BATTERY

BATTERY 

   It  is a electrochemical device which convets chemical energy into electrical energy into electrical enegy . it does not store electriocity. it is most important component of an automobile electrical system. it stores electric energy into chemical energy
# function of battery in automobile :-
      - it supplies electric current for the starting motor and ignition system . when the engine is started
- it supplies electric current fot the lights, sterio, heaters and other accesories whenever required

@ lead Acid battery :-

       a lead acid battery uses three chemical
* sponge lead insolid form (Pb-)
* lead-peroxide in past form (PbO2-)
* Sulphuric acid in liquid form (H2SO4)
# contruction :-
   a lead acid battery consist of following components

- Battery core :-

    it is a box made of moulded plastic or hard rubber. it has separate compartments for each cell at the bottom each cell at the bottom rest are made for plates

- Plates :-

      each cell copnsist of two types of battery plates such as negative plates and positive pltes . the colour of negative plate become gray and that bof positive plate is chocolate brown . there are a number of plates in a cell arranged alternatively with negative and positive plates

- Seperator :-

      it is placed between negative and positive plates . it is done to avoid direct contact between the plates so that there is no short circuiting . the separators are thin shades of non conducting material such as wood, rubber, fibres , glass etc

- Electrolyte :-

     it is filled in the battery after it is assembled . each cell is filled with electrolyte such that it fill the cell case upto 10 to 15 mm above the level of plates . the electrolyte used in lead acid battery is sulphuric acid solution
- cell cover and vent plug :-
      each cell is cover with moulded rubber or plastic. each covers has holes for positive plate connector negative plate connector are used to connect the cells in series. the vent holes allow the gasses to produced in battery to escape

# Working :-

    the negative plate contain lead (Pb) and postive plate contain peroxide (PbO2) . sulphuric acid solution works as electrolyte at covers both the plates . this is the fully charged stage od battery . when th positive and negative terminals of the battery are connected to an electrical device. the battery gives current to device and start discharging itself. following chemical reaction takes when the battery is discharging
PbO2 + 2H2SO4 + Pb(-) -------> PbSO4 + 2H2O + PbSO4
    when the battery is discahrged it needs recharging . now the reverse connection are made and following chemical reaction take place
  PbSO4 + 2H2O = PbSO4------> PbO2 + 2H2SO4 + Pb

      @ Specific gravity of electrolyte :-

            the specific gravity of elcctrolytic is a measure of sulphuric acid content in the electrolyte. the specific gravity of water is considered as 1
     put 1 kg of water on one side simple balance and one kg of electrolyte at other side of the balance
    now, if the electrolyte is heavier its side would go down all the liquids are either heavier or lighter than water . according their specific gravity is more or less
    the specific gravity of pure sulphuric acis is 1.835 . the specific gravity of electrolyte used in lead acid battery would be 1.265 . the specific gravity of electrolyte is fully discharge battery comes down to 1.100
- fully charged = 1.265-1.280
-75% chrged= 1.210-1.320
- 50% charges= 1.165-1.180
- 25% charged= 1.120-1.130
- completely charged = 1.070-1.100
# effect of temperature on specific gravity :-
        the specific gravity electrolyte decreases with the increase of its temperature or vice versa . the specific gravity of sulphuric acid solution is 1.265 at 27 degree celcius

@ Battery testing :-

      1. Specific gravity test :-

                this test is conducted to measure the specific gravity of the battery . it is done with the help of hydrometer as done with the help of hydrometer, there is a glass body in which a glass and float is put . the float has a scale on it to give the observation reading. a rubber ball is fixed on the top of the glass body its lower end tube is called sample tube
     to check the specific gravity the sample tube is immersed in battery through the filler hole. the rubber bulbs is than required . after removing the pressure from bulb the electrolyte comes out in the hydrometer
   now, the specific gravity is noted on the scle of float

2. Terminal voltage Test ;-

      the voltage difference between the battery terminal is measured with the help of a voltmeter . if the voltmeter reads 12.9 than it is fully charged