Lead Acid Cell vs. Button Cell
Lead acid cells were invented in 1859 by the French Physicist Gaston Plante, and are the oldest types of rechargeable batteries. These types of batteries typically weigh at 5kg, but can range from half a kilogram to over 30 kilograms on the consumer market. Though their chemistry means a very low energy-to-weight and energy-to-volume ratio in comparison to other modern batteries, their ability to supply high surge currents means that the cells maintain a large power-to-weight ratio. This makes them highly desirable for use in large appliances such as motor vehicles, which require the high current provided by this type of battery.
In comparison, Button cells are much smaller than lead acid cells. Button cells are shaped as small, squat cylinders usually 5 to 22mm in diameter and between 1 to 6mm in height and weigh little over several grams. The voltage and current produced by these batteries are small and steady, and these properties make them very suitable for powering small portable electronic devices such as wrist watches, pocket calculators, hearing aids, and sometimes pacemakers. These batteries are usually not rechargeable, and last a long time, though lifespan depends on chemical composition and use.
Lead acid calls use a chemical reaction in order to produce a voltage between the output terminals. The battery contains two plates, and the discharge process is driven by the conduction of electrons from the negative plate back into the cell at the positive plate. All lead acid sells use Lead Sulfate in their reactions. These chemicals were originally contained as a liquid, but a technique has now been developed in which a gel electrolyte is used, preventing leakage.
Negative plate reaction: Pb(s) + HSO−4(aq) → PbSO4(s) + H+(aq) + 2e-
Positive plate reaction: PbO2(s) + HSO−4(aq) + 3H+(aq) + 2e- → PbSO4(s) + 2H2O(l)
Overall reaction: Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l)
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