VRLA battery

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A valvic acid-led acid ( VRLA batteries ) is sometimes called sealed lead acid ( SLA ) , gel cell , or battery maintenance free . Due to its construction, the VRLA type absorbent glass and absorbent gel (AGM) can be installed in any orientation, and requires no constant maintenance. The term "maintenance free" is the wrong term because VRLA batteries still require regular cleaning and testing functions. They are widely used in large portable electric devices, off-grid power systems and similar roles, where large amounts of storage are required at lower cost than other low-maintenance technologies such as lithium-ion.

There are three main types of VRLA batteries, wet sealed VR cells, AGM, and gels. The gel cells add silica dust to the electrolyte, forming a thick gel like putty. These are sometimes referred to as "silicon batteries". AGM batteries (glass absorbent mats) equipped fiberglass mesh between the battery plate that serves to contain the electrolyte. Both designs offer advantages and disadvantages compared to conventional batteries and sealed VR wet cells, as well as one another.

Video VRLA battery

Basic principles

The lead acid cells consist of two lead plates, which act as electrodes, suspended in an electrolyte consisting of dilute sulfuric acid. VRLA cells have the same chemistry. "Wet cell" type VRLA contains acid in liquid form. In AGM and VRLA's gel type, the electrolyte is immobilized. In the GMS this is done with a fiberglass mat; in gel batteries or "gel cells", electrolytes in gel form such as pastes made by adding silica and other gelling agents to the electrolyte.

When the cell releases, lead and dilute acid undergo chemical reactions that produce lead sulfate and water (see lead-acid batteries for details of chemical reactions). When the cell is then filled, lead sulfate and water are converted back into lead and acid. In all lead-acid battery designs, current charging must be adjusted to match the battery's ability to absorb energy. If the charging current is too large, electrolysis will occur, breaking down the water into hydrogen and oxygen, in addition to the desired conversion of lead sulfate and water to lead, dioxide, lead, and sulfuric acid (as opposed to a disposal process). If these gases are allowed to escape, as in conventional flood cells, the batteries will need water (or electrolyte) added over time. In contrast, VRLA batteries retain the gas generated inside the battery as long as pressure remains at a safe level. Under normal operating conditions, the gas can then recombine within the battery itself, sometimes with the aid of the catalyst, and no additional electrolyte [1] is required. However, if the pressure exceeds the safety limit, the safety valve opens to allow excess gas to escape, and thus regulates the pressure back to a safe level (hence "valve-regulated" in "VRLA").

In a lead-acid battery that floods, the electrolyte liquid is a hazard during delivery and makes it unsuitable for many portable applications. In addition, the need to maintain a water level in a non-sealed battery makes it unsuitable for maintenance-free applications. Electrolytes immobilized in VRLA batteries (AGM and gel types) overcome this problem. In contrast, VRLA cells can not be recharged with water, and any loss of hydrogen can not be easily replaced. To some extent, this can be compensated by too much electrolyte inventory, at the cost of increasing the weight. But the main disadvantage of the VRLA design is that immobilization agents also inhibit chemical reactions that produce current. For this reason, VRLAs have lower peak power ratings than conventional designs. This makes them less useful for roles such as car starter batteries where the current high-current pulse usage pattern (during start) is followed by a long slow recharge cycle. VRLA is mostly found in roles where charging/charging cycles are slower, like power storage applications.

Flood design and VRLA require appropriate ventilation around the battery; both to prevent the hydrogen concentration from building (hydrogen gas is highly flammable), and to ensure that the battery receives adequate cooling.

Maps VRLA battery

Construction

VRLA cells can be made from flat plates similar to conventional flooded lead-acid batteries, or can be made in the form of spiral coils to make cylindrical cells.

The VRLA battery has a pressure relief valve that will activate when the battery starts to build up the hydrogen gas pressure, generally due to recharging. Valve activation enables some gas or electrolyte to be released, reducing the overall capacity of the battery. A rectangular cell may have a valve that is set to operate as low as 1 or 2 psi; spiral round cell, with an external metal container, can have a valve set as high as 40 psi.

The cover cell usually has a gas diffusers built into it which allows a safe deployment of any excess hydrogen that may be formed during excessive prices. They are not permanently sealed, but are set for "maintenance free". They can be oriented in any way, unlike normal lead-acid batteries, which must be kept upright to avoid acid spills and maintain the vertical orientation of the plates. Cells can be operated with horizontal plates ( pancake style), which can improve the lifecycle.

In high overcharge currents, water electrolysis occurs, removing hydrogen and oxygen gas through the battery valve. Care should be taken to prevent short-circuit and fast charging. Constant voltage filling is the usual, most efficient and fastest method of charging VRLA batteries, although other methods can be used. VRLA batteries may be constantly "floating" charged at about 2.35 volts per cell at 25 Ãƒ, Ã‚ Â° C. Some designs can be charged quickly (1 hour) at a high price. Continuous charging at 2.7 V per cell will damage the cell. Excessive current charging at high levels (faster rates than restoring rated capacity in three hours) will exceed the capacity of cells to recombine hydrogen and oxygen.

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History

The first lead-acid gel battery was discovered by Elektrotechnische Fabrik Sonneberg in 1934. The modern gel or VRLA battery was created by Otto Jache of Sonnenschein in 1957. The first AGM cell was Cyclon, patented by Gates Rubber Corporation in 1972 and now produced by Enersys. Cyclones are spiral-wound cells with thin tin foil electrodes. Some manufacturers confiscate technology to apply it in cells with conventional flat plates. In the mid-1980s, two British companies, Chloride and Tungstone, simultaneously introduced 10-year AGM batteries in capacities up to 400 Ah, stimulated by British Telecom's battery specifications to support a new digital exchange. In the same period, Gates acquired another British company, Varley, specializing in aircraft and military batteries. Varley adapted the Cyclon lead foil technology to produce flat plate batteries with exceptional high-level output. It gets approvals for various aircraft including BAe 125 and 146 business jets, Harrier and AV8B derivatives, and some F16 variants as the first alternative to normal NiCd batteries.

Moves to higher AGM battery capacity led by the Absolyte GNB range that extends up to 3900 Ah. The VRLA/AGM technology is now widespread in both stationary and vehicle batteries.

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AGM (Absorbent glass mat)

The AGM battery is different from the submerged lead acid battery in which the electrolyte is stored on a glass mat, as opposed to the flood-free plate. Very thin glass fibers are woven into mats to increase sufficient surface area to hold adequate electrolytes in cells for their lifetime. The fibers that make up the fine glass mat do not absorb or are affected by acid electrolytes. This mat is squeezed 2-5% after soaking in acid, before the making is finished and sealing.

The license plate in the GMS battery can be anything. Some are flat, others are bent or overthrown. The AGM battery, both in cycle and start, is built into a rectangular case for BCI battery code specifications.

The AGM battery provides better self-discharging characteristics than conventional batteries in different temperatures.

As with lead-acid batteries to maximize AGM battery life, it is important to follow the charging specifications and recommended voltage chargers. and there is also a correlation between depth of discharge (DOD) and battery life, with differences between 500 and 1300 cycles depending on depth of discharge.

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Gel battery

Initially a kind of gel cell was produced in the early 1930s for the supply of portable LT tubes (2, 4 or 6V) by adding silica to sulfuric acid. At this time the glass box was replaced by celluloid and later in the 1930s other plastics. Previous wet cells in glass jars use special valves to allow tilt from vertical to horizontal in one direction in 1927 to 1931 or 1932. Gel cells are less likely to leak when portable devices are handled roughly.

The modern gel battery (also known as "gel cell") is a VRLA battery with a purified electrolyte; sulfuric acid is mixed with smoky silica, which makes the resulting mass gel-like and immobile. Unlike lead-acid batteries wet cells, this battery does not need to be kept upright. The gel battery reduces the evaporation of electrolytes, spills (and subsequent corrosion problems) common to wet cell batteries, and has greater resilience to shock and vibration. Chemically they are almost the same as wet (unsealed) batteries except that the antimony in the lead plate is replaced with calcium, and gas recombination can occur.

Modern gel formulations and large-scale production come from Otto Jache's and Heinz Schroeder AS. Patent 4,414,302 awarded to the German company Accumulatorenfabrik Sonnenschein GmbH. With gel electrolytes, the separator is no longer a critical component, difficult to manufacture, and the life cycle increases, in some cases dramatically. Shedding of active ingredients from the plate is reduced.

More importantly, gas recombination is used to make batteries that are not "watered" and can be called maintenance free. One-way valves are set at 2 psi, and this is high enough for full recombination to take place. At the end of the charge when oxygen evolves from overcharge in a positive plate, it travels through the shrinkage cracks in the gel directly into the negative plate (made from the broad surface of pure sponge leads) and "burns" as quickly as it is made. This oxygen and hydrogen gas is adsorbed on the surface of metal lead plates containing metals combined to create water retained within the cell.

This sealed non-spill feature makes it possible to create very small VRLA batteries (1-12 Amp range) that match the growing portable electronic market. A large market for cheap, cheap lead acid batteries is produced quickly. Portable TVs, lights for news cameras, children's toy cars, emergency lights, and UPS systems for computer backups, to name a few, are powered with small sealed VRLA batteries.

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Apps

Many modern motorcycles and ATVs on the market use AGM batteries to reduce the likelihood of acid spills during cornering, vibration, or after accidents, and for packaging reasons. The lighter, smaller batteries can be mounted at odd angles if needed for motorcycle design. Due to higher production costs compared to lead-acid batteries, AGM batteries are currently used in luxury vehicles. As vehicles get heavier and are equipped with more electronic devices such as navigation and stability control, AGM batteries are used to lower vehicle weight and provide better electrical reliability compared to stagnant acid-lead batteries.

The BMW 5 Series from March 2007 combines AGM batteries along with devices to recover brake energy using regenerative braking and computer controls to ensure alternators charge when the car slows down. Vehicles used in racing cars can use AGM batteries because of their vibration resistance.

AGM in cycles are also commonly used outside solar power grids and wind power installations as energy storage banks and in large-scale amateur robotics, such as FIRST and IGVC competitions.

AGM batteries are routinely selected for remote sensors such as ice monitoring stations in the Arctic. The AGM battery, due to the lack of free electrolyte, will not crack and leak in this cold environment.

VRLA batteries are used extensively in electric wheelchairs, because very low gas and acid output make it much safer to use indoors. VRLA batteries are also used in UPS (uninterruptible power supply) as backup when power failure.

VRLA batteries are also a standard resource in the aircraft, because of their ability to withstand a wide range of flight attitudes and relatively large ambient temperature ranges with no ill effects. However, regime filling should be adjusted to various temperatures. AGM and Gel cells are commonly used in powerful aerobatic aircraft, for the same reason.

VRLA batteries are used in the US Nuclear Submarine fleet, due to its power density, removal of gassing, reduced maintenance, and enhanced security.

AGM and Gel-Cell batteries are also used for marine leisure purposes, with AGM becoming more commonly available. The marine battery in the AGM cycle is offered by a number of suppliers. They are usually favored because of low maintenance and spill quality, although they are generally regarded as a less cost-effective solution relative to traditional flood cells.

In telecommunications applications, VRLA batteries are in accordance with the criteria in the requirements document of Telcordia Technologies GR-4228, Certification Level of Lead-Acid Lead Rule (VRLA) Batteries Under the Requirements for Safety and Performance, is recommended for Outside Plant deployment (OSP) at locations such as Controlled Environmental Vaults (CEVs), Electronic Equipment Enclosures (EEEs), and cottages, and in uncontrolled structures such as cabinets. With respect to VRLA in telecommunications, the use of the Ohhr VRLA (OMTE) Type Measurement Equipment and OMTE measurement equipment is a fairly new process for evaluating the telecom battery factory. Proper use of ohmic test kits enables battery testing without the need to remove the battery from the service to perform costly and time-consuming debit tests.