The nickel--cadmium battery is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. The abbreviation Ni-Cd is derived from the chemical symbols of nickel and cadmium : the abbreviation NiCad is a registered trademark of SAFT Corporation, although this brand name is commonly used to describe all Ni--Cd batteries. Wet-cell nickel-cadmium batteries were invented in 1898. Among rechargeable battery technologies, NiCd rapidly lost market share in the 1990's, to NiMH and Li-ion batteries; market share dropped by 80%. A Ni-Cd battery has a terminal voltage during discharge of around 1.2 volts which decreases little until nearly the end of discharge. Ni-Cd batteries are made in a wide range of sizes and capacities, from portable sealed types interchangeable with carbon-zinc dry cells, to large ventilated cells used for standby power and motive power. Compared with other types of rechargeable cells they offer good cycle life and performance at low temperatures, fair capacity, and work well at high discharge rates (using the cell capacity in one hour or less). However, the materials are more costly than that of the lead acid battery, and the cells have high self-discharge rates. Sealed Ni-Cd cells were at one time widely used in portable power tools, photography equipment, flashlights, emergency lighting, hobby R/C, and portable electronic devices. The superior capacity of the Nickel-metal hydride batteries, and more recently their lower cost, has largely supplanted their use. Further, the environmental impact of the disposal of the heavy metal cadmium has contributed considerably to the reduction in their use. Within the European Union, they can now only be supplied for replacement purposes although they can be supplied for certain specified types of new equipment such as medical devices. Larger ventilated wet cell NiCd batteries are used in emergency lighting, standby power, and uninterruptible power supplies and other applications. History The first Ni--Cd battery was created by Waldemar Jungner of Sweden in 1899. At that time, the only direct competitor was the lead--acid battery, which was less physically and chemically robust. With minor improvements to the first prototypes, energy density rapidly increased to about half of that of primary batteries, and significantly greater than lead--acid batteries. Jungner experimented with substituting iron for the cadmium in varying quantities, but found the iron formulations to be wanting. Jungner's work was largely unknown in the United States. Thomas Edison patented a nickel-- or cobalt--cadmium battery in 1902, and adapted the battery design when he introduced the nickel--iron battery to the US two years after Jungner had built one. In 1906, Jungner established a factory close to Oskarshamn, Sweden to produce flooded design Ni--Cd batteries. Production in the United States The first production in the United States began in 1946. Up to this point, the batteries were "pocket type," constructed of nickel-plated steel pockets containing nickel and cadmium active materials. Around the middle of the twentieth century, sintered-plate Ni--Cd batteries became increasingly popular. Fusing nickel powder at a temperature well below its melting point using high pressures creates sintered plates. The plates thus formed are highly porous, about 80 percent by volume. Positive and negative plates are produced by soaking the nickel plates in nickel- and cadmium-active materials, respectively. Sintered plates are usually much thinner than the pocket type, resulting in greater surface area per volume and higher currents. In general, the greater amount of reactive material surface area in a battery, the lower its internal resistance. Recent developments In the past few decades, Ni--Cd batteries have had internal resistance as low as alkaline batteries. Today, all consumer Ni--Cd batteries use the "swiss roll" or "jelly-roll" configuration. This design incorporates several layers of positive and negative material rolled into a cylindrical shape. This design reduces internal resistance as there is a greater amount of electrode in contact with the active material in each cell. Characteristics The maximum discharge rate for a Ni--Cd battery varies by size. For a common AA-size cell, the maximum discharge rate is approximately 18 amps; for a D size battery the discharge rate can be as high as 35 amps. Attribution: Article text available under CC-BY-SA Creative Commons image source in video

• published: 18 Nov 2013
• views: 2