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INTRODUCTION:
Battery is a device that stores energy and makes in it an electrical form. An electrical battery is a device for creating or storing electrical energy composed of several similar cells that are connected together. An electrical cell is a single unit, possibly one cell in a battery of multiple cells.
In 1748, Benjamin Franklin coined the term battery to describe an array of charged glass plates. The voltaic pile was a chemical battery developed by Alessandro Volta in 1800. In 1800, William Nicholson and Anthony Carsile used a battery to decompose water into hydrogen and oxygen. Sir Humphry Davy researched the electrolysis (decomposition of substances) and deduced that electrolysis was the action in the voltaic cell that produced electricity. In 1820, John Frederic Daniell improved the voltaic cell. The daniell cell consisted of copper and zinc plates and copper and zinc sulfates. It was used to operate telegraphs and door bells. After that there are many types of cells such as fuel cell, carbon-zinc battery, lead-acid battery, air-cell battery, earth battery, nickel-iron battery, alkaline manganese battery, solar battery or solar cell and etc.
A battery is an electrochemical cell that can be charged electrically to provide a static potential for power or released electrical charge when needed. A battery generally consists of an anode, a cathode, and an electrolyte. Two or more connected cells that produce a direct current by converting chemical energy to electrical energy.
A cell consists of two dissimilar substances, a positive electrode and a negative electrode, that conduct electricity, and a third substance, an electrolyte, that acts chemically on the electrodes. A single cell that produces an electric current. The two electrodes are connected by an external circuit (e.g., a piece of copper wire); the electrolyte functions as an ionic conductor for the transfer of the electrons between the electrodes. The voltage, or electromotive force, depends on the chemical properties of the substances used, but is not affected by the size of the electrodes or the amount of electrolyte.
Batteries are classed as either dry cell or wet cell. In a dry cell the electrolyte is absorbed in a porous medium, or is otherwise restrained from flowing. In a wet cell the electrolyte is in liquid form and free to flow and move. Batteries also can be generally divided into two main types-rechargeable and non rechargeable, or disposable. Disposable batteries, also called primary cells, can be used until the chemical changes that induce the electrical current supply are complete, at which point the battery is discarded. Rechargeable batteries, also called secondary cells, can be reused after being drained. This is done by applying an external electrical current, which causes the chemical changes that occur in use to be reversed. The external devices that supply the appropriate current are called chargers or rechargers.
IMPROVEMENTS IN BATTERY:
Disposable:
Zinc-carbon battery
Alkaline battery
Silver-oxide battery
Lithium battery
Rechargeable:
Lead-acid battery
Gel battery
Nickel-Cadmium battery
NiMH battery
Li-ion battery
Li-Polymer battery
NAS battery
BATTERY CAPACITY:
The capacity of a battery to store charge is often expressed in ampere hours (1 A•h = 3600 coulombs). If a battery can provide one ampere (1 A) of current (flow) for one hour, it has a real-world capacity of 1 A•h. If it can provide 1 A for 100 hours, its capacity is 100 A•h. Likewise, 20 A for 2 hours equals 40 A•h capacity. But...
While a battery that can deliver 10 A for 10 hours can be said to have a capacity of 100 A•h, that is not how the rating is determined by the manufacturers. A 100 A•h rated battery most likely will not deliver 10 A for 10 hours. Battery manufacturers use a standard method to determine how to rate their batteries. Their rating is based on tests performed over 20 hours with a discharge rate of 1/20 (5%) of the expected capacity of the battery. So a 100 ampere-hour battery is rated to provide 5 A for 20 hours. The efficiency of a battery is different at different discharge rates. When discharging at 1/20 of their capacity, batteries are more efficient than at higher discharge rates.
An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy. Since the invention of the first battery (or "voltaic pile") in 1800 by Alessandro Volta, batteries have become a common power source for many household and industrial applications. There are two types of batteries: primary batteries (disposable batteries), which are designed to be used once and discarded, and secondary batteries (rechargeable batteries), which are designed to be recharged and used multiple times. Miniature cells are used to power devices such as hearing aids and wristwatches; larger batteries provide standby power for telephone exchanges or computer data centers.
Because of the chemical reactions within the cells, the capacity of a battery depends on the discharge conditions such as the magnitude of the current (which may vary with time), the allowable terminal voltage of the battery, temperature and other factors. Lithium iron phosphate (LiFePO4) batteries are the fastest charging and discharging.
PRINCIPLE OF OPEARATION:
ELECTROCHEMICAL CELL:
An electrochemical cell is a device capable of either deriving electrical energy from chemical reactions, or facilitating chemical reactions through the introduction of electrical energy. A common example of an electrochemical cell is a standard 1.5-volt "battery". (Actually a single "Galvanic cell"; a battery properly consists of multiple cells.)
A voltaic cell for demonstration purposes. In this example the two half-cells are linked by a salt bridge separator that permits the transfer of ions, but not water molecules. A salt bridge, in chemistry, is a laboratory device used to connect the oxidation and reduction half-cells of a galvanic cell (voltaic cell), a type of electrochemical cell. Salt bridges usually come in two types: glass tube and filter paper.
A battery is a device that converts chemical energy directly to electrical energy. It consists of a number of voltaic cells; each voltaic cell consists of two half cells connected in series by a conductive electrolyte containing anions and cations. Electrode is a solid electric conductor through which an electric current enters or leaves an electrolytic cell or other medium. One half-cell includes electrolyte and the electrode to which anions (negatively charged ions) migrate, i.e., the anode or negative electrode; the other half-cell includes electrolyte and the electrode to which cations (positively charged ions) migrate, i.e., the cathode or positive electrode. In the redox reaction that powers the battery, reduction (addition of electrons) occurs to cations at the cathode, while oxidation (removal of electrons) occurs to anions at the anode. The electrodes do not touch each other but are electrically connected by the electrolyte. Some cells use two half-cells with different electrolytes. A separator between half cells allows ions to flow, but prevents mixing of the electrolytes.
Each half cell has an electromotive force (or emf), determined by its ability to drive electric current from the interior to the exterior of the cell. The net emf of the cell is the difference between the emfs of its half-cells, as first recognized by Volta. Therefore, if the electrodes have emfs and , then the net emf is ; in other words, the net emf is the difference between the reduction potentials of the half-reactions.
The electrical driving force or across the terminals of a cell is known as the terminal voltage (difference) and is measured in volts. The terminal voltage of a cell that is neither charging nor discharging is called the open-circuit voltage and equals the emf of the cell. Because of internal resistance, the terminal voltage of a cell that is discharging is smaller in magnitude than the open-circuit voltage and the terminal voltage of a cell that is charging exceeds the open-circuit voltage. An ideal cell has negligible internal resistance, so it would maintain a constant terminal voltage of until exhausted, then dropping to zero.
CATEGORIES AND TYPES OF BATTERIES:
Batteries are classified into two broad categories
Primary batteries transform chemical energy to electrical energy. They can not be reliably recharged, since the chemical reactions are not easily reversible. Common type’s disposable batteries include zinc-carbon batteries and alkaline batteries.
Secondary batteries must be charged before use. Rechargeable batteries or secondary batteries 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. The oldest form of battery is the lead-acid battery. A common form of the lead-acid battery is the modern car battery.
BATTERY CELL TYPES:
There are many general types of electrochemical cells, according to chemical processes applied and design chosen. The variation includes galvanic cells, electrolytic cells, fuel cells, flow cells and voltaic piles.
EXTENDING BATTERY LIFE:
Battery life can be extended by storing the batteries at a low temperature, as in a refrigerator or freezer, which slows the chemical reactions in the battery. While the charge of rechargeable batteries can be extended from a few days up to several months. To reach their maximum voltage, batteries must be returned to room temperature.
EXPLOSION:
A battery explosion is caused by the misuse or malfunction of a battery, such as attempting to recharge a primary (non-rechargeable) battery, or short circuiting a battery. With car batteries, explosions are most likely to occur when a short circuit generates very large currents. Overcharging—that is, attempting to charge a battery beyond its electrical capacity—can also lead to a battery explosion, leakage, or irreversible damage to the battery. It may also cause damage to the charger or device in which the overcharged battery is later used.
LEAKAGE:
Many battery chemicals are corrosive, poisonous, or both. If leakage occurs, either spontaneously or through accident, the chemicals released may be dangerous.
GENERAL BATTERY CARE:
A battery that is not used for a long time will slowly discharge itself. The battery often serves as a big capacitor to protect against voltage peaks from your ac outlet. New batteries come in a discharged condition and must be fully charged before use. It is recommended that you fully charge and discharge the new battery two to four times to allow it to reach its maximum rated capacity. It is generally recommended that you perform an overnight charge (approximately twelve hours) for this. Note: It is normal for a battery to become warm to the touch during charging and discharging. When charging the battery for the first time, the device may indicate that charging is complete after just 10 or 15 minutes. This is a normal with rechargeable batteries. New batteries are hard for the device to charge; they have never been fully charged and are not broken in. Sometimes the device's charger will stop charging a new battery before it is fully charged. If this happens, remove the battery from the device and then reinsert it. The charge cycle should begin again. This may happen several times during the first battery charge. Don't worry; it's perfectly normal. Keep the battery healthy by fully charging and then fully discharging it at least once every two to three weeks.
Do not remove and carry a battery pack in your pocket, purse, or other container where metal objects (such as car keys or paper clips) could short-circuit the battery terminals. The resulting excessive current flow can cause extremely high temperatures and may result in damage to the battery pack or cause fire or burns.