Jumper Cable Diagram and How to Jump Start a Car

You might need to jump-start your car for a number of reasons. Your interior light may have drained the battery by being on all night, or you may have forgotten to turn off your headlights at a restaurant.

A dead battery is something that can happen to anyone at any time. If the lights and other electrical systems are still working, your battery might just need a jump start. Even if you have jumper cables in the trunk of your car, they won’t help much if you don’t know how to use them.

Jumper cables can save your life, and all you have to do is follow a few easy steps.

If the battery in your car is dead, you can jump-start it with a second car. Bring up the car that isn’t working so that the hoods of the two cars are only a few inches apart. Make sure to give them some room. The cars should be close enough for jumper cables to reach but not touching.

For the best results, the voltage of the two car batteries should be about the same. Read the information on the top of the batteries to see if the numbers are the same or close. If the working car has a higher voltage, jumping the battery could damage the other. In that case, you might want to ask another driver to help.

How do car jumper cables work?

Car jumper cables work by sending a charge from a battery that is working to a battery that is dead. Jumper cables have alligator clips that connect securely to the terminals on each battery.

Jumper Cable Diagram

jumper cable diagram
Jumper Cable Diagram and How to Jump Start a Car 1
jumper cable wiring diagram
Jumper Cable Diagram and How to Jump Start a Car 2

How to Link Jumper Cables Together

  1. Find someone who will jump your car.
  2. You need to park the car with the good battery close to the car with the dead battery.
  3. Open the hoods of both cars and find the batteries in each one. Some batteries have plastic covers that you have to take off before you can connect the jumper cables.
  4. There are both positive (+) and negative (-) posts on the batteries. Most of the time, the positive post is red, but not always. By default, you should always look for the plus and minus signs. Make sure to clean up any dust or dirt before you put the cable in place.
  5. Get out the jumper cables and connect the red clamp to the positive post of the dead battery. The clamp needs to be firmly attached. Then, you should clamp the end of the cable that matches the working battery’s positive post.
  6. Attach one of the black clamps to the negative post on the working battery.
  7. This is where it gets different. You can’t clamp the other end of the matching cable to the dead battery’s negative post; it has to be clamped somewhere else. Find a spot on the engine of the dead car where the metal is exposed. Either a bolt or a screw will do. This is for grounding.

How to Jump Start a Car

  1. First, start the car with a battery that works and let it run for a few minutes.
  2. Start the dead car’s engine and let it run for a few minutes.
  3. If the dead car starts right up, you can start to take the clamps off.
  4. Carefully unhook the black camp from the “dead” battery car, and then take the clamp off the other car.
  5. Remove the red clamp from the “good” battery car, then the “bad” one.

Once both cars are running again, you can take the jumper cables off. Take the clamps off one at a time, in the order they were put on. Remove the black clamp from the engine block and the black clamp from the working vehicle. Then take off both ends of the red cable, leaving only the clamp attached to the dead battery.

After you take the jumper cables off, you can turn off or park the car you used to start the dead battery. You should, however, let the other vehicle keep going. Let it sit for half an hour so the battery can get charged. You can also drive it a few times around the block to help the battery get charged up again.

If you don’t have another car to jump-start the dead battery, you might be able to use a jump box if you have one. This useful piece of gear, which is also called a battery pack, can easily take the place of the second vehicle. Just connect the jumper cables to the jump box and the dead battery and try to start the car. When it starts, take the cables off and let the car run at a slow speed.


Watch this video about how to safely jump start a vehicle with a dead battery, and the correct way to hook up jumper cables.

Why use a heavy-duty jumper cables?

Heavy-duty jumper cables will be thicker and have a higher gauge, which lets more electricity pass through quickly to jumpstart the car. This makes sure you can jumpstart your car even in the worst situations, like when it’s cold and your battery is almost dead.

What length should jumper cables be?

Popular Mechanics says that if you want to buy new jumper cables, you should look for ones that are 4 to 6 gauge and at least 20 feet (6 meters) long. If you can’t put two cars right next to each other, these extra-long cables will come in handy and make it easier to connect the batteries. Also look for jumpers with thicker cables and stronger clamps. They will last longer and be stronger.

Why should jumper cables have a good length?

Jumper cables need to be long enough because it’s not always possible to get the two cars right next to each other when you need to connect them.

How does a jumper clip work?

The end that connects to the battery is the clip. This is where the electricity from one battery to another first and last touches. The clips on jumper cables look like copper. This is important because copper is a good conductor of electricity, so clips that are only plated will not work as well.

How to get a jump start without a car?

Get a rechargeable battery pack so you can jump-start a car without a working car. You keep the battery pack charged by plugging it into a USB port, and then you connect the jumper cables to it just like you would with a dead battery.

What do the colors red and black on Jumper Cables mean?

You can tell the difference between the positive (red) wire and the negative (black) wire on jumper cables because they are red and black (black). These are the same as your battery’s positive and negative ends. To jump-start your car, you need to connect the positive (RED WIRE) to the positive battery terminal and the negative (BLACK WIRE) to the negative terminal.

How many amps does a jumper cable have?

Amperage ranges from 150 (A) to 1000 (A) for jumper cables (A). On the lower end of this range are the lighter-weight cables, and on the higher end are the heavy-gauge cables.

If the clamps touch, what happens?

Make sure the red and black clamps never touch, and make sure the cables don’t touch when you’re setting up, especially if the clamps are connected to a live battery. If the clamps touch when they are “hot,” it could cause one or both cars to short out, and it will definitely make sparks.

How to determine polarity of a post?

Find the posts with the (+) and (-) signs. Positive posts may be red, but that’s not always the case. The best way to tell if a post is positive or negative is to look for a plus or minus sign. (Make sure the posts are clean before you put the clamps on them.

What should a battery’s voltage be?

Make sure that both batteries have a voltage of 12v. Most do, but it’s still a good idea to check.

What happens if I put the jumper cables on backwards?

  • Problems with the battery.
  • Breakage of electrical parts
  • The damage to electronic systems
  • The jumper cables got damaged.

What to do if your car starts?

You should not stop your car from running. Let it sit for half an hour so the battery can get charged. You can also drive it a few times around the block to help the battery get charged up again.

Which jumper cable comes off first?

First, disconnect the negative cable from the car whose battery you jumped, then disconnect the negative cable from the car with the good battery. Then, remove the positive cable from the car with the good battery. Don’t touch any grounded part of either car with the clamp of the positive cable.