Car batteries often drain or die for any number of reasons, whether it's simply because the battery is old or because you accidentally left the headlights on overnight. When the battery does drain, a battery charger can prove an invaluable piece of equipment. There is a broad array of chargers on the market, each with an assortment of features and for varying prices. Most battery chargers, however, can be hooked up to a battery using the same technique.
Access the battery. If the battery is still in the vehicle, remove any guards protecting the terminals. You may need a screwdriver or small wrench to remove these guards. If the battery is out of the vehicle, simply place it on a sturdy work bench or table.
Place the positive clamp on the charger onto the positive post of the battery. Positive clamps and battery terminals are typically marked with the color red and a plus (+) symbol. Negative clamps and terminals are marked with black and a minus (-) symbol. If the battery remains in the vehicle, attach the negative charger clamp to a non-painted metal bracket or bolt. If the battery has been removed from the vehicle, attach the negative charger clamp directly onto the negative battery post.
Check the volt and amp settings on the charger. Some chargers will allow you to adjust for voltage and amperage. For a car battery, you want to make sure the charger is set to 12 volts. As for amperage, the lower the amps, the longer it will take to charge the battery. Use a low-amp setting to fully recharge the battery. If you want to start the vehicle immediately, use a high-amp setting.
Plug the battery charger's power cord into an electrical outlet and allow the battery to charge. Again, the exact time needed to charge the battery will depend on the charger's settings and how severely the battery has been drained. Most chargers will have an indicator light or gauge that will let you know when the battery has received a full charge. If you have an automatic charger, it should shut off once the battery is charged.
Turn the charger's power switch off after the battery has been fully charged. Then unplug the charger and disconnect the clamps from the battery. Remove the negative clamp first, followed by the positive clamp.