Transcript Battery Fundamentals

Battery Fundamentals
Chapter 26
© 2012
Delmar,
Cengage
Learning
© 2012
Delmar,
Cengage
Learning
Objectives
• Describe battery parts and operation
• Understand how a battery converts chemical
energy to electrical energy
• Explain battery capacity ratings
• Select the correct battery type to use in a variety
of applications
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© 2012
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Introduction
• Battery: heart of a vehicle's electrical system
– Converts electrical energy into chemical energy
• Converts chemical energy back into electrical
energy
– Provides power to accessories
– Supplies current to the starter
– Acts like a capacitor
• Starter motor: largest load
– Draws more than 100 amperes
– Battery voltage is low after use
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© 2012
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© 2012
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Battery Parts and Operation
• DC voltage
– Produced when two different metals are
immersed in an electrolyte solution
• Automotive batteries
– Plates provide 2.1 volts
– Fully charged positive plate: combination of lead
and oxygen (i.e., lead dioxide)
• Plates: grids with horizontal and vertical bars
• Battery's case filled with electrolyte mixture
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Battery Parts and Operation
(cont'd.)
• Battery cell
– Consists of a packet of several positive and
negative plates
• Battery terminals
– Connections are made of lead
– Some batteries have side terminals
• Battery case
– Most are constructed of lightweight plastic
• Cell caps
– Most battery tops have removable cell caps
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Battery Recharging and
Discharging
• Current flows to battery from charging system
– Battery explosions injure 15,000 people a year
• Battery discharging
– Positive and negative plates become alike as the
battery discharges
• Process is reversed during recharging
• After repeatedly charging and discharging
– Active material on the cell plates is worn
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Battery Capacity Ratings
• Battery capacity is related to:
– Surface of plates
– Weight of active materials on plates
– Strength of electrolyte solution
• Cold cranking amps (CCA) rating
– Most common method of rating batteries
– Some manufacturers rate batteries in watt-hours
• Reserve capacity
– Indicates how long a vehicle can be driven after
a charging system failure
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Battery Types
• Batteries are designed for specific uses
– Deep-cycle: original battery design that was used
in cars for many years
– Maintenance-free: have cell plates made of a
slightly different material
– Low-maintenance: revision of the maintenancefree battery
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Battery Plate Size
• Battery size is related to its reserve capacity
– Vehicles with larger engines and more
accessories require batteries with more plate
surface
• Recombination batteries
– Sealed batteries using electrolyte gel or
microporous nonwoven glass
• Absorbed glass mat batteries
– Do not use free-liquid or gel electrolyte
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Battery Selection
• BCI lists group numbers
– Indicate physical size of batteries
• Considerations
–
–
–
–
Must fit the battery box
Posts must be on the correct side of the battery
Battery holddown must fit the battery
Battery cannot be so high that it shorts on the
hood
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Battery Service Life
• Average battery
– Service life of three to five years
– Life is determined by amount of material shed
from surface of positive plates
• Effects of sulfation
– Usually reversible
• Effect of temperature on batteries
– Batteries do not work well in cold weather
• Engine becomes harder to crank
• Battery that is not fully charged will freeze easier
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Battery Cables
• Must be large enough to carry all current
demanded by starter
– Large cable is connected directly to the starter
– Cables for 12-volt systems are usually four or six
gauge
• Battery terminal clamps
– Made of plated steel, brass, or lead
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Battery Holddowns
• Battery must be held
in its tray
– Can fall out as the
car travels over
bumps
– Excessive vibration
can harm the
battery
• Holddowns are
made of steel or
plastic
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Reasons for Battery Failure
• Include:
– Damaged battery case can leak electrolyte
– Undercharging can cause sulfation
– Overcharging can cause buckled and warped
plates
– Vibration can cause more material to be shed
from plates
– Internal shorts between the plates can cause a
dead cell
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Hybrid Electric Vehicle and
Other Battery Types
• Other types of batteries include:
– Nickel metal hydride batteries
• Subject to memory effect
– Lithium-ion batteries
• Term used for all batteries that use lithium
• Typical hybrid battery
– Most hybrid automobiles use NiMH batteries
• Paper membranes absorb electrolyte
• Hybrid battery pack gets hot
– Has air cooling system
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© 2012
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© 2012
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© 2012
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© 2012
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