell is similar to that of standard cylindrical nickel-cadmium cells. It is sealed, has a safety vent and makes use of a cylindrical spiral-wound plate design. 

The D-cell was the first cell available within this range. It is rated at 2.5 Ah at the lOh rate. It is 61 mm in height and 34 min in diameter. The construction of this cell is similar to that of standard cylindrical nickel-cadmium cells. It is sealed, has a safety vent, makes use of a cylindrical spiral-wound plate design for high energy density and low internal impedance, and can be charged and discharged in any orientation. 

Sealed nickel-cadmium cells normally operate at internal pressures well below the vent pressure because gas evolved during charging is reasily recombined. Compliance with three essential design criteria is necessary to accomplish this ... 

Flooded battery — A battery (or a cell) containing an excess of electrolytic solution (in contrast to starved electrolyte batteries). Usually relevant to rechargeable -> lead-acid and -> nickel-cadmium batteries. Flooded battery design is typically applicable for heavy duty batteries, equipped with a vent valve that releases pressure buildup due to gas evolution. The excess electrolyte affects more sturdy batteries to become less susceptible to damage due to overcharge. In addition, the thermal conductivity of the electrolyte affords more efficient heat dissipation and thus higher -> power densities. 

Vented nickel-cadmium prismatic rechargeable single cells. 

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