Download Battery Service - Cengage Learning

Battery Service
Chapter 27
© 2012 Delmar, Cengage Learning
Objectives
• Inspect a battery and recommend and needed
service
• Service a battery
• Perform a variety of tests on a battery and make
a diagnosis from the results
• Select the best charge rate and recharge a
battery
• Perform battery service safely
• Safely and correctly jump-start a car
© 2012 Delmar, Cengage Learning
Introduction
• Batteries last an
average of three to five
years
– Manufacturers provide
a code to tell where
and when a battery
was made
• Letters A through M
represent the month
• Number represents
the year
© 2012 Delmar, Cengage Learning
Battery Inspection
• Inspect the following:
–
–
–
–
–
–
Date code on battery label
Battery case condition
Level of electrolyte
Condition of cables and terminals
Battery holddown and tray
Built-in hydrometer
© 2012 Delmar, Cengage Learning
Battery Service
• Replenish water through holes on the top
– Use clean filtered water
• Lead oxidation is often found on positive post
– Reduces or stops flow of current
• Corrosion looks like white powder
– Battery acid is corrosive
– Neutralized with a base such as baking soda
• New batteries may be shipped dry
– Add new electrolyte and allow to sit 15 minutes
© 2012 Delmar, Cengage Learning
Replacing a Battery
• Disconnect ground cable first
– Do not twist battery posts
– Remove hold down clamp and lift the battery out
• Causes of increased resistance
– Battery acid vapors and air
– Terminal clamp can be replaced if corroded
• Holddown bracket
– Must hold the battery firmly in place
• Reinstall the battery and holddown clamps
– Check that the battery starts the car
© 2012 Delmar, Cengage Learning
© 2012 Delmar, Cengage Learning
Battery Testing: Measuring a
Battery’s State of Charge
• Hydrometer: tests strength of electrolyte
– Compares weight of liquid to weight of pure water
– Batteries can freeze in cold weather
• Low charge battery freezes at 19°F
• Fully charged battery will not freeze
• Reading the hydrometer
– Follow guidelines
• Built-in hydrometer batteries
– Included in some maintenance free batteries
© 2012 Delmar, Cengage Learning
© 2012 Delmar, Cengage Learning
Battery Testing (cont'd.)
• Refractometers: more accurate and versatile
– Electrolyte is placed on measuring prism
• Open circuit voltage
– Can determine if battery has sufficient charge
• Before testing, remove surface charge
• Remove terminal clamps
• Check voltage across positive and negative
terminals
• Fully charged: 12.6 volts or higher
• Less than 12.4 volts: recharge
© 2012 Delmar, Cengage Learning
Battery Charging
• Constant volt charger reduces charging current
while maintaining output voltage
• Rate of charge: fast or slow
– Keep charging voltage below 15 volts
• Sulfation: lead sulfate in plates becomes hard
and resists recharge
• Slow charge: only way to completely recharge a
battery
– Impractical unless battery is removed from
vehicle
© 2012 Delmar, Cengage Learning
Storing a Vehicle
• When a vehicle is left for a month at a time
without being started
– Battery is still being discharged
• Half charged battery can often start an engine
during warm weather
– Hard on the battery
– Presents extra challenges for the alternator
• Disconnect the battery any time it is not to be
used for ten days or more
© 2012 Delmar, Cengage Learning
Battery Capacity Tests
• Battery conductance testing
– Means of quickly testing if a battery can conduct
current
– Indicates the amount of battery plate surface
available to react chemically with electrolyte
– New battery conducts 110%-140% its CCA rating
– Can detect shorts and open circuits in cells
– Reliable, but may give false positive result
© 2012 Delmar, Cengage Learning
Battery Capacity Tests (cont’d.)
• Battery load testing
– Battery capacity test that can be done to a
battery with at least a 75% state of charge
• Volt-amp tester (VAT)
– Used by some shops for the battery load test
– Has a voltmeter, an ammeter, and a variable
carbon pile rheostat
– Amount of current flow through the cables is
usually sensed by an inductive pickup
© 2012 Delmar, Cengage Learning
© 2012 Delmar, Cengage Learning
Battery Drain Test/Parasitic Load
• Parasitic load: circuit that causes a battery to
drain
– Electronic components draw small amounts of
current at all times
• Test by using an ammeter that can read tenths of
amp: less than 0.050 A is acceptable
• Using a test light: one candlepower or smaller is
acceptable
• Dirty battery can also cause a drain
– Test with a voltmeter between the negative
battery post and the top of the case
© 2012 Delmar, Cengage Learning
© 2012 Delmar, Cengage Learning
Battery Jump-Starting
• Dead batteries in good condition are common
– Remove and recharge
• Jumper cables
– Use high-quality braided-copper jumper cables
– Best jumper cables are rope stranded
• Jump-start procedure
– Connect hot cable first and ground cable last
• Do not connect other end of negative cable
– When engine starts, disconnect the ground
• Remove cables in reverse order
© 2012 Delmar, Cengage Learning
© 2012 Delmar, Cengage Learning
© 2012 Delmar, Cengage Learning
Hybrid Battery Service
• Low-voltage electrical system supplies power to
control high-voltage modules
– Also supplies power to engine and accessories
• Some hybrids use conventional battery
– Mounted under the hood
• Others use small 12-volt auxiliary battery
– Located in trunk
– Absorbed glass mat (AGM) battery
• AGM batteries cannot be fast charged
• Trickle-charged at maximum of 3.5 amps
© 2012 Delmar, Cengage Learning
Hybrid Battery Service (cont'd.)
• Most batteries are guaranteed for eight years or
100,000 miles
– Replacement battery packs: $3,000 to $8,000
– Recharging requires dealership service
• Intake vents for battery cooling
– Often on a shelf above the back seat
• If vents are blocked the battery will get hot
• Vehicle will run only on gasoline engine
© 2012 Delmar, Cengage Learning
Hybrid Battery Service (cont'd.)
• General hybrid safety
– Know what is safe to touch
• Orange means high voltage
– System is dangerous when key is in
– High-voltage battery pack contains high voltage
even after depowering
– Keep one hand in your pocket and do not lean
against the car
– Do not wear rings or watches
– Wear insulated gloves
© 2012 Delmar, Cengage Learning