Completely Discharged Battery

When battery voltage is below 11 volts, the weak electrolyte is very resistant to charger current. The battery will draw only a few milliamps of charger current and it may be some time before current flow to the battery is high enough to read on most ammeters.

If the current is measurable after the recommended times, the battery is good and the charging should proceed at the normal rate.

Remember that a completely discharged battery must be charged until the green eye appears.

Charging A Flat Battery

IMPORTANT: Unless this procedure is followed precisely, a perfectly good battery may be needlessly replaced.
A battery that is below 11 volts will require a battery charger that has the ability to produce 15.5-16 volts on the highest setting.
To test the Output capability of a battery charger, connect the battery charger to the battery that reads below 11 volts. Take a voltage reading across the positive and negative terminals of the battery with the charger on the highest setting. If the reading is not greater than 15.5 volts it will not start the chemical reaction needed to charge the battery. A higher output battery charger must be used.
1. Measure the voltage across the battery terminals with a DVOM. If the voltage is below 11 volts, the charge current will be low and it could take some time before the battery accepts more than a few milliamps.
2. Set the charging rate to the highest setting (for a 12 volt battery). If the battery charger has a timer, set the timer to 30 minutes. Check the battery for a green eye or excessive temperature (52 °C [125 °F]) every 30 minutes.
3. Some chargers may have polarity protection circuits in them. This prevents charging unless the leads of the charger are connected to the battery terminals correctly. A completely discharged battery may not have enough voltage to activate this circuit, even though the leads are hooked up correctly. This makes it appear that the battery does not want to accept charging current. Therefore, follow the manufacturer's operating instructions, telling how to by-pass the circuitry so that the charger can be turned on to charge the battery.
4. Battery chargers can vary in the amount of voltage and current they provide. The time required for a completely discharged battery to accept measurable charger current at various charging voltages may be as follows:





IMPORTANT: These are the times required for a battery to begin to take a charge.