Open-Circuit Voltage Test

A battery open-circuit voltage (no load) test will show the approximate state-of-charge of a battery. This test can be used in place of the hydrometer test when a hydrometer is not available, or for maintenance-free batteries with non-removable cell caps.

Before proceeding with this test, completely charge the battery (Refer to BATTERY SYSTEM/BATTERY - STANDARD PROCEDURE).
1. Before measuring the open-circuit voltage, the surface charge must be removed from the battery Turn ON the headlamps for fifteen seconds, then allow up to five minutes for the battery voltage to stabilize.
2. Disconnect and isolate both battery cables, negative cable first.

Testing Open Circuit Voltage:

3. Using a voltmeter connected to the battery posts (see the instructions provided by the manufacturer of the voltmeter), measure the open-circuit voltage.

Open Circuit Voltage Table:

See the Open-Circuit Voltage Table. This voltage reading will indicate the battery state-of-charge, but will not reveal its cranking capacity. If a battery has an open-circuit voltage reading of 12.4 volts or greater, it may be load tested to reveal its cranking capacity (Refer to BATTERY SYSTEM/BATTERY - STANDARD PROCEDURE).