It's one of the most basic things a driver can do, but the fact is that many car owners simply don't know how to jump a dead car battery. This skill is easy to learn and incredibly useful for those mornings where the car simply won't start. It can also turn you into a hero if a friend or relative ends up with the same problem. While you may be able to get someone to loan you their car and a pair of jumper cables, don't rely on them to know how to jump the car - it's best to learn yourself.
For starters, it's important to understand the risks of jumping a battery. Many people don't realize that doing so can be dangerous to both themselves and the vehicle. Batteries contain hydrogen gas, and all it takes is one misplaced spark to cause the part to explode. Not only would this cause untold damage to your car, it could also spray harmful battery acid everywhere and be a danger to you and the people around the vehicle. This is why it's important not to smoke while changing a battery, and try not to lean over the part itself unless you're placing or removing a cable.
Touching the cables together or reversing the connections may also lead to an unwanted surge in power. This won't cause the battery to explode, but it can do damage to the electrical components in the vehicle, and you could end up replacing more than a dead battery.
Once you know the safety risks and have taken proper precautions, it's time to start. Park the two vehicles close together and ensure that the engine is turned off in both. Also take the time to unplug any accessories that may be plugged into the vehicles, such as cell phone chargers or other electrical components.
Take the red (positive) cable and attach it to the positive terminal on the dead battery. This should be clearly marked with a (+) symbol. Now take the other end of that cable and attach it to the corresponding terminal on the charged battery. Next, take the black (negative) cable and attach it to the negative terminal on the charged battery.
Here's the part where many drivers make their mistake. This cable does not attach to the negative terminal on the dead battery. Instead, drivers should be attaching this clamp to a metal ground on the dead car. This may produce a spark, so it's best to do it away from the battery. Look for an unpainted bracket or bolt and simply clasp the clamp over that part, ensuring it remains tight.
Now start the engine of the car with the charged battery and let the vehicles idle for a few minutes. This essentially starts the process of transferring the charge from the good battery to the dead one. After five or ten minutes, try starting the engine on the dead car. If it doesn't start, let the cars idle for a little while longer before trying again. You may also need to adjust the jumper cables to get a better charge.
It's a good idea to run your car for at least 30 minutes after jumping it, as this will allow the alternator to recharge the battery. Of course, you should also look into the problem and see if there's anything wrong with the electrical system, especially if a drained battery is a regular occurrence.