Microsoft Word batteryservicemaster2 doc Page 1 © Autoshop101 com All rights reserved BATTERY SERVICE This Automotive Series BATTERY SERVICE has been developed by Kevin R Sullivan Professor of Automot[.]
BATTERY SERVICE This Automotive Series BATTERY SERVICE has been developed by Kevin R Sullivan Professor of Automotive Technology Skyline College All Rights Reserved v1.1 Visit us on the web at: www.autoshop101.com BATTERY SERVICE Battery services are routinely performed These services include: Testing Charging Cleaning Jumping a dead battery Adding water Page © Autoshop101.com All rights reserved BATTERY TESTING Battery testing has changed in recent years; although the three areas are basically the same, the equipment has improved Visual Inspection State of Charge a Specific Gravity b Open Circuit Voltage Capacity or Heavy Load Test Note: This does not include the Midtronics battery tester which has a different test procedure and will be discussed later in this module Page © Autoshop101.com All rights reserved VISUAL INSPECTION Battery service should begin with a thorough visual inspection This inspection may reveal simple, easily corrected problems Check for cracks in the battery case and broken terminals Either may allow electrolyte leakage, which requires battery replacement Check for cracked or broken cables or connections Replace, as needed Check for corrosion on terminals and dirt or acid on the case top Clean the terminals and case top with a mixture of water and baking soda A battery wire brush tool is needed for heavy corrosion on the terminals Check for a loose battery hold-down or loose cable connections Clean and tighten, as needed Page © Autoshop101.com All rights reserved VISUAL INSPECTION CONTINUED Check the electrolyte fluid level The level can be viewed through the translucent plastic case or by removing the vent caps and looking directly into each cell The proper level is 1/2" above the separators (about 1/8" below the fill ring shown below) Add distilled water if necessary Do not overfill Check for cloudy or discolored electrolyte caused by overcharging or vibration This could cause high self discharge Correct the cause and replace the battery STATE OF CHARGE The state of charge of a battery can be easily check in one of two ways: Specific Gravity Test Open Circuit Voltage Test Note: 1: A state of charge test is required to determine if there is sufficient charge in the battery to properly perform a capacity test (explained later) 2: The only exception to this is the MIDTRONICS Battery Tester This new state of the art capacitance tester will be discussed later in this module Page © Autoshop101.com All rights reserved SPECIFIC GRAVITY Specific gravity means exact weight A "Hydrometer" or a "Refractometer" compares the exact weight of electrolyte with that of water Strong electrolyte in a charged battery is heavier than weak electrolyte in a discharged battery By weight, the electrolyte in a fully charged battery is about 36% acid and 64% water The specific gravity of water is 1.000 The acid is 1.835 times heavier than water, so its specific gravity is 1.835 The electrolyte mixture of water and acid has a specific gravity of 1.270, usually stated as "twelve and seventy." Page © Autoshop101.com All rights reserved SPECIFIC GRAVITY READINGS By measuring the specific gravity of the electrolyte, you can tell if the battery is fully charged, requires charging, or must be replaced It can tell you if the battery is sufficiently charged for a capacity (heavy-load) test The battery must be at least 75% charged to perform a heavy load test (The heavy load test will be discussed later) In other words, each cell must have a specific gravity of 1.230 or higher to proceed CELL READINGS PERCENT CHARGED 1.270 100 % 1.230 75% 1.190 50% 1.145 25% 1.100 0% If the battery is less than 75% charged, it must be fully recharged before proceeding If the battery is 75% or higher proceed to a heavy load test A battery not sufficiently charged will fail because it is discharged SPECIFIC GRAVITY - EXCESSIVE CELL VARIATION READINGS Variation in specific gravity among cells cannot vary more than 0.050 The variance is the difference between the lowest cell and the highest cell A battery must be condemned for excessive cell variation if more that 0.050 In the example below, the highest SG reading is cell #1 (shown in green) while the lowest SG reading is cell #5 (shown in blue); the difference is 0.070 which requires battery replacement Cell #5 if failing Cell #1 Cell #2 Cell #3 Cell #4 Cell #5 Cell #6 1.260 1.230 1.240 1.220 1.190 1.250 Many factors contribute to cell variation; for example, if water was just added to that cell, the cell is then diluted with water resulting is a lower specific gravity reading Recharging the battery would correct this false reading In some cases if a battery that has cell variation slightly over the specification and is only about 50% charge, charging the battery at a slow rate of charge (5A) may reduce the cell variation, thus saving the battery Page © Autoshop101.com All rights reserved SPECIFIC GRAVITY TEST PROCEDURE (HYDROMETER) Wear suitable eye protection Remove vent caps or covers from the battery cells Squeeze the hydrometer bulb and insert the pickup tube into the cell closest to the battery's positive (+) terminal Slowly release the bulb to draw in only enough electrolyte to cause the float to rise Do not remove the tube from the cell Read the specific gravity indicated on the float Be sure the float is drifting free, not in contact with the sides of top of the barrel Bend down to read the hydrometer at eye level Disregard the slight curvature of liquid on the float Record your readings and repeat the procedure for the remaining cells Page © Autoshop101.com All rights reserved ADJUSTED SPECIFIC GRAVITY READINGS Temperature correction is needed because specific gravity changes with temperature Cold thickens the electrolyte and raises the specific gravity Heat thins the electrolyte and lowers the specific gravity Hydrometers are calibrated at 80'F (26.7'C) Electrolyte temperatures above or below 80'F must be adjusted For every 10'F increment below 80'F, subtract 0.004 to the hydrometer readings, and for each 10'F increment above 80'F, add 0.004 to the readings See the examples below Page © Autoshop101.com All rights reserved SPECIFIC GRAVITY TEST PROCEDURE (REFRACTOMETER) A Refractometer optically measures the specific gravity No temperature correction is needed Wear suitable eye protection Remove vent caps or covers from the battery cells Place one drop of electrolyte on the refractometer lens and close the prism Hold the refractometer up to the light and reading chart from view finder Record your readings and repeat the procedure for the remaining cells Page © Autoshop101.com All rights reserved SPECIFIC GRAVITY TEST PROCEDURE (AC Delco Battery with built- in Hydrometer) Wear suitable eye protection Observe the built-in hydrometer Green Dot is visible: the battery is sufficiently charged for further testing (Heavy Load Test) Dark Green Dot is visible: the battery needs to be recharged before further testing Light or Yellow Dot is visible: replace the battery Page 10 © Autoshop101.com All rights reserved HEAVY LOAD TEST PROCEDURE Install the load tester as shown in an earlier slide Load the battery by turning the Load Increase control until the ammeter reads times the amp-hour (AH) rating or one-half the cold-cranking ampere (CCA) rating Maintain the load for no more than 15 seconds, and note the voltmeter reading If the voltmeter reading during the test is 9.6 volts or higher, the battery is good 9.5 volts or below, the battery is defective and needs replacement Note: Results will vary with temperature Low temperatures will reduce the voltage reading, so the electrolyte should be at 70'F or above If not, use the following conversion table: Voltage Temperature 9.6 70'F or above 9.5 60'F 9.4 50'F 9.3 40'F 9.1 30'F 8.9 20'F 8.7 10'F 8.5 0'F Page 13 © Autoshop101.com All rights reserved CURRENT DRAINS Parasitic drains are the small current drains required to operate various electrical systems, such as the clock, computer memory, or alarms, that continue to work when the car is parked and the ignition is off All vehicles today have parasitic drains and over time will drain all batteries if not driven or charged periodically The problem is when the parasitic drain becomes excessive, usually over 35 milliamps Unwanted battery drain can also be the reason why a battery keeps discharging Unwanted battery drain can be a result of excessive parasitic drain, or if the top of the battery is wet or has excessive corrosion, it could create a path between the two battery posts, causing a current drain; usually 0.5 volt potential or higher will result in a battery discharge This is called Case Drain Page 14 © Autoshop101.com All rights reserved PARASITIC DRAIN Check for excessive battery drain or parasitic loads using an ammeter Make sure all electrical loads are off in the car, doors closed, and the key is out of the ignition switch Disconnect one of the battery cables from the battery, placing an ammeter in series between the battery post and cable clamp The current draw reading should be less than 35 milliamps A reading higher than this (or manufacturer specifications) would indicate excessive battery drain Something is "on", allowing current to flow running down the battery Vehicles today typically will draw less than 020 amps (20 milliamps) of current to maintain electronic memories and circuits Note: If the battery is disconnected parasitic drains may temporarily increase Circuits in the engine and body computers are activated and will run until internal timers runout This reactivation period could be anywhere from a few seconds to almost 30 minutes Whenever possible avoid disconnecting the battery while performing this test It is possible to place one lead of the ammeter on the battery post and the other on the battery clamp, while at the same time lifting the battery clamp off the battery post On side terminal batteries, connect the voltmeter with alligator clips and let sit until the timers run out Page 15 © Autoshop101.com All rights reserved BATTERY DISCHARGE / CASE DRAIN Check for battery discharge (case drain) across the top of the battery using a digital voltmeter Connect the negative (black) test lead to the battery's negative terminal post, and connect the positive (red) test lead to the top of the battery case If the meter reads more than 0.5 volt, clean the case top using a solution of baking soda and water Remove excess water from top of battery Page 16 © Autoshop101.com All rights reserved BATTERY CLAMP - POST RESISTANCE Resistance between the battery terminal post and the clamp can account for the battery not being completely recharged and is often a problem Although it may visually look all right, oxidation of the metal or slight corrosion can cause excessive resistance at the connection, thus creating a voltage drop and lowering current flow to the starter Battery post and clamps should be cleaned at each battery inspection To check for excessive resistance, perform a voltage drop between the battery terminal post and the clamp (shown below) while cranking the engine The voltage drop reading should be 0.0 volts Any voltmeter reading higher than "zero" volts requires cleaning the connection and rechecking Page 17 © Autoshop101.com All rights reserved MIDTRONICS BATTERY TESTER Midtronics' test equipment is safe and simple to use while providing an accurate diagnosis in seconds Midtronics battery testers are based on the measurement of battery conductance rather than a load test Midtronics can even test a discharged battery to determine its condition This tester is recommended by most automotive vehicle manufacturers The 500 series model shown below not only can test the battery but the starting and charging systems as well MIDTRONICS OPERATION Conductance is a measurement of the battery's ability to produce current To measure conductance, the tester creates a small signal that is sent through the battery, then measures a portion of the AC current response Conductance is a measure of the plate surface available in the battery which determines how much power the battery can supply As a battery ages, the plate surface can sulfate or shed active material, which adversely affects its ability to perform In addition, conductance can be used to detect cell defects, shorts, and open circuits, which will reduce the ability of the battery to deliver current Page 18 © Autoshop101.com All rights reserved MIDTRONICS BATTERY TEST PROCEDURE Connect the tester to the battery Push a couple of buttons (Enter information the unit requests, such as "in" or "out" of vehicle and rating method, such as CCA, CA, MCA, etc The automated test will take a few seconds giving accurate results Note: No load test is required and a state of charge test does not need to be done No skill is required Hook it up and go Although the Midtronics is not 100% accurate, it have proven to be more reliable than human error Page 19 © Autoshop101.com All rights reserved BATTERY CHARGING All battery chargers operate on the same principle: an electric current is applied to the battery to reverse the chemical action in the cells Never connect or disconnect leads with the charger turned ON Follow the battery charger manufacturer's instructions DO NOT attempt to charge a battery with frozen electrolyte When using a battery charger, always disconnect the battery ground cable first This will minimize the possibility of damage to the alternator or electronic components in the vehicle The battery can be considered fully charged when all cells are gassing freely and when there is no change in specific gravity readings for more than one hour A slow charge is or 10 amps while a fast charge is generally 15 amps or higher A slow charge is always preferred BATTERY CHARGER TYPES Battery chargers are available in two classifications: Manual and Automatic Automatic chargers (typically the type consumers purchase) pulse and cycle the charge current and voltage rates This automatic cycling rate protects the battery from damage and allows the charge rate to taper over time Manual chargers (shown below), also known as wheel chargers, are preferred by automotive professionals These charges not cycle, but rather provide a constant non tapering charge The constant charge rate allows the technician to accurately calculate the charge time to prevent overcharging of the battery Automatic Charger Manual Charger Page 20 © Autoshop101.com All rights reserved