Primary and secondary batteries battery, a D Cell, a C cell, an AA cell, an AAA cell, an AAAA cell, an A23 battery, a 9-volt PP3 battery'', and a pair of
button cells (CR2032 and LR44) Batteries are classified into primary and secondary forms: •
Primary batteries are designed to be used until exhausted of energy then discarded. Their chemical reactions are generally not reversible, so they cannot be recharged. When the supply of reactants in the battery is exhausted, the battery stops producing current and is useless. •
Secondary batteries can be recharged; that is, they can have their chemical reactions reversed by applying
electric current to the cell. This regenerates the original chemical reactants, so they can be used, recharged, and used again multiple times. Some types of primary batteries used, for example, for
telegraph circuits, were restored to operation by replacing the electrodes. Secondary batteries are not indefinitely rechargeable due to dissipation of the active materials, loss of electrolyte and internal corrosion. Primary batteries, or
primary cells, can produce current immediately on assembly. These are most commonly used in portable devices that have low current drain, are used only 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. In general, these have higher
energy densities than rechargeable batteries, but disposable batteries do not fare well under high-drain applications with
loads under 75
ohms (75 Ω). Common types of disposable batteries include
zinc–carbon batteries and
alkaline batteries. Secondary batteries, also known as
secondary cells, or
rechargeable batteries, must be charged before first use; they are usually assembled with active materials in the discharged state. Rechargeable batteries are (re)charged by applying electric current, which reverses the chemical reactions that occur during discharge/use. Devices to supply the appropriate current are called chargers. The oldest form of rechargeable battery is the
lead–acid battery, which are widely used in
automotive and
boating applications. This technology contains liquid electrolyte in an unsealed container, requiring that the battery be kept upright and the area be well ventilated to ensure safe dispersal of the
hydrogen gas it produces during overcharging. The lead–acid battery is relatively heavy for the amount of electrical energy it can supply. Its low manufacturing cost and its high surge current levels make it common where its capacity (over approximately 10 Ah) is more important than weight and handling issues. A common application is the modern
car battery, which can, in general, deliver a peak current of 450
amperes.
Composition Many types of electrochemical cells have been produced, with varying chemical processes and designs, including
galvanic cells,
electrolytic cells,
fuel cells,
flow cells and voltaic piles. A
wet cell battery has a liquid
electrolyte. Other names are
flooded cell, since the liquid covers all internal parts or
vented cell, since gases produced during operation can escape to the air. Wet cells were a precursor to dry cells and are commonly used as a learning tool for
electrochemistry. They can be built with common laboratory supplies, such as
beakers, for demonstrations of how electrochemical cells work. A particular type of wet cell known as a
concentration cell is important in understanding
corrosion. Wet cells may be
primary cells (non-rechargeable) or
secondary cells (rechargeable). Originally, all practical primary batteries, such as the
Daniell cell, were built as open-top glass jar wet cells. Other primary wet cells are the
Leclanche cell,
Grove cell,
Bunsen cell,
Chromic acid cell,
Clark cell, and
Weston cell. The Leclanche cell chemistry was adapted to the first dry cells. Wet cells are still used in
automobile batteries and in industry for standby power for
switchgear, telecommunication or large
uninterruptible power supplies, but in many places batteries with
gel cells have been used instead. These applications commonly use lead–acid or
nickel–cadmium cells.
Molten salt batteries are primary or secondary batteries that use a molten salt as electrolyte. They operate at high temperatures and must be well insulated to retain heat. A
dry cell uses a paste electrolyte, with only enough moisture to allow current to flow. Unlike a wet cell, a dry cell can operate in any orientation without spilling, as it contains no free liquid, making it suitable for portable equipment. By comparison, the first wet cells were typically fragile glass containers with lead rods hanging from the open top and needed careful handling to avoid spillage. Lead–acid batteries did not achieve the safety and portability of the dry cell until the development of the
gel battery. A common dry cell is the
zinc–carbon battery, sometimes called the dry
Leclanché cell, with a nominal voltage of 1.5
volts, the same as the
alkaline battery (since both use the same
zinc–
manganese dioxide combination). A standard dry cell comprises a
zinc anode, usually in the form of a cylindrical pot, with a
carbon cathode in the form of a central rod. The electrolyte is
ammonium chloride in the form of a paste next to the zinc anode. The remaining space between the electrolyte and carbon cathode is taken up by a second paste consisting of ammonium chloride and manganese dioxide, the latter acting as a
depolariser. In some designs, the ammonium chloride is replaced by
zinc chloride. A
reserve battery can be stored unassembled (unactivated and supplying no power) for a long period (perhaps years). When the battery is needed, then it is assembled (e.g., by adding electrolyte); once assembled, the battery is charged and ready to work. For example, a battery for an electronic artillery
fuze might be activated by the impact of firing a gun. The acceleration breaks a capsule of electrolyte that activates the battery and powers the fuze's circuits. Reserve batteries are usually designed for a short service life (seconds or minutes) after long storage (years). A
water-activated battery for oceanographic instruments or military applications becomes activated on immersion in water. On 28 February 2017, the
University of Texas at Austin issued a press release about a new type of
solid-state battery, developed by a team led by lithium-ion battery inventor
John Goodenough, "that could lead to safer, faster-charging, longer-lasting rechargeable batteries for handheld mobile devices, electric cars and stationary energy storage". The solid-state battery is also said to have "three times the energy density", increasing its useful life in electric vehicles, for example. It should also be more ecologically sound since the technology uses less expensive, earth-friendly materials such as sodium extracted from seawater. They also have much longer life.
Sony has developed a
biological battery that generates electricity from sugar in a way that is similar to the processes observed in living organisms. The battery generates electricity through the use of enzymes that break down carbohydrates. The sealed
valve regulated lead–acid battery (VRLA battery) is popular in the automotive industry as a replacement for the lead–acid wet cell. The VRLA battery uses an immobilized
sulfuric acid electrolyte, reducing the chance of leakage and extending
shelf life. VRLA batteries immobilize the electrolyte. The two types are: •
Gel batteries (or "gel cell") use a semi-solid electrolyte. •
Absorbed Glass Mat (AGM) batteries absorb the electrolyte in a special fiberglass matting. Other portable rechargeable batteries include several sealed "dry cell" types, that are useful in applications such as mobile phones and
laptop computers. Cells of this type (in order of increasing
power density and cost) include
nickel–cadmium (NiCd),
nickel–zinc (NiZn),
nickel–metal hydride (NiMH), and
lithium-ion (Li-ion) cells. Li-ion has by far the highest share of the dry cell rechargeable market. NiMH has replaced NiCd in most applications due to its higher capacity, but NiCd remains in use in
power tools,
two-way radios, and
medical equipment. In the 2000s, developments include batteries with embedded electronics such as
USBCELL, which allows charging an AA battery through a
USB connector,
nanoball batteries that allow for a discharge rate about 100x greater than current batteries, and
smart battery packs with state-of-charge monitors and battery protection circuits that prevent damage on over-discharge.
Low self-discharge (LSD) allows secondary cells to be charged prior to shipping.
Lithium–sulfur batteries were used on the longest and highest solar-powered flight.
Consumer and industrial grades Batteries of all types are manufactured in consumer and industrial grades. Costlier industrial-grade batteries may use chemistries that provide higher power-to-size ratio, have lower self-discharge and hence longer life when not in use, more resistance to leakage and, for example, ability to handle the high temperature and humidity associated with medical autoclave sterilization.
Combination and management Standard-format batteries are inserted into
battery holder in the device that uses them. When a device does not uses standard-format batteries, they are typically combined into a custom
battery pack which holds multiple batteries in addition to features such as a
battery management system and
battery isolator which ensure that the batteries within are charged and discharged evenly.
Sizes Primary batteries readily available to consumers range from tiny
button cells used for electric watches, to the No. 6 cell used for signal circuits or other long duration applications. Secondary cells are made in very large sizes; very large batteries can power a
submarine or stabilize an
electrical grid and help level out peak loads. , the world's largest battery was built in South Australia by
Tesla. It can store 129 MWh. A battery in
Hebei Province, China, which can store 36 MWh of electricity was built in 2013 at a cost of $500 million. Another large battery, composed of
Ni–Cd cells, was in
Fairbanks, Alaska. It covered —bigger than a football pitch—and weighed 1,300 tonnes. It was manufactured by
ABB to provide backup power in the event of a blackout. The battery can provide 40 MW of power for up to seven minutes.
Sodium–sulfur batteries have been used to store
wind power. A 4.4 MWh battery system that can deliver 11 MW for 25 minutes stabilizes the output of the Auwahi wind farm in Hawaii.
Comparison Many important cell properties, such as voltage, energy density, flammability, available cell constructions, operating temperature range and shelf life, are dictated by battery chemistry. == Performance, capacity and discharge ==