Lead Storage Battery Construction | Chemical Reactions | Battery Ratings 2022

LEAD STORAGE BATTERY 

Lead storage battery
Lead Stor­age Battery

A bat­tery con­sists of a num­ber of cells and each ell of the bat­tery con­sists of the fol­low­ing components. 

1. Con­tain­er

2.Positive Plate

3.Negative plate

4.Separator

5.Electrolyte

6.Cell cov­ers and vent plugs 

7.Cell con­nec­tors

8.Battery ter­mi­nals

1. Container

The con­tain­er hous­es the plates and the elec­trolyte. It is made of acid resist­ing mate­ri­als like glass or hard rub­ber depend­ing upon ser­vice requirements.

2. Positive plate

Pos­i­tive plate is made of lead-per­ox­ide (PbO) deposit­ed on a grid frame . The grid frame is made of anti­mo­ny-lead alloy. The colour of the pos­i­tive plate is dark brown.

3. Negative plate

Neg­a­tive plate is made of spongy lead (Pb). It is also deposit­ed on a grid frame for stiff­ness and strength. The colour of the neg­a­tive plate is grey. The num­ber of neg­a­tive plates in a bat­tery is always one more than the pos­i­tive plates to make use of both the sides of the pos­i­tive plate most effectively. 

4. Separator

It is made of thin sheet of e Sep­a­ra­tors are placed between­ma­te­ri­als. Ser­sheet of porous insu­lat­ing­placed between pos­i­tive and The pos­i­tive and neg­a­tive plates aree sep­a­ra­tors. The sep­a­ra­tors ee cir­cu­la­tion of the elec­trolyte betweene made of spe­cial­ly treat­ed wood,egative plates. The poN­ICt­ed elec­tri­cal­ly by the sep­a­ra­tors. Thsep­a­rat­ed ele­must allow free cir­cathe plates.glass, rub­ber etc. 

5. Electrolyte

The elec­trolyte is dilute sul­phuric acid (H.SO). terv grade sul­phuric acid is used for the pre­rrolyte. The spe­cif­ic grav­i­ty of the elec­trolyte is The rec­om­mend­ed val­ue of the spe­cif­ic grav­i­ty isof elec­trolyte. The spec1.21 for longer life of the batteries.

6. Cell cov­ers and Vent plugs

Each cell has a cov­er made of mould­ed hard rub­ber. Open­ings are pro­vid­ed in these cov­ers for two ter­mi­nal posts and vent plug. Vent plug has a vent hole for easy escape of gas formed inside the cell dur­ing charg­ing. Vent plugs can be eas­i­ly removed for adding electrolyte.

7. Cell connectors

Cell con­nec­tors are used to con­nect the divid­ual cells in series to give the required volt­age. Lead alloys are the material

8. Bat­tery terminals 

A bat­tery has two ter­mi­nals, the +ve and the ‑ve. polar­i­ties are marked on the ter­mi­nals. The mals are gen­er­al­ly made of lead alloys.terminals are gen

CHEMICAL REACTIONS DURING DISCHARGING IN LEAD STORAGE BATTERY

When the cell is ful­ly charged its pos­i­tive p or anode is PbO2, which is dark choco­late brown colour and the neg­a­tive plate or cath­ode is Pb which grey in colour.

When the cell dis­charges, it sends cur­rent through the exter­nal load.During dis­charg­ing the elec­trolyte H,50, is dis­so­ci­at­ed into pos­i­tive H, and neg­a­tive SO. ions. As the cur­rent with­in the cell is flow­ing from cath­ode to anode, H, ions move towards the anode and so, ions move towards the cathode.

At anode, H, com­bines with the oxy­gen of pbo: and H, SO, attacks lead to form PbSO4,. At cath­ode , S04 com­bines with Pb to form PbSO4,.

PHYSICAL CHANGES DURING DISCHARGING IN LEAD STORAGE BATTERY

Both the plates become Pbso4 which is whitish in colour.

Due to for­ma­tion of water spe­cif­ic grav­i­ty of the elec­trolyte decreases 

The volt­age of the cell decreases 

The cell gives out energy 

CHEMICAL REACTIONS DURING CHARGING IN LEAD STORAGE BATTERY

To recharge a dis­charged cell, direct cur­rent is passed through the cell in the reverse direc­tion by con­nect­ing the anode to the pos­i­tive ter­mi­nal of d.c. source and cath­ode to the neg­a­tive ter­mi­nal of the source 

Dur­ing charg­ing the H, ions move towards cath­ode and so4, ions move towards the anode and the fol­low­ing chem­i­cal changes takes place. 

PHYSICAL CHANGES DURING CHARGING 
IN LEAD STORAGE BATTERY

  1. Both the plates become Pbso4 which is whitish in colour
  2. Due to for­ma­tion of water spe­cif­ic grav­i­ty of the elec­trolyte decreases
  3. The volt­age of the cell decreases
  4. The cell gives out energy

ELECTRICAL CHARACTERISTICS OF LEAD ACID CELL 

The three impor­tant char­ac­ter­is­tics of lead acid cells are

1.Voltage

2.Capacity

3.Efficiency

1. Voltage

The open cir­cuit volt­age of a ful­ly charged cell is approx­i­mate­ly 2.2 volt. This val­ue is not fixed but depends on

c) Tem­per­a­ture

When the tem­per­a­ture increasethe volt­age is not much increases. 

2. Capac­i­ty

It is mea­sured in amp-hour (Ah). The capac­i­ty is always giv­en at a spec­i­fied rate of dis­charge. The capac­i­ty depends upon the following. 

Rate of discharge 

The capac­i­ty of a cell is mea­sured in Ah depends on the dis­charge rate. Capac­i­ty decreas­es with increased rate of dis­charge. Rapid rate of dis­charge means, greater fall in volt­age of the cell due to inter­nal resis­tance of cell. More­over, with rapid dis­charge, the weak­en­ing of acid in the pores of the plates is also greater 

Temperature

At high temperature 

1.The chem­i­cal reac­tions with­in the cell take place­more vigrously. 

2.The resis­tance of acid is decreased.

Hence high tem­per­a­ture, increas­es the capac­i­ty of the lead acid cell. 

Hence it is bet­ter to oper­ate the bat­tery at a high temperature.

How­ev­er at high temperature. 

The acid attacks the anti­mo­ny ‑lead alloy grid,terminal posts and wood­en separators. 

The paste is rapid­ly changed into lead sul­phate­sul­pha­tion is always accom­pa­nied by expan­sion of paste at the pos­i­tive plates and resul­to in buck­ling and crack­ing of the grid. Hence, it isnot advis­able to work bat­tery above 40°C.

Density of electrolyte

As the den­si­ty of the elec­trolyte affects the inter­nal resis­tance and the vigrous of chem­i­cal reac­tion, den­si­ty of elec­trolyte has an impor­tant effect on the capac­i­ty capac­i­ty increas­es with the density.

Quan­ti­ty of active mate­ri­alsCapac­i­ty of the bat­tery depends upon the amount of active mate­r­i­al. For obtain­ing cells of greater capac­i­ty it is nec­es­sary to pro­vide the plates with larg­er amount of active material. 

3) Effi­cien­cy

1.The Ah effi­cien­cy decreas­es due to self dis­char­ge­of the plates caused due to local reac­tions.
2.Due to leak­age of cur­rent because of faulty insu­la­tion between the cells of the bat­tery the Wh effi­cien­cy decre­cas­es when the increas­ing of charge volt or reduc­ing of dis­charge volt.

  1. The Ah effi­cien­cy is of lead acid cell nor­mal­ly between 90–95%. and the Wh effi­cien­cy varies between 72–80%.

2 thoughts on “Lead Storage Battery Construction | Chemical Reactions | Battery Ratings 2022

  • April 29, 2022 at 7:41 pm
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  • May 1, 2022 at 5:32 pm
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    Reply

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