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BATTERIES

BATTERIES. Heart of the electrical system. Functions. Supply energy to electrical systems when the vehicle is not running Operating cranking system Store energy Supply extra power when demand exceeds supply. THE GALVANIC REACTION. Creates a charge differential by chemical reaction

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BATTERIES

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  1. BATTERIES Heart of the electrical system

  2. Functions Supply energy to electrical systems when the vehicle is not running Operating cranking system Store energy Supply extra power when demand exceeds supply

  3. THE GALVANIC REACTION • Creates a charge differential by chemical reaction • Production of current when two dissimilar metals are placed in electrolyte • Creates corrosion between dissimilar metals [steel & aluminum]

  4. TYPES OF BATTERIES • The term battery means a collection of galvanic cells connected • Current 12 volt batteries have 6 series-connected cells housed in a polypropylene case • Each cell has positive and negative plates [anode & cathode]

  5. The negative plates are connected to each other and so are the positive plates • Negative and positive plates are arranged alternately in each cell • Positive and negative plates are insulated from each other by electrically insulating separator plates • This assembly is submerged in cell case full of electrolyte, 64% water 36% sulfuric acid

  6. CELL CONNECTORS • Cell elements are connected in series • Positive strap of one cell is connected to negative strap of the adjacent cell • Connections are made through the cell partitions in the case or over the top of the partitions

  7. PLATES • Plates are cast from lead • Then are covered in a paste unique to the polarity of each plate • Positive plate paste is made from lead oxide • Negative plate paste is sponge lead • Antimony is added to plate material to minimize corrosion

  8. SEPERARTOR PLATES • Prevent the battery grid plates from shorting out • Thin glass fiber plates • Allows electrolyte to flow easily through out cell while insulating the plates from each other • Plates sometimes shed the paste that was bonded to them at manufacturing commonly caused by vibration or deep cycling • To prevent this from shorting out sediment chambers are used to collect this material

  9. ELECTROLYTE • Battery acid [electrolyte] is typically 36% sulphuric acid and 64% water • Electrolyte is measured by specific gravity • Specific gravity is the weight of a liquid or solid versus that of the same volume of water • Specific gravity of water is 1.000 • Specific gravity of electrolyte is 1.265 at 80 degrees F

  10. When specific gravity is low the battery is said to be what?? In a state of discharge Battery could freeze in colder climates If specific gravity is too high the plate grids in the battery could be damaged Battery acid is very corrosive and will cause skin and eye damage, clothing, metal and painted surfaces damage

  11. 84 FACTOR • Actual specific gravity of electrolyte in any cell in a battery relates directly to its voltage • Voltage can be calculated by adding .840 to the specific gravity reading 1.265 + 0.840 =2.100 volts

  12. DISCHARGE CYCLE • The positive plate reacts with the sulfuric acid, which results in an oxygen molecule being released into the electrolyte • The negative plate reacts with the electrolyte to form lead sulfate • The action will occur until both the positive and negative plates are coated with lead sulfate

  13. CHARGE CYCLE • The sulfate coatings on the plates are returned to reform electrolyte • Water molecules are reduced to hydrogen and oxygen • The hydrogen combines the electrolyte to form sulfuric acid • The oxygen is drawn to the positive plates to reconstruct the lead peroxide coating

  14. When a battery is in the charge cycle, gassing is caused by electrolysis. • Gassing is the conversion of water in the electrolyte to hydrogen and oxygen gas • Forming an explosive combination!!!

  15. DEEP CYCLE BATTERIES • Similar in many respects to the standard battery • However plates are made much thicker to avoid? • Buckling caused by the heat created internal resistance

  16. SULFATION • Condition occurs when battery becomes discharged to the point that the sulfate coating hardens on the plates and can no longer be converted

  17. MAINTENANCE-FREE BATTERIES • Essentially the same construction as lead batteries • Uses substances such as calcium, cadmium, and strontium instead of antimony on the plates • These substances reduce gassing during the charging cycle • Additionally an expansion or condensing chamber is used to contain the gassing

  18. GELLED ELECTROLYTE BATTERIES • Gel cell • Similar to standard electrolyte batteries • Main difference of the gel cell is the electrolyte • The gel battery uses a special thixotropic electrolyte that when stirred or shaken liquefies but returns to the gelled state when left at rest

  19. ADVANTAGES • For this reason it never requires refilling • Spill-proof and leak-proof • Vent no oxygen or hydrogen during charging • Vibration resistant • Double the service life of maintenance free battery • Can sustain deep cycling

  20. DISADVANTAGES • Weigh more • Will fail if overcharged • Requires special chargers [automatic, temperature-sensing, voltage-regulated] • Vulnerable to abuse

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