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16 décembre 2010 4 16 /12 /décembre /2010 03:22

A battery pack is a set of any number of (preferably) identical batteries or individual battery cells. They may be configured in a series, parallel or a mixture of both to deliver the desired voltage, capacity, or power density. The term battery pack is often used in reference to RC hobby toys and battery electric vehicles       (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

Components of battery packs include the individual batteries or cells, and the interconnects which provide electrical conductivity between them. Rechargeable battery packs often contain a temperature sensor, which the battery charger uses to detect the end of charging     (Dell Studio XPS 1340 Battery)    .

Interconnects are also found in batteries as they are the part which connects each cell, though batteries are most often only arranged in series strings.

When wiring a pack in parallel there are various methods and one should take into consideration the balance of the electrical circuit   (Dell Studio XPS 1640 Battery)   .

Battery regulators are sometimes used to keep the peak voltage of each individual battery or cell below its maximum value so to allow weaker batteries to be fully charged, bringing the whole pack back into balance. Active balancing can also be performed by battery balancer devices which can shuttle energy from strong batteries to weaker ones in real time for even better balance (Dell Vostro 1710 Battery)   .

A well-balanced pack lasts longer and delivers better performance so it is a rather beneficial component of high capacity or expensive packs.

For an inline package, cells are selected and stacked with solder in between them. The cells are pressed together and a current pulse generates heat to solder them together and to weld all connections internal to the cell  (Sony VGP-BPS13 battery) .

Calculating State Of Charge

SOC or State of charge is the equivalent of a fuel gauge for a battery. SOC cannot be determined by a simple voltage measurement, because the terminal voltage of a battery may stay substantially constant until it is completely discharged  (Sony VGP-BPS13/B battery)    .

In some types of battery, electrolyte specific gravity may be related to state of charge but this is not measurable on typical battery pack cells, and is not related to state of charge on most battery types. Most SOC methods take into account voltage and current as well as temperature and other aspects of the discharge and charge process to in essence count up or down within a pre-defined capacity of a pack  (Sony VGP-BPS13/S battery)    .

More complex state of charge estimation systems take into account the Peukert effect which relates the capacity of the battery to the discharge rate.

Advantages

An advantage of a battery pack is the ease with which it can be swapped into or out of a device  (Sony VGP-BPS13A/B battery)  .

This allows multiple packs to deliver extended runtimes, freeing up the device for continued use while charging the removed pack separately.

Another advantage is the flexibility of their design and implementation, allowing the use of cheaper high-production cells or batteries to be combined into a pack for nearly any application       (Sony VGP-BPS13B/B battery)  .

At the end of product life, batteries can be removed and recycled separately, reducing the total volume of hazardous waste.

Disadvantages

Packs are often simpler for end users to repair or tamper with than a sealed non-serviceable battery or cell  (Sony VGP-BPL9 battery).

Though some might consider this an advantage it is important to take safety precautions when servicing a battery pack as they pose a danger as potential chemical, electrical, and fire risks.

A battery charger is a device used to put energy into a secondary cell or (rechargeable) battery by forcing an electric current through it      (Sony VGP-BPL15 battery)   .

The charge current depends upon the technology and capacity of the battery being charged. For example, the current that should be applied to recharge a 12 V car battery will be very different from the current for a mobile phone battery    (Dell Inspiron E1505 battery) .

Types of battery chargers

Simple

A simple charger works by supplying a constant or DC pulsed DC power source to a battery being charged. The simple charger does not alter its output based on time or the charge on the battery      (Dell Latitude E6400 battery)      .

This simplicity means that a simple charger is inexpensive, but there is a tradeoff in quality. Typically, a simple charger takes longer to charge a battery to prevent severe over-charging. Even so, a battery left in a simple charger for too long will be weakened or destroyed due to over-charging    (HP Pavilion dv6000 Battery)   .

These chargers can supply either a constant voltage or a constant current to the battery.

Trickle

A trickle charger, also known as a battery trickle charger, is typically a low-current (500–1,500 mA) battery charger. A trickle charger is generally used to charge small capacity batteries (2–30 Ah)        (Sony Vaio VGN-FZ31S battery)     .

These types of battery chargers are also used to maintain larger capacity batteries (> 30 Ah) that are typically found on cars, boats, RVs and other related vehicles. Utilizing the battery charger is this fashion is how these battery chargers got their name. In larger applications, the current of the battery charger is sufficient only to provide a maintenance or trickle current (trickle is commonly the last charging stage of most battery chargers)     (Sony Vaio VGN-FZ31S battery)    .

Depending on the technology of the trickle charger, it can be left connected to the battery indefinitely. Battery chargers that can be left connected to the battery without causing the battery damage are also referred to as smart or intelligent chargers  (SONY VGN-FZ38M Battery)     .

Timer-based

The output of a timer charger is terminated after a pre-determined time. Timer chargers were the most common type for high-capacity Ni-Cd cells in the late 1990s for example (low-capacity consumer Ni-Cd cells were typically charged with a simple chargers) (SONY VGN-FZ31z Battery)    .

Often a timer charger and set of batteries could be bought as a bundle and the charger time was set to suit those batteries. If batteries of lower capacity were charged then they would be overcharged, and if batteries of higher capacity were charged they would be only partly charged      (Sony VGN-FZ31Z Battery)    .

With the trend for battery technology to increase capacity year on year, an old timer charger would only partly charge the newer batteries.

Timer based chargers also had the drawback that charging batteries that were not fully discharged, even if those batteries were of the correct capacity for the particular timed charger, would result in over-charging    (SONY VAIO VGN-FZ38M Battery)   .

Intelligent

Output current depends upon the battery's state. An intelligent charger may monitor the battery's voltage, temperature and/or time under charge to determine the optimum charge current at that instant. Charging is terminated when a combination of the voltage, temperature and/or time indicates that the battery is fully charged      (SONY VGN-FZ31E Battery)    .

For Ni-Cd and NiMH batteries, the voltage across the battery increases slowly during the charging process, until the battery is fully charged. After that, the voltage decreases, which indicates to an intelligent charger that the battery is fully charged. Such chargers are often labeled as a ΔV, "delta-V," or sometimes "delta peak", charger, indicating that they monitor the voltage change  (SONY  VGN-FZ31J Battery)      .

The problem is, the magnitude of "delta-V" can become very small or even non-existent if (very) high  capacity rechargeable batteries are recharged.This can cause even an intelligent battery charger to not sense that the batteries are actually already fully charged, and continue charging. Overcharging of the batteries will result in some cases      (SONY VGN-FZ31M Battery)   .

However, many so called intelligent chargers employ a combination of cut off systems, which should prevent overcharging in the vast majority of cases.

A typical intelligent charger fast-charges a battery up to about 85% of its maximum capacity in less than an hour, then switches to trickle charging, which takes several hours to top off the battery to its full capacity     (SONY VGN-FZ31B Battery)   .

Fast

Fast chargers make use of control circuitry in the batteries being charged to rapidly charge the batteries without damaging the cells' elements. Most such chargers have a cooling fan to help keep the temperature of the cells under control     (SONY VGP-BPS13 Battery) .

Most are also capable of acting as standard overnight chargers if used with standard NiMH cells that do not have the special control circuitry. Some fast chargers, such as those made by Energizer, can fast-charge any NiMH battery even if it does not have the control circuit     (Dell Inspiron 1320 Battery)    .

Pulse

Some chargers use pulse technology in which a pulse is fed to the battery. This DC pulse has a strictly controlled rise time, pulse width, pulse repetition rate (frequency) and amplitude. This technology is said to work with any size, voltage, capacity or chemistry of batteries, including automotive and valve-regulated batteries      (Dell Inspiron 1320n Battery)     .

With pulse charging, high instantaneous voltages can be applied without overheating the battery. In a Lead-acid battery, this breaks down lead-sulfate crystals, thus greatly extending the battery service life.

Several kinds of pulse charging are patented. Others are open source hardware   (Dell Inspiron 1464 Battery)     .

Some chargers use pulses to check the current battery state when the charger is first connected, then use constant current charging during fast charging, then use pulse charging as a kind of trickle charging to maintain the charge.

Some chargers use "negative pulse charging", also called "reflex charging" or "burp charging"     (Dell Inspiron 1564 Battery)   .

Such chargers use both positive and brief negative current pulses. There is no significant evidence, however, that negative pulse charging is more effective than ordinary pulse charging.

Inductive

Inductive battery chargers use electromagnetic induction to charge batteries      (Dell Inspiron 1764 Battery)     .

A charging station sends electromagnetic energy through inductive coupling to an electrical device, which stores the energy in the batteries. This is achieved without the need for metal contacts between the charger and the battery. It is commonly used in electric toothbrushes and other devices used in bathrooms      (Dell Studio 1450 Battery)      .

Because there are no open electrical contacts, there is no risk of electrocution.

USB-based

Since the Universal Serial Bus specification provides for a five-volt power supply, it is possible to use a USB cable as a power source for recharging batteries    (Dell Studio 1457 Battery)     .

Products based on this approach include chargers for cellular phones and portable digital audio players. They may be fully compliant USB peripheral devices adhering to USB power discipline, or uncontrolled in the manner of USB decorations.

Solar chargers

Solar chargers convert light energy into DC current. They are generally portable, but can also be fixed mount     (Dell Latitude D610 Battery)  .

Fixed mount solar chargers are also known as solar panels.Solar panels are often connected to the electrical grid, where as portable solar chargers as used off-the-grid (i.e. cars, boats, or RVs).

Although portable solar chargers obtain energy from the sun only, they still can (depending on the technology) be used in low light (i.e. cloudy) applications      (Toshiba NB100 Battery)     .

Portable solar charger are typically used for trickle charging, although some solar charger (depending on the wattage), can completely recharge batteries. Although Portable wind turbines are also sold. Some, including the Kinesis K3, can work either way.

Charge rate

Charge rate is often denoted as C or C-rate and signifies a charge or discharge rate equal to the capacity of a battery in one hour (Toshiba Satellite M65 battery)    .

For a 1.6Ah battery, C = 1.6A. A charge rate of C/2 = 0.8A would need two hours, and a charge rate of 2C = 3.2A would need 30 minutes to fully charge the battery from an empty state, if supported by the battery. This also assumes that the battery is 100% efficient at absorbing the charge     (Toshiba Satellite M60 battery)     .

Applications

Since a battery charger is intended to be connected to a battery, it may not have voltage regulation or filtering of the DC voltage output. Battery chargers equipped with both voltage regulation and filtering may be identified as battery eliminators   (Dell Latitude D830 Battery)      .

Mobile phone charger

Most mobile phone chargers are not really chargers, only adapters that provide a power source for the charging circuitry which is almost always contained within the mobile phone     (Dell Latitude D620 Battery)    .

They are notably diverse, having a wide variety of DC connector-styles and voltages, most of which are not compatible with other manufacturers' phones or even different models of phones from a single manufacturer.

Users of publicly accessible charging kiosks must be able to cross-reference connectors with device brands/models and individual charge parameters and thus ensure delivery of the correct charge for their mobile device    (Dell Inspiron Mini 10 Battery)     .

A database-driven system is one solution, and is being incorporated into some designs of charging kiosks.

Mobile phones can usually accept relatively wide range of voltages , as long as it is sufficiently above the phone battery's voltage. However, if the voltage is too high, it can damage the phone       (Sony VGN-FW11S Battery)   .

Mostly, the voltage is 5 volts or slightly higher, but it can sometimes vary up to 12 volts when the power source is not loaded.

There are also human-powered chargers sold on the market, which typically consists of a dynamo powered by a hand crank and extension cords. There are also solar chargers       (Sony VGN-FW11M Battery) .

China and other countries are making a national standard on mobile phone chargers using the USB standard.Starting in 2010, SonyEricsson, Apple, Nokia, Motorola, Samsung and RIM will begin making handsets with a standard phone charger based on the micro-USB connector         (Sony VGN-FW139E/H battery)    .

On October 22, 2009, the International Telecommunication Union announced a standard for a universal charger for mobile handsets (Micro-USB).

Battery charger for vehicles

There are two main types of charges for vehicles:

  • To recharge a fuel vehicle's starter battery, where a modular charger is used.
  • To recharge an electric vehicle (EV) battery pack    (Dell Latitude E5400 Battery) .

Battery electric vehicle

These vehicles include a battery pack, so generally use series charger.

A 10 Ampere-hour battery could take 15 hours to reach a fully charged state from a fully discharged condition with a 1 Ampere charger as it would require roughly 1.5 times the battery's capacity       (Dell Latitude E4200 Battery)    .

Public EV charging heads (aka: stations) provide 6 kW (host power of 208 to 240 VAC off a 40 amp circuit). 6 kW will recharge an EV roughly 6 times faster than 1 kW overnight charging.

Rapid charging results in even faster recharge times and is limited only by available AC power and the type of charging system (Dell Vostro A840 Battery)   .

On board EV chargers (change AC power to DC power to recharge the EV's pack) can be:

  • Isolated: they make no physical connection between the A/C electrical mains and the batteries being charged. These typically employ some form of Inductive charging. Some isolated chargers may be used in parallel  (Dell Inspiron 300M Battery)   .
  • This allows for an increased charge current and reduced charging times. The battery has a maximum current rating that cannot be exceeded
  • Non-isolated: the battery charger has a direct electrical connection to the A/C outlet's wiring (Dell Studio 1737 battery)  .
  • Non-isolated chargers cannot be using in parallel  .

Power Factor Correction (PFC) chargers can more closely approach the maximum current the plug can deliver, shortening charging time     (Dell Inspiron E1505 battery)  .

Charge stations

There is a list of public EV charging stations in the U.S.A. and worldwide

Project Better Place is deploying a network of charging stations and subsidizing vehicle battery costs through leases and credits (Dell RM791 battery) .

Non-contact magnetic charging

Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have developed an electric transport system (called Online Electric Vehicle, OLEV) where the vehicles get their power needs from cables underneath the surface of the road via non-contact magnetic charging      (Dell XPS M1530 battery)    ,

(where a power source is placed underneath the road surface and power is wirelessly picked up on the vehicle itself. As a possible solution to traffic congestion and to improve overall efficiency by minimizing air resistance and so reduce energy consumption, the test vehicles followed the power track in a convoy formation     (Dell XPS M2010 battery)    .

Use in experiments

A battery charger can work as a DC power adapter for experimentation. It may, however, require an external capacitor to be connected across its output terminals in order to "smooth" the voltage sufficiently, which may be thought of as a DC voltage plus a "ripple" voltage added to it        (Dell Vostro 1000 battery)     .

Note that there may be aninternal resistance connected to limit the short circuit current, and the value of that internal resistance may have to be taken into consideration in experiments.

Prolonging battery life

Many rumors circulate about the best practices to prolong battery life    (Acer Aspire One battery)    .

What practices are best depend on the type of battery. It is "rumored" that Nickel-based cells, such as NiMH and NiCd, need to be fully discharged before each charge, or else the battery loses capacity over time in a phenomenon known as "memory effect". However, this is only partially accurate     (Toshiba Satellite P10 Battery)   :

nickel alloy cells can be charged at any point throughout their discharge cycle ‏– they do not have to be fully discharged. Memory effect should instead be prevented by fully discharging the battery once a month (once every 30 charges). This extends the life of the battery since memory effect is prevented while avoiding full charge cycles which are known to be hard on all types of dry-cell batteries, eventually resulting in a permanent decrease in battery capacity   (SONY VGN-FZ210CE Battery)   .

Most modern cell phones, laptops, and most electric vehicles use Lithium-ion batteries. Contrary to some recommendations, these batteries actually last longest if the battery is frequently charged; fully discharging them will degrade their capacity relatively quickly  (Dell Precision M70 Battery)       .

When storing however, lithium batteries degrade more while fully charged than if they are only 40% charged. Degradation also occurs faster at higher temperatures. Degradation in lithium-ion batteries is caused by an increased internal battery resistance due to cell oxidation     (Dell KM958 battery)  .

This decreases the efficiency of the battery, resulting in less net current available to be drawn from the battery.

Internal combustion engine vehicles, such as boats, RVs, ATVs, motorcycles, cars, trucks, and more use lead acid batteries. These batteries employ a sulfuric acid electrolyte and can generally be charged and discharged without exhibiting memory effect  (Toshiba Satellite L305 Battery) ,

though sulfation (a chemical reaction in the battery which deposits a layer of sulfates on the lead) will occur over time. Keeping the electrolyte level in the recommended range is necessary. When discharged, these batteries should be recharged immediately in order to prevent sulfation      (Toshiba Satellite T4900 Battery)   .

These sulfates are electrically insulating and therefore interfere with the transfer of charge from the sulfuric acid to the lead, resulting in a lower maximum current than can be drawn from the battery. Sulfated lead acid batteries typically need replacing (Toshiba PA3399U-2BRS battery)     .

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   (Toshiba Satellite A200 Battery) .

Half-cells

An electrochemical cell consists of two half-cells. Each half-cell consists of an electrode, and an electrolyte. The two half-cells may use the same electrolyte, or they may use different electrolytes    (Toshiba Satellite 1200 Battery)  .

The chemical reactions in the cell may involve the electrolyte, the electrodes or an external substance (as in fuel cells which may use hydrogen gas as a reactant). In a full electrochemical cell, species from one half-cell lose electrons (oxidation) to their electrode while species from the other half-cell gain electrons (reduction) from their electrode     (Toshiba Satellite M300 Battery)  .

A salt bridge (i.e. filter paper soaked in KNO3) is often employed to provide ionic contact between two half-cells with different electrolytes—to prevent the solutions from mixing and causing unwanted side reactions. As electrons flow from one half-cell to the other, a difference in charge is established      WD passport essential (500GB/640GB) .

If no salt bridge were used, this charge difference would prevent further flow of electrons. A salt bridge allows the flow of ions to maintain a balance in charge between the oxidation and reduction vessels while keeping the contents of each separate. Other devices for achieving separation of solutions are porous pots and gelled solutions     WD passport essential (250GB/320GB) .

A porous pot is used in the Bunsen cell (right).

Equilibrium reaction

Each half-cell has a characteristic voltage. Different choices of substances for each half-cell give different potential differences. Each reaction is undergoing anequilibrium reaction between different oxidation states of the ions—when equilibrium is reached the cell cannot provide further voltage  WD  passport essential SE (750GB/1TB)     .

In the half-cell which is undergoing oxidation, the closer the equilibrium lies to the ion/atom with the more positive oxidation state the more potential this reaction will provide. Similarly, in the reduction reaction, the further the equilibrium lies to the ion/atom with the more negative oxidation state the higher the potential    WD  passport elite(250GB/320GB) .

Electrode potential

The cell potential can be predicted through the use of electrode potentials (the voltages of each half-cell). (See table of standard electrode potentials). The difference in voltage between electrode potentials gives a prediction for the potential measuredWD passport elite(500GB/640GB) .

Cell potentials have a possible range of about zero to 6 volts. Cells using water-based electrolytes are usually limited to cell potentials less than about 2.5 volts, because the very powerful oxidizing and reducing agents which would be required to produce a higher cell potential tend to react with the water        WD  passport studio for Mac(320GB/500GB) .

Electrochemical cell types

Main types

Cells are classified into two broad categories,

  • Primary cells irreversibly (within limits of practicality) transform chemical energy to electrical energy. When the initial supply of reactants is exhausted, energy cannot be readily restored to the electrochemical cell by electrical means  WD  passport studio for Mac(500GB/640GB) .
  • Secondary cells can be recharged; that is, they can have their chemical reactions reversed by supplying electrical energy to the cell, restoring their original composition     WD  Elements series(250GB/320GB) .

Primary electrochemical cells

Primary electochemical cells can produce current immediately on assembly. Disposable cells are intended to be used once and discarded. 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      WD  Elements SE(500GB/640GB) .

Common types of disposable cells include zinc-carbon cells and alkaline cells. Generally, these have higher energy densities than rechargeable cells, but disposable cells do not fare well under high-drain applications with loads under 75 ohms (75 Ω)  WD Elements SE(750GB/1TB) .

Secondary electrochemical cells

Secondary electrochemical cells must be charged before use; they are usually assembled with active materials in the discharged state. Rechargeable electrochemical cells or secondary electrochemical cells can be recharged by applying electric current, which reverses the chemical reactions that occur during its use      WD  Elements desktop(500GB/640GB) .

Devices to supply the appropriate current are called chargers or rechargers.

The oldest form of rechargeable cell is the lead-acid cell. This electrochemical cell is notable in that it contains a liquid in an unsealed container, requiring that the cell be kept upright and the area be well ventilated to ensure safe dispersal of the hydrogen gas produced by these cells during overcharging      WD  Elements desktop(750GB/1TB) .

The lead-acid cell is also very heavy for the amount of electrical energy it can supply. Despite this, its low manufacturing cost and its high surge current levels make its use common where a large capacity (over approximately 10Ah) is required or where the weight and ease of handling are not concerns         WD  Elements desktop(1.5 TB/2TB) .

An improved type of liquid electrolyte cell is the sealed valve regulated lead acid (VRLA) cell, popular in the automotive industry as a replacement for the lead-acid wet cell. The VRLA cell uses an immobilized sulphuric acid electrolyte, reducing the chance of leakage and extending shelf life  WD  passport essential SE (750GB/1TB)--USB 3.0)      .

VRLA cells have the electrolyte immobilized, usually by one of two means:

  • Gel cells contain a semi-solid electrolyte to prevent spillage.
  • Absorbed Glass Mat (AGM) cells absorb the electrolyte in a special fibreglass matting  WD  passport essential (500GB/640GB)

Other portable rechargeable cells are (in order of increasing power density and cost): nickel-cadmium cells (NiCd), nickel metal hydride cells (NiMH), and lithium-ion cells(Li-ion). By far, Li-ion has the highest share of the dry cell rechargeable market WD  passport for Mac(320GB/500GB) .

Meanwhile, NiMH has replaced NiCd in most applications due to its higher capacity, but NiCd remains in use in power tools, two-way radios, andmedical equipment      WD  passport for Mac(640GB/1TB) .

An electrolytic cell decomposes chemical compounds by means of electrical energy, in a process called electrolysis; the Greek word lysis means to break up. The result is that the chemical energy is increased. Important examples of electrolysis are the decomposition of water into hydrogen and oxygen, and bauxite into aluminium and other chemicals  My book essential 4 generation  (640GB/1TB) .

Components

An electrolytic cell has three component parts: an electrolyte and two electrodes (a cathode and an anode). The electrolyte is usually a solution of water or other solvents in which ions are dissolved. Molten salts such as sodium chloride are also electrolytes WD  My book essential 4 generation( 1.5TB/2TB) .

When driven by an external voltage applied to the electrodes, the electrolyte provides ions that flow to and from the electrodes, where charge-transferring, or faradaic, or redox, reactions can take place. Only for an external electrical potential (i.e. voltage) of the correct polarity and large enough magnitude can an electrolytic cell decompose a normally stable, or inert chemical compound in the solution    WD  My book elite( 1TB/1.5TB) .

The electrical energy provided undoes the effect of spontaneous chemical reactions.

Galvanic cells compared to electrolytic cells

In contrast, a battery or Galvanic cell, converts chemical energy into electrical energy, by using spontaneous chemical reactions that take place at the electrodes    WD  My book studio(1TB/2TB) .

Each galvanic cell has its own characteristic voltage (defined as the energy release per electron transfer from one electrode to the other). A simple galvanic cell will consist only of an electrolyte and two different electrodes. (Galvanic cells can also be made by connecting two half-cells, each with its own electrode and electrolyte, by an ion-transporting "bridge," usually a salt bridge; these cells are more complex.     WD  My book essential 4 generation( 1.5TB/2TB) .

The electrodes typically are two metals, which naturally have different reaction potentials relative to the electrolyte. This causes electrons of one of the electrodes to preferentially enter the solution at one electrode, and other electrons to leave the solution at the other electrode      WD  My book elite(640GB/2TB) .

This generates an electric current across the electrolyte, which will drive electric current through a wire that makes an exterior connection to each of the electrodes. A galvanic cell uses electrodes of different metals, whereas an electrolytic cell may use the same metal for cathode and anode       Seagate  expansion portable (320GB/500GB) .

A rechargeable battery, such as a AA NiMH cell or a single cell of a lead-acid battery, acts as a galvanic cell when discharging (converting chemical energy to electrical energy), and an electrolytic cell when being charged (converting electrical energy to chemical energy).which converts electric energy into chemical enrgy Seagate  expansion (1.5TB/2TB) .

Anode and cathode definitions depend on charge and discharge

Michael Faraday defined the cathode as the electrode to which cations flow (positively charged ions, like silver ions Ag+), to be reduced by reacting with (negatively charged) electrons on the cathode  Seagate  Freeagent Desktop (500GB/1TB) .

Likewise he defined the anode as the electrode to which anions flow (negatively charged ions, like chloride ions Cl−), to be oxidized by depositing electrons on the anode. Thus positive electric current flows from the cathode to the anode. To an external wire connected to the electrodes of a battery, thus forming an electric circuit, the cathode is positive and the anode is negative  Seagate  Freeagent Go(250GB/320GB) .

Consider two voltaic cells, A and B, with the voltage of A greater than the voltage of B. Mark the positive and negative electrodes as cathode and anode, respectively. Place them in a circuit with anode near anode and cathode near cathode, so the cells will tend to drive current in opposite directions    Seagate  Freeagent Go(500GB/640GB) .

The cell with the larger voltage discharges, making it a voltaic cell. Likewise the cell with the smaller voltage charges, making it an electrolytic cell. For the electrolytic cell, the external markings of anode and cathode are opposite the chemical definition. That is, the electrode marked as anode for discharge acts as the cathode while charging and the electrode marked as cathode acts as the anode while charging    Seagate  Freeagent Go(750GB/1TB) .

Uses

As already noted, water, particularly when ions are added (salt water or acidic water) can be electrolyzed (subject to electrolysis). When driven by an external source of voltage, H+ ions flow to the cathode to combine with electrons to produce hydrogen gas in a reduction reaction     Seagate  Freeagent Goflex(250GB/320GB) .

Likewise, OH− ions flow to the anode to release electrons and an H+ ion to produce oxygen gas in an oxidation reaction.

In molten sodium chloride, when a current is passed through the salt the anode oxidizes chloride ions (Cl−) to chlorine gas, releasing electrons to the anode      Seagate Freeagent Goflex(500GB/640GB) .

Likewise the cathode reduces sodium ions (Na+), which accept electrons from the cathode and deposits on the cathode as sodium metal.

NaCl dissolved in water can also be electrolyzed. The anode oxidizes chloride ions (Cl−), and Cl2 gas is still produced Seagate  Freeagent Goflex(750GB/1TB) .

However, at the cathode, instead of sodium ions being reduced to sodium metal, water molecules are reduced to hydroxide ions (OH−) and hydrogen gas (H2). The overall result of the electrolysis is the production of chlorine gas and aqueous sodium hydroxide (NaOH) solution  Seagate  Freeagent Goflex Pro(500GB/750GB) .

Commercially, electrolytic cells are used in electrorefining and electrowinning of several non-ferrous metals. Almost all high-purity aluminium, copper, zinc and lead is produced industrially in electrolytic cells      Seagate  Freeagent Goflex desktop(1TB/2TB) .

Battery nomenclature

Standard battery nomenclature describes portable dry cell batteries that are interchangeable in physical dimensions and electrical characteristics between manufacturers     Seagate  Freeagent go for Mac(320GB/640GB) .

The long history of disposable dry cells means that many different manufacturer-specific and national standards were used to designate sizes, long before international standards were reached. Technical standards for battery sizes and types are set by standards organizations such as International Electrotechnical Commission (IEC) and American National Standards Institute (ANSI)       Samsung  G2 protable (250gb/320GB) .

Popular sizes are still referred to by old standard or manufacturer designations, and some non-systematic designations have been included in current international standards due to wide use.

The complete nomenclature for the battery will fully specify the size, chemistry, terminal arrangements and special characteristics of a battery       Samsung  G2 protable (500GB/640GB) .

The same physically interchangeable cell size may have widely different characteristics; physical interchangeability is not the sole factor in substitution of batteries.

National standards for dry cell batteries have been developed by ANSI, JIS, British national standards, and others  Samsung  S2 protable (320GB/500GB) .

Civilian, commercial, government and military standards all exist. Two of the most prevalent standards currently in use are the IEC 60086 series and the ANSI C18.1 series. Both standards give dimensions, standard performance characteristics, and safety information     Samsung S1 Mini (120GB/160GB) .

Modern standards contain both systematic names for cell types that give information on the composition and approximate size of the cells, as well as arbitrary numeric codes for cell size      Samsung  S1 Mini (250GB/320GB) .

History of the ANSI standard

Standardization in the United States started in 1919, when the US National Bureau of Standards published recommended test procedures and standard dimensions of cells .American standards were revised several times during the following decades, as new sizes of cells were introduced and new chemistry developed, including chloride, alkaline, mercury and rechargeable types Samsung story station (1TB/1.5TB) .

The first American Standards Association (predecessor to ANSI) standard C18 appeared in 1928. It listed cell sizes using a letter code, roughly in order of size from smallest (A) to larger types. The only numerical designation was the 6-inch tall "No. 6" cell. The 1934 edition of the C18 standard expanded the nomenclature system to include series and parallel arrays of cells  Samsung Story station (1.5TB/2TB) .

In 1954, mercury batteries were included in the standard. The 1959 edition identified types suitable for use with transistor radios. In 1967, NEMA took over responsibility for development from the National Bureau of Standards. The 12th edition of C18 began to be harmonized with the IEC standard. Rechargeable batteries were introduced in the C18 standard in 1984, and lithium types were standardized in 1991      Samsung story station Esata(1TB/1.5TB) .

In 1999 the ANSI standards were extensively revised and separate safety standards provided. The current edition of the ANSI standards designates sizes with an arbitrary number, with a prefix letter to designate shape, and with a suffix letter or letters to identify different chemistry, terminals, or other features     Samsung  G3 station (1TB/1.5TB) .

International Electrotechnical Commission standardization

The International Electrotechnical Commission (IEC) was established in 1906 and co-ordinates development of standards for a wide range of electrical products. The IEC maintains two committees, TC21 established in 1933 for rechargeable batteries, and TC 35 established in 1948 for primary batteries, to develop standards      Maxtor  one touch 4 plus (500GB/750GB) .

The current designation system was adopted in 1992. Battery types are designated with a letter/number sequence indicating number of cells, cell chemistry, cell shape, dimensions, and special characteristics. Certain cell designations from earlier revisions of the standard have been retained     Maxtor one touch 4 plus (1TB/1.5TB) .

The first IEC standards for battery sizes were issued in 1957. Since 1992, International standard IEC 60086 defines an alphanumeric coding system for batteries. British standard 397 for primary batteries was withdrawn and replaced by the IEC standard in 1996  Maxtor cool black(640GB/1TB) .

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