Swaminarayan college of engineering and technology

• Topic: BATTERY

• Prepared by: Anjali Sharma Guide By: Jigna Parmar Shivani Gupta

BATTERY :A series, parallel or series-parallel group of cells

is called a Battery.

For a circuit, if higher voltage is required - a battery containing number of cells connected in series. if larger current is required- number of cells connected in parallel if larger current and higher voltage is required- a battery containing number of cells connected in series parallel(mixed) combination is used.

The following storage batteries are in common use: Lead-Acid battery Nickel –Iron battery Nickel – Cadmium battery

Lead Acid Battery :• Following are the important materials used in a lead

acid battery :1. Positive Plate or Anode : It is made up of lead

peroxide(PbO2) plate of chocolate, dark brown colour.They are of two types :

(i) Plante Plates(i) Plante Plates(ii) Faure of Pasted Plates.(ii) Faure of Pasted Plates.

2. Negative Plates or Cathorde : It is made up of pure lead(Pb).

3. Electolyate: aqueous solution of sulhuric acid (H2SO4) is used as electrolyt .

4. Container : containing plates and electrolyte is placed in a container. Made of hard rubber and bitumen compound,glass,moulded plastic,ceramic etc.

5. Separators : The separators are used to prevent them from coming in contact with each other

Continue to Lead Acid Battery…

6.Bottom blocks : Bottom blocks are used to provide a sufficient clear space for plates internal short circuit.

7. Plate Connectors : To connect the positive plates together, separate connectors are used. similarly negative plates are connected together. They are made of lead and alloy.

8. Vent Plug : made up of rubber and screwed to the cover of the cell provided for free exit of gas formed inside the battery and prevent the escape of electrolyte.

9. Partition Wall : for separation two cells.10.Cell connectors : To connect cells in series together.

They are lead alloy bars.

Working of a Lead Acid Battery :A Lead – Acid Lead – Acid battery is a device for storing

electrical energy in the form of chemical energy.The active elements in a lead – acid battery are (i) Lead- peroxide(PbO2) as positive plate (ii) Spongy lead (Pb) as negative plate.

Both the plates are suspended in an electrolyte of sulphuric acid (H2SO4) of specific gravity 1.28. The function of lead acid battery may be divided in two parts.

DischargingDischarging ChargingCharging

A Lead – Acid Lead – Acid battery is a device for storing electrical energy in the form of chemical energy.The active elements in a lead – acid battery are (i) Lead- peroxide(PbO2) as positive plate (ii) Spongy lead (Pb) as negative plate.

Both the plates are suspended in an electrolyte of sulphuric acid (H2SO4) of specific gravity 1.28. The function of lead acid battery may be divided in two parts.

DischargingDischarging ChargingCharging

Discharging : • When the external resistance is connected across the

anode and cathode of a fully charged battery,the current flows through the resistance,the direction of current is from cathode to anode through the electrolyte.Thus the external resistance absorbs electrical energy. This is called discharging.

• The sulphure acid when dissolved, its molecules are dissociated into hydrogen ions (2H+) and sulphate ions (SO4

--) which move freely in the electrolyte.• Sulphate ions move towards cathode and hydrogen oins

towards the anode.H2SO4 --> 2H+ + SO4

--

• Each sulphate ion (SO4--) moves towards the cathode

and becomes radical SO4.

• When the external resistance is connected across the anode and cathode of a fully charged battery,the current flows through the resistance,the direction of current is from cathode to anode through the electrolyte.Thus the external resistance absorbs electrical energy. This is called discharging.

• The sulphure acid when dissolved, its molecules are dissociated into hydrogen ions (2H+) and sulphate ions (SO4

--) which move freely in the electrolyte.• Sulphate ions move towards cathode and hydrogen oins

towards the anode.H2SO4 --> 2H+ + SO4

--

• Each sulphate ion (SO4--) moves towards the cathode

and becomes radical SO4.

Discharging Of A Battery:

At cathode,SO4

-- - 2e --> SO4 (radical)• Sulphate radical attacks the metallic lead cathode and

form lead sulphatePb + SO4 -> PbSO4

At anode,• Each hydrogen ion (H+) liberated from sulphuric acid

now moves to the anode and become hydrogen atom.2H+ + 2e -> 2H

• Since it is directly in contact with anode (PbO2), so it attacts and forms lead sulphate (PbSO4),

PbO2 + 2H -> PbO + H2OPbO + H2SO4 -> PbSO4 + H2O

PbO2 + H2SO4 + 2H -> PbSO4 + 2H2O

At cathode,SO4

-- - 2e --> SO4 (radical)• Sulphate radical attacks the metallic lead cathode and

form lead sulphatePb + SO4 -> PbSO4

At anode,• Each hydrogen ion (H+) liberated from sulphuric acid

now moves to the anode and become hydrogen atom.2H+ + 2e -> 2H

• Since it is directly in contact with anode (PbO2), so it attacts and forms lead sulphate (PbSO4),

PbO2 + 2H -> PbO + H2OPbO + H2SO4 -> PbSO4 + H2O

PbO2 + H2SO4 + 2H -> PbSO4 + 2H2O

• Thus during discharging :

The electrodes are converted into lead sulphate(PbSO4)

Voltage of the battery fall from 2V to 1.8V. Density of electrolyte decreases from 1.28 to

1.15. Chemical energy stored is converted into

electrical energy.

• Thus during discharging :

The electrodes are converted into lead sulphate(PbSO4)

Voltage of the battery fall from 2V to 1.8V. Density of electrolyte decreases from 1.28 to

1.15. Chemical energy stored is converted into

electrical energy.

Charging : • During charging process,

excess electrons are supplied to the cathode. This creates a shortage of electrons at the anode.

• For charging, anode is connected to the positive terminal of the d.c. source and cathode is connected to the negative terminal of the sourceas shown in Fig.-->

• During charging, molecules of sulphuric acid (H2SO4) in solution again break up into hydrogen ions (2H+) and sulphate ions (SO4

--).

• During charging process, excess electrons are supplied to the cathode. This creates a shortage of electrons at the anode.

• For charging, anode is connected to the positive terminal of the d.c. source and cathode is connected to the negative terminal of the sourceas shown in Fig.-->

• During charging, molecules of sulphuric acid (H2SO4) in solution again break up into hydrogen ions (2H+) and sulphate ions (SO4

--).

At anode,SO4

-- ions move to the anode and give up its additional 2 electrons and become radical SO4 with the anode electrode PbSO4 and form lead peroxide (PbO2) and sulphuric acid (H2SO4).

SO4-- - 2e -> SO4

PbSO4+ SO4 + 2H2O -> PbO2 + 2H2SO4 At cathode,

Electrons liberated at anode through external circuit. Each hydrogen ion (H+) on reaching the cathode, takes one electron from cathode and become hydrogen atom

2H+ + 2e --> 2HThis atom react with lead sulphate cathode

forming lead and sulphuric acid according to ,PbSO4 + 2H -> H2SO4 + Pb

At anode,SO4

-- ions move to the anode and give up its additional 2 electrons and become radical SO4 with the anode electrode PbSO4 and form lead peroxide (PbO2) and sulphuric acid (H2SO4).

SO4-- - 2e -> SO4

PbSO4+ SO4 + 2H2O -> PbO2 + 2H2SO4 At cathode,

Electrons liberated at anode through external circuit. Each hydrogen ion (H+) on reaching the cathode, takes one electron from cathode and become hydrogen atom

2H+ + 2e --> 2HThis atom react with lead sulphate cathode

forming lead and sulphuric acid according to ,PbSO4 + 2H -> H2SO4 + Pb

• Thus during charging:

Lead sulphate anode gets converted into Lead Peroxide.

Lead Sulphate cathode gets converted into lead.

Voltage of the battery increases. Density of Sulphuric Acid increases. Electrical energy is stored in form of the

chemical energy.

• Thus during charging:

Lead sulphate anode gets converted into Lead Peroxide.

Lead Sulphate cathode gets converted into lead.

Voltage of the battery increases. Density of Sulphuric Acid increases. Electrical energy is stored in form of the

chemical energy.

Various Condition during charging & discharging

Capacity Of A Battery :

It is defined as the product of discharge current and time in hours.It is measured in Ampere hours(Ah).Mathematically, the product of discharge current in amperes and the time for discharge in hours till the voltage falls to a specified value is called capacity of a battery.

Battery Capacity = ID X TD AhWhere, ID = Current in ampere

TD = Time in hours

Sometimes the capacity of the battery is specified in watt-hour(Wh).

It is defined as the product of discharge current and time in hours.It is measured in Ampere hours(Ah).Mathematically, the product of discharge current in amperes and the time for discharge in hours till the voltage falls to a specified value is called capacity of a battery.

Battery Capacity = ID X TD AhWhere, ID = Current in ampere

TD = Time in hours

Sometimes the capacity of the battery is specified in watt-hour(Wh).

Watt-hour capacity is defined as the product of the average voltage during discharge and ampere-hour capacity of a battery.

Watt-hour capacity of a battery,

= Ah capacity x average voltage during discharge

= ID TD x VD Wh

• Where, ID = Discharge current

TD = Time of discharge

VD = Average voltage during discharge

Capacity of the battery depends on the following : Rate of discharge Density of Electrolyte Rise in temperature Size of the plates

Watt-hour capacity is defined as the product of the average voltage during discharge and ampere-hour capacity of a battery.

Watt-hour capacity of a battery,

= Ah capacity x average voltage during discharge

= ID TD x VD Wh

• Where, ID = Discharge current

TD = Time of discharge

VD = Average voltage during discharge

Capacity of the battery depends on the following : Rate of discharge Density of Electrolyte Rise in temperature Size of the plates

Efficiency of a Battery :Efficiency of a battery is the ratio of output during

discharging to the input to the battery during charging. The efficiency of a battery can be defined in following two ways :

1) Ampere-hour (Ah) efficiency :It is defined as the ratio of output in ampere-hours during

discharging to the input in ampere-hours during charging of the battery is called ampere-hour efficiency of the battery. It is also called as quantity efficiency of the battery.

• Mathematically,Ampere-hour efficiency,η Ah = Ampere-hours of discharge x 100 / Ampere-hours of charge

= Id Td x 100 / Ic TcWhere,Id = Current during discharge (A)Td = time of discharge (hours)Ic = current during charging ( A)Tc = time of charging (hours)

2) Watt-hour (Wh) efficiency :It is defined as the ratio of energy delivered in watt-hours

during discharge and energy drawn in watt-hours during charging .It is also known as energy efficiency.

• Mathematically,• Energy or watt-hour efficiency,

η Wh = Output in Watt-hours x 100 / Input in watt-hours = current delivered x time of discharge x avg.

potential diff. during discharge / current drawn x time of charge x avg. p.d.during charging = Id Td Vd x 100 / Ic Tc Vc

= (Id Td / Ic Tc ) x ( Vd / Vc) x 100 = η Ah x ( Vd / Vc) x 100

• Where,Vd = average terminal voltage during dischargeVc = average terminal voltage during charging

It varies from 72 to 80 %.

2) Watt-hour (Wh) efficiency :It is defined as the ratio of energy delivered in watt-hours

during discharge and energy drawn in watt-hours during charging .It is also known as energy efficiency.

• Mathematically,• Energy or watt-hour efficiency,

η Wh = Output in Watt-hours x 100 / Input in watt-hours = current delivered x time of discharge x avg.

potential diff. during discharge / current drawn x time of charge x avg. p.d.during charging = Id Td Vd x 100 / Ic Tc Vc

= (Id Td / Ic Tc ) x ( Vd / Vc) x 100 = η Ah x ( Vd / Vc) x 100

• Where,Vd = average terminal voltage during dischargeVc = average terminal voltage during charging

It varies from 72 to 80 %.