• Ni-Cd(Nickel Cadmium) batteries

Alkaline Nickel battery technology originated in 1899, when Waldmar Jungner invented the NiCd battery. The materials were expensive compared to other battery types available at the time and its use was limited to special applications. In 1932, the active materials were deposited inside a porous nickel-plated electrode and in 1947, research began on a sealed NiCd battery, which recombined the internal gases generated during charge rather than venting them. These advances led to the modern sealed NiCd battery, which is in use today.

The NiCd prefers fast charge to slow charge and pulse charge to DC charge. All other chemistries prefer a shallow discharge and moderate load currents. The NiCd is a strong and silent worker; hard labor poses no problem. In fact, the NiCd is the only battery type that performs best under rigorous working conditions. It does not like to be pampered by sitting in chargers for days and being used only occasionally for brief periods. A periodic full discharge is so important that, if omitted, large crystals will form on the cell plates (also referred to as 'memory') and the NiCd will gradually lose its performance.

Among rechargeable batteries, NiCd remains a popular choice for applications such as two-way radios, emergency medical equipment, professional video cameras and power tools. Over 50 percent of all rechargeable batteries for portable equipment are NiCd. However, the introduction of batteries with higher energy densities and less toxic metals is causing a diversion from NiCd to newer technologies.

The reaction at positive electrode at discharging is

NiO·OH(s) + H2O(l) + e- ----> Ni(OH)2(s) + OH-(aq)

The reaction at negative electrode at discharging is

Cd(s) + 2OH-(aq) ----> Cd(OH)2(s) + 2e-

The total reaction at discharging is

2NiO·OH(s) + 2H2O(l) + Cd(s) ----> 2Ni(OH)2(s) + Cd(OH)2(s)

The direction of reaction when charge is reverse to the above.