Battery Open Circuit Voltage Test

An open circuit voltage, no load test will show the state of charge in a battery. Also, if it will pass a load test of 50 percent of the battery cold crank rating.

Refer to Battery Load Test. If a battery has an open circuit voltage reading of 12.4 volts or greater, and will not pass a load test, it is defective and replacement would be required. To test open circuit voltage, perform the following operation:
1. Remove both battery cables, negative first. If the battery has been boosted, charged, or loaded just prior to this operation, allow the battery a few minutes to stabilize.

Testing Open Circuit Voltage:

2. Using a voltmeter, connect test leads to the battery side terminal and measure the open circuit voltage.

Battery Open Circuit Voltage
Open Circuit Volts Charge Percentage
11.7 Volts OR LESS 0%
12.0 Volts 25%
12.2 Volts 50%
12.4 Volts 75%
12.6 Volts OR MORE 100%

3. This voltage reading will show the battery state of charge. It will not reveal battery cranking capacity. Refer to Battery Open Circuit Voltage table.