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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