Grand Fury/Salon V8-318 5.2L VIN P 2-bbl (1984)
8.9
20
8.7
10
8.5
0
Open Circuit Voltage Test & Possible Causes of Battery Failure Information
Open Circuit Voltage Test
If the battery fails the load test, check the state of charge. The open circuit or no-load voltage test is a good measure of the state of charge after the
battery has stabilized from the load test. Be sure to let the battery recover from the load test for at least two minutes before checking the no-load voltage
to estimate the percent of charge.
BATTERY PERCENT OF CHARGE CHART
Open Circuit Voltage
Percent of Charge
11.7 or less
0
12.0
25
12.2
50
12.4
75
12.6 or more
100
Because the voltage changes in the open circuit voltage test are small, most battery testers use special voltmeters with expanded scales to show the
percent of charge. If the percent of charge is 75% or more, the battery is considered to be at a nominal state of charge. If the battery failed the load test
and is at 75% state of charge or more, it should be replaced. On the other hand, if the battery is under 75%, it should be charged and load tested again.
If the battery fails the load test a second time, the battery should be replaced.
POSSIBLE CAUSES OF BATTERY FAILURES IN VEHICLE
Battery failures are often NOT the fault of the battery, but caused by existing conditions in the vehicle. Some of the most common are:
1.
Corroded Battery Posts or Connectors - When charging or replacing a battery, the posts and cables should ALWAYS be thoroughly cleaned. The
film of corrosion that accumulates on these connections can cause a poor connection even when the cables are tight. It is also important to check
the cables themselves. Corrosion can "WICK" down into the cable beneath the insulation and cause excessive amounts of resistance in the cable.
2.
Electrical Leakage or "Key Off" Loads - Vehicles normally have a "Key Off" load or drain due to the requirement of the electronics and
computers in the vehicle. A "Key Off" drain of 15 to 25 milliamps is entirely normal, and poses no short-term problems for the battery.
There are, however, a number of electrical components in the vehicle that can draw in excess of 50 milliamps and cause a discharged battery. To
check for this condition, turn off all accessories in the car and close all doors, trunk, and turn off all lights. If there is an underhood lamp, remove
the bulb. Now you can check for a battery draw by either one of the following methods:
a.
Remove the POSITIVE battery cable, and connect an ohmmeter between the DISCONNECTED battery cable and the vehicle's chassis or
engine block. An ohmmeter reading of 100 ohms or less is an indication of a draw that is 0.1 amp or more. This would be excessive and
would require correction.
b.
Remove the NEGATIVE battery cable, and connect an ammeter with a 0 TO 10 AMP SCALE between the cable and the NEGATIVE post of
the battery. Observe the reading on the ammeter VERY CLOSELY.
If the ammeter indicates a current draw, WAIT 2 MINUTES and again check the meter. Due to such items as illuminated entry systems and
ignition key illumination TIMERS, you may have a false indication of current draw until they time out. After 2 minutes the ammeter should
show 0 current draw. If it does NOT show 0, there is an excessive draw condition that must be corrected PRIOR to continuing the test. If the
ammeter DOES return to ZERO, remove the large scale meter and install an ammeter that will read below ONE ampere. A reading of 0.1 amp
or more would indicate an excessive draw condition that must be located and corrected.
Further Points to Consider
Proper operation of the charging system should be confirmed. The drive belts must be properly tightened, wiring connectors properly attached, the
voltage regulator functioning properly, correct alternator output, and no electrical loads left on inadvertently.
POLICY:
Information only
