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Lead-Acid Batteries (Glossary) |
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| Lead-acid batteries are by far the most popular battery systems and have been the subject of the longest and most thorough research and documentation. They are the uncontested masters of the fields of starter, power and stationary batteries because of their economic efficiency. However, in the field of small cells the lead accumulator was quickly ousted by the Nickel-cadmium system. On the one hand because of the higher energy density of these accumulators, and on the other because a maintenance-free, gas and electrolyte-proof encapsulated model could be developed very quickly. One special feature of lead accumulators is the fact that both electrodes are made of the same metal. Both the anode and cathode are lead plates, the electrolyte consists of approx. 30 - 36% sulphuric acid (battery acid). During discharge lead sulphate is produced at the anode of metallic lead, the opposite reaction takes place at the cathode. The following, greatly simplified, reaction takes place during discharge and charging:  Neither the lead nor the lead sulphate are significantly soluble in sulphuric acid, which is why the electrolyte remains practically unchanged, apart from the so-called gassing that has to be compensated by the regular addition of water. Maintenance-free and gas-tight versions of lead accumulators are available, however, on the market. Typical performance data and uses  Cell terminal voltage: approx. 2 volts Service life in charge cycles: 200 to 2,000 For use in ambient temperatures: (-30°C) -20°C to +50°C (+60°C) Typical energy density: 25 - 35 (45) Wh/kg (theoretically up to 175 Wh/kg) Typical volumetric energy density: 100 Wh/l Typical power density: 50 - 100 W/kg Typical spontaneous discharge: 1 - 3 % per monthOne disadvantage is the high weight of lead accumulators and their quite low energy density. In most applications this disadvantage is compensated by the high economic efficiency of the lead system. However, if extreme resistance to cold, a high energy or power density are or prime importance, other systems are generally preferable. Historical development In the year 1860, Gaston Planté developed the first accumulator in the form of a lead battery, 10 years before the first industrially manufactured generators to charge such accumulators were available. This type of rechargeable battery is still the most widespread type of accumulator, particularly as a starter, power or emergency power battery. Nevertheless, the lead accumulator has not remained unchanged since its invention but has been repeatedly optimised in all of its components. © Marc Stenzel |
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