You can recharge a flat car battery in a number of ways. It should be noted however that the best way to charge a flat battery if you do not feel comfortable doing it yourself is to have the vehicle towed to a reputable repair shop. If you choose to proceed on your own, make sure that you feel confident and know what you are doing. The most common method is to purchase a car battery charger from an automotive parts store or retailer such as Sears. This will run you between $30 to $200. Follow the instructions on the charger and make sure that the vehicle is in a properly ventilated place, in order to allow the release of any gasses from amassing and causing a fire or explosion.