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Two common ways are topping charge and equalizing charge. A topping charge can be performed by fully charging the SLA battery, removing it from the charger for hours, and then applying charge again. The process must be repeated several times in order to check the full discharge and recharge capacity of the battery.

Another way to power a stationary sealed lead-acid battery is by performing an equalizing charge. Equalizing charge can also be considered as forced overcharge, which is keeping the battery charged for an hour or two after reaching a full charge status. This process may remove sulfation in the battery, which is likely formed during low-charge conditions when it is idle.

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What is a sealed lead-acid battery? The Two Types Of Sulfation. What Is Battery Corrosion? The hydrogen ions screen the charged electrode from the solution which limits further reaction unless charge is allowed to flow out of electrode. The total reaction can be written as. The net energy released per mol g of Pb s converted to PbSO 4 s , is ca. The sum of the molecular masses of the reactants is For a 2-volt cell, this comes to watt-hours per kilogram of reactants, but in practice a lead—acid cell gives only 30—40 watt-hours per kilogram of battery, due to the mass of the water and other constituent parts.

In the fully charged state, the negative plate consists of lead, and the positive plate lead dioxide. The electrolyte is concentrated sulfuric acid, which stores most of the chemical energy. Overcharging with high charging voltages generates oxygen and hydrogen gas by electrolysis of water , which is lost to the cell. The design of some types of lead-acid battery allow the electrolyte level to be inspected and topped up with any water that has been lost.

Due to freezing-point depression , the electrolyte is more likely to freeze during winter weather as the battery discharges and the concentration of sulfuric acid decreases. The reverse occurs during charge. This motion can be electrically driven proton flow or Grotthuss mechanism , or by diffusion through the medium, or by flow of a liquid electrolyte medium.

Since the electrolyte density is greater when the sulfuric acid concentration is higher, the liquid will tend to circulate by convection. Therefore, a liquid-medium cell tends to rapidly discharge and rapidly charge more efficiently than an otherwise similar gel cell. Because the electrolyte takes part in the charge-discharge reaction, this battery has one major advantage over other chemistries: It is relatively simple to determine the state of charge by merely measuring the specific gravity of the electrolyte; the specific gravity falls as the battery discharges.

Some battery designs include a simple hydrometer using colored floating balls of differing density. When used in diesel-electric submarines , the specific gravity was regularly measured and written on a blackboard in the control room to indicate how much longer the boat could remain submerged. The battery's open-circuit voltage can also be used to gauge the state of charge.

IUoU battery charging is a three-stage charging procedure for lead-acid batteries. For a single cell, the voltage can range from 1. Float voltage varies depending on battery type i. Equalization voltage, and charging voltage for sulfated cells, can range from 2. The lead—acid cell can be demonstrated using sheet lead plates for the two electrodes. However, such a construction produces only around one ampere for roughly postcard-sized plates, and for only a few minutes.

The cells initially had low capacity, so a slow process of "forming" was required to corrode the lead foils, creating lead dioxide on the plates and roughening them to increase surface area.

Lead-acid storage battery

Initially this process used electricity from primary batteries; when generators became available after , the cost of production of batteries greatly declined. In , Camille Alphonse Faure patented a method of coating a lead grid which serves as the current conductor with a paste of lead oxides, sulfuric acid and water, followed by curing phase in which the plates were exposed to gentle heat in a high humidity environment. The curing process caused the paste to change to a mixture of lead sulfates which adhered to the lead plate.

Then, during the battery's initial charge called "formation" the cured paste on the plates was converted into electrochemically active material the "active mass". The grid developed by Faure was of pure lead with connecting rods of lead at right angles. In contrast, present-day grids are structured for improved mechanical strength and improved current flow. In addition to different grid patterns ideally, all points on the plate are equidistant from the power conductor , modern-day processes also apply one or two thin fibre-glass mats over the grid to distribute the weight more evenly.

However, high-antimony grids have higher hydrogen evolution which also accelerates as the battery ages , and thus greater outgassing and higher maintenance costs. These issues were identified by U. Thomas and W. Haring at Bell Labs in the s and eventually led to the development of lead- calcium grid alloys in for standby power batteries on the U. Related research led to the development of lead- selenium grid alloys in Europe a few years later.

These metallurgical improvements give the grid more strength, which allows it carry more weight, i. High-antimony alloy grids are still used in batteries intended for frequent cycling, e. Since the s, batteries designed for infrequent cycling applications e. Lead-calcium alloy grids are cheaper to manufacture the cells thus have lower up-front costs , and have a lower self-discharge rate, and lower watering requirements, but have slightly poorer conductivity, are mechanically weaker and thus require more antimony to compensate , and are strongly subject to corrosion and thus a shorter lifespan than cells with lead-selenium alloy grids.

The open circuit effect is a dramatic loss of battery cycle life which was observed when calcium was substituted for antimony. It is also known as the antimony free effect. Modern-day paste contains carbon black , blanc fixe barium sulfate and lignosulfonate. The blanc fixe acts as a seed crystal for the lead—to— lead sulfate reaction. The blanc fixe must be fully dispersed in the paste in order for it to be effective. The lignosulfonate prevents the negative plate from forming a solid mass during the discharge cycle, instead enabling the formation of long needle—like dendrites.

The long crystals have more surface area and are easily converted back to the original state on charging. Carbon black counteracts the effect of inhibiting formation caused by the lignosulfonates. Sulfonated naphthalene condensate dispersant is a more effective expander than lignosulfonate and speeds up formation. This dispersant improves dispersion of barium sulfate in the paste, reduces hydroset time, produces a more breakage-resistant plate, reduces fine lead particles and thereby improves handling and pasting characteristics. It extends battery life by increasing end-of-charge voltage.

Sulfonated naphthalene requires about one-third to one-half the amount of lignosulfonate and is stable to higher temperatures. Once dry, the plates are stacked with suitable separators and inserted in a cell container. The alternate plates then constitute alternating positive and negative electrodes, and within the cell are later connected to one another negative to negative, positive to positive in parallel.

The separators inhibit the plates from touching each other, which would otherwise constitute a short circuit. In flooded and gel cells, the separators are insulating rails or studs, formerly of glass or ceramic, and now of plastic. In AGM cells, the separator is the glass mat itself, and the rack of plates with separators are squeezed together before insertion into the cell; once in the cell, the glass mats expand slightly, effectively locking the plates in place. In multi-cell batteries, the cells are then connected to one another in series, either through connectors through the cell walls, or by a bridge over the cell walls.

All intra-cell and inter-cell connections are of the same lead alloy as that used in the grids. This is necessary to prevent galvanic corrosion. Deep cycle batteries have a different geometry for their positive electrodes.

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  8. The positive electrode is not a flat plate but a row of lead-oxide cylinders or tubes strung side by side, so their geometry is called tubular or cylindrical. The advantage of this is an increased surface area in contact with the electrolyte, which higher discharge and charge currents than a flat-plate cell of the same volume and depth-of-charge. Tubular-electrode cells have a higher power density than flat-plate cells. And, less active material at the electrode also means they have less material available to shed before the cell becomes unusable. Separators between the positive and negative plates prevent short-circuit through physical contact, mostly through dendrites "treeing" , but also through shedding of the active material.

    Separators allow the flow of ions between the plates of an electro-chemical cell to form a closed circuit. Wood, rubber, glass fiber mat, cellulose , and PVC or polyethylene plastic have been used to make separators. Wood was the original choice, but deteriorated in the acid electrolyte. Rubber separators are stable in battery acid and provide valuable electrochemical advantages that other materials cannot. An effective separator must possess a number of mechanical properties; such as permeability , porosity, pore size distribution, specific surface area , mechanical design and strength, electrical resistance , ionic conductivity , and chemical compatibility with the electrolyte.

    Materials used for Lead Acid Storage Battery Cells

    In service, the separator must have good resistance to acid and oxidation. The area of the separator must be a little larger than the area of the plates to prevent material shorting between the plates. The separators must remain stable over the battery's operating temperature range. In the absorbed glass mat design, or AGM for short, the separators between the plates are replaced by a glass fibre mat soaked in electrolyte. There is only enough electrolyte in the mat to keep it wet, and if the battery is punctured the electrolyte will not flow out of the mats.

    Principally the purpose of replacing liquid electrolyte in a flooded battery with a semi-saturated fiberglass mat is to substantially increase the gas transport through the separator; hydrogen or oxygen gas produced during overcharge or charge if the charge current is excessive is able to freely pass through the glass mat and reduce or oxidize the opposing plate respectively.

    In a flooded cell the bubbles of gas float to the top of the battery and are lost to the atmosphere. This mechanism for the gas produced to recombine and the additional benefit of a semi-saturated cell providing no substantial leakage of electrolyte upon physical puncture of the battery case allows the battery to be completely sealed, which makes them useful in portable devices and similar roles.

    Additionally the battery can be installed in any orientation, though if it is installed upside down then acid may be blown out through the over pressure vent. To reduce the water loss rate calcium is alloyed with the plates, however gas build-up remains a problem when the battery is deeply or rapidly charged or discharged.

    To prevent over-pressurization of the battery casing, AGM batteries include a one-way blow-off valve, and are often known as "valve regulated lead—acid", or VRLA, designs. Another advantage to the AGM design is that the electrolyte becomes the separator material, and mechanically strong. This allows the plate stack to be compressed together in the battery shell, slightly increasing energy density compared to liquid or gel versions.

    AGM batteries often show a characteristic "bulging" in their shells when built in common rectangular shapes, due to the expansion of the positive plates. The mat also prevents the vertical motion of the electrolyte within the battery. When a normal wet cell is stored in a discharged state, the heavier acid molecules tend to settle to the bottom of the battery, causing the electrolyte to stratify. When the battery is then used, the majority of the current flows only in this area, and the bottom of the plates tend to wear out rapidly.

    This is one of the reasons a conventional car battery can be ruined by leaving it stored for a long period and then used and recharged. The mat significantly prevents this stratification, eliminating the need to periodically shake the batteries, boil them, or run an "equalization charge" through them to mix the electrolyte. Stratification also causes the upper layers of the battery to become almost completely water, which can freeze in cold weather, AGMs are significantly less susceptible to damage due to low-temperature use.

    While AGM cells do not permit watering typically it is impossible to add water without drilling a hole in the battery , their recombination process is fundamentally limited by the usual chemical processes. Hydrogen gas will even diffuse right through the plastic case itself. Some have found that it is profitable to add water to an AGM battery, but this must be done slowly to allow for the water to mix via diffusion throughout the battery.

    When a lead-acid battery loses water, its acid concentration increases, increasing the corrosion rate of the plates significantly. AGM cells already have a high acid content in an attempt to lower the water loss rate and increase standby voltage, and this brings about shorter life compared to a lead-antimony flooded battery. This is the reason lead acid batteries are called storage batteries, because they only store a charge. The size of the battery plates and amount of electrolyte determines the amount of charge lead acid batteries can store.

    The size of this storage capacity is described as the amp hour AH rating of a battery. A typical volt battery used in a RV or marine craft has a rating AH, which means it can supply 10 amps of current for Lead acid batteries can be connected in parallel to increase the total AH capacity. In figure 2 below, six single 2.

    Lead Acid Battery Recharge Cycle

    In figure 3, above a fully charged battery is connected to a load light bulb and the chemical reaction between sulfuric acid and the lead plates produces the electricity to light the bulb. This chemical reaction also begins to coat both positive and negative plates with a substance called lead sulfate also known as sulfation shown as a yellow build-up on plates.

    This build-up of lead sulfate is normal during a discharge cycle. As the battery continues to discharge, lead sulfate coats more and more of the plates and battery voltage begins to decrease from fully charged state of In figure 5 the battery is now fully discharged, the plates are almost completely covered with lead sulfate sulfation and voltage has dropped to NOTE: Discharging a lead acid battery below Lead sulfate sulfation now coats most of the battery plates. Lead sulfate is a soft material, which can is reconverted back into lead and sulfuric acid, provided the discharged battery is immediately connected to a battery charger.

    If a lead acid battery is not immediately recharged, the lead sulfate will begin to form hard crystals, which can not be reconverted by a standard fixed voltage NOTE: Always recharge your RV or Marine battery as soon as possible to prevent loss of battery capacity due to the build-up of hard lead sulfate crystals!

    Lead-Acid Battery Bank Frequently Asked Questions | CivicSolar

    Proper recharging and maintenance requires an intelligent charging system that can vary the charging voltage based on the state of charge and use of your RV or Marine battery. Progressive Dynamics has developed intelligent charging systems that solve battery problems and reduce battery maintenance. In order to recharge a volt lead acid battery with a fully charged terminal voltage of During the battery recharge cycle lead sulfate sulfation begins to reconvert to lead and sulfuric acid.

    During the recharging process as electricity flows through the water portion of the electrolyte and water, H2O is converted into its original elements, hydrogen and oxygen. These gasses are very flammable and the reason your RV or Marine batteries must be vented outside. Gassing causes water loss and therefore lead acid batteries need to have water added periodically. Sealed lead acid batteries contain most of these gasses allowing them to recombine into the electrolyte.

    Working of Lead Acid Battery | Lead Acid Secondary Storage Battery

    If the battery is overcharged pressure from these gasses will cause relief caps to open and vent, resulting in some water loss. Most sealed batteries have extra electrolyte added during the manufacturing process to compensate for some water loss. The battery shown in figure 7 above has been fully recharged using a fixed charging voltage of Notice that some lead sulfate sulfation still remains on the plates.

    This build-up will continue after each recharging cycle and gradually the battery will begin to loose capacity to store a full charge and eventually must be replaced. Lead sulfate build up is reduced if battery is given an Equalizing Charge once every 10 discharge cycles or at least once a month. An Equalizing Charge increases charging voltage to This higher voltage causes gassing that equalizes re-mixes the electrolyte solution. Since most RV and Marine craft owners seldom remember to perform this function, Progressive Dynamics has developed the microprocessor controlled Charge Wizard.