Alkaline Manganese Dioxide - 1.5 Volts per cell
| The Alkaline Battery |
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During the Second World War this basic technology was further developed to produce a more reliable and robust battery. Allied Forces fighting in the Far East, in particular, found that the environment of high temperature combined with high humidity was extremely detrimental to existing battery types. The new development, the alkaline cell, became the second most widely used consumer battery. The alkaline cell has the zinc anode at the centre of the cell in powder form and the manganese dioxide/graphite cathode as hard-compressed cylindrical pellets surrounding the anode. Synthetic paper acts as the separator. A chemically aggressive and strongly alkaline gelled solution of potassium hydroxide acts as the electrolyte and gives its name to the system. The large surface area of the zinc and efficient electrolyte allows for high current chemical reactions and the compressed cathode allows more active ingredients to be contained within the specified volume. The alkaline cell, not only provides a high and more stable electrical performance, it also contains the reactive chemicals within sealed passive components, thus minimising the possibility of leakage. This more complex design and greater weight of reactive chemicals increases manufacturing costs but value for money is obtained by using the correct battery system for the appliance. Alkaline batteries also have a reputation for long shelf life typically retaining 85% of performance even after 5 years storage. Recently alkaline battery manufactures have started to offer high-power alkaline batteries. These batteries are the same size and voltage as the standard product but have the capability to provide the higher power required by products such as digital cameras, minidisks and mobile phones. This performance is gained at the expense of general-purpose use, where a performance reduction is observed. These systems have a nominal operational voltage of 1.5 volts, and this has become the ISO standard operating voltage for many consumer appliances. However, the quoted 1.5 operating voltage is a misnomer. The start-up voltage is 1.5 volts but, during the operating discharge life of the battery it will fall and the battery can be considered exhausted when the voltage falls to 0.8 of a volt. This is a problem that many appliance manufactures fail to recognise by designing equipment that operates down to only 1.2 or 1.1 volts. As a result the battery appears to have a short life and can be discarded with as much as 50% of its potential energy unused. The current range of battery types have also been used to determine internationally agreed battery dimensions. Manufactures of battery powered appliances are reluctant to move away from these ISO standard sizes and voltages because, understandably, consumers prefer purchasing readily available battery sizes, rather than seek out infrequently stocked, unusual sizes and systems. Thus standardisation has inhibited other systems, particularly those producing higher voltages, from entering the market place; the exception being systems designed for specialist applications. |
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