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Nickel Cadmium Battery
Since their development and practical application in 1961,
Nickel Cadmium batteries have been widely used due to their
reliability proven through years of use and their ease of
use in a variety of applications such as for rough use.
NiCad rechargeable batteries can be recycled, and it is
important to do so because of the toxic metal cadmium contained
in the batteries. There is growing environmental concern
over the presence of the toxic metal Cd in the battery.
Although they cost 2 to 3 times more than equivalent lead
acid batteries, nickel-cadmium batteries are widely used
in portable power applications, e.g. electric tools and
TV cameras: they are the major battery type in the IRIS
system e.g. BB521, BB590. The main advantages are a higher
energy density, especially at high discharge rates, and
a longer cycle life, typically 500 to 2000 cycles, as opposed
to the 200 to 700 cycles for automobile and sealed lead
acid batteries. Unlike lead-acid cells, individual NiCad
cells can be deeply discharged and left in this condition
without harm. It is, however, bad practice to deeply discharge
a battery of series-connected cells due to possible damage
through voltage reversal of weaker cells.
Unfortunately, NiCad cells tend to lose their charge fairly
rapidly, especially above 35°C. Furthermore, if partially
discharged to a given level and then recharged on a regular
basis, some types of cell suffer a temporary loss of capacity
called the memory effect. This effect is reversible and
full capacity can be restored by several deep discharge/charge
cycles at a low rate and some modern chargers include a
facility to do this at intervals (called charger-analyzers).
Another operational problem of NiCad batteries is that the
voltage varies very little during discharge making it difficult
to estimate the state of charge.
Work Cited
“Nickel-Cadmium Batteries”. Retrieved 19 June
2002 [online]
http://www.corrosion-doctors.org/secondaries/nickel.htm
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