A meter reading of 12.2 volts or 12.0 volts will indicate a charge rate of 50 percent and 25 percent, respectively. Any readings below 11.9 volts will indicate a fully discharged battery, and damage may have occurred to the storage device. Voltage readings that are 10.5 volts and below show that the battery is severely damaged and needs to be replaced.
Follow the battery manufacturer’s specifications and maintenance details whenever servicing any lead acid battery. Special precautions may apply for some types of batteries.
Always charge any lead acid battery in a well ventilated area. The charging process emits a highly flammable gas that can be ignited by any open flames.
Items you will need: 12-volt car headlamp, Voltmeter