NiCd battery

Cadmium consumption in 2001 was about 16000 tonne (according to the World Bureau of Metal Statistics), 17% less than the previous year. Japan used the metal mainly for NiCd batteries and was the largest consumer country. Belgium and the 

The International Cadmium Association (ICdA) in Brussels, Belgium, made an estimate of cadmium consumption for different end uses in 2001. Batteries account for 75%, pigments 12%, coatings and plating 8%, and stabihzers for plastics and similar purposes 4%. The remaining small amount of cadmium, 1%, is used in some very special applications such as nonferrous alloys and as cadmium telluride (CdTe) for electronic compounds. 

The soft and ductile cadmium metal has low friction. Threaded components, such as screws, were cadmium-plated in order to avoid locking. For this use zinc is not suitable, but tin has proved to be a good alternative. 

The use of rechargeable batteries has changed dramatically in recent years. Power is required for a lot of portable products, such as telephones, computers and household appHances, as web as for stationary reserve power stations. The answer has been 

NiCd batteries. In our modern sodety this battery type still provides a large fraction of the actual power, in spite of environmental problems with cadmium. However, for small portable appliances, but not for the big reserve power stations, alternatives have been found. In fact the annual cadmium use is increasing for these applications. 

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Cadmium (Cd) anode cells are at present manufactured based on nickel-cadmium, silver-cadmium, and mercury-cadmium couples. Thus wastewater streams from cadmium-based battery industries carry toxic metals cadmium, nickel, silver, and mercury, of which Cd is regarded the most hazardous. It is estimated that globally, manufacturing activities add about 3-10 times more Cd to the atmosphere than from natural resources such as forest fire and volcanic emissions. As a matter of fact, some studies have shown that NiCd batteries contribute almost 80% of cadmium to the environment,4,23 while the atmosphere is contaminated when cadmium is smelted and released as vapor into the atmosphere4 Consequently, terrestrial, aquatic, and atmospheric environments become contaminated with cadmium and remain reservoirs for human cadmium poisoning. 

Vented NiCd. The vented NiCd battery is one of the best-known power sources in the commercial and military fields, particularly for aircraft and communication applications. It has excellent high rate and low temperature performance capabilities. It also has a long useful life capability and is both physically and electrochemically rugged. 

The sealed nickel—metal hydride battery has characteristics very similar to those of the sealed NiCd battery. The main difference is that the NiMH battery uses hydrogen, absorbed in a metal alloy, for the active negative material in place of the cadmium used in the NiCd battery. The NiMH batteries have a higher energy density and are considered more environmentally friendly than the NiCd battery. The sealed NiMH battery, however, does not have the very high rate capability of NiCd battery, and is less tolerant of overcharge. 

Ikoma et al. carried out a detailed investigation to study the self-discharge mechanism and contribution of separators.They used nonwoven fabric made of conventional polyamide (FA), FF (with surfactant), and a nonwoven fabric whose main material was sulfonated-FF (hydrophilic) as separators. When nonwoven fabric made of chemically stable sulfonated-FF is used as a separator instead of a conventional polyamide separator, the self-discharge rate of the NiMH battery was strongly depressed, to the same level as that of NiCd battery. 2 >o-242.243... 

The initial flow rate decrease is caused by the NiCd battery discharge characteristic. Direct error can also result from the effect of inlet pressure changes on flow as shown in Figure 2(3). Since the pump is working on a compressable fluid, air, any increase in the pressure drop reduces the flow rate. 

Power source Wall plug in AC 2 X 9-volt alkaline battery NiCd rechargeable battery pack Wall plug in AC one 8-volt sealed lead-acid battery 2 X 9-volt alkaline or lithium batteries external lead-acid battery pack Four D-cell alkaline batteries AC power kit with two rechargeable NiCd batteries... 

Commercialization of amorphous silicon solar cells started in 1980 when Sanyo introduced calculators powered only by small solar-cell panels (total area 5 cm2). Shortly thereafter, Fuji Electric also started producing a-Si H solar cells for calculators. As of 1983, a-Si H photovoltaic devices are produced for several other applications such as photodetectors, power supplies for watches, and NiCd battery chargers. Before the end of 1984 one may see a-Si H solar panels used in larger-scale applications such as irrigation and remote electrification. 

The overall reaction that occurs in a NiCd battery is ... 

Leclanche cells are not rechargeable once the reactants are depleted, the battery must be discarded and replaced. Batteries that are not rechargeable are called primary batteries. A rechargeable battery is called a secondary battery or a storage battery. The nickel-cadmium (NiCd) battery is a popular rechargeable battery that uses the following redox reaction ... 

Finally, the conversion of the primary metal into the product and the form which are actually utilized in the battery system should be considered. For example, the electrode materials in lead acid batteries are normally cast lead or lead-alloy grids. The materials utilized in NiCd batteries are cadmium oxide and high surface area nickel foams or meshes. Technically, all of these factors should be considered to produce a detailed life cycle analysis. However, again, these differences are generally quite small compared to the principal variables - composition, performance and spent battery disposal option. 

The SEI data is based mainly on earlier emission numbers for NiCd battery manufacturing, whereas the OECD monograph data represents updated emissions in the European Union as of 1994 compared to total volumes of cadmium utilized for NiCd battery production, based on information from the International Cadmium Association. All of this data indicates that most of the cadmium remains in the product and is not lost during NiCd battery manufacturing. A similar conclusion can be inferred with respect to nickel and cobalt, the other materials in a NiCd battery which might be likely to be regarded as hazardous and contribute to an adverse environmental impact. Iron, of... 

Table III. Partitioning of Cadmium in NiCd Battery Manufacturing...

In addition, two sets of data from the Battery Association of Japan (BAJ), formerly known as the Japan Storage Battery Association (JSBA), equally clearly demonstrate that the levels of cadmium emissions to air and water in Japan have decreased steadily over the period from 1980 through 1992 in spite of the greatly accelerated production of NiCd batteries in Japan during that same time period (Mukunoki and Fujimoto 1996). Japan is the world s largest producer of NiCd batteries, and currently accounts for over 70% of the world s NiCd battery production. If there is any country where potential enviromnental contamination by cadmium from NiCd battery manufacture should be... 

Figure 4. Japanese River Water Cadmium Concentration and NiCd Battery Production...

Table V. Basic Performance Parameters of AA NiCd Battery...

During the normal use and maintenance of a battery system, they are neither destroyed nor dissipated nor do they emit any harmful substances. Battery systems may be sealed or vented. If they are sealed, then no emissions occur during normal use and maintenance. If they are vented, then water vapor, hydrogen gas or oxygen gas may be vented, depending on the system and whether it is charging or discharging. A 1994 report (Stockholm Environmental Institute 1994), for example estimated that the dissipation rates for both industrial and consumer NiCd batteries were 0.01 percent per year. The International Cadmium Association believes, based on surveys of its NiCd battery producer members, that the dissipation rates are virtually zero, or so low as to be undetectable. 

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