© 2012 delmar, cengage learning battery service chapter 27
TRANSCRIPT
© 2012 Delmar, 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