What Are the Symptoms of a Bad/Failing or Corroded Battery Cable?

Most people know that they need a working car battery to be able to start their car but what role do the battery cables play?  What happens if a battery cable starts to fail or go bad?

So how do you know if your negative or positive battery cable is going bad?  The most common symptoms of a bad or corroded battery cable are problems with starting your car, a low voltage battery, dim headlights, frayed battery cables, corrosion on battery terminals, and hot battery cables.

Now that you know the most common symptoms of a bad or failing battery cable how do you diagnose one?  How much does it cost to replace a bad battery cable?  These questions answered and more below.

What Do Battery Cables Do?

Before we go into the specifics of how to diagnose a failing or bad battery cable it’s important to understand what they do, if you already understand the differences between a positive and negative battery cable skip this section.

On your car battery, there are two terminals positive and negative.  The positive terminal provides electricity to the electronics in the car.  While the negative terminal connects your car battery to the frame of your car to provide a ground connection.

The positive battery cable connects to your car’s starter and alternator and provides electricity from the battery to the starter to get your car’s engine started up.  The negative battery cable or ground cable is connected to the frame of your vehicle to provide a stable ground connection which is essential for the battery and electronics of your car to operate.

So know that you know more about the differences between the negative and positive battery cables in your car what are the symptoms of a bad battery cable?

What are the Symptoms of a Bad or Failing Battery Cable?

1. Car Won’t Start

The battery cables attached to your car need to have a strong connection to the car starter and the frame of the vehicle to be able to start up your car.  Over time battery cables can become frayed, corroded, or disconnected which won’t allow your car to start up.

If your car won’t start it doesn’t automatically mean that you have a bad battery, you could just have a problem with your battery cables not providing a good connection to the frame of your car or the car’s alternator.

2. Low Voltage Battery

Another symptom of a failing battery cable is having a low voltage battery.  If your positive battery cable is damaged your car’s alternator won’t be able to fully charge your car’s battery resulting in a low voltage battery.

Your car’s battery should be above 12.6 volts when your car is off and should be between 13.7 to 14.7 volts while your car is running.  If your voltage reading is different than what I described above you could have a problem with your positive battery cable, your battery, or your alternator.

If you’re unsure of where to start, check out my other article what are the symptoms of a bad alternator.  If you think that your alternator is fine then you may also want to have your battery tested to make sure that there isn’t a problem with the battery itself.

3. Dim Headlights

Another symptom of a bad negative battery cable is dim or flickering headlights.  Your headlights need a proper connection to the car battery to be able to provide enough electricity to the headlights to illuminate the road in front of your car.

If your battery cables are starting to fail or don’t have a strong connection to the battery terminals because of corrosion it can cause your headlights to be dimmer than normal or flicker while driving down the road.

4. Battery Cable is Frayed or Damaged

Another sign that your negative battery cable is bad and needs to be replaced is a frayed or damaged battery cable.  Inspect your battery cables for damage, they should be smooth and not have any nicks or corrosion on them.

If you do notice any fraying or damage to the cable itself it’s best to have the cable replaced.  You can repair battery cables but they are cheap enough to just replace them if there is an issue.

What are the Symptoms of a Corroded Battery Cable?

1. Corrosion on Battery Terminals

Having a little bit of corrosion on your battery terminals is fine but if you notice large amounts of corrosion on your battery terminals this could be indicative of a larger problem with your positive or negative battery cables.

Corrosion on your car’s battery terminals is caused by hydrogen gas escaping your car battery and then mixing with the oxygen in the air flowing into your engine bay.  If you notice corrosion on your battery terminals you’d want to remove it before it starts to take hold of the battery cables.

2. Hot Battery Cable

Corrosion on your battery cables can increase the resistance or the flow of electricity through the cable.  If you remember from science class “electrical current flows due to the exchange of electrons between atoms. As electrons move through a metal conductor, some collide with atoms, other electrons, or impurities. These collisions cause resistance and generate heat.”

So with that said if your negative battery cable is hot to the touch either when the car is running or shortly after turning off the car there is a good chance that the resistance in the negative battery cable is high, causing the negative battery cable to heat up.  The best solution for this problem is replacing the negative battery cable.

How Do You Diagnose a Corroded Battery Cable?

Corrosion on the battery terminals can then cause corrosion on the battery cables if left on the battery terminals long enough so that should be your first indicator that corrosion has started to take hold of your battery cable.

Inspect the end of your battery cable for corrosion.  If the end of the cable has started to corrode it’s best to replace the cable altogether as with corrosion you can’t really tell how much corrosion has started to take hold inside of an insulated cable.

If you’d like to test your negative battery cable using a multimeter to make sure that the resistance in it isn’t too high check out the youtube video below.

How To Get Rid of Corrosion On Battery Terminals

If you see corrosion on your battery terminals you would want to clean off the corrosion by pouring cola on it.  Alternatively, you could also make a paste out of baking soda and water to use to clean your car battery terminals with an old toothbrush or a rag.  The video below shows how to use baking soda to clean your battery terminals.

Why is the Negative Battery Cable Hot?

Usually, if your negative battery cable is getting hot while the engine is running or shortly after turning off the engine then there is something causing resistance in the cable that is creating heat.  Battery cables are made from metal and can corrode over time.

Corrosion inside of battery cables can sometimes be hard to spot because battery cables are typically covered with a plastic or rubber shield to help prevent them from corroding, but that doesn’t mean that battery cables are immune from corrosion.

How Much Does It Cost to Replace a Negative Battery Cable?

Negative car battery cables are fairly inexpensive to replace because there really isn’t much to them.  They are really just a thick metal cable surrounded by plastic or rubber to insulate them with a battery terminal on the end.  You can usually find a replacement negative battery cable in the $20-$30 range.

Replacing a negative battery cable is something that most people can do on their own because they typically attach to the frame of the car right around where the car battery is located.  So you’d just need to remove the old negative battery cable and then replace it with a new one.

How Do You Start A Car With Bad Battery Cables?

You may not be able to start your car at all if you have bad car battery cables.  If your battery cables are slightly corroded then they should allow your car to start up.  But if your car battery cables are frayed or spliced then your battery cable may be beyond repair and need to be replaced to allow your car to start up again.

Can a Bad Battery Cable Drain a Car Battery?

A bad battery cable typically won’t drain a battery but it can prevent it from charging.  The electrical system of your car needs a good ground connection to be able to allow your car to start up and to allow the alternator in your car to produce electricity.

Usually, if your battery is draining after sitting for a bit there is something connected to the car that is draining the battery slowly.  Most cars won’t allow devices plugged in to draw electricity from the car battery while the car is off but if your car does allow you to plug in devices while the car is powered off then check there first.

You could also have a problem with the wiring of the car causing it to drain the car battery.  This is what’s known as a parasitic drain.

Do Car Battery Terminals Get Hot?

Car battery terminals can get hot if the battery cable attached to them gets hot, but battery terminals themselves won’t get hot just because the battery is charging or just sent electricity to the starter to start up the car.

How Do I Know if My Battery Terminals are Bad?

Most of the time your car battery will go bad before you ever have a problem with your battery terminals.  What you can do if you see corrosion on your battery terminals is clean them with a solution of your choice and a brush.  You can mix baking soda and water to create a paste or use a cola drink to pour onto your battery terminals to clean them.

Sources:

https://nationalmaglab.org/education/magnet-academy/watch-play/interactive/heat-resistance