How to Extend Car Battery Cables?

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this...Read more

Difficulty in starting the engine, or it starts but intermittently won’t turn off, and these reasons make you think about How to Extend Car Battery Cables?

The battery cables are the conductor of the electrical system in your car that helps to start the car and other electrical equipment of the car such as the radio. However, you don’t need to go to an expert or any mechanical engineer to do this job. You can complete this task by yourself at home.

All you need are tools such as solder, two terminals, two terminal lug nuts, Rosin paste or fluid, two cables – brass or tinned, and Shrinkable sheathing.

Therefore, this article will guide you on effortlessly extending car battery cables. Keep reading to know more.

How to Extend Car Battery Cables?: A Complete Step-By-Step Process

Firstly, taking precautions when working in an electrical environment it’s essential because you might get injured. Wear safe gear such as safety gloves and glasses to protect yourself.

How to Extend Car Battery Cables

Select the Cable

You must check the cables before purchasing as they should be suitable according to your car. However, there are different cables for different car machines.

Start Preparing the Cables.

Take a thick pair of cable cutters that can smoothly cut the cables without hassle. Also, don’t use a saw or knife to cut the wire.

It can jagg and cut the cables unevenly, making your work harder. Moreover, you must use a heavy-duty cutter to cut the cables for even and perfect results.

Add two 4-5 pieces

It is easy to sheathe on before the terminals are connected. So, slip it towards the wire and roll the way through half of the cable, and it will cover any exposed metal strand at the end of the cable.

Attach the Terminal Lugs

Apply the flux paste inside the terminals and exposed cables. You need to heat this connection to make it a powerful electrical connection between the two things. Also, apply this paste with a cotton pad.

Now, insert the exposed cable end into the lug of the terminal. However, push as hard and far as possible, and some flux will squash out from the terminal.

Use a Flat Nail Punch or Crimper

You need to ridge the terminal lug towards the cables, so you can use a crimper or nail punch. But, if you own a crimper machine, use it for this job. Or put it in the center of the nut and hammer it hard to ridge the terminal in the wire.

Proper Heating

This process requires a torch or any heating source to heat the lug unless the rosin flux starts boiling. Take a torch, put it on and roll the cable in front of the torch. So, the cable is properly heated.

Solder Wire

Solder round both connections using a non-acidic and nonreactive solder wire where the terminal ends and exposed cables begin. Furthermore, let it set for around 1-2 minutes, and then start other steps.

Shrink Tube

Use a shrink tube to wrap the exposed metal and heat the shrink near the connection.

It should be a smooth terminal lug that can be connected to the battery.

Attaching the Terminals

The terminal should be clamped in a vice clamp. The terminal gets heated up. So, it must not move as you put the hot solder and cable.

Apply Rosin Flux

To connect the terminals, you must apply rosin flux with a cotton pad and coat it in all over the terminals parts and wire, which will be connected. However, if you bought a pre-solder or per-rosined terminal, you leave this step.

Use Torch Again to Heat

Use the torch again to heat up, which will set the formula to attach the parts easily. Also, you must do this process in an open environment or airy area, and you might see bubbles forming from boiling the formula.

Preheat the Cable

You must preheat the cable for around 12 to 15 seconds and then insert the cable through to the terminal. Both connections heat up, making the process faster and easier.

Solder Connection

You have to solder the attachments between the terminal and cable precisely as you have done to the terminal lug. You have to solder the edges of the terminal to the exposed cable.

Ways to Install Car Battery Cables?

You can alter the car’s battery cables to extend for any emergency case. Here we have mentioned a step-by-step guide that will help you remove the cables and how you can change the extended cables of your car.

How to Install Car Battery Cables

Remove the Covering of The Cable

If any boxes or tape is covering the end of the cable, you need to remove them.

  • Ensure not to cut any wires while accessing the bolts.
  • You need to cut off the tape that the bolt used to secure the terminal but prevents you from reaching it.

Disconnect the Cables

To disconnect the cables, you need to start from the negative cables and cut the electrical power on your car.

  • Lose the bolts that are holding the cables in place.
  • You might have difficulty screwing the nut, so you can use WD-40 to remove and oxidize the rust.
  • Make sure that negative and positive cables are kept separately.

Remove the Battery from The Car.

Most cars don’t require this step, but eventually, it makes the process easier and has a bracket to hold the battery in place, yet after removing the brackets, it needs to unscrew two bolts.

Remove Both Cables

The bolts are located at the other end of the cable, the engine block. You can use a wrench to screw the bolt, holding the negative cable in place.

  • Remember how cables were routed through the engine bay, so it won’t interfere with any moving part
  • Ensure the car is not hot or will burn you due to heat.

Measure the Cables

Purchasing cables according to your car should match the length with the same terminal connector on both ends.

  • You must check the length of the cables by comparing the old wires to the new ones.
  • The terminal end should match according to the older cables.

Install the New Cable

You need to monitor if there is any plastic protection in the old wires, then you must take them out and put them into the new ones.

  • Take a steel-toothbrush to clean the ends of the connector of the cables. It’ll provide a good electrical connection
  • It should be a bare metal that allows electrical power from the cables passing through.

Connect the Cables

Here you have to attach the positive cable first. Use the same bolt you remove to disconnect and attach the old cable to the new cables.

  • Use a bare steel wire brush to remove the bolt’s rust or corrosion. However, if it’s too rusted, then replace it.
  • The bolt should be tight, so it won’t fall off while driving.
  • You must run the new positive cable through the engine bay the same way as it was.

Put the Battery Back in The Car.

After installing the new cables, you put the battery back in the car. Be careful the battery terminals should not come into contact, or you’ll shock yourself.

  • A bracket that holds the battery bolt back in place securely.
  • You must place the battery in the same position so the positive and negative terminals are easier to connect accordingly.

Attach the Positive Battery Cable

Now, you can attach the cables to the battery, use a corrosion inhibitor on the terminal to slide the new positive cable, and install the negative cable.

  • Tighten the cable with the bolt.
  • Ensure the cables are connected securely. If the cables are loose or come to contact with anything, the engine will turn off.


Here we have mentioned the most frequently asked question that you should know about extended cables.

Why Do I Need to Extend Battery Cables?

There are two main reasons to extend your battery cables: safety measurements. It might stop other drivers from needing to go out and to access the battery. However, the second reason is that longer jumper cables provide more time for users to work.

Is It Safe to Extend the Cables of The Car?

Yes! It’s completely safe to extend the cables of your car if needed. You must check the extended cable length before selecting or cutting one.

What to Do if The Extended Cable Doesn’t Match the Length?

You can take two extension cables. Suppose one does not match the length. Take two cables that are long enough to reach the required length. And attach both separate wires to a battery.

However, to balance the voltage, ensure multiple pairs of cables must be used and remove the cable extensions when not in use.

Bottom Line

How to extend car battery cables can appear challenging but can be achieved by following the above-mentioned steps. However, you must take safety precautions and wear safety gear to avoid unfortunate incidents.

Yet, if you face issues regarding any of these, we’ll also recommend that you consult with a professional for further assistance.

Hi, I'm Luis Johnson, an automobile technician, and power equipment professional. By profession, I'm a businessman and operate a car workshop. I have created this site Batteryquery to help people purchase the right battery for their vehicles. The reason behind creating this site is to help my customers purchase the right car battery who often purchase the wrong one due to their lack of knowledge.

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