"Traditionally, cordless power tools have used nickel-cadmium batteries.
"However, some observers believe nickel-cadmium has reached is capacity
ceiling. Many end users are demanding longer run times and better
performance. Cadmium also poses an environmental hazard. As a result,
nickel-cadmium cells are increasingly being replaced by other types of
rechargeable batteries.
"Many cordless tool manufacturers are converting to nickel-metal
hydride, a technology that has similar characteristics to
nickel-cadmium, in that it accepts fast and continuous charging.
"The typical nickel-metal hydride cell costs more and has half the
service life of the typical nickel-cadmium battery, but it also has 30
percent more capacity, increased power density and less memory effect.
The battery doesn't have to be fully discharged before being recharged.
Increased energy density offers longer service life between charges,
while lack of cadmium, lead or mercury makes it environmentally friendly.
"Other battery technology may soon be available to cordless tool users,
such as lithium-ion, lithium-ion polymer, lithium-iron disulfide and
zinc-air. Portable fuel cells are another power option that may be
coming soon to a cordless tool near you. But, widespread application of
these technologies is currently limited due to exorbitant costs."