How to jump off a car battery

Dead batteries are one of the most common vehicle problems. Although you learn basic car maintenance in drivers ed, jump starting a car is not something everyone learns how to do. Having the right emergency equipment is a great start, but you have to know how to use it. So, here is what you need to know about how to jump a car.

What do you need to jump a car?

Jumpstarting a dead battery is something nearly every driver will have to do at least once. Before you can recharge and get going, here’s what you’ll need to jumpstart your car: 

• Jumper cables

• Power source – either a portable jump battery (a jump box) or another vehicle

Jumper cables are long, thickly insulated cables with toothy clips on one or both ends. The clips are distinguished by color, usually red and black, to indicate positive and negative polarity. The red clip is positive. The black clip is negative. 

Jump boxes are portable batteries used to jumpstart a vehicle with special jump cables. These cables connect the jump battery directly to the dead car battery. Roadside assistance usually uses a jump box when helping stalled vehicles.

How to Use Jumper Cables to Jump a Car With Another Vehicle

Most people don’t keep a charged jump box in their vehicle (although it’s highly recommended) so bringing a dead battery back to life usually requires jump starting it with another donor vehicle and a pair of jumper cables. 

It’s not too complicated, but you do need to know the steps to take and how to hook up the cables to ensure the safety of everyone and the vehicles. Here’s what to do!

Step 1 - Get the Vehicles Ready

Before you do anything make sure that the battery giving the jump has enough voltage and is a matching voltage system type (12V, 6V, etc). If everything looks good, position the donor vehicle so that the vehicles are either nose-to-nose or side-by-side. The vehicles need to be close enough to have the jumper cables reach each battery. 

Now do the following:

• Put both cars in park or neutral.

• Turn the ignitions off.

• Put on the parking brake.

• Open the car hoods and secure them.

Step 2 - Attach the Jumper Cables 

With everything in position it’s time to get the jumper cables in place and get your vehicle back up and running. 

Attaching the Clips: 

Attach the clips to the terminals in the following order: 

• Red to Dead - Connect the positive (red) clip to the positive terminal on the battery of the dead car. 

• Red to Donor - Connect the positive (red) clip to the positive terminal on the donor battery on the other car. 

• Black to Donor - Connect the black clip to the negative terminal of the donor car. 

• Black to Metal - Connect the black clip to an unpainted metal part of the dead car that is not directly next to the battery. One of the metal struts that hold the hood open is a good spot. 

Step 3 - Start the Donor Vehicle 

Now that everything is hooked up it’s time to start up the donor vehicle so that it can supply power to the dead battery. Let the donor vehicle run for a few minutes. 

Step 4 - Test the Dead Battery

After a few minutes check one of the interior lights of the car being jumped. If it goes on, power is getting to the battery.

Step 5 - Start the Dead Car

Start up the car with the dead battery. Hopefully, everything goes as expected and the vehicle is drivable again.

Step 6 - Unclip the Jumper Cables

Now that the vehicle is running you can unclip the jumper cables in the reverse order that you connected them:

• The black clip on the unpainted metal.

• The black clip from the negative terminal.

• Red clip from the donor car.

• Red clip from the dead car’s battery.

It’s best to allow the vehicle to run without stopping for at least 10-20 minutes to get the battery juiced back up.

What If the Car Doesn’t Start After the Jumpstart? 

If the dead car doesn’t start after a few minutes of being charged then check the connections and try again. If the car does not start after several attempts, the battery may be too far gone to be jump started. 

What You Need to Know About Batteries to Jumpstart a Car

Car batteries have two larger nubs, called terminals. There is a positive terminal and a negative terminal. Each should be clearly marked. Connecting cables to the right terminal is important to completing the circuit and giving power to the dead battery. 

Positive Terminal – The positive terminal is usually the bigger of the two terminals. It is marked with “POS” or “+”. It will connect to the positive clip on the jumper cable, which is usually red. 

Negative Terminal – The negative terminal on the battery is usually marked with “NEG” or “-“. This will attach to the other clip, which is usually black. 

As long as you’ve got that down and have a pair of jumper cables you should be able to get your battery back up and running. 

Important Jumpstarting Safety Tips

• Read the owner’s manual. Some cars are not recommended for jump starting because they have sensitive circuitry.

• Never try to jump corroded, cracked, leaking or visibly damaged batteries.

• Never try to jump frozen batteries.

• Never try to jump dry batteries.

• Don’t touch the clips together. 

For more safe driving tips and defensive driving information, check out the  idrivesafely.com blog!

Jump starting a car is commonly done from another car, although it can be done from a jump battery. You will be connecting the two cars’ batteries with the jumper cables. Make sure cars are in the right distance to have the jumper cables reach each battery. Pull the cars so that they are either nose-to-nose aligned or side-by-side.

Protect the donor battery

To ensure that the car donating a charge (the donor car) is protected, take these precautions: 

• Match the kind of voltage system of the donor battery to the dead battery to be jumped. For example, a 6V and a 12V should not be used together. 
• Connect alligator clips in the right order.
• Make sure the donor battery is not low.

The order of the connection (red to dead, red to donor, black to dead, black to metal) reduces the chance of shorting the good battery. 

A quick test that there is enough voltage for the donor, be sure that the car giving he jump start’s headlights are steady and bright when the car is started. If the headlights dim, that can signal that the battery is low.

*This article was updated on 9/22/2020