<P> Primary batteries make up about 90% of the $50 billion battery market, but secondary batteries have been gaining market share . About 15 billion primary batteries are thrown away worldwide every year, virtually all ending up in landfills . Due to the toxic heavy metals and strong acids or alkalis they contain, batteries are hazardous waste . Most municipalities classify them as such and require separate disposal . The energy needed to manufacture a battery is about 50 times greater than the energy it contains . Due to their high pollutant content compared to their small energy content, the primary battery is considered a wasteful, environmentally unfriendly technology . Due mainly to increasing sales of wireless devices and cordless tools which cannot be economically powered by primary batteries and come with integral rechargeable batteries, the secondary battery industry has high growth and has slowly been replacing the primary battery in high end products . </P> <P> A secondary cell, commonly referred to as a rechargeable battery is an electrochemical cell that can be run as both a galvanic cell or as an electrolytic cell . This is used as a convenient way to store electricity, when current flows one way the levels of one or more chemicals build up (charging), while it is discharging they reduce and the resulting electromotive force can do work . </P> <P> A fuel cell is an electrochemical cell that converts the chemical energy from a fuel into electricity through an electrochemical reaction of hydrogen fuel with oxygen or another oxidizing agent . Fuel cells are different from batteries in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy comes from chemicals already present in the battery . Fuel cells can produce electricity continuously for as long as fuel and oxygen are supplied . </P> <P> The first fuel cells were invented in 1838 . The first commercial use of fuel cells came more than a century later in NASA space programmes to generate power for satellites and space capsules . Since then, fuel cells have been used in many other applications . Fuel cells are used for primary and backup power for commercial, industrial and residential buildings and in remote or inaccessible areas . They are also used to power fuel cell vehicles, including forklifts, automobiles, buses, boats, motorcycles and submarines . </P>

What is the term for a type of cell that converts