© 2012 Delmar, Cengage Learning Battery Service Chapter 27

© 2012 Delmar, Cengage Learning

Battery Service

Chapter 27


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


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


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


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


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



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



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


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


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


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


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



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



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




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


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


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

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© 2012 Delmar, Cengage Learning Battery Service Chapter 27