It's bound to happen sooner or later. Maybe you left the headlights on, or perhaps you didn't close the door all the way. Regardless, when there's a parasitic drain such as this, your car's battery may die. Assuming the battery is still good, however, you can usually jump start it by connecting it to a charged battery. The other battery will send some of its charge to the dead battery, giving it enough juice to start the car and engage the alternator.
However, there's a wrong way and a right way to jump start a car. Failure to do it correctly could result in injury and/or damage to the battery. So, what's the right way to jump start your car?
Prepare Your Supplies
The only things you'll need to jump start your car is a pair of jumper cables, safety goggles, and another car with a healthy battery. Some people assume that longer jumper cables are better, but this isn't necessarily true. On the contrary, the longer the cables, the greater the loss of charge as it travels between the batteries. The only real benefit in using a long pair of jumper cables is the convenience it offers of being able to jump start your car at a distance.
How to Jump Start
Before connecting the jumper cables, make sure both vehicles are parked facing each other. They should be as close possible but without directly touching. If the vehicle has an automatic transmission, set it to park. If it has a manual transmission, set it to neutral. Parking brakes should be engaged on both vehicles.
With the hoods of both vehicles open, connect the positive end of the jumper cables to the positive terminal of the dead battery. Next, attach the other positive end of the jumper cables to the positive terminal of the good battery. You should then connect the negative end of the jumper cables to the good battery, followed by connecting the other negative end to a metal part of the car with the bad battery.
Assuming you've connected the jumper cables correctly, go ahead and start the car with the good battery. After allowing it to run for a few minutes, turn the ignition of the car with the bad battery. It should have enough charge by now to engage and turn on, at which point you can disconnect the jumper cables and close the hood.