(NiCd) A rechargeable battery technology that is widely used for portable hand tools. It uses a nickel and cadmium plate and potassium hydroxide as the electrolyte. Originally invented in Sweden in 1899, it became popular in the 1950s after a sealed version was developed. Nickel cadmium provides more charge per pound than lead acid batteries, but less than nickel metal hydride. Its major problem is the so-called "memory effect," in which the battery seems to remember how full it was when last charged and will not charge past that point the next time. To maintain the longest charge, nickel cadmium batteries should be completely discharged periodically. See batteries.