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A battery is a device that produces electrons through electrochemical reactions, and contains positive (+) and negative (-) terminals. A battery consists of one or more electrochemical cells, which transform stored chemical energy directly into electrical energy. When an external load connects to a battery, electrons cross from the negative to the positive terminal, creating an electrical current. This current may power a motor, a light bulb, a clock, a computer, a cellphone, and other electronic devices or equipment. Battery flow speed is determined by the battery’s internal resistance and outside load.
Batteries are available in numerous sizes, which range from the miniature cells used in wrist watches and power hearing devices to batteries the size of rooms that are used to offer standby power for data centers and telephone exchanges.
Batteries are generally classified into primary and secondary batteries. Primary batteries are disposable batteries. They are built to be used only once and then discarded. This is because the chemical reactions that take place within primary batteries cannot be reversed, and the active materials do not go back to their original forms. These battery types are normally used in portable devices, which require minimal current drain. Common varieties of disposable or primary batteries include alkaline batteries and zinc-carbon batteries.
Secondary batteries, also called rechargeable batteries, are built to be recharged and reused many times. Secondary batteries usually include active materials that are assembled in a discharged state. These batteries can be recharged upon the application of electric current, which helps to reverse the chemical reactions that take place when the battery is used. Devices designed to supply a suitable current source are known as chargers or rechargers. Lead-acid batteries are the most ancient type of rechargeable battery.
Dry cell batteries are another type of rechargeable battery. These are covered units and are therefore particularly useful in portable devices, including laptops and mobile phones. Other battery types include lithium-ion (Li-ion), nickel metal hydride (NiMH), nickel-zinc (NiZn), and nickel-cadmium (NiCd) cells. So far, Li-ion batteries have the highest market value. On the other hand, NiMH has replaced NiCd in most applications because of its better capacity, although NiCd is still used in medical equipment, power tools and two-way radios.