Download 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
 Production of current when two dissimilar
metals are placed in electrolyte
 Creates corrosion between dissimilar
metals [steel & aluminum]
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TYPES OF BATTERIES
The term battery means a collection of
galvanic cells connected
 Current 12 volt batteries have 6 seriesconnected cells housed in a polypropylene
case
 Each cell has positive and negative plates
[anode & cathode]
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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
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
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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
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SEPERARTOR PLATES
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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
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
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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
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
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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
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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
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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!!!
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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
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SULFATION
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Condition occurs when battery becomes
discharged to the point that the sulfate
coating hardens on the plates and can no
longer be converted
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
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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
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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
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DISADVANTAGES
Weigh more
 Will fail if overcharged
 Requires special chargers [automatic,
temperature-sensing, voltage-regulated]
 Vulnerable to abuse
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