Lead-Acid batteries were the first type of rechargeable battery ever invented. They were invented in 1859 by the French physicist, Gaston Plante. They are very useful in vehicles due to their low cost, robust nature, high tolerance for abuse and large power-to-weight ratio. lead-acid batteries are not only used in cars, but can be used in submarines, for lighting, in portable equipment, as uninterpretable power supplies, among others.
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When it is charged, each cell contains electrodes of elemental lead (Pb), and lead dioxide (PbO2), in an electrolyte of sulfuric acid (H2SO4). In the discharged state, both electrodes turn into lead (II) sulfate (PbSO4), and the electrolyte loses its dissolved sulfuric acid, becoming mainly water. As a result of the freezing point depression of water, the battery discharges and the concentration of sulfuric acid decreases, making the battery more susceptible to freezing during winter weather. (Battery Technology – Galvanic cells that store chemical energy. (n.d.).)
The chemical reactions from discharged to charged are as follows:
There are several shortcomings to this type of battery however. Lead acid car batteries can be very dangerous due to the open cells with liquid electrolyte that the large majority of them contain. Overcharging with high voltages will produce oxygen and hydrogen gas by the electrolysis of water, creating an unstable mix. (Charging the lead-acid battery. (n.d.) ) The acid electrolyte can also be corrosive. They are also toxic and improper disposal can be extremely harmful to the environment. They are also extremely heavy and bulking. Sulphatian is a process that can occur within these batteries causing irreversible damage. Sulphation may occur if a battery is stored for prolonged periods in a completely discharged state or very low state of charge, or if it is never fully charged, or if electrolyte has become abnormally low due to excessive water loss from overcharging and/or evaporation. Sulphation is the increase in internal resistance of the battery due to the formation of large lead sulphate crystals which are not readily reconverted back to lead, lead dioxide and sulphuric acid during re-charging. In extreme cases the large crystals may cause distortion and shorting of the plates. Sometimes sulphation can be corrected by charging very slowly (at low current) at a higher than normal voltage. (Lead Acid Batteries. (n.d.) )
Although it has been 140 years since the invention of the battery, improvements are still being made regularly. As well, despite much advancement in technology and competition from other types of batteries, the lead acid battery remains the most popular in its field.