The Nickel Cadmium, NiCd or Ni-Cd Battery was the first type of rechargeable cell that could be used for portable electronics equipment. Although the Lead Acid battery had been available for many years, it was mainly used for automotive batteries. Th NiCd might easily be used as a direct replacement for many conventional primary batteries and its usage quickly caught on. Currently few NiCd batteries can be bought, but did fill a gap in the market that no other battery of the time could meet. Occasionally old Nickel Cadmium Battery can still be found in stocks or possibly even in use.

NiCd or Ni-Cd Cells are able to provide an almost direct replacements for zinc carbon or alkaline primary batteries. They generally are able to retain less charge than these cells, but have the obvious advantage that they are able to be re-charged. This means that although the initial purchase cost is higher than the equivalent primary cells, costs can be saved after a few charge / discharge cycles.

Ni-Cd Battery Pack Manufacturer tell you the NiCd cells have an extremely low leverl of inner resistance. A good excellent alkaline cell may have an inner resistance of about 300 milli-ohms when new. This figure might rise to about 900 milli-ohms when 20% discharged and several ohms when almost completely discharged. A NiCd has very much lower figures, and any innernal resistance can be ignored for most purposes as it's of the order of only a few milli-ohms, dependent upon the exact type of cell and the maker. This does mean that the cell is capable of producing very high currents, especially if the cell is inadvertently short-circuited. In light of this care has to be taken to make sure this doesn't occur as large quantities of heat could be produced.