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 (refer to step 4 below), 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 output capability of a battery charger, connect battery charger to battery that reads below 11 volts. Take a voltage reading across positive and negative terminals of battery with charger on highest setting. If reading is not greater than 15.5 volts it will not start the chemical reaction needed to charge battery. A higher output battery charger must be used.

1. Measure voltage across battery terminals with a DVOM. If voltage is below 11 volts, charge current will be low and it could take some time before battery accepts more than a few milliamps.
2. Set charging rate to highest setting (for a 12 volt battery). If battery charger has a timer, set timer to 30 minutes. Check 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 charger are connected to 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 battery does not want to accept charging current. Therefore, follow manufacturer's operating instructions, telling how to by-pass circuitry so that the charger can be turned on to charge battery.
4. Battery chargers can vary in 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 times are required for a battery to begin to take a charge.