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.

(NiMH) A rechargeable battery technology that has approximately 30-50% more charge per pound than nickel cadmium. Introduced in the early 1990s, it uses nickel and metal hydride plates with ...