NiCad stands for nickel-cadmium, the materials used in the battery packs for many notebook computers. NiCad batteries can provide considerable power, but they need to be recharged every three or four hours. Full recharging can take as much as twelve hours, although newer batteries can be recharged in just a few hours.
Older NiCad batteries suffer from a phenomenon known as the memory effect. If they were only partially drained and then recharged, they lost their capacity to be fully charged. This is not such a problem with modern NiCad batteries.
Even with full drainage (called deep discharging), all batteries have a limit to the number of times they can be recharged. The maximum for most NiCad batteries is about one thousand recharges.