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17 décembre 2010 5 17 /12 /décembre /2010 05:57

battery charger is a device used to put energy into a secondary cell or (rechargeable) battery by forcing an electric current through it.The charge current depends upon the technology and capacity of the battery being charged  (Dell XPS M1210 Batteryhttp://www.hdd-shop.co.uk .

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.

Simple

A simple charger works by supplying a constant or DC pulsed DC power source to a battery being charged  (Dell Studio XPS 1340 Battery) .

The simple charger does not alter its output based on time or the charge on the 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     (Dell Studio XPS 1640 Battery)  .

Even so, a battery left in a simple charger for too long will be weakened or destroyed due to over-charging. 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   (Dell Vostro 1710 Battery)      .

A trickle charger is generally used to charge small capacity batteries (2–30 Ah). 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   (Sony VGP-BPS13 battery)    .

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). Depending on the technology of the trickle charger, it can be left connected to the battery indefinitely       (Sony VGP-BPS13/B battery)   .

Battery chargers that can be left connected to the battery without causing the battery damage are also referred to as smart or intelligent chargers.

Timer-based

The output of a timer charger is terminated after a pre-determined time  (Sony VGP-BPS13/S battery)    .

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).

Often a timer charger and set of batteries could be bought as a bundle and the charger time was set to suit those batteries  (Sony VGP-BPS13A/B battery)   .

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. With the trend for battery technology to increase capacity year on year, an old timer charger would only partly charge the newer batteries      (Sony VGP-BPS13B/B battery)    .

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.

Intelligent

Output current depends upon the battery's state   (Sony VGP-BPL9 battery)   .

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 VGP-BPL15 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 ?V, "delta-V," or sometimes "delta peak", charger, indicating that they monitor the voltage change  (Dell Inspiron E1505 battery)     .

The problem is, the magnitude of "delta-V" can become very small or even non-existent if (very) high[quantify] 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    (Dell Latitude E6400 battery)  .

Overcharging of the batteries will result in some cases. 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     (HP Pavilion dv6000 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 Vaio VGN-FZ31S 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  (Sony Vaio VGN-FZ31S 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   (SONY VGN-FZ38M 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  (SONY VGN-FZ31z 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". 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  (Sony VGN-FZ31Z Battery)  .

Inductive

Main article: Inductive charging

Inductive battery chargers use electromagnetic induction to charge batteries. A charging station sends electromagnetic energy through inductive coupling to an electrical device, which stores the energy in the batteries     (SONY VAIO VGN-FZ38M Battery) .

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. Because there are no open electrical contacts, there is no risk of electrocution  (SONY VGN-FZ31E Battery)   .

USB-based

Pay-per-charge kiosk, illustrating the variety of mobile phone charger connectors

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     (SONY  VGN-FZ31J 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  (SONY VGN-FZ31M Battery)      .

Solar chargers

Further information: Solar charger and energy harvesting

Solar chargers convert light energy into DC current. They are generally portable, but can also be fixed mount. Fixed mount solar chargers are also known as solar panels    (SONY VGN-FZ31B Battery)   .

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      (SONY VGP-BPS13 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  (Dell Inspiron 1320 Battery)    .

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. 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   (Dell Inspiron 1320n Battery) .

This also assumes that the battery is 100% efficient at absorbing the charge.

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 Inspiron 1464 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 Inspiron 1564 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     (Dell Inspiron 1764 Battery)     .

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. A database-driven system is one solution, and is being incorporated into some designs of charging kiosks      (Dell Studio 1450 Battery)  .

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. 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    (Dell Studio 1457 Battery)   .

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.

China and other countries are making a national standard on mobile phone chargers using the USB standard  (Dell Latitude D610 Battery)   .

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.On October 22, 2009, the International Telecommunication Union announced a standard for a universal charger for mobile handsets (Micro-USB)     (Toshiba NB100 Battery) .

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     (Toshiba Satellite M65 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     (Toshiba Satellite M60 battery)     .

Public EV charging[17] 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 Latitude D830 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 Latitude D620 Battery)   .
  • This allows for an increased charge current and reduced charging times. The battery has a maximum current rating that cannot be exceeded   (Dell Inspiron Mini 10 Battery)   .
  • Non-isolated: the battery charger has a direct electrical connection to the A/C outlet's wiring. Non-isolated chargers cannot be using in parallel   (Sony VGN-FW11S Battery)   .
  • Power Factor Correction (PFC) chargers can more closely approach the maximum current the plug can deliver, shortening charging time      (Sony VGN-FW11M Battery) .

Charge stations

Main article: Charging station

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 (Sony VGN-FW139E/H 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 Latitude E5400 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 Latitude E4200 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 A840 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. What practices are best depend on the type of battery  (Dell Inspiron 300M 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: nickel alloy cells can be charged at any point throughout their discharge cycle ?– they do not have to be fully discharged     (Dell Studio 1737 battery) .

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   (Dell Inspiron E1505 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 RM791 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 XPS M1530 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  (Dell XPS M2010 battery)   .

These batteries employ a sulfuric acid electrolyte and can generally be charged and discharged without exhibiting memory effect, 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    (Dell Vostro 1000 battery)     .

When discharged, these batteries should be recharged immediately in order to prevent sulfation. 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      (Acer Aspire One battery)  .

Recharging alkaline batteries is a way of renewing expended alkaline batteries. The term 'battery' here also means 'cell'.

Some alkaline batteries are designed to be recharged, but the most common types are not (i.e. they are 'primary' batteries) and it may be dangerous to attempt to recharge them     (Toshiba Satellite P10 Battery)   .

It is important to read the manufacturer's data about any battery before attempting to recharge it. Most manufacturers of primary batteries clearly forbid recharging. Despite this advice, some alkaline batteries have successfully been recharged. Sometimes chargers can be found on the open market which are claimed to recharge primary alkaline batteries     (SONY VGN-FZ210CE Battery) .

The performance of a recharged primary battery can be unpredictable.

Introduction

Ordinary alkaline batteries can be charged with a pulsed charger of a frequency between 40 and 200 Hz, with an 80% duty cycle. Pulsed charging appears to reduce the risk of electrolyte (usuallyKOH) leakage   (Dell Precision M70 Battery)  .

The charging current is usually very low to avoid rapid production of gasses which can rupture the cell. Cells that have leaked electrolyte are both a safety hazard and unsuitable for reuse.

Safety

Attempting to recharge a discharged alkaline battery can cause the production of gas within the canister    (Dell KM958 battery) .

As the canister is normally sealed, very high pressures can be created within it. This can rupture the seal, resulting in leakage of the contents (for example aqueous potassium hydroxide and identifiable in more severe cases as a hissing sound from the battery), or even an explosion     (Toshiba Satellite L305 Battery)   .

Warning signs include bulging of the ends of the battery. Recharging a battery produces heat within the battery. Sometimes the heat can be excessive, with the attendant risks of fire, explosion and/or injury.

Potassium hydroxide is corrosive and may cause injury, especially to the eyes and skin or corrode the battery contacts in the equipment    (Toshiba Satellite T4900 Battery)   .

Eye protection is always advisable when recharging any batteries.

Some materials used in batteries are damaging to the environment, so no batteries of any kind should be disposed of in ordinary garbage which may for example reach landfill     (Toshiba PA3399U-2BRS battery)   .

In some jurisdictions it is illegal to dispose of batteries in ordinary waste streams, and free collection points for used 'portable' batteries are often available wherever batteries are on sale to the public.

How It Works

As an alkaline battery is discharged, chemicals inside the battery react to create an electric current  (Toshiba Satellite A200 Battery) .

However, once the chemicals have reached chemical equilibrium, the reaction stops, and the battery is "dead." By driving a current through the battery in the reverse direction, the equilibrium can be shifted backwards towards the original reactants. Different batteries rely on different chemical reactions     (Toshiba Satellite 1200 Battery)   .

Some reactions are readily reversible, some are not. The reactions used in most alkaline batteries fall into the latter category.

Alkaline batteries and alkaline cells (a battery being a collection of multiple cells) are a type of disposable battery or rechargeable battery dependent upon the reaction between zinc and manganese dioxide (Zn/MnO2)    (Toshiba Satellite M300 Battery) .

Compared with zinc-carbon batteries of the Leclanché or zinc chloride types, while all produce approximately 1.5 volts per cell, alkaline batteries have a higherenergy density and longer shelf-life. Compared with silver-oxide batteries, which alkalines commonly compete against in button cells, they have lower energy density and shorter lifetimes but lower cost    WD passport essential (500GB/640GB) .

The alkaline battery gets its name because it has an alkaline electrolyte of potassium hydroxide, instead of the acidic ammonium chloride or zinc chloride electrolyte of the zinc-carbon batteries which are offered in the same nominal voltages and physical size. Other battery systems also use alkaline electrolytes, but they use different active materials for the electrodes  WD passport essential (250GB/320GB) .

History

The alkaline battery was invented by Canadian engineer Lewis Urry in the 1950s while working for the Eveready Battery company.

Chemistry

In an alkaline battery, the anode (negative terminal) is made of zinc powder (which allows more surface area for increased rate of reaction therefore increased electron flow) and the cathode (positive terminal) is composed of manganese dioxide  WD  passport essential SE (750GB/1TB)      .

Alkaline batteries are comparable to zinc-carbon batteries, but the difference is that alkaline batteries use potassium hydroxide (KOH) as an electrolyte(mixed with the powdered zinc) rather than ammonium chloride or zinc chloride.

Section through an alkaline battery

The half-reactions are    WD  passport elite(250GB/320GB) :

Zn (s) + 2OH? (aq) ? ZnO (s) + H2O (l) + 2e?

2MnO2 (s) + H2O (l) + 2e? ?Mn2O3 (s) + 2OH? (aq)

Capacity

Several sizes of button and coin cells. Some are alkaline and others aresilver oxide. 2 9v batteries were added as a size comparison. Enlarge to see the button and coin cells’ size code markings     WD passport elite(500GB/640GB) .

Capacity of an alkaline battery is larger than an equal size Leclanché or zinc-chloride cell because the manganese dioxide anode material is purer and denser, and space taken up by internal components such as current collectors is less. An alkaline cell can provide between three and five times as much operating time     WD  passport studio for Mac(320GB/500GB) .

The capacity of an alkaline battery is strongly dependent on the load. An AA-sized alkaline battery might have an effective capacity of 3000 mAh at low drain, but at a load of 1 ampere, which is common for digital cameras, the capacity could be as little as 700 mAh   WD  passport studio for Mac(500GB/640GB) .

The voltage of the battery declines steadily during use, so the total usable capacity depends on the cut-off voltage of the application. Unlike Leclanche cells the alkaline cell delivers about as much capacity on intermittent or continuous light loads. On a heavy load, capacity is reduced on continuous discharge compared with intermittent discharge, but the reduction is less than for Leclanche cellsWD  Elements series(250GB/320GB) .

Voltage

The nominal voltage of a fresh alkaline cell is 1.5 V. Multiple voltages may be achieved with series of cells. The effective zero-load voltage of a non discharged alkaline battery varies from 1.50 to 1.65 V, depending on the chosen manganese dioxide and the contents of zinc oxide in the electrolyte        WD  Elements SE(500GB/640GB) .

The average voltage under load depends on discharge and varies from 1.1 to 1.3 V. The fully discharged cell has a remaining voltage in the range of 0.8 to 1.0 V.

Current

The amount of current an alkaline battery can deliver is roughly proportional to its physical size    WD Elements SE(750GB/1TB) .

This is a result of decreasing internal resistance as the internal surface area of the cell increases. A general rule of thumb is that an AA alkaline battery can deliver 700 mA without any significant heating. Larger cells, such as C and D cells, can deliver more current. Applications requiring high currents of several amperes, such as high powered flashlights and portable stereos, will require D-sized cells to handle the increased load      WD  Elements desktop(500GB/640GB) .

Construction

Alkaline batteries are manufactured in standardized cylindrical forms interchangeable with zinc-carbon batteries, and in button forms. Several individual cells may be interconnected to form a true "battery", such as those sold for use with flashlights and the 9 volt transistor-radio battery      WD  Elements desktop(750GB/1TB) .

A cylindrical cell is contained in a drawn steel can, which is the cathode current collector. The cathode mixture is a compressed paste of manganese dioxide with carbon powder added for increased conductivity. The paste may be pressed into the can or deposited as pre-molded rings    WD  Elements desktop(1.5 TB/2TB) .

The hollow center of the cathode is lined with a separator, which prevents mixing of the anode and cathode materials and short-circuiting of the cell. The separator is made of a non-woven layer of cellulose or a synthetic polymer. The separator must conduct ions and remain stable in the highly alkaline electrolyte solution    WD  passport essential SE (750GB/1TB)--USB 3.0) .

The anode is composed of a dispersion of zinc powder in a gel containing the potassium hydroxide electrolyte. To prevent gassing of the cell at the end of its life, more manganese dioxide is used than required to react with all the zinc.

When describing standard AAA, AA, C, sub-C and D size cells, the anode is connected to the flat end while the cathode is connected to the end with the raised button     WD  passport essential (500GB/640GB) .

Recharging of alkaline batteries

Some alkaline batteries are designed to be recharged (see rechargeable alkaline battery), but most are not. Attempts to recharge may cause rupture, or the leaking of hazardous liquids which will corrode the equipment      WD  passport for Mac(320GB/500GB) .

Leaks

Over time, alkaline batteries are prone to leaking potassium hydroxide, a caustic agent that can cause respiratory, eye and skin irritation      WD  passport for Mac(640GB/1TB) .

This can be avoided by not attempting to recharge disposable alkaline cells, not mixing different battery types in the same device, replacing all of the batteries at the same time, storing in a dry place, and removing batteries for storage of devices   My book essential 4 generation  (640GB/1TB) .

Once a leak has formed due to corrosive penetration of the outer steel shell, potassium hydroxide forms a feathery crystalline structure that grows and spreads out from the battery over time, following up metal electrodes to circuit boards where it commences oxidation of copper traces and other components, leading to permanent circuitry damage   WD  My book essential 4 generation( 1.5TB/2TB) .

The leaking crystalline growths can also emerge from seams around battery covers to form a furry coating outside the device, that then damages objects in contact with the leaking device such as varnish on wood shelves, and then oxidation and graying of the wood itself      WD  My book elite( 1TB/1.5TB) .

Disposal

When introduced in the 1960s, alkaline batteries contained a small amount of mercury amalgam to control side reactions at the zinc cathode. Improvements in the purity and consistency of materials have allowed manufacturers to reduce the mercury content in modern cells    WD  My book studio(1TB/2TB) .

Unlike other types of batteries, alkaline batteries are allowed to be disposed of as regular domestic waste in some locations. This, however, may not be environmentally friendly, as some alkaline batteries produced before 1996 contain mercury      WD  My book essential 4 generation( 1.5TB/2TB) .

For example the state of California has deemed all batteries as hazardous waste when discarded, and has banned the disposal of batteries with other domestic waste. In the US, one company shreds and separates the battery case metals, manganese and zinc  WD  My book elite(640GB/2TB) .

Another company mixes batteries in as a feedstock in steel making furnaces, to make low-grade steel such as rebar; the zinc fumes are recovered separately. In Europe battery disposal is controlled by the WEEE regulations, and as such alkaline batteries must not be thrown in with domestic waste       Seagate  expansion portable (320GB/500GB) .

They should be disposed through local recycling stations/waste dumps. In the EU most stores that sell batteries are required by law to accept old batteries for recycling  Seagate  expansion (1.5TB/2TB) .

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