Types of Batteries
1. Primary Batteries: Non rechargeable batteries in which once the electrolyte has been fully used up, energy cannot be readily restored and the battery needs to be discarded. This particular class of batteries has been facing stiff competition from rechargeable battery segment, but still holds a niche market in applications like wrist watches electric keys, toys and military missions. Carbon-Zinc or Leclanche batteries and Alkaline-Manganese batteries are the most common primary batteries in consumer applications. Primary batteries offer the highest energy densities, with the Lithium based cells offering more than thrice the energy than corresponding secondary batteries. These do offer an initial cost advantage, but in the long run are more costlier than the secondary batteries owing to their reusability after recharging which is absent in primary batteries.
2. Secondary Batteries: The batteries in which a reversible reaction is responsible for the generation of electricity such that they can be reverted back to the original reactant state fall under the category of secondary batteries. Recharging is effected by passing electric current through the battery.
The oldest form of rechargeable battery is the Lead-Acid battery. Lead Acid battery market is dominating primarily because of the unavailability of any able competitive solution in the market and that they offer lowest cost per watt-hour despite of their low specific energy. The desire to make these batteries maintenance free, the flooded battery type evolved into two variants: Sealed Lead Acid or Gel cells and Valve Regulated Lead Acid (VRLA) Batteries. The flooded battery types are still seen in automobiles, UPS etc. But due to this evolution, the lead acid batteries now cannot charge to their true potential where gassing and water depletion in the acid may take place. Further, these must be stored in fully charged state or else sulfation may cause the degradation of the battery performance. The amount of electric power that can be delivered is often a function of amount of lead present.
Starter Batteries which contain more number of finer lead plates are suited for cranking automobiles with a high surge and fast discharge. Deep cycle batteries which contain more lead are suited for applications requiring longevity and deep discharging as in the case of golf cars and handicap chairs. Absorbent Glass Mat is another improved lead acid battery where electrolyte is absorbed in a mat of glass fibers making the battery spill proof and increasing performance characteristics. The disposal of Lead Acid batteries poses certain environmental problems due to hazards like lead poisoning. Nevertheless it continues to and is expected to retain a large market segment and companies constantly continue to innovate this battery under different names like Firefly Energy, Altraverda Bipolar, Axion Powe etc.
Nickel Cadmium (NiCd) Batteries have a matured technology and are used in places where long service life and economy amidst difficult environmental conditions is required. An easy alternative to this chemistry is the relatively environment friendly Nickel Metal Hydride (NiMH) technology which has improved specific energy ratings. Faster charging and long shelf life coupled with economical pricing and availability in various sizes make them an attractive option for small consumer products. However they seem to suffer from Memory effects hence needing periodic full discharges and also suffer from high self discharge.
Lithium-ion Batteries are the most promising battery systems for portability in consumer products and electric power trains. Lithium is placed on the top in the electrochemical potential list and provides high specific energy per unit weight. It is further divided into three categories, Lithium ion Cobalt, Lithium ion manganese and Lithium ion phosphate which have their own different applications due to varying specific energies, discharge currents and service lives. Other different types of Li-Ion batteries include Li-Polymer and lithium-ion-polymer. Cost reduction, absence of too environment sensitive material and high specific energies have led to the rise of popularity of Li-ion batteries to such an extent that about 34% of the batteries sold are now Li-Ion. These circuits need protection circuits to limit voltage and current and are subject to aging even if kept unused.
Another classification of batteries is on the basis of the state of electrolyte viz Wet Cells in which the electrolyte is in liquid state as in Leclanche cells and Dry Cells where the electrolyte is in the form of a gel or paste as in the common zinc-carbon battery. Other types may include ‘Molten salt battery’ which uses a molten salt as electrolyte and ‘Reserve battery’ which are activated only when the internal components are in place.
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