Battery Test Procedures On Vehicle:
BATTERY TEST PROCEDURES ON VEHICLE:FIGURE 1:
BUILT-IN TEST INDICATOR (HYDROMETER)
The test indicator is a built-in hydrometer on top of the battery case and provides visual information for battery testing (Figure 1). The test indicator is to be used with accepted diagnostic procedures only. It should not be used to determine if battery is good or bad.
It is important when observing the test indicator that the battery be relatively level and that it has a clean top to see correct indications. A light may be required to view indicator.
WARNING: DO NOT USE OPEN FLAME.
FIGURE 2:
BUILT-IN TEST INDICATOR (STATE OF CHARGE)
One of three conditions can be observed from the test indicator. They are as follows:
1. Green dot (Figure 2 - State of Charge - Chart 1). Any green appearance is interpreted as above 75% state of charge. This indicates that the battery is adequately charged for testing. On rare occasions following prolonged cranking, the green dot may still be visible. Should this occur, charge the battery as described in "Battery Charging Procedures".
2. A dark or black dot (Figure 2 - State of Charge - Chart 1). A dark or black dot indication is a result of the battery being partially discharged below a 75% state of charge level. The battery should be checked as described in "Battery Charging Procedures" until Green Dot is visible prior to performing any other tests.
3. Bright or Yellow Dot.
WARNING: ON RARE OCCASIONS, TEST INDICATOR MAY TURN LIGHT YELLOW OR BRIGHT IN COLOR. THIS INDICATES LOW ELECTROLYTE LEVEL. IN THIS CASE, THE VEHICLE CHARGING SYSTEM SHOULD BE THOROUGHLY CHECKED FOR BATTERY OVERCHARGED CONDITION AS COVERED IN APPLICABLE SECTION OF THE SERVICE MANUAL. ALTHOUGH BATTERY MAY APPEAR SERVICEABLE, REPLACE THE BATTERY. DO NOT ATTEMPT TO CHARGE, TEST, OR JUMP START THE VEHICLE.
IGNITION OFF BATTERY DRAIN
Vehicle batteries have a normal small continuous drain with ignition switch turned off. A 20-35 milliampere drain is common. This is due to digital clocks and solid state devices, that operate while the ignition is off. In addition, there may be other conditions in the electrical system that causes excessive Electrical Drain on a battery. Shorted or pinched wires, misadjusted switches, faulty components and other conditions may cause battery to discharge at a very fast rate even when all accessories are turned off. To check for electrical drain refer to "Ignition Off Drain Test".
FIGURE 3:
IGNITION OFF DRAIN TESTS
To test for excessive ignition off drain, verify that all electrical accessories are OFF. Turn off all lights, remove ignition key, and close all doors and decklid. If the vehicle is equipped with electronic accessories (illuminated entry, automatic load leveler, body computer, or highline radio), allow the systems to automatically shut off (time out), up to 3 minutes.
1. Raise the hood and disconnect both battery cables, negative first.
2. Reconnect the negative cable and connect a typical 12-volt test light between the positive cable clamp and the positive battery post (Figure 3). Remove the engine compartment lamp bulb, if one exists. If the test light does not light, proceed to step 4. If the test light does light, proceed to step 3. The test light will indicate a drain greater than 2 Amps.
FIGURE 4:
3. Locate the fuse panel and remove fuses or circuit breakers one at a time, and observe after each fuse or circuit breaker is removed. If the light goes out when a certain fuse or circuit breaker is removed, that circuit may have a defect. Refer to wiring diagrams for component and splice locations. If excessive drain has been corrected, proceed to step 4.
CAUTION: IGNITION OFF DRAIN GREATER THAN 2 AMPS COULD DAMAGE AN AMMETER WHEN USED ON THE LOW (MILLIAMPEREMETER) SCALE. WHEN A BATTERY IS CONNECTED TO A PREMIER ELECTRICAL SYSTEM, THE HEADLIGHTS ARE ENERGIZED FOR A VERY BRIEF PERIOD OF TIME. THIS HIGH CURRENT POWER SURGE COULD BLOW THE FUSE IN THE AMMETER, OR DAMAGE THE AMMETER IF IT IS CONNECTED WITHOUT A TEST LIGHT IN THE CIRCUIT AS SHOWN IN FIGURE 4.
4. With the test light connected as shown in step 2, connect an ammeter set on the low (milliampere) scale between the positive cable clamp and the positive post (Figure 4). Remove test light leaving meter connected. A reading of 35 milliamperes or less indicates normal electrical draw. If amperemeter reads more than 35 milliamperes, excessive drain must be corrected.
5. Locate the fuse panel and remove fuses or circuit breakers one at a time, and observe the meter after each fuse or circuit breaker is removed. If the reading drops below 35 milliamperes when a certain fuse or circuit breaker is removed, that circuit may have a defect. Refer to wiring diagrams for component and splice locations to locate and eliminate excessive drain.
6. Connect battery cable.
7. Tighten cable clamps securely.
FIGURE 2:
LOAD TEST
1. Observe the test indicator for presence of green dot (Figure 2). If not visible, charge battery prior to testing.
FIGURE 5:
2. Observing polarity, connect a voltmeter and a battery load tester across the battery terminals (Figure 5).
LOAD TEST RATE - CHART 2
Load Cold
Test Cranking Reserve
(Amps) Rating @ 0~F Capacity
250 Amp 500 Amp 110 Minutes
FIGURE 6:
3. Apply a 300 Amp load for 15 seconds to remove the surface charge from the battery (Figure 6). Remove load.
4. Wait 15 seconds to let the battery recover and apply a load equal to 1/2 of the cold crank ampere rating of battery (250 Amps). See Load Test Rate - Chart 2.
5. Read the voltage after 15 seconds with the specified load applied, then remove the load.
6. If voltage did not drop below the minimum listed in Load Test - Chart 3, battery is good and should be returned to service. (Battery temperature must be estimated.)
7. If the battery passes the load test, it is in good condition and no further tests are necessary. If it fails the load test, it should be replaced.
OPEN CIRCUIT VOLTAGE
Open circuit or no load voltage is a good measure of battery state of charge after battery has stabilized. The battery is stablized if there has been no heavy load applied immediately preceeding the open circuit test. If a heavy load has been applied such as a heavy load test, the battery will have to sit with no load for a few minutes to recover.
1. Remove both battery cables and place a voltmeter between battery posts.
2. Chart 4 shows the relationship between open circuit voltage and state of charge:
BATTERY CHARGE PERCENT - CHART 4
Open Circuit Volts Percent Charge
11.7 volts or less 0%
12.0 25%
12.2 50%
12.4 75%
12.6 or more 100%
Because the change in voltage relative to the state of charge is small, most battery testers use special voltmeters with scales expanded to better show percent charge. If the charge is 75% (12.4 volts) or more, the battery is considered charged. If it failed the load test with more than a 75% charge, it should be replaced.