Open-circuit Voltage TestThis test is mainly for maintenance-free batteries, but it can also be performed on conventional and low-maintenance batteries if a hydrometer is not available. An open-circuit voltage test checks battery voltage by connecting an accurate digital voltmeter to the battery posts after disconnecting the battery ground cable. Before making an open-circuit voltage test on a battery, first load the battery with 15 amps for one minute. If the battery is installed in a car, this can be done by turning on the headlights without the engine running. Open-circuit voltage levels and their corresponding percentages of charge are given in Table d. Table d. Open-circuit Voltage and Battery Charge
The battery is in satisfactory condition if the open-circuit voltage is at least 12.4 volts. If the open-circuit voltage is at this level or above, but the battery lacks power for starting, have a load voltage test performed to determine the battery's service condition. If the open-circuit voltage is below 12.4 volts, recharge the battery. If the battery cannot be recharged to at least 75%, it should be replaced. New maintenance-free batteries should not be installed unless they are at least 75% charged. |
