Battery / Cell
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Cell: A storage device which stores the electrical energy in the form of chemical energy allows to recover b k iin the back h form f off electrical l i l energy.
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B tt Battery: C bi ti / Combination/group off cells ll
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The capacity of a battery to store charge is often expressed in ampere hours (1 Ah = 3600 coulombs) coulombs). If a battery can provide one ampere (1 A) of current (flow) for one hour, it has a real-world capacity of 1 Ah If it can provide 1 A for 100 hours Ah. hours, its capacity is 100 Ah. Battery manufacturers use a standard method to determine how to rate their batteries. The battery is discharged at a constant rate of current over a fixed period of time, such as 10 hours or 20 hours, down to a set terminal voltage per cell. So a 100 ampere-hour ampere hour battery is rated to provide 5 A for 20 hours at room temperature. The efficiency of a battery is different at different discharge rates.
Primary cells
Secondary cells
Primary cells are those cells, which cannot be re-charged the h d after f h substances(electrolyte, b ( l l electrode and container) used in it becomes use less The common primary cells in use are less. are, a. Simple voltaic cell (one fluid cell). b. Daniel cell (two fluid cell). c. Leclanche cell (two fluid cell). d. Dry y cell. e. Standard cell or Weston cadmium cell
Secondary cells are those cells, which can be re-charged and use again once they discharged or used for the work for number of times with out re-newing re newing it it’s s materials. materials Most commonly used secondary cells are, a Lead acid cell a. cell. b. Nickel iron alkaline cell. c. Nickel cadmium alkaline cell.
a. It gives high current capacity. b. Its internal resistance is very low. c. It gives a constant current. d. It posses very high efficiency. e. It posses fairly constant emf. f It posses good f. d mechanical h i l strength. t th g. It posses large storage capacity
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A VRLA battery (valve-regulated lead–acid battery) more commonly known as a sealed battery is a lead–acid rechargeable battery. Because of their construction construction, VRLA batteries do not require regular addition of water to the cells,, and vent less g gas than flooded lead-acid batteries
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No water top up Long life on float service Excellent shelf life No corrosive fumes Ready to use Stackable with horizontal orientation Low weight and volume Safe to use Faster installation ll
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Yes.
Though it needs no periodical maintenance schedule like top up, Batteries are required…..
Cleaning
of Inter cell connectors and T Terminals i l and d applying l i petroleum t l jjelly ll as and when required Measurement of individual cell voltages g monthly and Record.
Equalization charge as and when required
Ensure
charger settings are as per the B Battery recommendations d i
Float charging – 2.15V per cell It maintains the battery fully charged condition during standby operation by delivering a small amount of current to cancel the effect of battery natural self di h discharge. Equalizing charging (2.7V/cell) once in 3 months Recharge a battery capacity through recovering all useable active materials in the cell plates. Boost charging Boost charging is a quick charging process process, which is generally required, if the battery is drained to a large extent.
The capacity of the battery is measured in ampere-hour. The capacity of the battery depends upon the following factors. a. Number and area of the positive plate. b. Discharge voltage. A cell should not be discharged below 1.8 V. If it is discharged g below 1.8 V it may y cause to reduce the capacity. p y c. Discharge rate. Capacity decreases with increase rate of discharge. d. Specific gravity of electrolyte. With rapid rate of discharge causes to weaken the electrolyte y so the chemical action also weakens and there by y the capacity decreases. When the specific gravity increases the capacity of the battery increases. e. Quantity Q y of electrolyte. y Electrolyte y level should be at the top p plate p level. f. The design of separator. The design of the separator should be thin. g. Temperature. When the temperature increases the resistance of the battery decreases and the capacity p y increases.
A simple lead acid battery consists of positive and negative electrodes Immersed in an electrolyte. electrolyte The positive electrodes are Pbo2 (lead oxide) and the negative electrodes are Pb (spongy lead). The electrolyte l l iis dil dilute sulphuric l h i acid. id On Discharging the battery Pbo2 + Pb +2 H2 so4 Pbso4 + Pbso4 + 2 H2o Lead acid is converted into lead sulphate. Spongy lead is also converted into lead sulphate and H2 so4 used up in the process process. Only water is remain remain. So the specific gravity of the cell comes down. On Charging the battery Pbso4 + Pbso4 + 2 H2o Pbo2 + Pb +2 H2 so4
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The instrument used to measure the specific gravity is called
y Hydrometer
It is the weight of the sulfuric acid-water mixture compared to an equal volume of water. Pure water has a specific gravity of 1. Specific gravity = Density of the substance / density of pure water. = kg / cm2 kg / cm2 = (No unit) Specific gravity is only number. It has no unit. Specific gravity of fully charged lead acid battery is 1.215. Specific gravity should always be corrected to 27°C. Corrected specific gravity is equal to indicated specific gravity ± (t - 27°C)*0.0007. ) Indicated specific gravity = 1.205 and ‘t’ means electrolyte temperature
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After batteries are fully charged, the sp. Gravity of the electrolyte of all cells to be adjusted to the service gravity i.e. 1.210 /1.250 ± 0.005, at 27ºc. the batteries to be put on charge for proper mixing. If sp. Gravity in cells more than service gravity corrected to 27ºc. 27 c. Take out acid and add battery grade water, when on charge for proper mixing. Adjust sp. Gravity to the service gravity corrected to 270 c. As applicable with respective batteries. If the sp. Gravity of the cells less than the service gravity at 270 c take out acid and add 1.400 sp. Gr. Acid by few drops, on charge for proper mixing. Adjust the sp. Gravity to the service gravity at 270 c as applicable. After adjustment of the specific gravity, continue the charging for 1- 2 hours for proper mixing of the electrolyte. Stop the charging and allow the batteries to cool, before commissioning.
a. The color of the + ve plates will be dark brown. This can be seen only if the battery has transparent cover. b Voltage per cell will be a 2 b. 2.15 15 volts volts. c. Gassing in the will electrolyte will indicate. But the current is splitting up water to H2 and O2. Because the positive and negative plates are fully converted to their original constituents
p g normal discharge g of batteryy Sulphation: During Pb so4 is formed. This Pb so4 is chemically reversible by passing current. These split up to their original constituents constituents. But under certain condition crystalline lead sulphate is formed (Example: under charging after some ti time without ith t trickle t i kl charging). h i ) This Thi Pb so4 4 iis chemically irreversible. So if the sulphation occurs the battery y life decreases. Efficiency y decreases and the active material starts falling of the grid.
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Possibility of battery explosion
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Corrosive atmosphere by acid spray.
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Fire hazard.
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Higher electrolyte temp - ah capacity i increases b but lif life reduces. d Lower electrolytic temp - ah capacity reduces since chemical reaction rate reduces
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proof acid resistant p
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Conduct test – to check the capacity batteries Impedance test – to check the utilization of active materials
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Use only DC ‘constant current’ charger only for initial charging of batteries. Ensure the charger in working condition and capable of supplying requisite volt & amps required for the batteries to be charged. Take care of polarity and connect the pos. Terminal of batteries with the pos. & neg. Terminal with neg. Of the charger, respectively. Charging may be done in 2 steps or single step. In our tropical country advisable to charge in single step, specially in summersummer For ‘2 step charging’ the initial current to be 12% of the C10 capacity of battery upto 2.36 VPC and followed by 6% of the C10 rated capacity of the battery upto 2.75 VPC. (For 500Ah battery p & 30 amps p respectively).p y For ‘single g step’ p charging, g g 60 amps the battery to be charged continuously at the current 6% of the C10 rated capacity of the battery upto 2.75 VPC, till the end of charging e.g. 30 amps upto 2.75 VPC for a 500 Ah battery till end.
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Maintenance is an important issue. The battery should be cleaned using a baking soda and water mix; a couple of table spoons to a pint of water. t Cable connection needs to be clean and tightened. Many battery problems are caused by dirty and loose connections. A serviceable battery needs to have the fluid level checked. Use only mineral free water water. Distilled water is best best. Don't Don t overfill battery cells especially in warmer weather. The natural fluid expansion in hot weather will push excess electrolytes from the battery. To prevent corrosion of cables on top post batteries use a small bead of silicon sealer at the base of the post and place a felt battery washer over it. Coat the washer with high temperature grease or petroleum jelly (Vaseline), then place cable on the post and tighten. Coat the exposed cable end with the grease. Most folks don't know that just the gases from the battery condensing on metal parts cause most corrosion.
Container trouble Rough handling: any storage battery to be handled as if made of glass, though the containers made SAN or FRP. batteries t i d with ith hard h d rubber, bb FRP Heavy H b tt i should h ld be b handled h dl d by more than one person or by mechanical handling and not to be dropped / dragged. This will lead container crack/ damage. Explosion in cell: may cause due to open flame, electrical sparks and clogged vent holes. Bulging of container: this is be due to under curing of the container. Stacking should be restricted to max. 3 high, with hard board in between layers ` Terminals/ connector corrosion Too much topping water added to cells B tt Battery poorly l sealed l d Loose vent caps / float guide Electrolyte spillage Battery cable damaged, or loose Connecting bare wires directly to battery terminals terminals. Loose terminal connections Non application or renewal of petroleum jelly for protection `
High sp. Gravity of electrolyte Over filling of battery water. Low sp. Gravity of electrolyte High level of electrolyte Low level electrolyte I Impurities ii ` Loss of capacity Impurities in the electrolyte sulphation Loose active materials Incorrect proportions of acid and water in the electrolyte Separators clogged Shedding h dd Low level of electrolyte Effect of age `
Sulphation in cells Over discharge Allowing a battery to stand idle Starvation Allowing electrolyte to fall below the top of plates Impurities Addi Adding acid id iinstead t d off water t ` Bucking of plates: Over discharge Continued operation with battery in starved condition Charging at high rates Non- uniform distribution of current over the plates, due to repeated deep discharge ` Shedding of active materials Normal shedding Excessive charging rate, rate or overcharging Charging sulphated plates at too high rate Charging only a part of the plate Deep discharge battery on normal charge. Freezing. g `
Internal short circuit Worn out separators Lead run Foreign material Accumulation ccu u at o of o sediment sed e t ` Reversal of plates Assembling of the cell in reverse direction. Charging a battery in wrong direction. Lagging / defective cell in battery bank will be reversed if not taken care in time ` Earth / surface leakage in battery Over filling of battery water water. Careless hydrometer use, spillage of electrolyte. Careless acid filling during initial filling & charging. `
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Think Safety First. Do read entire tutorial Do regular inspection and maintenance especially i ll iin h hot weather. h Do recharge batteries immediately after discharge. discharge Do buy the highest RC reserve capacity or AH amp hour battery that will fit your configuration.
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Don't add new electrolyte (acid). Don Don'tt use unregulated high output battery chargers to charge batteries. Don't disconnect battery cables while the engine is running (your battery acts as a filter) filter). Don't put off recharging batteries. Don't add tap water as it may contain minerals th t will that ill contaminate t i t th the electrolyte. l t l t Don't discharge a battery any deeper than you possibly have to. D ' llet a b h touch h and db il Don't battery get h hot to the boil violently when charging. Don't mix size and types of batteries.
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Lead acid batteries are 100% recyclable. The plastic and l i containers i d covers off old ld batteries b i are neutralized, reground and used in the manufacture of new battery cases. The electrolyte can be processed for recycled wastewater uses. In some cases, the electrolyte is cleaned and reprocessed and sold as battery grade electrolyte. In other instances, the sulfate content is removed as Ammonia Sulfate and used in fertilizers. The separators are often used as a fuel source for the recycling process.
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Always use insulated tools while working on battery Do not allow metal objects/ tools to rest on the battery or falls across the terminals Isolate the battery from charger while working on it. Do not tamper with cell vents Do not attempt to move the installed battery without removing connectors Do not expose the battery to an open flame or sparks in the immediate vicinity Do not touch un insulated battery connectors
