What is Battery & Their types:
Battery:
A battery is a source of electrical energy, which is provided by one or more electrochemical cells of the battery after the conversion of stored chemical energy.
Introduction: 
In today’s life, batteries play an important part as many household and industrial appliances use batteries as their power source.
Batteries can be divided into two major categories.
1) Primary batteries
2) Secondary batteries
Primary batteries:
A primary battery is a disposable kind of battery. Once used, it cannot be recharged. Alkaline batteries, Mercury batteries, Silver-Oxide batteries, and Zinc carbon batteries are examples of primary batteries
Secondary batteries:
Secondary batteries are rechargeable batteries. Once empty, it can be recharged again. This charging and discharging can happen many times depending on the battery type. Lead-Acid batteries and Lithium batteries fall into the secondary battery category.
Unfortunately, there is no single battery technology available on the market today that can be considered “The Solution” for all classes of portable battery-operated devices. There are a variety of batteries in use, each with its advantages and disadvantages. There are two main categories of batteries.
(1)PRIMARY BATTERIES
(2) SECONDARY BATTERIES
PRIMARY BATTERIES: 
sometimes also called single-use, or throw away batteries because they have to be discarded after they run empty as they cannot be recharged for reuse. Primary batteries can produce current immediately on assembly. Disposable batteries are intended to be used once and discarded.
These are most commonly used in portable devices that have a low current drain, and are only used intermittently, or are used well away from an alternative power source, such as in alarm and communication circuits where other electric power is only intermittently available. Disposable primary cells cannot be reliably recharged, since the chemical reactions are not easily reversible and active materials may not return to their original forms. Battery manufacturers recommend against attempting to recharge primary cells.
Primary Batteries are included.
Carbon Zinc (Heavy Duty):
The lowest cost primary cell (household) is the zinc-acidic manganese dioxide battery. They provide only very low power, but have a good shelf life and are well suited for clocks and remote controls.
Alkaline Cell: 
The most commonly used primary cell (household) is the zinc-alkaline manganese dioxide battery. They provide more power-per-use than Carbon-zinc and secondary batteries and have an excellent shelf life.
Lithium Cells:
Lithium batteries offer performance advantages well beyond the capabilities of conventional aqueous electrolyte battery systems. Their shelf-life can be well above 10-years and they will work at very low temperatures. Lithium batteries are mainly used in small formats (coins cells up to about AA-size) because bigger sizes of lithium batteries are a safety concern in consumer applications. Bigger (i.e. ‘D’) sizes are only used in military applications.
Silver Oxide Cells:
These batteries have a very high energy density but are very expensive due to the high cost of silver. Therefore, silver oxide cells are mainly used in a button cell format for watches and calculators.
Zinc Air Cells:
These batteries have become the standard for hearing aid batteries. They have a very long run time because they store only the anode material inside the cell and use the oxygen from the ambient air as a cathode.
(2) SECONDARY BATTERIES:
Mostly called rechargeable batteries because they can be recharged for reuse. They are usually assembled with active materials in the discharged state. Rechargeable batteries or secondary cells can be recharged by applying electric current, which reverses the chemical reactions that occur during its use. Devices to supply the appropriate current are called chargers or rechargers.
Secondary batteries are included:
Rechargeable Alkaline batteries:
Secondary alkaline batteries, the lowest cost rechargeable cells, have a long shelf life and are useful for moderate-power applications. Their cycle life is less than most other secondary batteries, but they are a great consumer choice as they combine the benefits of the popular alkaline cells with the added benefit of a re-use after recharging. They have no toxic ingredients and can be disposed of in regular landfills (local regulations permitting).
Nickel-Cadmium: 
Secondary Ni-Cd batteries are rugged and reliable. They exhibit a high power capability, a wide operating temperature range, and a long cycle life, but have a low run-time per charge. They have a self-discharge rate of approximately 30% per month. They contain about 15% toxic, carcinogenic cadmium and have to be recycled.
Nickel-Metal Hydride:
Secondary Nickel-Metal batteries are an extension of the old-fashioned NiCad batteries. Nickel-Metal batteries provide the same voltage as NiCad batteries but offer at least 30% more capacity. They exhibit good high current capability and have a long cycle life. The self-discharge rate is higher than NiCad at approximately 40% per month. Nickel-Metal cells contain no toxic cadmium, but they still contain a large number of nickel oxides and also some cobalt, which are known human carcinogens and should be recycled.
Lithium-Ion:
Secondary Li-Ion batteries are the latest breakthrough in rechargeable batteries. They are at least 30% lighter in weight than NiMH batteries and provide at least 30% more capacity. They exhibit good high current capability and have a long cycle life. The self-discharge rate is better than NiMH at approximately 20% per month. Overheating will damage the batteries and could cause a fire. Li-Ion cells contain no toxic cadmium, but they still contain either cobalt oxides or nickel oxides, which are known human carcinogens and should be recycled.
Lead-Acid: 
Secondary lead-acid batteries are the most popular rechargeable batteries worldwide. Both the battery product and the manufacturing process are proven, economical, and reliable. However, because they are heavy, Lead-Acid batteries are not being used in portable, consumer applications. Lead is a toxic, carcinogenic compound and should not enter the regular waste stream. Recycling of Lead-Acid batteries is the environmental success story of our time, approx. 93% of all battery lead is being recycled today in reused in the production of new Lead-Acid batteries.
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