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ELECTRICAL I LESSON 2 BATTERY SERVICE • Use the Navigation buttons to progress through this lesson. Battery capacity ratings • Battery capacity ratings are set up by the Battery Council International (BCI) and the Society of Automotive Engineers (SAE). The ratings show the battery’s ability to deliver current and voltage under different conditions. A battery’s ability to deliver current depends on: • The surface area of the plates • The mass of the plate material • The mass of sulfuric acid in the electrolyte • Internal Resistance • Battery Temperature Rating Methods • Ampere-Hour Rating • The amount of current a battery can produce for 20 hours at 80oF before its voltage drops below 10.5 volts (1.75v per cell). • 3 amps for 20 hours would be 60A-hr. Rating Methods • Cold Cranking Rating • The amount of current a battery can produce for 30 seconds at 0oF before its voltage drops below 7.2 volts. (1.2v per cell) Rating Methods • Reserve Capacity Rating • The number of minutes a battery can produce 25 amps before its voltage falls below 10.5 volts (1.75v per cell) Battery Size • A BCI group number identifies a battery by size dimensions, post arrangement, voltage, and hold down location. A battery manufacturer may make a variety of current capacity batteries in the same group. (see chart in AE1 Manual) Battery Installation Requirements • Close to starter and alternator or generator • Away from exhaust components • Held down securely to reduce vibration • Accessible for service Battery Output Requirements Multiple Battery Connections • Series • Batteries connected in series will increase the overall voltage. The current capacity will be limited to the lowest rated battery. Multiple Battery Connections • Parallel • Batteries connected in parallel will increase the overall current if the voltages are the same. Multiple Battery Connections • Series - Parallel • Batteries connected in series-parallel increases both voltage and current. Causes for Battery Failure • Overcharging • Excessive current through the battery caused by extra high charging voltage generates excess heat. The heat can cause plate warpage and shedding. Heat also creates evaporative electrolyte loss. Internal battery temperature should be kept below 120oF. • Undercharging • A battery that is partially discharged has lead sulfate (PbSO4) in the plate material. If the battery is not recharged completely, the lead sulfate crystallizes and then the battery plate material can not be restored by recharging. This condition is called a sulfated battery. • A battery that is stored for a period of months will discharge internally and a sulfated condition will result. • Concrete floor myth!!! Causes for Battery Failure • Excessive Deep Cycling • When a starting battery is completely discharged and recharged repeatedly the plate material will shed from the grid and reduce the current capacity. • Vibration • Vibration causes the plate material to fall off the grid. The plate material may collect in the bottom of the cell and short the positive and negative plates together. Vibration can also cause open internal connections between cells. Battery Service and Testing Battery Service • Safety Precautions • keep sparks and flames away • charge in a well-ventilated area • charger should be UNPLUGGED and TURNED OFF before connecting to a battery, in a well-ventilated area • remove jewelry • add only distilled water to a battery • never attempt to charge or boost a frozen battery • always disconnect the negative (ground) cable first and reconnect it last • do not pound on cable clamps Battery Service • Battery Inspection • check case for physical damage or missing caps • check case for dirt and moisture which could cause current flow across the case. Clean with baking soda & water. • check for electrolyte leakage around battery posts • check for post and cable corrosion or damage • check condition of hold down • check heat shield condition • check electrolyte level if possible, it should cover the top of the cell plates Battery Testing • State-of-Charge • Load or Capacity Test • 3 - minute charge test State-of-Charge • Two Methods: Open Circuit Voltage & Specific Gravity • Open circuit voltage - OCV • Using a digital voltmeter of 0.5% or better accuracy, measure the battery voltage when it is not loaded at 80oF. Check electrolyte level before measuring voltage. • 12.6v > fully charged • 12.4v > 75% charged • 12.2v > 50% charged • If the battery’s voltage is above 12.6v, it has a surface charge that must be removed. Load the battery for 15 to 30 seconds (100A) with a carbon pile or the starter. Allow voltage to stabilize for 2 minutes before re-measuring OCV. State-of-Charge con’t • Specific Gravity • Compares the density of the electrolyte to that of water to determine state of charge. An hydrometer is used to measure the specific gravity of the electrolyte at 80oF. The reading must be adjusted if the electrolyte temperature is above or below 80oF. • Add 0.004 for every 10o above 80o. Subtract 0.004 for every 10o below 80o. • 1.260 - 1.280 > fully charged • 1.230 - 1.250 > 75% charged • 1.200 - 1.220 > 50% charged. • If the difference between cells is 0.050, replace the battery. – see pg.181, vol. II Load or Capacity Test • This test determines the battery’s ability to deliver a large amount of current while maintaining its voltage at a usable level. The battery must be at least 75% charged when performing this test. • Using a carbon pile load the battery, for 15 seconds, to ½ the CCA or 3 times the ampere-hour rating. The voltage should remain at least 9.6v • If the battery is not marked for its rated capacity use the following guide lines for load: Engine Displacement Load Current Less than 3.0L 170A 3.0L to 5.5L 200A More than 5.5L 250A • If a load tester is not available, disable the engine's ignition of fuel system and crank the engine for 15 seconds. – See pg. 85, Vol. II 3 - minute charge test • Determines if the battery is sulfated. Can not be performed accurately on maintenance free batteries. • disconnect the (-) cable and properly connect a battery charger. • charge at a rate below 40A, but over 25A for 3 minutes • measure charging voltage after 3 minutes, then turn off charger • if the voltage was less than 15.5v, recharge the battery • if the voltage was over 15.5v, replace the battery Battery Charging • When charging a battery the following guidelines should be followed. • well ventilated area • place a damp cloth over the top to reduce gassing • disconnect (-) cable • check electrolyte level, caps or “eye’ • do not let battery temperature exceeds 120oF • except for Delco maintenance free batteries, do not allow charging voltage to rise above 15.5v • if a Delco maintenance free battery has been discharged for more than a few days, begin charging at a high current rate and voltage of at least 18v. – See pg. 182 Vol. II Jump Starting Procedure • 1. connect (+) to dead battery • 2. connect (+) to good battery • 3. connect (-) to good battery • 4. connect (-) to engine ground 18 inches or more from dead battery – do not let vehicles touch or boost with more than 16 volts – see pg. 186 Vol. II End Lesson Two • To return the the Automotive Electrical I course outline click here. • To visit the AC Delco battery web site click here. • To visit the Exide battery web site click here. • To visit the Johnson Controls battery web site click here. • To visit the Ovonic battery web site click here. • To visit the Black Panther battery web site click here.
