There is some thinking required to jump a battery. Many folks who jump a battery do not allow the cables to stay connected untill the dead battery has enough voltage to allow the alternator to begin to refill the dead battery with more voltage. A dead battery can be thot of as a empty container. A fully charged battery is as a container full. Jumping a battery fills the container with a small amount of voltage with is used by the engine running. An alternator needs at least 12 volts to make 15 volts using just about 2 amps to make about 80 amps. A good jump for a dead battery is at least 5-10 minutes. Frank