vhse eet-cell and battery (class note)-part2

7/26/2019 VHSE EET-Cell and Battery (Class Note)-Part2

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Electrical & Electronics Technology

GVHSS,Veeranakavu

1NOTES

II YEAR EET

Unit 1 - Cells and Batteries PART 2

Syllabus

Unit-1 Cells and Batteries

Interconnection of Cells- Series and parallel, Instruments and tools used for

battery testing, Battery bank installation, testing and commissioning. Types of lead

acid battery- Liquid vented, Tubular- Sealed or VRLAAGM & Gel, Applications

of Nickel cadmium & Lithium ion cells.

Sabukumar.S,TVM


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2Internal Resistance of a cell

It is the resistance offered by the cell to the flow of current. A cell possesses

internal resistance because of the resistance of

Electrolyte

Electrodes

Terminals of the battery

The factors affecting internal resistance of a cell are

a) Size of electrodes

b) Distance between the plates

c) Number of electrodes

CHARGING METHODS

Generally there are two types of charging such as constant current and

constant voltage method.

Constant current method

In this method of charging the batteries are connected in series and

connected to a circuit as shown in fig. The charging current is kept constant

throughout the charging period by adjusting the rheostat in the circuit as the

battery voltage goes up.

In order to avoid excessive gassing or over heating the charging may be

carried out in two steps, an initial charging of comparatively higher current and a

finishing rate of low current. The current at which the battery is charged is decided

by the ampere hour capacity. Usually the charging current shall be 1/8th of the Ah

capacity.

During the charging period, the temperature of the electrolyte should not

exceed beyond 40 to 450C because of the danger of plate buckling. So the


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3temperature of electrolyte is carefully watched and if the temperature approaches

danger limit the charging current should be reduced.

In this system, a number of batteries can be connected in series with the

battery charger. The voltage of the battery charger should be greater than the total

voltage of the battery. Otherwise the battery will discharge through the circuit.

This type of charging system is used only for

1) newly constructed battery

2) completely discharged battery

3) Battery which is kept idle for a long period.

Constant voltage method


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4In this method, the voltage of the battery is kept constant by varying the

current. Initially the charging current is very high and decreases as the battery

charges. The time of charging is reduced to half and increases the capacity

compared to constant current method. But the efficiency is low.

Trickle charging

Due to leakage action and other open circuit losses, a fully charged battery

losses its charge even when open circuit. Hence to keep the battery always in

charging condition, the battery is charged by a very small current for a long

period. This type of charging is called trickle charging.

Connection of Battery

a) Series connection

Batteries are connected in series for obtaining more e.m.f than that of one

battery. In this method, the negative terminal of first battery is connected to the

positive terminal of the second battery and negative of the second battery to

positive of the third and so on, such connection is called series connection. In this

connection the total voltage is the sum of the individual battery voltages. But same

current flows in all the batteries. Due to this the charge capacity of series

connected batteries is as same

as the charge capacity of a

single battery.

Total e.m.f ET = n. E

n = number of battery.

E= E.M.F of one cell.

b) Parallel connection

Batteries are connected in parallel for obtaining more current or current for

more time than that with one battery. If the positive terminals of all batteries are


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5connected together and negative terminals of

all batteries are connected together, such

connection is called parallel connection. In

this connection the total current is the sum of

the individual battery current and the total

voltage is the voltage of one battery. In

parallel connection, the total capacity of the

battery bank (group of batteries) will be equal

to the sum of the capacities of individual

batteries.

ET = E

Tools and Instruments used for testing &

maintenance of battery

The following tools required for battery maintenance

Pliers (to open nuts& bolts, tie the wires & hold live wires)

Wire cutter to cut & strip the wire

Spanner 12-13 ( To open nut bolts of contacts)

Cleaning brush ( To clean battery contact terminals)

Polish paper (To clean the rough contact surface)

The following are the commonly used instruments used for battery testing Battery Hydrometer (For measuring the specific gravity of electrolyte)


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6

Battery Tester & multimeter (Used for checking the voltage, current &

internal resistance)

Clamp meter (Clipping type

multi meter to measure voltage, current and resistance not by physical

connection but by clamping on the wire connected)

Battery Fault Detection

1) Electrical fault Detection


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7The electrical faults can be detected with the help of multi meter and battery tester.

We can check voltage and current using this meter.

BATTERY BANK INSTALLATION PROCEDURE

The battery bank installation and commissioning is mainly of 2 types1) Replacing old battery bank by new batteries

2) Installation and commissioning of complete new battery bank

In the first case all infra-structure for battery installation will be there. But in

the second case ensure the availability of infra structures such as battery room,

battery charger, Battery stand, cabling from charger to battery and from battery to

load. The following steps are involved in the battery bank installation and

commissioning.

For replacement of old battery banks, ensure that the battery bank is

isolated from all loads.

Switch OFF the charger connected to the battery.

Remove all cables, inter cell/row connectors.

Place the new batteries on the battery stand. While doing this the

polarity of batteries should be confirmed.

Connect the inter cell connectors and charger to the battery cables &

make it ready for initial charging.

Do the initial charging till cell voltage reaches 2.35 V 2.45V. Take

hourly reading of cell voltage, sp. Gravity and temperature.

Once the cell voltage reaches 2.35 V2.45V reduce charging current to

finishing rate and continue charging by keeping the total input AH

rating same.


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8 While charging the temperature should not exceed 50

0C. If it exceeds

this value, stop charging allow temperature to come down to 400C and

continue charging.

After reaching full charge, keep batteries idle for 4 hrs and then

discharge the batteries as per specification mentioned(C/10 or C/20)

after isolating from the charger.

Record cell voltage, sp. Gravity & temperature of all cells. Make sure

that no cell over discharged. Then recharge again and again note down

all the parameters. If sp. Gravity of any cell falls below standard value,

then adjust the sp. gravity by adding conc.H2SO

4.

Again recharge the batteries and keep them on float charging.

Test Instruments Required

1. Multimeter.

2. Battery loading unit.

This iscapable of providing a constant current load to the battery under test.

Commissioning Test Procedure

1. Battery Charger

1. Visual Inspection: The battery charger cleanliness to be verified. Proper

cable termination of incoming AC cable and the outgoing DC cable and the

cable connection between battery and charger to be ensured. A stable

incoming AC supply to the battery charger is also to be ensured.2. Voltage levels in the Float charge mode and the Boost charge mode to be set

according to specifications using potentiometer provided.

3. Battery low voltage, Mains Off, charger Off etc., conditions are simulated

and checked forproper alarm / indication. Thus functional correctness of the

battery charger is ensued.


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94. After the boost charging duration, the battery charger is to be put in float

charging (trickle charge) mode for continuous operation.

Some chargers automat ica lly swi tch to f loat charge modeafter the charging

current reduces below a certain value.

5. Voltage and current values are recorded during the boost charging and float-

charging mode.

This test establishes thecorrect operation of the battery charger within the

specified voltage and current levels in various operational modes.

2. Battery Unit

1. Mandatory Condition: The battery set should have been properly charged asper the commissioning instructions of the battery manufacturer for the

duration specified.

2. Visual Inspection: Cleanliness of battery is checked and the electrolyte level

checked as specified on the individual cells. The tightness of cell connections

on individual terminals should be ensured.

3. Individual cell voltages to be recorded before the start of the test.

4. Loading of the battery to be started at the specified current value.

Individual cell voltages of the battery set are to be recorded every half

an hour.

5. It is to be ensured that all the cell voltages are above the end-cell

voltage specified by the manufacturer.

If any of the cell voltages falls below the threshold level specified by the

manufacturer, this cell number is to be noted and the cell needs to be

replaced.

6. Test set automatically stops loading after set duration (or) when

minimum voltage reached for the battery set.

7. Test to be continued until the battery delivers the total AH capacity itis designed for.

Value of AH and individual cell voltages to be recorded every half an hour.

Acceptance Limits


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10This test establishes the AH capacity of battery set at required voltage.

The acceptance limit for the test is to ensure the battery set is capable

of supplying the required current at specified DC voltage without breakdown

for the required duration.

Types of Lead Acid Batteries

Tubular Batteries

The tubular battery

provides high performance,

long life and lower

maintenance costs. Unique

design features provide

higher capacity but not

sacrificing battery cycle life,

while maintaining normal

watering intervals

Positive plate:It is a tubular plate which can prevent the active material from

falling off. The grid of positive plate is Pb-Sb Multi-Alloy

Separator: With the combined application of porous rubber and porous PVC, the

separator has high porosity and good corrosion-resistance

Acid-Proof bolt:It is of a special shape of funnel having the function of filtering

acid smog and retarding flame. It can measure the density and temperature of

electrolyte. The design life of the battery is more than 20 years. Ensuring sufficient

electrolytes for battery discharge

CONSTRUCTION


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11 Positive plate Tubular plate with die cast Pb-Ca alloy grid

Negative plateBalanced Pb-Ca grid for improved recombination efficiency

SeparatorLeaf shape rubber separator

ElectrolyteDilute high purity sulphuric acid of 1.240 specific gravity

Pillar seal100% factory tested, proven two layers epoxy resin seal

Relief valveComplete with integrated flame arrestor

Advantages

Maintenance convenient.

Non-Spill able construction design.

Transparent containers, convenient to observe. Special filter installation for acid fog proof.

High quality and high reliability.

Super long service life.

Special pole sealed technology.

Super reliability.

Application:

Telecom

Electric Utilities

Control Equipments

Security Systems

Medical Equipments

UPS systems

Railroad Utilities

Photovoltaic Systems

Renewable Energy Systems


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12Tubular Vs Normal Battery

Tubular Batteries ormal Flat plate batteries

Life expectancy 4 to 5 years Maximum 3 years

Low water loss Needs frequent water topping up

Cyclic Life is High Low cyclic life

Operate consistently even at high

temperatures.

Useful only at recommended

temperature conditions.

Suitable for High end applications. Not recommended for heavy

applications.

Complex design. Simple design.

High Price. Affordable price.

Fast charging battery. Charges slowly compared to tubular

batteries.

Recommended for high productive

applications.

Recommended for small homes and

budget-conscious people.

Highly reliable Reliable

Unique Design Features and Benefits

Higher energy density than flat plate positive plate constructed batteries means

better performance


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13 Greater surface area optimizes active material utilization which allows for

higher voltages under load, resulting in superior performance in high rate

and cold storage applications.

It resist corrosion which is superior to gravity cast flat plate construction

and improves battery life

Uniform distribution of active material and weight is achieved through a wet

filling process which enhances plate uniformity

Round, non-woven tubular gauntlets provide superior resistance to active

material shedding

Fully enveloped separators reduce the chance of short circuiting

1" sediment space to prevent short circuits

Rubber terminal bushings absorb impact and shock on rough floors.

Nickelcadmium battery

The nickelcadmium battery (Ni-Cd

battery or NiCad battery) is the most

commonly used alkaline rechargeable

battery. They use nickel hydroxide Ni

(OH)2 for the positive electrode (cathode),

metallic cadmium Cd as the negative

electrode (anode) and an alkaline

potassium hydroxide KOH electrolyte.

Poly vinyl chloride is used as separator.

The abbreviation Ni-Cd is derived from

the chemical symbols of nickel (Ni) and cadmium (Cd).


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14NiCd batteries are used in cordless and wireless telephones, emergency

lighting, and other applications. With a relatively low internal resistance, they can

supply high surge currents. This makes them a favourable choice for remote-

controlled electric model airplanes, boats, and cars, as well as cordless power

tools and camera flash units.

Larger flooded cells are used for aircraft starting batteries, electric vehicles,

and standby power.

Advantages

It facilitates fast charging and has a longer life. It allows charging at low temperatures.

It is the most rugged battery that can withstand both electrical and mechanical

abuse and it is normally used for heavy duty industrial applications.

Their small size and high rate discharge capacity made portable tools and other

consumer applications practical for the first time.

Low internal resistance (less than half the equivalent NiMH cells) Wide temperature range (Up to 70C)

Typical cycle life is over 500 cycles.

The sealed nickel-cadmium cell can be stored in the charged or discharged

state without damage.

The electrolyte is commonly available, low costpotassium hydroxide KOH.

Available in a large variety of sizes and capacities.

Disadvantages

Low energy density.

Memory effect and not eco friendly due to the use of Cadmium.


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15 Cadmium is a high cost heavy metal and its use in consumer products is now

deprecated on environmental grounds.

Low cell voltage of 1.2 Volts compared with primary alkaline cells 1.5 Volts.

Applications

Motorized equipment

Power tools

Two way radios

Electric razors

Commercial and industrial portable products

Medical instrumentation

Emergency lighting

Toys

Lithium ion Battery

A lithium-ion Battery is also a

secondary storage battery. Lithium

ions move from the negative electrode

(cathode) to the positive electrode of

Li-ion cell during discharge and back

when charging. This metal case holds

a long spiral comprising three thin

sheets pressed together:

APositive electrode

ANegative electrode


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16 Aseparator

Inside the case these sheets are submerged in an organic solvent that acts as

the electrolyte. Ether is one common solvent. The separator is a very thin sheet of

micro perforated plastic. As the name implies, it separates the positive and

negative electrodes while allowing ions to pass through. The positive electrode is

made of Lithium cobalt oxide, or LiCoO2. The negative electrode is made of

carbon. When the battery charges, ions of lithium move through the electrolyte

from the positive electrode to the negative electrode and attach to the carbon.

During discharge, the lithium ions move back to the LiCoO2from the carbon.

The movement of these lithium ions happens at a fairly high voltage, so each

cell produces 3.7 volts. This is much higher than the 1.5 volts typical of a normal

AA alkaline cell.

Advantages

Light weight because the electrodes of a lithium-ion battery are made of

lightweightlithium andcarbon.

Less loss: A lithium-ion battery pack loses only about 5 percent of its charge

per month.

Lithium-ion batteries can handle hundreds of charge/discharge cycles.

Very high energy density. A typical lithium-ion battery can store 150 watt-

hours of electricity in 1 kilogram of battery .A lead-acid battery can store

only 25 watt-hours per kilogram.

Disadvantages


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17 They start degrading as soon as they leave the factory. They will only last

two or three years from the date of manufacture whether you use them or

not.

They are extremely sensitive to high temperatures.

More expensive.

There is a small chance that, if a lithium-ion battery pack fails, it will burst

into flame.

Uses

Portable devices: these include mobile phones and smart

phones, laptops and tablets, digital cameras and camcorders and torches

(flashlights).

Power tools: Li-ion batteries are used in tools such as cordless

drills, sanders, saws and a variety of garden equipment.

Electric vehicles: Because of their light weight, Li-ion batteries are used for

propelling a wide range of electric vehicles such as aircraft, electric

cars, hybrid vehicles, advanced electric wheel chairs, radio-controlledmodels, model aircraft and telecommunications applications.

Valve regulated Lead-Acid Battery

Valve-Regulated Sealed Lead-Acid Battery (VRLA BATTERY) is a new type

of sealed lead-acid battery

system. . It is a backup battery

for portable equipment and office

and factory automation. VRLA

battery has high power density,

low self-discharge, and provides

high performance while remaining economical to use. In addition to these


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18advantages, the sealed construction eliminates the necessity to fill it with water.

Thus, this battery is maintenance free.

Absorbed Glass Mat (AGM) Battery

Absorbent Glass Mat commonly known as AGM, is a type of battery under

sealed lead-acid batteries. They are created in a flat, rectangular design. One

feature of AGM batteries is the thin glass fibers interwoven into a mat. This makes

the battery spill-proof, as the fibers containing

the glass mat do not absorb the acid

composition. Because of this, AGM batteries can

be used without the limitations of hazardous

materials.AGMs unique composition allows the

batteries to produce high currents and longer life


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19span. The technology also minimizes internal resistance and helps the battery to

survive low temperatures. Users can benefit fromAGMs deep cycling capability.

Uses

Used for military aircrafts and UPS (uninterrupted power supply) because

of its weight, safety and long-lasting power.

AGM batteries are used in powering cars and car accessories such as

steering wheels, windshields and heated seats.

Used for motor homes and robotic applications.

Advantages of AGM Batteries

Low internal resistance

Longer, efficient usage

Ability to survive low temperatures

Spill proof

Water retention

Faster charging time

Disadvantages of AGM Batteries

More expensive than other batteries

Its performance and capacity gradually declines in time

AGM batteries are sensitive to overcharging

They are less eco-friendly when compared to other batteries because of its

reduced electrolyte


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20Gel Battery

The gel battery is similar to A G M battery, the difference is the use of silica

gel instead of fibrous silica gel.

vhse eet-cell and battery (class note)-part2

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