DIY

Car Battery Cable Replacement: A Complete DIY Guide

Reading Time: 5 minutes

Battery cables are essential because they connect the battery to the vehicle. Even though the battery cables are made from thick-gauge copper wire, they can eventually become damaged or corroded to the point of requiring replacement.

The good news is, If you have the knowledge and proper tools, battery cable replacement is usually a job that you can tackle yourself.

a typical car battery cable
Made from thick-gauge copper wire, battery cables provide the electrical connections between the battery and the vehicle.

How to Test the Battery Cables

There are two cables—a positive and a negative—attached to the battery. The positive cable connects the battery to the starter motor and the car’s electrical system, while the negative cable connects the battery to a grounding point. Each cable attaches to the battery with a terminal end.

Damaged or corroded battery cables can cause the engine to crank sluggishly or refuse to crank/start.

If you suspect that one (or both) of your car’s battery cables may be faulty, the first step in proving (or disproving) this theory is to perform a visual inspection. Check the cables for obvious signs of damage, such as breakage or excessive corrosion. Replace the cables as necessary if any problems are found.

There are also instances where the cables may have damage or corrosion that’s not visible. In such a scenario, the best way to detect a faulty cable is to perform a voltage drop test on the starting circuit. A voltage drop test is an excellent way to pinpoint a high resistance issue (e.g., excessive corrosion) that’s inhibiting current flow through the cable.

Before you perform a voltage drop test, however, you need to make sure that the battery is fully charged. You can test a battery’s state of charge using a digital multimeter (DMM). To do so, follow these steps:

Note: The following are general guidelines for educational and entertainment purposes only. Consult your vehicle’s factory information for specific repair instructions and recommended safety procedures.

  • Put on your safety glasses.
  • Set the DMM to the 20 volts DC setting.
  • Connect the black meter lead to the negative battery terminal and the red meter lead to the positive battery terminal.
  • A battery that’s sufficiently charged should have at least 12.2 volts.
mechanic fixing car battery
Battery cables can eventually become damaged or corroded to the point of requiring replacement.

Once you ensure the battery is fully charged, you can perform voltage drop tests on the battery cables. To test the positive battery cable:

  • Set the DMM to the 2 volts DC setting.
  • Disable the ignition system or the fuel system to prevent the engine from starting.

    Note: You can usually do this by disconnecting the electrical connectors from the ignition coils at each cylinder (if the vehicle is so equipped) or by removing the fuel injection relay or fuse. Do NOT disconnect the spark plug wires.
  • Connect the red meter lead to the cable’s positive terminal at the battery and the black meter lead to the cable’s other end at the starter’s battery terminal.
  • Have an assistant turn the ignition key to the “START” position and note the reading on the meter.

    Note: If the engine cranks, do not allow it to crank for more than 15 seconds while it’s disabled.
  • Typically, the reading should be less than 0.2 volts. Anything more usually indicates the cable has a high resistance condition and should be replaced.

Next, you’ll want to perform a voltage drop test on the negative battery cable. The process is very similar to testing the positive side of the circuit.

  • Connect the red meter lead to the cable’s negative terminal at the battery and the black meter lead to the cable’s other end at the engine.
  • Have an assistant turn the ignition key to the “START” position and note the reading on the meter. Typically, the reading should be less than 0.2 volts. Anything more usually indicates the cable has a high resistance condition and should be replaced.

Below, you’ll find a video that demonstrates testing voltage drop across the battery cables of a heavy-duty truck. The concept is the same for light-duty vehicles.

How to Replace Battery Cables

Once you’ve determined one of the battery cables is faulty, you can move forward and replace it.

What’s involved with replacing battery cables will vary, depending on the year, make, and model of the vehicle. So, before you jump right in, it’s a good idea to consult the instructions for your application in a repair manual or repair database.

Below, you’ll find a general overview of what’s typically involved with replacing the battery cables.

Tools and Equipment Needed to Replace a Battery Cable

The tools needed to replace a battery cable will vary, depending on the type of car you have.

In general, however, you’ll need:

  • Jack and jack stands
  • Repair manual or access to a repair database
  • Safety glasses
  • Wheel chocks
  • Wrench set

Battery Cable Replacement Instructions

Replacing a battery cable is usually a fairly straightforward task. The following steps will give you an idea of what the job usually involves.

orange car battery cables
The positive cable connects the battery to the starter motor and the car’s electrical system, while the negative cable connects the battery to a grounding point.

Note: The following are general guidelines for educational and entertainment purposes only. Consult your vehicle’s factory information for specific repair instructions and recommended safety procedures.

Battery Cable Removal:

  1. Put on your safety glasses.

  2. Safely raise and support the vehicle using a jack and jack stands. Set the parking brake and chock the rear wheels.

  3. Disconnect the negative battery cable from the battery. Isolate the cable so that it cannot make contact with the battery.

  4. Disconnect the positive battery cable from the battery.

  5. Remove the fastener (s) securing the battery’s hold-down device in place.

  6. Remove the hold-down device from the vehicle.

  7. Carefully remove the battery from the vehicle.

  8. With the battery out of the way, trace both battery cables back to where they connect to the vehicle.

    Tip: The positive battery cable attaches to the starter motor and usually the power distribution block. Meanwhile, the negative battery cable typically attaches to grounding points on the chassis, engine, and body.

  9. Remove whatever fasteners are securing the cables to the vehicle, then remove the cables from the engine compartment.
disconnecting negative battery
Disconnecting the negative battery cable.

Battery Cable Installation:

  1. Compare the new battery cables to the old battery cables to ensure that both are the same design.

    Note: If the cables are universal fit, they may need to be trimmed to length and/or have the terminal ends replaced.

  2. Make sure the battery cable connection points at the vehicle are free of any rust or corrosion. The battery terminals must also be free of any corrosion build-up. Clean these locations if necessary.

  3. Connect the new battery cables to the vehicle with the appropriate fasteners.

  4. Reinstall the battery and its hold-down device.

  5. Reconnect the positive battery cable to the battery.

  6. Reconnect the negative battery cable to the battery.

  7. Safely remove the jack stands and lower the vehicle.

  8. Start the vehicle to check that everything is working as it should.

How Much Does Battery Cable Replacement Cost?

If you choose to have a professional replace your car’s battery cables, you can usually expect to pay somewhere between $250 and $400 to get the job done. Of course, the exact price will depend on various factors, such as the year, make, and model of your vehicle.

You can save money by replacing the battery cables yourself if you have the tools and the know-how. CarParts.com has a wide variety of replacement battery cables available for various makes and models.

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