Lead-acid cells portable

By far the largest sector of the battery industry worldwide is based on the lead-acid aqueous cell whose dominance is due to a combination of low cost, versatility and the excellent reversibility of the electrochemical system, Lead-acid cells have extensive use both as portable power sources for vehicle service and traction, and in stationary applications ranging from small emergency supplies to load levelling systems. In terms of sales, the lead-acid battery occupies over 50% of the entire primary and secondary market, with an estimated value of 100 billion per annum before retail mark-up. 

Portable valve-regulated lead-acid cells can operate in any orientation without acid leakage and find use in many different applications, such as in electronic cash registers, alarm systems, emergency lighting unit equipment, telephone boxes, switching stations, minicomputers and terminals, electronically controlled petrol pumps, cordless television sets and portable instruments and tools. 

An estimation of the european market for other types of cells has been made and is presented in Table 2. It is estimated that the number of Ni-MH and Li-Ion cells as well as portable lead-acid cells sold in Europe represent 25% of the world market. When the... 

VG 96924 Portable lead-acid cells and batteries for military applications. 

Monobloc batteries, using the cylindrical cell, are produced with two to six cells interconnected in a single plastic container. These 4-, 6-, and 12-V batteries have performance characteristics similar to those of the single cell. The monobloc design is illustrated in Fig. 24.3. A newer type of small cylindrical lead-acid cell made within film electrodes has been introduced. This design has been characterized by Atwater et al. for use in portable electronic and communication applications. 

Thin flat prismatic sealed lead-acid cells have been designed for portable applications as they offer more flexibility in the design of the battery. They use space more efficiently than cylindrical cells, resulting in a higher volumetric energy density, and the slim design is adaptable to small-footprint equipment. " An exploded view of a typical flat cell is shown in Fig. 24.5. 

Secondaiy batteries consist of a series of electrochemical cells. The most popular types are the lead-acid type used for starting, lighting, and electrical systems in motor vehicles and the small rechargeable batteries used in laptops, camcorders, digital phones, and portable electronic appliances. 

The electrolyte was a solution of ammonium chloride that bathed the electrodes. Like Plante s electrochemistry of the lead-acid battery, Leclanche s electrochemistry survives until now in the form of zinc-carbon dry cells and the use of gelled electrolyte.12 In their original wet form, the Leclanche electrochemistry was neither portable nor practicable to the extent that several modifications were needed to make it practicable. This was achieved by an innovation made by J. A. Thiebaut in 1881, who through encapsulating both zinc cathode and electrolyte in a sealed cup avoided the leakage of the liquid electrolyte. Modern plastics, however, have made Leclanche s chemistry not only usable but also invaluable in some applications. For example, Polaroid s Polar Pulse disposable batteries used in instant film packs use Leclanche chemistry, albeit in a plastic sandwich instead of soup bowls.1... 

Batteries have been developed from many pairs of chemicals capable of being oxidized and reduced. Some systems are rechargeable after the chemicals in the battery have been exhausted, the reactions can be reversed by the application of an external source of electricity. The lead-acid automobile battery is a familiar example. In many applications, such as cell phones and laptop computers, the weight of a portable electricity supply is critical. This has led to the development of batteries based on lightweight lithium chemistry, for which challenges still remain. 

Aluminium-air cells were first developed for portable applications such as mooring lights, and for recharging nickel-cadmium and lead-acid storage batteries. They have been fabricated in many unusual designs, e.g. the concentric rope battery which has an aluminium core surrounded by a separator and then the oxygen cathode. The rope may be several hundred metres long and can provide 0.03 W/m for a period of 6 months on immersion in the sea. 

In recent years the market for small, portable lead-acid batteries has grown considerably. Almost all portable batteries are VRLA designs. Both cylindrical and rectangular (prismatic) unit cells are made and assembled into multicell packs. 

The difference in the reactivity between the two metals used in the cell creates a particular voltage reading on the voltmeter shown in Figure 6.23b. The more the two metals differ in reactivity, the larger is the voltage shown and delivered by the cell. This method can be used to confirm the order of reactivity of the metals (Chapter 10, p. 150). Other types of chemical cell in common use are dry cells used in radios, torches, and so on, and lead-acid accumulators used in motor vehicles. These are convenient and portable energy sources. 

Compared with conventional batteries such as lead acid, Ni-Cd, and Ni-MH, Li-ion batteries provide higher energy density and higher power density. Since the Li-ion battery was introduced in 1992, a huge worldwide market has developed for portable cell phones and laptop computers. In 2000, Li-ion batteries represented half of the worldwide rechargeable battery market with a value of 3 billion, and still growing. 

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