Volts simply represent the pressure of electricity that flows through a cable, and ampere is the unit used to measure the amount of current required to power a device. If you multiply voltage and amperes, you find wattage. This represents the power consumption of a device. Charging a 12-volt battery using a 6-volt setting is easily possible, but it takes twice the time. For example, charging a dead 12-volt battery using a 12-volt charge may take 12 to 18 hours, while charging a 12-volt battery using a 6-volt charge may take 24 to 36 hours.
Put your 12-volt battery on a suitable stable work surface with a battery charger nearby.
Connect the battery charger to the 12-volt battery. Begin by attaching the black negative cable from your battery charger to the negative terminal of your 12-volt battery. Use the spring clips or clamps on the end of the cable to connect the cable and terminal securely. The negative terminal is labeled "-." Connect the red positive cable to the positive terminal of your battery using the same method. The positive terminal is labeled "+."
Charge the battery. Set the battery charger to charge at 6 volts. Plug in and then turn on your battery charger. The display on the battery charger conveys that the charger is charging, or a light illuminates to confirm the battery is charging.
Leave the charger on for 24 hours. It cannot damage your battery. Read the charge display on the charger after 24 hours. If the charge rate is low, your battery is charged. If it's still charging at the full rate, leave it on for another six hours.
Turn off the battery charger when the battery is charged.
Unplug the battery charger from the electricity supply.
Remove the battery charger cables from the battery. Then your battery is ready to use.