Battery (electricity)

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Battery
Various cells and batteries (top-left to bottom-right): two AA, one D, one handheld ham radio battery, two 9-volt (PP3), two AAA, one C, one camcorder battery, one cordless phone battery.
Type	Power source
Working principle	Electrochemical reactions, Electromotive force
First production	1800s
Electronic symbol
The symbol for a battery in a circuit diagram. It originated as a schematic drawing of the earliest type of battery, a voltaic pile.

An electric battery is a device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each cell contains a positive terminal, or cathode, and a negative terminal, or anode. Electrolytes allow ions to move between the electrodes and terminals, which allows current to flow out of the battery to perform work.^[1]

Primary (single-use or "disposable") batteries are used once and discarded; the electrode materials are irreversibly changed during discharge. Common examples are the alkaline battery used for flashlights and a multitude of portable devices. Secondary (rechargeable batteries) can be discharged and recharged multiple times; the original composition of the electrodes can be restored by reverse current. Examples include the lead-acid batteries used in vehicles and lithium ion batteries used for portable electronics.

Batteries come in many shapes and sizes, from miniature cells used to power hearing aids and wristwatches to battery banks the size of rooms that provide standby power for telephone exchanges and computer data centers.

According to a 2005 estimate, the worldwide battery industry generates US$48 billion in sales each year,^[2] with 6% annual growth.

Batteries have much lower specific energy (energy per unit mass) than common fuels such as gasoline. This is somewhat offset by the higher efficiency of electric motors in producing mechanical work, compared to combustion engines.

History

The usage of "battery" to describe a group of electrical devices dates to Benjamin Franklin, who in 1748 described multiple Leyden jars by analogy to a battery of cannon^[3] (Benjamin Franklin borrowed the term "battery" from the military, which refers to weapons functioning together^[4]).Alessandro Volta described the first electrochemical battery, the voltaic pile in 1800.^[5] This was a stack of copper and zinc plates, separated by brine soaked paper disks, that could produce a steady current for a considerable length of time. Volta did not appreciate that the voltage was due to chemical reactions. He thought that his cells were an inexhaustible source of energy,^[6] and that the associated corrosion effects at the electrodes were a mere nuisance, rather than an unavoidable consequence of their operation, as Michael Faraday showed in 1834.^[7]

Although early batteries were of great value for experimental purposes, in practice their voltages fluctuated and they could not provide a large current for a sustained period. The Daniell cell, invented in 1836 by British chemist John Frederic Daniell, was the first practical source of electricity, becoming an industry standard and seeing widespread adoption as a power source for electrical telegraph networks.^[8] It consisted of a copper pot filled with a copper sulfate solution, in which was immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode.^[9]

These wet cells used liquid electrolytes, which were prone to leakage and spillage if not handled correctly. Many used glass jars to hold their components, which made them fragile. These characteristics made wet cells unsuitable for portable appliances. Near the end of the nineteenth century, the invention of dry cell batteries, which replaced the liquid electrolyte with a paste, made portable electrical devices practical.^[10]

Principle of operation

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.

Batteries convert chemical energy directly to electrical energy. A battery consists of some number of voltaic cells. Each cell consists of two half-cells connected in series by a conductive electrolyte containing anions and cations. One half-cell includes electrolyte and the negative electrode, the electrode to which anions (negatively charged ions) migrate; the other half-cell includes electrolyte and the positive electrode to which cations (positively charged ions) migrate. Redox reactions power the battery. Cations are reduced (electrons are added) at the cathode during charging, while anions are oxidized (electrons are removed) at the anode during discharge.^[11] The electrodes do not touch each other, but are electrically connected by the electrolyte. Some cells use different electrolytes for each half-cell. A separator allows ions to flow between half-cells, 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.^[12] Thus, if the electrodes have emfs ${\mathcal {E}}_{1}$ and ${\mathcal {E}}_{2}$, then the net emf is ${\mathcal {E}}_{{2}}-{\mathcal {E}}_{{1}}$; in other words, the net emf is the difference between the reduction potentials of the half-reactions.^[13]
The electrical driving force or $\displaystyle {\Delta V_{{bat}}}$ across the terminals of a cell is known as the terminal voltage (difference) and is measured in volts.^[14] 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,^[15] 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.^[16]
An ideal cell has negligible internal resistance, so it would maintain a constant terminal voltage of ${\mathcal {E}}$ until exhausted, then dropping to zero. If such a cell maintained 1.5 volts and stored a charge of one coulomb then on complete discharge it would perform 1.5 joules of work.^[14] In actual cells, the internal resistance increases under discharge^[15] and the open circuit voltage also decreases under discharge. If the voltage and resistance are plotted against time, the resulting graphs typically are a curve; the shape of the curve varies according to the chemistry and internal arrangement employed.

The voltage developed across a cell's terminals depends on the energy release of the chemical reactions of its electrodes and electrolyte. Alkaline and zinc–carbon cells have different chemistries, but approximately the same emf of 1.5 volts; likewise NiCd and NiMH cells have different chemistries, but approximately the same emf of 1.2 volts.^[17] The high electrochemical potential changes in the reactions of lithium compounds give lithium cells emfs of 3 volts or more.^[18]

Categories and types of batteries

From top to bottom: a large 4.5-volt (3R12) 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 irreversibly transform chemical energy to electrical energy. When the supply of reactants is exhausted, energy cannot be readily restored to the battery.^[19]
• Secondary batteries can be recharged; that is, they can have their chemical reactions reversed by supplying electrical energy to the cell, approximately restoring their original composition.^[20]

Some types of primary batteries used, for example, for telegraph circuits, were restored to operation by replacing the electrodes.^[21] Secondary batteries are not indefinitely rechargeable due to dissipation of the active materials, loss of electrolyte and internal corrosion.

Primary batteries

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.^[22]
In general, these have higher energy densities than rechargeable batteries,^[23] 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

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. 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.
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.^[24] 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.

Recent developments include batteries with embedded electronics such as USBCELL, which allows charging an AA battery through a USB connector,^[25] 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.

Battery cell types

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.^[26]

Wet cell

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.

Dry cell

Line art drawing of a dry cell:
1. brass cap, 2. plastic seal, 3. expansion space, 4. porous cardboard, 5. zinc can, 6. carbon rod, 7. chemical mixture.

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.

Molten salt

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.

Reserve

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.

Battery cell performance

A battery's characteristics may vary over load cycle, over charge cycle, and over lifetime due to many factors including internal chemistry, current drain, and temperature.

Capacity and discharge

A device to check battery voltage

A battery's capacity is the amount of electric charge it can deliver at the rated voltage. The more electrode material contained in the cell the greater its capacity. A small cell has less capacity than a larger cell with the same chemistry, although they develop the same open-circuit voltage.^[27] Capacity is measured in units such as amp-hour (A·h).

The rated capacity of a battery is usually expressed as the product of 20 hours multiplied by the current that a new battery can consistently supply for 20 hours at 68 °F (20 °C), while remaining above a specified terminal voltage per cell. For example, a battery rated at 100 A·h can deliver 5 A over a 20-hour period at room temperature.

The fraction of the stored charge that a battery can deliver depends on multiple factors, including battery chemistry, the rate at which the charge is delivered (current), the required terminal voltage, the storage period, ambient temperature and other factors.^[27]

The higher the discharge rate, the lower the capacity.^[28] The relationship between current, discharge time and capacity for a lead acid battery is approximated (over a typical range of current values) by Peukert's law:

$t={\frac {Q_{P}}{I^{k}}}$

where

$Q_{P}$ is the capacity when discharged at a rate of 1 amp.

$I$ is the current drawn from battery (A).

$t$ is the amount of time (in hours) that a battery can sustain.

$k$ is a constant around 1.3.

Batteries that are stored for a long period or that are discharged at a small fraction of the capacity lose capacity due to the presence of generally irreversible side reactions that consume charge carriers without producing current. This phenomenon is known as internal self-discharge. Further, when batteries are recharged, additional side reactions can occur, reducing capacity for subsequent discharges. After enough recharges, in essence all capacity is lost and the battery stops producing power.

Internal energy losses and limitations on the rate that ions pass through the electrolyte cause battery efficiency to vary. Above a minimum threshold, discharging at a low rate delivers more of the battery's capacity than at a higher rate.

Installing batteries with varying A·h ratings does not affect device operation (although it may affect the operation interval) rated for a specific voltage unless load limits are exceeded. High-drain loads such as digital cameras can reduce total capacity, as happens with alkaline batteries. For example, a battery rated at 2000 mAh for a 10- or 20-hour discharge would not sustain a current of 1 A for a full two hours as its stated capacity implies.

C rate

The C-rate is a measure of the rate at which a battery is being discharged. It is defined as the discharge current divided by the theoretical current draw under which the battery would deliver its rated capacity in one hour. ^[29] A 1C discharge rate would deliver the battery's rated capacity in 1 hour. A 2C discharge rate means it will discharge twice as fast (30 minutes). A 1C discharge rate on a 1.6 Ah battery means a discharge current of 1.6 A. A 2C rate would mean a discharge current of 3.2 A. Standards for rechargeable batteries generally rate the capacity over a 4 hour, 8 hour or longer discharge time. Because of internal resistance loss and the chemical processes inside the cells, a battery rarely delivers nameplate rated capacity in only one hour. Types intended for special purposes, such as in a computer uninterruptible power supply, may be rated by manufacturers for discharge periods much less than one hour.

Fast-charging, large and light batteries

As of 2012^[update] Lithium iron phosphate (LiFePO
4) battery technology was the fastest-charging/discharging, fully discharging in 10–20 seconds.^[30]

As of 2013, the world's largest battery was in Hebei Province, China. It stored 36 megawatt-hours of electricity at a cost of $500 million.^[31] Another large battery, composed of Ni–Cd cells, was in Fairbanks, Alaska. It covers 2,000 square metres (22,000 sq ft)—bigger than a football pitch—and weighs 1,300 tonnes, It was manufactured by ABB to provide backup power in the event of a blackout. The battery can provide 40 megawatts of power for up to seven minutes.^[32] Sodium–sulfur batteries have been used to store wind power.^[33] A 4.4 megawatt-hour battery system that can deliver 11 megawatts for 25 minutes stabilizes the output of the Auwahi wind farm in Hawaii.^[34] Lithium–sulfur batteries were used on the longest and highest solar-powered flight.^[35] The recharging speed of lithium-ion batteries can be increased by manufacturing changes.^[36]

Battery lifetime

Available capacity of all batteries drops with decreasing temperature. In contrast to most of today's batteries, the Zamboni pile, invented in 1812, offers a very long service life without refurbishment or recharge, although it supplies current only in the nanoamp range. The Oxford Electric Bell has been ringing almost continuously since 1840 on its original pair of batteries, thought to be Zamboni piles.

Self-discharge

Disposable batteries typically lose 8 to 20 percent of their original charge per year when stored at room temperature (20°–30 °C).^[37] This is known as the "self-discharge" rate, and is due to non-current-producing "side" chemical reactions that occur within the cell even when no load is applied. The rate of side reactions is reduced for batteries are stored at lower temperatures, although some can be damaged by freezing.

Old rechargeable batteries self-discharge more rapidly than disposable alkaline batteries, especially nickel-based batteries; a freshly charged nickel cadmium (NiCd) battery loses 10% of its charge in the first 24 hours, and thereafter discharges at a rate of about 10% a month. However, newer low self-discharge nickel metal hydride (NiMH) batteries and modern lithium designs display a lower self-discharge rate (but still higher than for primary batteries).

Corrosion

Internal parts may corrode and fail, or the active materials may be slowly converted to inactive forms.

Physical component changes

The active material on the battery plates changes chemical composition on each charge and discharge cycle, active material may be lost due to physical changes of volume; further limiting the number of times the battery can be recharged.

Rechargeable batteries.

Most nickel-based batteries are partially discharged when purchased, and must be charged before first use.^[38] Newer NiMH batteries are ready to be used when purchased, and have only 15% discharge in a year.^[39]

Some deterioration occurs on each charge–discharge cycle. Degradation usually occurs because electrolyte migrates away from the electrodes or because active material detaches from the electrodes.

Low-capacity NiMH batteries (1700–2000 mA·h) can be charged some 1,000 times, whereas high-capacity NiMH batteries (above 2500 mA·h) last about 500 cycles.^[40] NiCd batteries tend to be rated for 1,000 cycles before their internal resistance permanently increases beyond usable values.

Charge/discharge speed

Fast charging increases component changes, shortening battery lifespan.^[40]

Overcharging

If a charger cannot detect when the battery is fully charged then overcharging is likely, damaging it.^[41]

Memory effect

NiCd cells, if used in a particular repetitive manner, may show a decrease in capacity called "memory effect".^[42] The effect can be avoided with simple practices. NiMH cells, although similar in chemistry, suffer less from memory effect.^[43]

An analog camcorder battery [lithium ion].

Environmental conditions

Automotive lead–acid rechargeable batteries must endure stress due to vibration, shock, and temperature range. Because of these stresses and sulfation of their lead plates, few automotive batteries last beyond six years of regular use.^[44] Automotive starting (SLI: Starting, Lighting, Ignition) batteries have many thin plates to maximize current. In general, the thicker the plates the longer the life. They are typically discharged only slightly before recharge.

"Deep-cycle" lead–acid batteries such as those used in electric golf carts have much thicker plates to extend longevity.^[45] The main benefit of the lead–acid battery is its low cost; its main drawbacks are large size and weight for a given capacity and voltage.

Lead–acid batteries should never be discharged to below 20% of their capacity,^[46] because internal resistance will cause heat and damage when they are recharged. Deep-cycle lead–acid systems often use a low-charge warning light or a low-charge power cut-off switch to prevent the type of damage that will shorten the battery's life.^[47]

Storage

Battery life can be extended by storing the batteries at a low temperature, as in a refrigerator or freezer, which slows the side reactions. Such storage can extend the life of alkaline batteries by about 5%; rechargeable batteries can hold their charge much longer, depending upon type.^[48] To reach their maximum voltage, batteries must be returned to room temperature; discharging an alkaline battery at 250 mA at 0 °C is only half as efficient as at 20 °C.^[23] Alkaline battery manufacturers such as Duracell do not recommend refrigerating batteries.^[22]

Battery 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.

Hazards

Explosion

A battery explosion is caused by misuse or malfunction, such as attempting to recharge a primary (non-rechargeable) battery, or a short circuit. Car batteries are most likely to explode when a short-circuit generates very large currents. Car batteries produce hydrogen, which is very explosive, when they are overcharged (because of electrolysis of the water in the electrolyte). The amount of overcharging is usually very small and generates little hydrogen, which dissipates quickly. However, when "jumping" a car battery, the high current can cause the rapid release of large volumes of hydrogen, which can be ignited explosively by a nearby spark, for example, when disconnecting a jumper cable.

When a battery is recharged at an excessive rate, an explosive gas mixture of hydrogen and oxygen may be produced faster than it can escape from within the battery, leading to pressure build-up and eventual bursting of the battery case. In extreme cases, battery acid may spray violently from the casing and cause injury. Overcharging—that is, attempting to charge a battery beyond its electrical capacity—can also lead to a battery explosion, in addition to leakage or irreversible damage. It may also cause damage to the charger or device in which the overcharged battery is later used. In addition, disposing of a battery via incineration may cause an explosion as steam builds up within the sealed case.

Leakage

Leaked alkaline battery.

Many battery chemicals are corrosive, poisonous or both. If leakage occurs, either spontaneously or through accident, the chemicals released may be dangerous.

For example, disposable batteries often use a zinc "can" both as a reactant and as the container to hold the other reagents. If this kind of battery is over-discharged, the reagents can emerge through the cardboard and plastic that form the remainder of the container. The active chemical leakage can then damage the equipment that the batteries power. For this reason, many electronic device manufacturers recommend removing the batteries from devices that will not be used for extended periods of time.

Toxic materials

Many types of batteries employ toxic materials such as lead, mercury, and cadmium as an electrode or electrolyte. When each battery reaches end of life it must be disposed of to prevent environmental damage.^[49] Battery are one form of electronic waste (e-waste).

E-waste recycling services recover toxic substances, which can then be used for new batteries.^[50]

Of the nearly three billion batteries purchased annually in the United States, about 179,000 tons end up in landfills across the country.^[51]

In the United States, the Mercury-Containing and Rechargeable Battery Management Act of 1996 banned the sale of mercury-containing batteries, enacted uniform labeling requirements for rechargeable batteries and required that rechargeable batteries be easily removable.^[52] California and New York City prohibit the disposal of rechargeable batteries in solid waste, and along with Maine require recycling of cell phones.^[53] The rechargeable battery industry operates nationwide recycling programs in the United States and Canada, with dropoff points at local retailers.^[53]

The Battery Directive of the European Union has similar requirements, in addition to requiring increased recycling of batteries and promoting research on improved battery recycling methods.^[54]

In accordance with this directive all batteries to be sold within the EU must be marked with the "collection symbol" (A crossed-out wheeled bin). This must cover at least 3% of the surface of prismatic batteries and 1.5% of the surface of cylindrical batteries. All packaging must be marked likewise.^[55]

Ingestion

Batteries may be harmful or fatal if swallowed.^[56]

Small button cells can be swallowed, in particular by young children. While in the digestive tract, the battery's electrical discharge may lead to tissue damage;^[57] such damage is occasionally serious and can lead to death.

Ingested disk batteries do not usually cause problems unless they become lodged in the gastrointestinal tract. The most common place for disk batteries to become lodged is the esophagus, resulting in clinical sequelae. Batteries that successfully traverse the esophagus are unlikely to lodge elsewhere. The likelihood that a disk battery will lodge in the esophagus is a function of the patient's age and battery size. Disk batteries of 16 mm have become lodged in the esophagi of 2 children younger than 1 year.^{[citation needed]} Older children do not have problems with batteries smaller than 21–23 mm. Liquefaction necrosis may occur because sodium hydroxide is generated by the current produced by the battery (usually at the anode). Perforation has occurred as rapidly as 6 hours after ingestion.^[58]

Battery chemistry

Primary batteries and their characteristics

Chemistry	Anode (-)	Cathode (+)	Maximum Voltage (Theoretical) (V)	Working Voltage (Practical) (V)	Specific energy [MJ/kg]	Elaboration	Shelf Life at 25 °C (80% Capacity) (Months)
Zinc–carbon	Zn	MnO2	1.6	1.2	0.13	Inexpensive.	18
Zinc–chloride			1.5			Also known as "heavy-duty", inexpensive.
Alkaline (zinc–manganese dioxide)	Zn	MnO2	1.5	1.15	0.4–0.59	Moderate energy density. Good for high- and low-drain uses.	30
Nickel oxyhydroxide (zinc–manganese dioxide/nickel oxyhydroxide)			1.7			Moderate energy density. Good for high drain uses.
Lithium (lithium–copper oxide) Li–CuO			1.7			No longer manufactured. Replaced by silver oxide (IEC-type "SR") batteries.
Lithium (lithium–iron disulfide) LiFeS2			1.5			Expensive. Used in 'plus' or 'extra' batteries.
Lithium (lithium–manganese dioxide) LiMnO2			3.0		0.83–1.01	Expensive. Used only in high-drain devices or for long shelf-life due to very low rate of self-discharge. 'Lithium' alone usually refers to this type of chemistry.
Lithium (lithium–carbon fluoride) Li–(CF)n	Li	(CF)n	3.6	3.0			120
Lithium (lithium–chromium oxide) Li–CrO2	Li	CrO2	3.8	3.0			108
Mercury oxide	Zn	HgO	1.34	1.2		High-drain and constant voltage. Banned in most countries because of health concerns.	36
Zinc–air	Zn	O2	1.6	1.1	1.59[59]	Used mostly in hearing aids.
Zamboni pile	Zn	Ag or Au		0.8		Very long life Very low (nanoamp) current	>2000
Silver-oxide (silver–zinc)	Zn	Ag2O	1.85	1.5	0.47	Very expensive. Used only commercially in 'button' cells.	30
Magnesium	Mg	MnO2	2.0	1.5			40

Secondary (rechargeable) batteries and their characteristics

Chemistry	Cell Voltage	Specific energy [MJ/kg]	Comments
NiCd	1.2	0.14	Inexpensive. High-/low-drain, moderate energy density. Can withstand very high discharge rates with virtually no loss of capacity. Moderate rate of self-discharge. Environmental hazard due to Cadmium – use now virtually prohibited in Europe.
Lead–acid	2.1	0.14	Moderately expensive. Moderate energy density. Moderate rate of self-discharge. Higher discharge rates result in considerable loss of capacity. Environmental hazard due to Lead. Common use – Automobile batteries
NiMH	1.2	0.36	Inexpensive. Performs better than alkaline batteries in higher drain devices. Traditional chemistry has high energy density, but also a high rate of self-discharge. Newer chemistry has low self-discharge rate, but also a ~25% lower energy density. Used in some cars.
NiZn	1.6	0.36	Moderately inexpensive. High drain device suitable. Low self-discharge rate. Voltage closer to alkaline primary cells than other secondary cells. No toxic components. Newly introduced to the market (2009). Has not yet established a track record. Limited size availability.
AgZn	1.86 1.5	0.46	Smaller volume than equivalent Li-ion. Extremely expensive due to silver. Very high energy density. Very high drain capable. For many years considered obsolete due to high silver prices. Cell suffers from oxidation if unused. Reactions are not fully understood. Terminal voltage very stable but suddenly drops to 1.5 volts at 70–80% charge (believed to be due to presence of both argentous and argentic oxide in positive plate – one is consumed first). Has been used in lieu of primary battery (moon buggy). Is being developed once again as a replacement for Li-ion.
Lithium ion	3.6	0.46	Very expensive. Very high energy density. Not usually available in "common" battery sizes. Very common in laptop computers, moderate to high-end digital cameras, camcorders, and cellphones. Very low rate of self-discharge. Terminal voltage unstable (varies from 4.2 to 3.0 volts during discharge). Volatile: Chance of explosion if short-circuited, allowed to overheat, or not manufactured with rigorous quality standards.

Homemade cells

Almost any liquid or moist object that has enough ions to be electrically conductive can serve as the electrolyte for a cell. As a novelty or science demonstration, it is possible to insert two electrodes made of different metals into a lemon,^[60] potato,^[61] etc. and generate small amounts of electricity. "Two-potato clocks" are also widely available in hobby and toy stores; they consist of a pair of cells, each consisting of a potato (lemon, et cetera) with two electrodes inserted into it, wired in series to form a battery with enough voltage to power a digital clock.^[62] Homemade cells of this kind are of no practical use.

A voltaic pile can be made from two coins (such as a nickel and a penny) and a piece of paper towel dipped in salt water. Such a pile generates a very low voltage but, when many are stacked in series, they can replace normal batteries for a short time.^[63]

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.^[64]

Lead acid cells can easily be manufactured at home, but a tedious charge/discharge cycle is needed to 'form' the plates. This is a process in which lead sulfate forms on the plates, and during charge is converted to lead dioxide (positive plate) and pure lead (negative plate). Repeating this process results in a microscopically rough surface, increasing the surface area. This increases the current the cell can deliver. For an example, see.^[65]

Daniell cells are easy to make at home. Aluminium–air batteries can be produced with high-purity aluminium. Aluminium foil batteries will produce some electricity, but are not efficient, in part because a significant amount of (combustible) hydrogen gas is produced.

Secularism

From Wikipedia, the free encyclopedia

 

Secularism is the principle of the separation of government institutions and persons mandated to represent the state from religious institutions and religious dignitaries. One manifestation of secularism is asserting the right to be free from religious rule and teachings, or, in a state declared to be neutral on matters of belief, from the imposition by government of religion or religious practices upon its people.^{[Notes 1]} Another manifestation of secularism is the view that public activities and decisions, especially political ones, should be uninfluenced by religious beliefs and/or practices.^{[1][Notes 2]}

Secularism draws its intellectual roots from Greek and Roman philosophers such as Marcus Aurelius and Epicurus; from Enlightenment thinkers such as Denis Diderot, Voltaire, Baruch Spinoza, James Madison, Thomas Jefferson, and Thomas Paine; and from more recent freethinkers and atheists such as Robert Ingersoll and Bertrand Russell.

The purposes and arguments in support of secularism vary widely. In European laicism, it has been argued that secularism is a movement toward modernization, and away from traditional religious values (also known as secularization). This type of secularism, on a social or philosophical level, has often occurred while maintaining an official state church or other state support of religion. In the United States, some argue that state secularism has served to a greater extent to protect religion and the religious from governmental interference, while secularism on a social level is less prevalent.^[2][3] Within countries as well, differing political movements support secularism for varying reasons.^[4]

Overview

George Jacob Holyoake (1817–1906), British writer who coined the term "secularism."

The term "secularism" was first used by the British writer George Jacob Holyoake in 1851.^[5] Although the term was new, the general notions of freethought on which it was based had existed throughout history.

Holyoake invented the term "secularism" to describe his views of promoting a social order separate from religion, without actively dismissing or criticizing religious belief. An agnostic himself, Holyoake argued that "Secularism is not an argument against Christianity, it is one independent of it.
It does not question the pretensions of Christianity; it advances others. Secularism does not say there is no light or guidance elsewhere, but maintains that there is light and guidance in secular truth, whose conditions and sanctions exist independently, and act forever. Secular knowledge is manifestly that kind of knowledge which is founded in this life, which relates to the conduct of this life, conduces to the welfare of this life, and is capable of being tested by the experience of this life."^[6]

Barry Kosmin of the Institute for the Study of Secularism in Society and Culture breaks modern secularism into two types: hard and soft secularism. According to Kosmin, "the hard secularist considers religious propositions to be epistemologically illegitimate, warranted by neither reason nor experience." However, in the view of soft secularism, "the attainment of absolute truth was impossible and therefore skepticism and tolerance should be the principle and overriding values in the discussion of science and religion."^[7]

State secularism

Motto of the French republic on the tympanum of a church.

In political terms, secularism is a movement towards the separation of religion and government (often termed the separation of church and state). This can refer to reducing ties between a government and a state religion, replacing laws based on scripture (such as the Torah and Sharia law) with civil laws, and eliminating discrimination on the basis of religion. This is said to add to democracy by protecting the rights of religious minorities.^[8]

Other scholars, such as Jacques Berlinerblau of the Program for Jewish Civilization at Georgetown University, have argued separation of church and state is but one possible strategy to be deployed by secular governments. What all secular governments, from the democratic to the authoritarian, share is a concern about relations between church and state. Each secular government may find its own unique policy prescriptions for dealing with that concern (separation being but one of those possible policies. French models in which the state carefully monitors and regulates the church being another) ^[9]

The Hindu varna system had distinct Kshatriya varna (the ruling class) and Brahman varna (the priest, teachers and preachers). This ensured that a Hindu state can never be a theocracy and separateness of state affairs and religious affairs is maintained. All empires following this varna system like Gupta empire, Mauryan empire, and many other Indian empires can be considered secular states because of the documented use of varna system.^[10]

Maharaja Ranjeet Singh of the Sikh empire of the first half 19th century successfully established a secular rule in the Punjab. This secular rule allowed members of all races and religions to be respected and to participate without discrimination in Ranjeet Singh darbar and he had Sikh, a Muslim and a Hindu representatives heading the darbar.^[11] Ranjit Singh also extensively funded education, religion, and arts of various different religions and languages.^[12]

Secularism is often associated with the Age of Enlightenment in Europe and plays a major role in Western society. The principles, but not necessarily practices, of separation of church and state in the United States and Laïcité in France draw heavily on secularism. Secular states also existed in the Islamic world during the Middle Ages (see Islam and secularism).^[13]

Due in part to the belief in the separation of church and state, secularists tend to prefer that politicians make decisions for secular rather than religious reasons.^[14] In this respect, policy decisions pertaining to topics like abortion, contraception, embryonic stem cell research, same-sex marriage, and sex education are prominently focused upon by American secularist organizations such as the Center for Inquiry.^[15][16]

Most major religions accept the primacy of the rules of secular, democratic society but may still seek to influence political decisions or achieve specific privileges or influence through church-state agreements such as a concordat.^{[citation needed]} Many Christians support a secular state, and may acknowledge that the conception has support in Biblical teachings, particularly the statement of Jesus in the Book of Luke: "Then give to Caesar what is Caesar's, and to God what is God's.".^{[citation needed]} However, some Christian fundamentalists (notably in the United States) oppose secularism, often claiming that there is a "radical secularist" ideology being adopted in current days and see secularism as a threat to "Christian rights"^[17] and national security.^[18] The most significant forces of religious fundamentalism in the contemporary world are Fundamentalist Christianity and Fundamentalist Islam. At the same time, one significant stream of secularism has come from religious minorities who see governmental and political secularism as integral to preserving equal rights.^[19]

Some of the well known states that are often considered "constitutionally secular" are USA,^[20] France, India,^[21] Mexico^[22] South Korea, and Turkey although none of these nations have identical forms of governance.

Secular society

In studies of religion, modern democracies are generally recognized as secular. This is due to the near-complete freedom of religion (beliefs on religion generally are not subject to legal or social sanctions), and the lack of authority of religious leaders over political decisions. Nevertheless, religious beliefs are widely considered^{[by whom?]} a relevant part of the political discourse in many of these countries.^[which?] This contrasts with other Western countries^[which?] where religious references are generally considered out-of-place in mainstream politics.

The aspirations of a secular society could characterize a secular society as one which:

1. Refuses to commit itself as a whole to any one view of the nature of the universe and the role of man in it.
2. Is not homogeneous, but is pluralistic.
3. Is tolerant. It widens the sphere of private decision-making.
4. While every society must have some common aims, which implies there must be agreed on methods of problem-solving, and a common framework of law; in a secular society these are as limited as possible.
5. Problem solving is approached rationally, through examination of the facts. While the secular society does not set any overall aim, it helps its members realize their aims.
6. Is a society without any official images. Nor is there a common ideal type of behavior with universal application.

Positive Ideals behind the secular society:

1. Deep respect for individuals and the small groups of which they are a part.
2. Equality of all people.
3. Each person should be helped to realize their particular excellence.
4. Breaking down of the barriers of class and caste.^[23]

Modern sociology has, since Max Weber, often been preoccupied with the problem of authority in secularized societies and with secularization as a sociological or historical process.^[24] Twentieth-century scholars whose work has contributed to the understanding of these matters include Carl L. Becker, Karl Löwith, Hans Blumenberg, M. H. Abrams, Peter L. Berger, Paul Bénichou and D. L. Munby, among others.

Some societies become increasingly secular as the result of social processes, rather than through the actions of a dedicated secular movement; this process is known as secularization.

Secular ethics

George Holyoake's 1896 publication English Secularism defines secularism as:

Secularism is a code of duty pertaining to this life, founded on considerations purely human, and intended mainly for those who find theology indefinite or inadequate, unreliable or unbelievable. Its essential principles are three: (1) The improvement of this life by material means. (2) That science is the available Providence of man. (3) That it is good to do good. Whether there be other good or not, the good of the present life is good, and it is good to seek that good.^[25]

Holyoake held that secularism and secular ethics should take no interest at all in religious questions (as they were irrelevant), and was thus to be distinguished from strong freethought and atheism. In this he disagreed with Charles Bradlaugh, and the disagreement split the secularist movement between those who argued that anti-religious movements and activism was not necessary or desirable and those who argued that it was.

Contemporary ethical debate is often described as "secular", with the work of Derek Parfit and Peter Singer, and even the whole field of contemporary bioethics, having been described or self-described as explicitly secular or non-religious.^{[26][27][28][29]}

American interpretation of secularism

It has been argued that the definition of secularism has frequently been misinterpreted.^[30][31] In a 2012 Huffington Post article titled Secularism Is Not Atheism, Jacques Berlinerblau, Director of the Program for Jewish Civilization at the Edmund A. Walsh School of Foreign Service at Georgetown University, wrote that "Secularism must be the most misunderstood and mangled ism in the American political lexicon. Commentators on the right and the left routinely equate it with Stalinism, Nazism and Socialism, among other dreaded isms. In the United States, of late, another false equation has emerged. That would be the groundless association of secularism with atheism. The religious right has profitably promulgated this misconception at least since the 1970s."^[30]

Secularist website Concordat Watch also backed the notion that secularism has at times been mistaken as a word that reflects one's personal religious views, stating that "Some opponents of church-state separation redefine “secularism” as “state neutrality” to allow their group, among others, to get state funding. Others try to discredit it by conflating “secularism” with “atheism”. But it's a political, rather than a religious doctrine and its purpose is to help level the playing field in order to give a better chance for human rights."^[31]

Organizations

Groups such as the National Secular Society (United Kingdom) and Americans United campaign for secularism are often supported by Humanists. In 2005, the National Secular Society held the inaugural "Secularist of the Year" awards ceremony. Its first winner was Maryam Namazie, of the Worker-Communist Party of Iran. And of the Council of Ex-Muslims of Britain^[32] which aims to break the taboo that comes with renouncing Islam and to oppose apostasy laws and political Islam.^[33]
The Scottish Secular Society is active in Scotland and is currently focused on the role of religion in education. In 2013 it raised a petition at the Scottish Parliament to have the Education (Scotland) Act 1980 changed so that parents will have to make a positive choice to opt in to Religious Observance.

Another secularist organization is the Secular Coalition for America. The Secular Coalition for America lobbies and advocates for separation of church and state as well as the acceptance and inclusion of Secular Americans in American life and public policy. While Secular Coalition for America is linked to many secular humanistic organizations and many secular humanists support it, as with the Secular Society, some non-humanists support it.

Local organizations work to raise the profile of secularism in their communities and tend to include secularists, freethinkers, atheists, agnostics, and humanists under their organizational umbrella.

Student organizations, such as the Toronto Secular Alliance, try to popularize nontheism and secularism on campus. The Secular Student Alliance is an educational nonprofit that organizes and aids such high school and college secular student groups.

In Turkey, the most prominent and active secularist organization is Atatürk Thought Association (ADD), which is credited for organizing the Republic Protests – demonstrations in the four largest cities in Turkey in 2007, where over 2 million people, mostly women, defended their concern in and support of secularist principles introduced by Mustafa Kemal Atatürk.

Leicester Secular Society founded in 1851 is the world's oldest secular society.