Charging a Completely Discharged Battery (Off The Vehicle)

Unless this procedure is properly followed, a perfectly good battery may be needlessly replaced.

The following procedure should be used to recharge a completely discharged battery:

1. Measure the voltage at the battery terminals with an accurate voltmeter. If the reading is below 10 volts, the charge current will be very low, and it could take some time before the battery accepts the current in excess of a few milliamperes. Refer to the paragraph above to Charging Time Required which focuses on the factors affecting both the charging time required and the rough estimates in the table below. Such low current may not be detectable on ammeters available in the field.
2. Set the battery charger on the high setting.
IMPORTANT: Some charges feature polarity protection circuitry, which prevents charging unless the charger leads are correctly connected to the battery terminals. A completely discharged battery may not have enough voltage to activate this circuitry, even though the leads are connected properly, making it appear that the battery will not accept charging current. Therefore, follow the specific charger manufacturer's instruction for bypassing or overriding the circuitry so that the charger will turn on and charge a low-voltage battery.
3. Battery chargers vary in the amount of voltage and current provided. The time required for the battery to accept a measurable charger current at various voltages may be a follows:

• If the charge current is not measurable at the end of the above charging times, the battery should be replaced.
• If the charge current is measurable during the charging time, the battery is good, and charging should be completed in the normal manner.
IMPORTANT: It is important to remember that a completely discharged battery must be recharged for a sufficient number of ampere hours (AH) to restore the battery to a usable state. As a general rule, using the reserve capacity (RC) rating as the number of ampere hours of charge usually brings the green dot into view.
• If the charge current is still not measurable after using the charging time calculated by the above method, the battery should be replaced.
• If the charge current is measurable during the charging time, the battery is good, and charging should be completed in the normal manner.