How to Jump Start a Car Using Jumper Cables

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Jump Starting a Car with a Dead Battery

Car engine jump start between two vehicles
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Batteries go dead for all sorts of reasons, and it often is because we leave a light on in the vehicle. In that case, it's a good thing because that means a simple jump start will get you back on the road without permanent vehicle damage. It's easy to jump start your car if you have a dead battery. 

What You Need to Jump Start a Car

1. Another car, running
2. Jumper cables
3. Safety glasses
4. Wire brush (optional for cleaning connections)

To begin, park the running car next to the dead car so the jumper cables can reach both batteries. (Parking the cars so they face each other is the best option.) If you aren't sure where the batteries are under each hood, take a peek before you park.

Important Tip: Never drive with your hood raised. Not only does it hamper visibility, but you could damage your hood components or the hood itself.

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How to Connect the Jumper Cables to Your Battery

Jump starting your car, easy connections.
On the dead battery, attach the positive (red) cable to the battery, but attach the negative (black) cable to a section of bare metal in the engine compartment. Even a nut or bolt end will do. photo by Matt Wright, 2010

With both cars parked next to each other, turn both keys to the "off" position. Not only will this protect your car's electrical system from any surges, it's always safer under the hood with the engine off.

How to Connect Jumper Cables to a Car

  1. Locate the "+" (positive) and "-" (negative) sides of each battery. They should be clearly marked on the battery itself. On newer cars, the positive (+) side often has a red cover over the battery post and wires.
  2. Attach the red cable to the "+" side of the good battery
  3. Attach the other end of the red cable to the "+" side of the dead battery
  4. Attach the black cable to the "-" side of the good battery
  5. Attach the other end of the black cable to a section of unpainted metal on the dead car. This can be as small as the head of a bolt located nearby.

Important Tips: Attach the jumper cable to the most secure attachment point you can find on the car's permanent battery cables. If they are corroded, it may help to wiggle the jumper cable end around a bit while it's attached to the car's cables or battery.

You might be tempted to attach it to the "-" side of the dead battery, but this isn't recommended. In the old days, batteries leaked small amounts of acid, which could turn into flammable gas around the battery. This gas could explode if the cable caused a spark just above the battery.

Some people tend to clamp the negative cable onto the rubber cable covering of the positive side while they walk across to the other car. Don't do it! If one of those sharp teeth were to pierce the rubber cover and reach the wires inside, you could do serious electrical damage to one or both vehicles.

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Starting the Car With the Dead Battery

First, start the car with the good battery and leave it running. If the battery in the dead was was really badly drained, it may help to leave them connected for a minute with the good car running before you try to start the dead car. 

Turn the key in the dead car to start and it should fire right up. If you continue to have starting problems, you might need to install a new battery. You can disconnect the jumper cables right away.

Disconnecting the Jumper Cables

Disconnecting the jumper cables doesn't need to happen in any specific order, but be sure you don't let the red and black cables touch each other at the end when they are still connected to one battery. If the dead car doesn't turn over or turns over very slowly, check to see if your battery or connections are corroded. If they are, sometimes a little wiggling while the cable clamp is connected will make your connection better. Otherwise, it might be a good time to clean your battery connections. If your car still does not start, see the no-start checklist.