HomeTips & GuidesCar Battery Cable Replacement: A DIY Guide

Car Battery Cable Replacement: A DIY Guide

Battery cables in internal combustion engines serve the same purpose: to power electrical components and recharge the battery. Therefore, a car battery cable replacement is imperative if these components wear out.

We’ll detail the steps you should follow to replace these cables below. But first, let’s look at how this cable works and the indicators of faultiness.

How a Battery Cable Works

Battery cables connect the battery to the vehicle, and they are two because batteries have two terminals.

The positive battery cable sends power to the starter motor and the vehicle’s computer before starting the car. It also powers all electrical components, such as the head unit,  before you start the engine. The alternator takes over this powering function after you start the car.

But for power to flow, there must be a potential difference. The negative battery cable connects to the vehicle’s chassis, providing a universal ground (low potential) for all the electrical components.

A connected car battery

A connected car battery

This setup creates a closed-loop electrical system where power flows from the positive terminal to the negative terminal.

Symptoms of a Worn or Frayed Battery Cable

A bad battery cable presents the same symptoms as a dead battery because it interferes with the power supply. For instance, the engine can hesitate when starting due to a disconnection in the power or ground wires.

Also, the dashboard battery warning light can illuminate if the computer fails to detect the battery or senses a lower voltage. Some vehicles turn on the check engine light, as well.

An illuminated car battery warning light

An illuminated car battery warning light

Other symptoms include clicking noises and dimming lights (headlights and interior lights).

Since these signs are similar, we recommend diagnosing the issue to determine if the cables are faulty or if the issue is a battery failure.

How To Diagnose Battery Cable Issues

Step 1: Check the Battery Cables for Signs of Visible Wear or Damage

Follow them from the battery terminal to the point where they connect to the vehicle while checking for corroded parts, breakage, and other signs that indicate damage.

Replace the cables if you spot an anomaly. But if they look healthy, they might have an internal fault. 

Step 2: Measure the Voltage Drop 

However, the battery cable issue might interfere with the battery charging process. Measure the voltage across the terminals using a digital multimeter with the knob set to 20V DC.

A healthy automotive battery should have a voltage of about 12.2V. If it’s lower, recharge it externally before testing the cables.

A mechanic measuring the voltage across a car battery’s terminals

A mechanic measuring the voltage across a car battery’s terminals

Instead of doing a continuity test, we’ll test the voltage drop on each line. If there’s perfect continuity, the drop should be less than 0.2V.

Follow these steps to test the positive battery cable. Disconnect the ignition system first to prevent the engine from starting (try disconnecting the ignition coil).

  • Set the digital multimeter to 2V DC
  • Connect the red probe to the cable’s positive battery terminal joint
  • Link the black probe to the starter motor’s battery terminal
  • Have someone crank the engine (turn the ignition key to start)

Test the negative cable using the same steps, but change the probe connections to the wire’s start and endpoints.

The negative wire-chassis ground connection

The negative wire-chassis ground connection

The voltage reading should be less than 0.2V. If it’s higher, the cable has high resistance and needs a replacement.

Reconnect the ignition system after the test.

Car Battery-Cable Replacement Steps

Battery cables don’t have a lifespan rating, so you can’t replace them after covering a specific mileage.

 But certain factors like exposure to the elements, vibration, and friction accelerate wear. Therefore, proper installation is vital to ensuring the cables last. Here’s how to do it.

You’ll need the following tools.

  • Socket wrench
  • Screwdriver
  • Wrench
  • Ratchet
  • Safety equipment (gloves and eye protection)

Step 1: Preparations

Turn off the engine and remove the keys from the ignition to prevent accidental starting. After that, put on the gloves and safety goggles.

Step 2: Disconnect the Battery Terminals

Loosen the terminals from the battery studs using a socket wrench or screwdriver. Begin with the negative battery terminal to avoid electrical shorts.

Step 3: Trace the Battery Cable Routes

Trace the positive battery cable’s route to the fuse box and note other connections along the way, if any. 

Take pictures using your phone to record this manufacturer-recommended route so you can use it when installing the replacement.

The positive battery cable connection to the fuse box

The positive battery cable connection to the fuse box

Do the same with the negative battery cable. Trace its route to the chassis ground connection.

Step 4: Remove the Battery Cables

Loosen and remove the nuts securing the negative cable to the chassis and the positive cable to the fuse box.

Step 5: Clean the Connection Points

Clean any corrosion (salts) on the battery posts, the nuts removed earlier, and the bolts on the chassis and fuse box. 

Replace the nuts if worn out. Also, inspect the battery connectors for any signs of excessive corrosion. If the damage is extensive, replace them.

Step 6: Install the New Battery Cables

Lay out the new cables via the routes you traced earlier and secure them to the chassis.

Connect these cables to the car, beginning with the positive cable. Link it to the fuse box and positive terminal.

Next, connect the black battery cable to the chassis ground and the negative battery terminal.

A technician tightens wrench bolts to fasten the negative terminal to the battery post.

A technician tightens wrench bolts to fasten the negative terminal to the battery post.

Step 7: Test the Installation

Start the vehicle and check if all electrical systems are healthy. If the dashboard battery warning or check engine light does not turn off, you might have to clear the error using an OBD-2 scanner.

Can You Drive With Worn/Frayed Battery Cables?

You can, but since the car has a battery disconnection, voltage spikes from the alternator can damage sensitive components. 

The battery smoothens and regulates the voltage going to these electrical components.

But starting the car can be problematic. So, you might be unable to drive it until you fix the issue. 

If you own a manual, you can push start the vehicle, but this is not possible with an automatic.

Wrap Up

Replacing these battery cables is a simple DIY project that can cost hundreds of dollars if you get a professional technician to fix it. 

The DIY way is better for your wallet, and we recommend changing both positive and negative cables even if you find only one being faulty.

Contact us if you need these cables or any other car wires, and we’ll recommend the best ones.

Hey, I am Lillian Yang, Sales manager of Cloom Tech.

I am a responsible, intelligent and experienced business professional with an extensive background in the electronics industry.

Reach me at [email protected] to get a quote for your projects.

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