lead-acid batteries was discovered in 1859 by the French physicist Gaston PlantÃÆ'Â © and is the oldest rechargeable battery type. Despite having a very low energy-to-weight ratio and low energy-to-volume ratio, its ability to supply high surge currents means that the cell has a relatively large strength to weight ratio. These features, along with low cost, make them attractive for use in motor vehicles to provide the high currents required by the car starter motor.
Because the price is cheaper compared to newer technologies, lead-acid batteries are widely used even when surge currents are not important and other designs can provide higher energy densities. Large-format lead-acid designs are widely used for backup storage of power supplies in cell phone towers, high availability settings such as hospitals, and stand-alone power systems. For this role, standard cell modification versions can be used to increase storage time and reduce maintenance requirements. Gel-cells and absorbed glass mats are common batteries in this role, collectively known as VRLA (valve-regulated lead-acid) batteries.
In 1999 sales of lead-acid batteries accounted for 40-45% of the value of batteries sold worldwide except China and Russia, and the manufacturing market value was around $ 15 billion.
Video Lead-acid battery
Histori
French scientist Nicolas Gautherot observed in 1801 that cables that had been used for his own electrolysis experiments would provide a small amount of "secondary" currents after the main battery had been disconnected. In 1859, a lead-acid battery from Gaston PlantÃÆ'Â © was the first rechargeable battery by passing a backflow through it. PlantÃÆ'Â's first model consists of two tin sheets separated by a rubber strip and rolled into a spiral. His battery was first used to light the lights on the train car while stopping at a station. In 1881, Camille Alphonse Faure created an improved version consisting of a major network grid, in which the lead oxide paste was pressed, forming a slab. This design is easier to produce in bulk. The earliest manufacturer (from 1886) lead-acid battery is Henri Tudor.
Using gel electrolyte as a liquid substitute allows the battery to be used in various positions without leakage. The gel electrolyte battery for each position date from the 1930s, and even in the late 1920s portable radio suitcase kit allows vertical or horizontal (but not reversed) cells due to the valve design (see Third Edition Constructor Wireless Constructor by Frederick James Camm). In the 1970s, a regulated-lead (acid-sealed) lead-acid battery was developed, including a type of modern absorbable glass mat, enabling operations in any position.
Maps Lead-acid battery
Electrochemical
Debit
In good condition both positive and negative plates become lead (II) sulfate ( PbSO
4 ), and the electrolyte loses a lot of its soluble sulfuric acid and becomes primarily water. The exhaust process is driven by the conduction of electrons from the negative plate back to the cell on the positive plate in the external circuit.
- Negative plate reactions
- Pb (s) HSO -
4 (aq) -> PbSO < span>
4 (s) H < span> (aq) 2e - The release of two electrons performs giving a net negative charge electrode
As the electrons accumulate, they create an electric field that attracts hydrogen ions and expels sulfate ions, leading to a double layer near the surface. The hydrogen ion filters the charged electrode from a solution which limits the reaction further unless the charge is allowed to flow out of the electrode.
- Positive plate reactions
- PbO
2 ( s) HSO - 4 (aq) 3 H (aq) 2e - -> PbSO < br> H
2 O (l)
Reaksi total dapat ditulis sebagai
- Pb (s) PbO
2 (s) 2 H
2 SO
4 (aq) -> 2 PbSO
4 (s) 2 H
2 O (l)
The molecular mass of the reactants is 642.6 g/mol, so theoretically a cell can produce two remote charges (192,971 coulombs) of 642.6 g of reactant, or 83.4 ampere-hours per kilogram (or 13.9 ampere-hours per kilogram for 12 volt battery). For a 2-volt cell, this reaches 167 watt-hours per kilogram of reactant, but the acid-acid cell in practice only gives 30-40 watt-hours per kilogram of battery, due to water mass and other constituent parts...
Charging
In a fully charged state, negative plates consist of lead, lead and lead dioxide, with concentrated sulfuric acid electrolytes.
Overcharging with high charging voltage produces oxygen and hydrogen gas with electrolysis of water, which is lost to the cell. The design of several types of lead-acid batteries allows electrolyte levels to be checked and recharged with water that has been lost.
Because the freezing point of electrolyte depression, due to the discharge of the battery and the sulfuric acid concentration decreases, the electrolyte is more likely to freeze during the winter when it runs out.
ion movement
During discharge, H the negative plate moves into the electrolyte solution and is then consumed into the positive plate, while HSO -
4 is consumed on both plates. The reverse occurs during charging. This movement can either be electrically driven protons or Grotthuss mechanisms, or through diffusion through the media, or by a liquid medium electrolyte stream. Because the density is greater when the concentration of sulfuric acid is higher, the liquid will tend to circulate by convection. Therefore, the liquid-medium cells tend to rapidly out and quickly fill more efficiently than similar gel cells.
Measuring fill level
Because electrolytes take part in charge-discharge reactions, these batteries have one major advantage over other chemicals. It is relatively simple to determine the state of charge by simply measuring the electrolyte type of gravity; Specific gravity falls when the battery is released. Some battery designs include simple hydrometers using colored floating balls with different densities. When used in diesel-electric submarines, specific gravity is regularly measured and written on the board in the control room to show how much longer the ship can remain submerged.
Battery open-circuit voltage can also be used to measure the state of charge. If connections to individual cells are accessible, then the charge status of each cell can be determined that can provide guidance on the overall health of the battery, otherwise the overall battery voltage can be assessed.
Note that there is no technique that gives an indication of charge capacity, just the level of charging. The rechargeable battery charge capacity will decrease with age and use, which means that it may no longer be in accordance with the intended purpose even when fully charged in nominal. Other tests, usually involving current draining, are used to determine the residual charge capacity of the battery.
Voltage for general use
IUoU battery charging is a three-stage charging procedure for lead-acid batteries. The theoretical voltage of the lead-acid battery is 2Ã,V for each cell. For a single cell, the voltage can range from 1.8 V loaded at full discharge, up to 2.10 V on open circuit with full charge. Floating voltage varies depending on the type of battery, ie flood cell, gel electrolyte, absorbed glass mat (AGM), and ranges from 1.8 V to 2.27 V. The voltage equation, and the charging voltage for sulfate cells, may range from 2 , 67 V to nearly 3Ã, V. (only until the charge current flows) The specific value for the given battery depends on the design and manufacturer's recommendations, and is usually provided at an initial temperature of 20Ã, ° C (68Ã,  ° F), requiring adjustment for ambient conditions.
Construction
Plates
Lead-acid cells can be demonstrated using tin plate sheets for two electrodes. However, such constructions only generate about one ampere for the postcard-sized plates, and only a few minutes.
Gaston PlantÃÆ'Â © finds a way to provide a much larger effective surface area. In the PlantÃÆ'Â © design, positive and negative plates are formed from two lead spiral foils, separated with a sheet of cloth and rolled. The cells initially have a low capacity, so a slow "forming" process is required to corrode lead foil, creating lead dioxide in the plate and drying it to increase the surface area. Initially this process uses electricity from the primary battery; when the generator became available after 1870, the cost of battery production greatly decreased. Plate PlantÃÆ'Â Â © is still used in some stationary applications, where the plates are mechanically grooved to increase its surface area.
In 1880, Camille Alphonse Faure patented the method of tin lattice coating (which serves as the current conductor) with lead oxide paste, sulfuric acid and water, followed by a preservation phase in which the plates were exposed to a soft, high heat. moisture environment. The curing process causes the paste to turn into a lead sulfate mixture attached to the tin plate. Then, during the initial charge of the battery (called "formation") the paste preserved on the plate is converted into an electrochemical active ingredient ("active mass"). The Faure process significantly reduces the time and cost to produce lead-acid batteries, and provides a substantial increase in capacity compared to PlantÃÆ'® batteries. The Faure method is still used today, with only an additional increase to insert the composition, curing (which is still done with steam, but is now a very tightly controlled process), and the structure and composition of the grid used by the paste.
The grid developed by Faure is pure lead with a connecting rod from tin at a right angle. Instead, the grid is currently structured to increase mechanical strength and increase current flow. In addition to the different grid patterns (ideally, all the points on the plate are much the same from the electrical conductors), the modern process also applies one or two thin fiber-glass strips on top of the grid to distribute the weight more evenly. And while Faure has been using pure lead for his grid, within a year (1881) it has been replaced by an antimony-tin (8-12%) alloy to provide additional stiffness structures. However, high antimony grids have higher evolution of hydrogen (which also accelerates with battery life), and thus greater outgassing and higher maintenance costs. These problems were identified by U. B. Thomas and W. E. Haring at Bell Labs in the 1930s and ultimately led to the development of a tin calcium grid alloy in 1935 for standby battery power on the US telephone network. Related research led to the development of a combined lead-selenium network in Europe a few years later. Both lead-calcium and lead-selenium alloys still add antimony, albeit in much smaller amounts than older high-rise antimony networks: the tin-calcium tissue has 4-6% antimony while the selenium-tin cells have 1-2%. These metallurgical improvements provide strength to the lattice, allowing it to carry more weight, the more active materials, so that the plates can be thicker, which in turn contributes to battery life as there is more material available to be released before the battery becomes can be used. High antimony alloy grids are still used in batteries intended for frequent cycling, for example in a start-motor application where the frequent expansion/contraction of the plates needs to be compensated, but where outgassing is not significant because the charging current remains low. Since the 1950s, batteries designed for rare bike applications (eg, standby battery power) have increasingly a network of lead-calcium or lead-selenium alloys because these have less hydrogen evolution and thus lower maintenance costs. The louvers of lead calcium alloy are less expensive to produce (cells have lower initial cost), and have a lower self-release rate, and lower watering requirements, but have slightly worse conductivity, are mechanically weaker ( and therefore require more antimony to compensate), and are particularly susceptible to corrosion (and thus shorter lives) than cells with lead-selenium alloy grids.
The open circuit effect is also known as the antimony free effect.
Modern pastes contain black carbon, blanc fixe (barium sulfate) and lignosulfonate. Blanc fixe acts as a seed crystal for lead-to-lead sulfate reactions. The blanc fixe should be fully dispersed in the paste to be effective. Lignosulphonates prevent negative plates from forming solid mass during the expenditure cycle, while allowing for the formation of long dendrites such as needles. Long crystals have more surface area and are easily converted back to initial conditions during charging. Black carbon negates the inhibitory effect of formation caused by lignosulfonate. Sulfonated naphthalene condensate dispersant is a more effective expander than lignosulfonate and accelerates the formation. This dispersion increases the dispersion of barium sulfate in the paste, reduces the hydroset time, produces a more resistant to damage plate, reduces fine lead particles and thereby improves handling and insertion characteristics. This extends battery life by increasing the charge-end voltage. Sulfonated naphthalene requires about one-third to one-half the amount of lignosulfonate and is stable to a higher temperature.
Once dried, the plates are stacked with the appropriate separator and put in a cell container. Alternate plates then form a positive and negative electrode alternately, and inside the cell are then connected to each other (negative to negative, positive to positive) in parallel. The dividers block the plates touching each other, which otherwise form short circuits. In submerged cells and gels, the separator is an isolated rail or stud, previously of glass or ceramic, and now of plastic. In AGM cells, the separator is the glass mat itself, and the plate rack with separator is squeezed together before it is inserted into the cell; once inside the cell, the glass mat enlarges slightly, effectively locking the plate in place. In multi-cell batteries, cells are then connected to each other in series, either through connectors through cell walls, or by bridges over cell walls. All intra-cell and inter-cell connections are of the same lead alloy as used in the grid. This is necessary to prevent galvanic corrosion.
Called "cycle in" batteries use different geometry for their positive electrode. In this geometry, the positive electrode is not a flat plate but a row of tubes or a tin oxide tube is coupled side by side (hence the term "tubular" or "cylinder" battery for this geometry). The advantage of this geometry is the increase in surface area in contact with the electrolyte, which in turn allows higher discharge/charge flow than flat plate cells with equal volume and depth of charge. Tubular electrode cells show higher power density than flat plate cells. This makes the tubular/cylindrical geometry plate particularly suitable for high current applications with weight limits/storage space, such as for forklifts or for starting a marine diesel engine. However, since the tubes/cylinders have less active materials in the same volume, they also have lower energy density than flat plate cells. And, less active materials in the electrodes also mean they have less material available to be released before the cells become unusable. Tubular/cylindrical electrodes are also more complicated to produce uniformly, which tends to make them more expensive than flat plate cells. This trade-off limits the range of applications where tubular/cylindrical batteries mean for situations where there is not enough space to install higher-capacity flat-plate units (and thus larger).
Approximately 60% of the weight of the automotive lead-acid battery of the automotive type, rated at about 60 AÃ,h (8.7 kg of 14.5 kg battery) is lead or internal parts made of lead; the balance is the electrolyte, separator, and casing.
Separator
The separator between the positive and negative plates prevents short-circuit through physical contact, mostly through dendrites ("trees"), but also through the shedding of the active ingredient. The separator allows the flow of ions between the electro-chemical cell plates to form a closed circuit. Wood, rubber, fiber glass mats, cellulose, and PVC or polyethylene plastic have been used to make separators. Wood is the original choice, but deteriorates in acidic electrolytes. Rubber separators are stable in battery acid and provide valuable electrochemical advantages that other materials can not.
Effective separator must have a number of mechanical properties; such as permeability, porosity, pore size distribution, specific surface area, design and mechanical strength, electrical resistance, ionic conductivity, and chemical compatibility with electrolytes. In the service, the separator must have good resistance to acid and oxidation. The separation area should be slightly larger than the plate area to prevent material shorting between the plates. The separator must remain stable during the battery operating temperature range.
The absorbed glass mat (GMS)
In the design of absorbed glass mats, or short-term GMS, the separator between the plates is replaced with a glass fiber mat that is immersed in an electrolyte. There is only enough electrolyte on the mat to keep it wet, and if the battery is hollowed out, the electrolyte will not flow out of the mat. In principle the purpose of replacing the liquid electrolyte in a battery flooded with semi-saturated fiberglass mat is to substantially increase gas transport through the separator; Hydrogen or Oxygen Gas is produced during overcharge or charge (if overcurrent charge) can freely pass through a glass mat and reduce or oxidize the opposite plate in sequence. In cells that flood gas bubbles float to the top of the battery and disappear into the atmosphere. The mechanism for the gas produced to recombine and the added benefit of a semi-saturated cell that does not provide significant electrolyte leakage on the physical prick of the battery casing allows the battery to be completely sealed, which makes it useful in portable devices and similar roles, in addition to the battery can be mounted in any orientation, although if mounted upside down the acid can be blown out through excessive ventilation.
To reduce the rate of water loss, calcium is mixed with the plates, but gas buildup remains a problem when the battery is filled or discharged. To prevent over-pressurization of battery cases, AGM batteries include one-way blow-off valves, and are often known as "valve regulated lead-acid", or VRLA, designs.
Another advantage to GMS design is that the electrolyte becomes a separator, and is mechanically strong. This allows the pile of dishes to be compressed together in the battery shell, slightly increasing the energy density compared to the liquid version or gel. AGM batteries often exhibit characteristics "protruding" in their shells when constructed in the form of common rectangles, due to the expansion of positive plates.
The mattress also prevents vertical movement of the electrolyte inside the battery. When normal wet cells are stored in a depleted state, heavier acidic molecules tend to settle at the bottom of the battery, causing stratified electrolytes. When the battery is in use, most of the current flows only in this area, and the bottom of the plate tends to run out quickly. This is one of the reasons why a conventional car battery can be damaged by letting it be stored for a long time and then used and refilled. Mats significantly prevent this stratification, eliminating the need to shake the battery periodically, boil it, or run a "charge of equity" through them to mix the electrolyte. Stratification also causes the top layer of the battery to be almost completely water, which can freeze in cold weather, AGM is significantly less susceptible to damage due to the use of low temperatures.
While AGM cells do not allow watering (usually impossible to add water without drilling holes in the battery), their recombination process is essentially limited by ordinary chemical processes. Hydrogen gas will even diffuse through the plastic box itself. Some have found it advantageous to add water to an AGM battery, but this should be done slowly to allow water to mix through diffusion throughout the battery. When the lead-acid battery loses water, its acid concentration increases the rate of plate corrosion significantly. The AGM cell already has a high acid content in an effort to decrease the water loss rate and increase the standby voltage, and this brings a shorter life than the lead flooded antimony batteries. If the open circuit voltage of the AGM cell is significantly higher than 2.093 volts, or 12.56Ã,V for a 12Ã,V battery, then it has a higher acid content than the flooded cell; while this is normal for AGM batteries, is not desirable for long life.
AGM cells that are intentionally or inadvertently filled will show a higher open circuit voltage corresponding to water loss (and increased acid concentration). An overcharge amp will free 0.335 grams of water; some of these released hydrogen and oxygen will recombine, but not all of them.
Gel electrolyte
During the 1970s, researchers developed a sealed version or "gel battery", which mixed the silica gel agent into the electrolyte (silica-gel acid-based batteries used in portable radios from the early 1930s were not fully sealed). This transforms the liquid interior from the cell into a semi-rigid paste, giving many of the same benefits from the GMS. Such designs are even less susceptible to evaporation and are often used in situations where little or no regular maintenance is possible. The gel cells also have a lower freezing point and a higher boiling point than the liquid electrolyte used in conventional wet cells and AGM, which makes it suitable for use in extreme conditions.
The only downside to the gel design is the gel prevents the rapid movement of ions in the electrolyte, which reduces carrier mobility and thus improves current capability. For this reason, gel cells are most commonly found in energy storage applications such as off-grid systems.
"Free maintenance" , "sealed" and "VRLA"
Both gel design and AGM are sealed, require no watering, can be used in any orientation, and use valves for gas blowoff. For this reason, both designs can be called maintenance-free, sealed and VRLA. However, it is very common to find resources that state that these terms refer to one or another of these designs, in particular.
Apps
The majority of the world's lead-acid batteries are ranging cars, lights and ignition (SLI) batteries, with an estimated 320 million units shipped in 1999. In 1992 about 3 million tons of lead was used in battery manufacturing.
Battery stand-by (stationary) wet cells designed for disposal are generally used in large backup power supplies for telephone and computer centers, grid energy storage, and off-grid household power systems. Lead-acid batteries are used in emergency lighting and for power pumps in case of power failure.
The traction battery (propulsion) is used in golf carts and other battery electric vehicles. Large lead-acid batteries are also used to power electric motors in diesel-electric submarines (conventional) when submerged, and used as emergency personnel on nuclear submarines as well. The acid-regulated lead acid batteries can not shed their electrolytes. They are used in backup power supplies for alarms and smaller computer systems (especially in uninterruptible power supplies UPS) and for electric scooters, electric wheelchairs, electric bicycles, marine applications, battery electric vehicles or micro hybrid vehicles, and motorcycle.
The lead-acid battery is used to supply the filament voltage (heater), with 2 V common in the receiver of the initial vacuum tube (valve).
Portable batteries for head lamps miner hat usually have two or three cells.
Cycles
Battery start
Lead-acid batteries designed to start automotive engines are not designed for deep disposal. They have a large number of thin plates designed for maximum surface area, and therefore maximum current output, which can be easily damaged by deep discharge. Repeated emptying will result in a loss of capacity and ultimately premature failure, because electrodes are destroyed by mechanical stresses arising from cycling. Starting a battery stored on a continuous floating charge will experience corrosion on the electrode which will also lead to premature failure. Therefore, the starting battery must keep the circuit open but filled regularly (at least once every two weeks) to prevent sulfation.
Battery start has a lighter weight than an inner cycle battery of the same size, because thinner and lighter cell plates do not extend to the bottom of the battery case. This allows loose loose material to fall off the plate and collect at the bottom of the cell, extending battery life. If the loose debris is quite looming, it may touch the bottom of the plate and cause cell failure, resulting in loss of voltage and battery capacity.
Battery in-cycle
Specially designed deep-cycle cells are much less susceptible to degradation due to cycling, and are required for applications where batteries regularly run out, such as photovoltaic systems, electric vehicles (forklifts, golf carts, electric and other cars) and power supplies never interrupted. This battery has a thicker plate that can provide less peak current , but can withstand frequent usage.
Some batteries are designed as a compromise between the starter (high current) and the inner cycle. They can be dumped to a greater extent than automotive batteries, but less of an inner cycle battery. They can be referred to as "sea/motorcycle" batteries, or "recreational batteries".
Fast and slow charging and debiting
The capacity of lead-acid batteries is not a fixed quantity but varies depending on how quickly it runs out. The empirical relationship between the level of discharge and capacity is known as Peukert's law.
When the battery is charged or discharged, only the reacting chemicals, which are at the interface between the electrode and the electrolyte, are initially affected. With time, the charge stored in chemicals in the interface, often called "interface cost" or "surface charge", is spread by the diffusion of these chemicals throughout the volume of the active ingredient.
Consider batteries that have completely discharged (such as occur when leaving a car light at night, a current draw of about 6 amps). If then given a quick charge of just a few minutes, the battery plate just fills up near the interface between the plate and the electrolyte. In this case the battery voltage may rise to a value near the charger's voltage; this causes the charging current to decrease significantly. After a few hours, the cost of this interface will spread to the volume of the electrode and electrolyte; this causes the interface charge so low that it may not be enough to start the car. As long as the charging voltage remains below the gas voltage (about 14.4 volts in normal lead-acid batteries), battery failure is not possible, and in time the battery has to return to a nominal charged state. Valid regulated (VRLA)
In the regulated lead acid valve (VRLA), the hydrogen and oxygen produced in the cell are largely reunited into the water. Leakage is minimal, although some electrolytes can still pass if recombination can not follow gas evolution. Because VRLA batteries do not require (and make it impossible) routine electrolyte level checks, they have been called care-free batteries . However, this is somewhat mistaken. VRLA cells do require treatment. When the electrolyte is lost, the VRLA cells "dry out" and lose capacity. This can be detected by taking a regular internal resistance, measurement of conductance or impedance. Regular testing reveals whether more involved testing and maintenance is required. Recent treatment procedures have been developed that allow "rehydration", often recovering significant lost capacity.
This type of VRLA became popular on motorcycles around 1983, because acid electrolytes were absorbed into the separator, so it could not spill. Separators also help them withstand vibrations better. They are also popular in stationary applications such as telecom sites, due to their small footprint and installation flexibility.
The electrical characteristics of VRLA batteries are somewhat different from wet-cell lead-lead batteries, requiring caution in charging and discharging.
Sulfation and desulfation
The lead-acid battery loses the ability to receive charge when disposed of for too long due to sulfation, lead sulfate crystallization. They generate electricity through multiple chemical sulfate reactions. Lead and lead dioxide, the active ingredient on the battery plate, reacts with sulfuric acid in the electrolyte to form lead sulfate. The lead sulfate is formed in a finely divided amorphous state, and easily returns to lead, lead dioxide and sulfuric acid when the battery recharges. When the battery cycle passes through various discharges and charges, some lead sulfates do not recombine into the electrolyte and slowly convert to a stable crystalline form that is no longer soluble in charging. Thus, not all leads are returned to the battery plate, and the amount of usable active material needed for electricity generation decreases over time.
Sulfation occurs in lead-acid batteries when they experience insufficient charging during normal operation. It inhibits charging; the sulphate deposit eventually expands, breaks the plate and damages the battery. Finally so many areas of the battery plate can not supply the current whose battery capacity is greatly reduced. In addition, the sulphate part (lead sulfate) is not returned to the electrolyte as sulfuric acid. It is believed that large crystals physically block the electrolyte from entering the pores of the plates. Sulfation can be avoided if the battery is fully charged immediately after the discharge cycle. The white layer on the plate can be visible (in the battery with a clear case, or after disassembling the battery). Sulfurized batteries show high internal resistance and can only produce a fraction of normal discharge currents. Sulfation also affects the charge cycle, resulting in longer charging times, less efficient and incomplete charging, and higher battery temperatures.
The SLI battery (start, lighting, ignition, ie car battery) is severely damaged because the vehicle is not normally used for a relatively long time. Deep cycles and battery motive power are subject to controlled overcharging on a regular basis, eventually failing due to corrosion of the plate grid positively rather than sulfation.
There is no known and independently verified way to reverse sulfation. There are commercial products that claim to achieve desulfasi through various techniques (such as charging pulses), but no peer-reviewed publications verify their claims. The prevention of toxins remains the best course of action, by regularly filling up the full lead-acid battery.
Stratification
Typical lead-acid batteries contain mixtures with various concentrations of water and acids. Sulfuric acid has a higher density than water, which causes the acid to form on the plate during charging to flow down and collect at the bottom of the battery. Eventually the mixture will again reach a uniform composition with diffusion, but this is a very slow process. Repeated partial filling and usage cycle will increase electrolyte stratification, reducing battery capacity and performance due to lack of acid at the upper limit of plate activation. Stratification also increases corrosion on the top of the plate and sulfation at the bottom.
Excessive filling periodically produces a gas reaction product on the plate, causing a convection current that mixes the electrolyte and completes the stratification. The electrolytic stirring technique will have the same effect. Batteries in moving vehicles are also subject to sloshing and splashes in cells, as the vehicle accelerates, brakes, and rotates.
Risk of explosion
Overcharging causes electrolysis, emitting hydrogen and oxygen. This process is known as "gassing". Wet cells have open ventilation to release any gas produced, and VRLA batteries depend on valves that are attached to each cell. Catalytic lids are available for flooded cells to recombine hydrogen and oxygen. VRLA cells usually reintegrate hydrogen and oxygen produced inside cells, but malfunctions or overheating can cause gas to accumulate. If this happens (for example, on overcharging), the valve emits gas and normalizes the pressure, generating a distinctive acidic odor. However, the valves can fail, as if dirt and debris build up, allowing pressure to build.
The accumulation of hydrogen and oxygen sometimes burns in the internal explosion. The explosive force can cause the battery casing to explode, or cause the top to fly, spraying acid and clogging fragments. Explosions in one cell can ignite a mixture of flammable gases in the remaining cells. Similarly, in poorly ventilated areas, connecting or disconnecting closed circuit (such as load or charger) to battery terminals can also cause sparks and explosions, if any gas is released from the cell.
Individual cells inside the battery can also experience a short circuit, causing an explosion.
VRLA battery cells usually swell when internal pressure rises. Deformation varies from cell to cell, and is larger at the tip where the wall is not supported by other cells. Batteries that are over pressurized must be carefully isolated and discarded. Personnel working near batteries at risk of explosion should protect their eyes and get skin from burns by spraying acids and flames by wearing face shirts, dresses and gloves. Using goggles instead of face protectors sacrifices safety by letting the face be exposed to the possibility of acid, casing or battery parts, and heat from potential explosions.
Environment
Environmental issues
According to a 2003 report entitled "Getting the Lead Out", by the Environmental Defense and Ecological Center of Ann Arbor, Michigan, the vehicle's battery on the road contains about 2,600,000 metric tons (2,600,000 tonnes long; 2,900,000 tons) of lead. Some lead compounds are highly toxic. Long-term exposure to even a small amount of these compounds can cause brain and kidney damage, hearing loss, and learning problems in children. The automotive industry uses more than 1,000,000 metric tons (980,000 tonnes, 1,100,000 short tons) annually, with 90% going to be a conventional lead-acid vehicle battery. Although lead recycling is an established industry, over 40,000 metric tons (39,000 tonnes long, 44,000 short tons) end up in landfills every year. According to the Federal Inventory Release, another 70,000 metric tons (69,000 ton long, 77,000 short tons) are released in mining and major manufacturing processes.
Efforts are underway to develop alternatives (especially for automotive use) due to concerns about the improper environmental consequences of disposal and tin smelting operations, among other reasons. Alternatives are not possible to replace them for applications such as start engine or power backup system, because the battery, although heavy, is low cost.
Recycling
The recycling of lead acid batteries is one of the most successful recycling programs in the world. In the United States 99% of all lead batteries are recycled between 2009 and 2013. An effective pollution control system is a must to prevent lead emissions. Continuous improvements in battery recycling plants and furnace designs are needed to offset emission standards for lead smelters.
Additive
Chemical additives have been used since lead-acid batteries become commercial goods, to reduce lead sulfate deposits on plates and improve battery conditions when added to the electrolyte from the released lead-acid battery. Such care is rare, if ever, effective.
Two compounds used for the purpose are Epsom and EDTA salts. Epsom salts reduce internal resistance to weak or damaged batteries and allow a small amount of extended life. EDTA can be used to dissolve sulfate deposits from very empty plates. However, this solute is then no longer available to participate in the normal charge/discharge cycle, so that the battery is temporarily revived with EDTA will have a reduced life expectancy. The remaining EDTA in lead-acid cells forms an organic acid that will accelerate the corrosion of tin plates and internal connectors.
The active ingredients change the physical shape during charging/discharging, resulting in growth and distortion of the electrode, and shedding electrode to the electrolyte. After the active ingredients fall out of the plate, it can not be restored to its original position with any chemical treatment. Similarly, internal physical problems such as crack plates, rusted connectors, or damaged separators can not be chemically returned.
Corrosion problem
Corrosion of external metal parts from lead-acid batteries is generated from chemical reactions from battery terminals, lugs and connectors.
Corrosion at the positive terminal is caused by electrolysis, due to the mismatch of the metal alloys used in the manufacture of battery terminals and cable connectors. White corrosion usually causes crystals or zinc sulfate. The aluminum connector corrode the aluminum sulfate. The copper connector produces a blue and white corrosion crystal. The corrosion of battery terminals can be reduced by coating the terminals with petroleum jelly or commercially available products for the purpose.
If the battery is fully charged with water and electrolyte, thermal expansion may force some fluid out of the battery vents to the top of the battery. This solution can then react with tin and other metals in the battery connector and cause corrosion.
Electrolytes can seep from the plastic seal to the lead where the battery terminals pierce the plastic box.
Acidic smoke that evaporates through the ventilation cap, often caused by overfilling, and inadequate battery box ventilation can allow sulfuric acid smoke to build and react with open metal.
Maintenance precautions
Ammonia can neutralize spilled battery acid. Excess ammonia and water evaporate, leaving ammonium sulfate residue. Sodium bicarbonate (baking soda) is also commonly used for this purpose.
Sizing nomenclature
With many possible electrical attributes, the number number nomenclature is used by many battery manufacturers to deliver basic information such as voltage, ampere-hour capacity, and terminal. The format follows a pattern like & lt; mfr & gt; & lt; voltage & gt; & lt; capacity & gt;.
Some vendors add a suffix, indicating terminal type, terminal location, and battery dimension. Batteries for passenger motor vehicles usually use BCI size nomenclature.
See also
References
- General
- Lead Acid Battery Removal (House Strength # 77 June/July 2000) [1]
- Battery Plate Sulfation (MagnaLabs) [2]
- Battery Desulfation [3]
- Lead Acid Battery [4]
- DC supply! (April 2002) [5]
- Some Technical Details on Lead Acid Batteries [6]
External links
- Battery Council International (BCI), a trade organization of lead-acid battery manufacturers.
- Cars and Batteries Cycle Deep Frequently Asked Questions
- Case Study in Environmental Medicine - Lead Toxicity
- Lead Acid Battery Removal (Home Power # 77 June/July 2000)
- Battery Desulfation
Source of the article : Wikipedia
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