Why Did My Jumper Cables Melt? [Causes and Solutions]

Ensuring you have a jumper cable before any trip is essential. But what if your jumper cable melts when you need it the most? What causes the jumper cables to melt?

Jumper cables are for jumpstarting a car with a weak or dead battery. But if the process is not done right, it can cause the jumper cables to melt.

The reason for your jumper cable to melt vary, but the most common ones include the following:

  • Reserved or crossed jumper cable connection
  • Loose terminal connections
  • Low-quality jumper cables
  • Damaged jumper cables
  • Electrical problems in the car to be jump-started

Read on for detailed information about the causes of jumper cable melting and how to prevent it.

What is a Car Jumper Cable, and What Are Its Use? 

As the name suggests, jumper cables are a set of red and black wires with battery clamps on both ends used for jumpstarting a car.

Before we proceed, note that you only need jumper cables if you have a car powered by an internal combustion engine. You don’t need it for an electric vehicle that uses an electric motor for propulsion.

For an internal combustion engine to crank, it requires a spinning torque or force. This is usually provided by a starter motor in gasoline or diesel engines.

The starter motor relies on the car battery for electric power. But car batteries do not have an indefinite lifespan. Their cells weaken over time and may not store enough energy to power the starter motor. That is why you may need jumper cables to help you start your car.

A jumper cable allows you to ask another driver for help if your battery is dead or too weak to start your car. Your battery gets charged if you connect the two car batteries. It will power the starter motor to crank your engine.

Jumper Cable Melting: Most Common Causes

Jumper cables may melt if they are improperly or loosely connected, have low quality, and the car being jump-started has wiring faults. Let’s discuss these causes in detail.

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1. Reserved or Crossed Jumper Cable Connection

This is the most common mistake many drivers commit, and you may be a victim. Reversing the connections will cause your jumper cable to melt, regardless of the quality.

A reversed polarity connection is when you cause an electric current to flow in reverse back to the dead battery. The current flowing this way encounters high resistance, leading to excess heat generation that will melt the jumper cable insulation material.

Reversing the connections not only melts your cable but also damages the battery and may smoke your car electronics. If you are lucky, you can only escape with a melted jumper cable, but only if your reflexes are fast.

Reversed connections can also cause electrical shock. There may be reverse polarity if you feel a slight tingle when holding the jumper cables. We will discuss how to correctly connect jumper cables later in this post.

2. Loose Terminal Connections

Why do your jumper cables melt even if you connect them correctly? There can be many reasons for this, one of which is loose connections.

Large amounts of current flow from the healthy battery to the dead one when connected with a jumper cable. So, if the connections are loose, the jumper cables can overheat to the point of melting the insulation material.

Sparkling at the battery terminals is a sign of a loose connection. Consider connecting the two batteries again, ensuring it’s tightly connected.

Loose battery terminal connections can be due to damaged jump wire clamps due to rusting or corrosion at the battery terminals. That is why you should always store your jumper cables properly and away from moisture.  

3. Low-Quality Jumper Cables

Many people think it is a good idea to save a few bucks when buying new jumper cables. They for the cheapest products, but these come with their flaws.

Cheap or low quality are often thin since the manufacturer is economical with the material. The thin wires inside that insulation material cannot handle the high current that flows through them when you jumpstart your car.

Characteristically, a thin wire has high resistance. If an electrical current tries to pass through, a lot of heat that melts the insulation material is generated.

Consider the thickness of the wires as well as the rubber material that covers them for safety when buying a new jumper cable.

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4. Damaged Jumper Cables

Your jumper cables can get damaged, leading to the compromise of electrical property. Many people do not take keeping jumper cables seriously, but that should never be the case.

Jumper cables exposed to high temperatures may split or crack. In the worst case, the insulation material cracks, which can cause more dangers when jumpstarting your car.

Split copper wires cannot withstand large currents that flow through them when jumpstarting your car. That results in large amounts of heat generated, which melts the cables.

5. Wrong Jumper Cable Material

What also determines the cable quality is their conductors. They are made of metallic wires that allow an electric current to flow through them. Unfortunately, there is no standard conductor material for jumper cables.

Copper is the ideal conductor for jumper cables, but is more expensive. As a result, some manufacturers use aluminum.

Despite being an electrical conductor, an aluminum cable requires more current and is likely to overheat when jumpstarting your car. It may be easy on your pocket but costly in the long run.

6. Electrical Problems in the Car

Sometimes the reason why your jumper cable melts has nothing to do with the cables or connectors. The jumper cable may melt if an electrical fault exists in the car being jump-started.

The most common electrical faults are short to the ground or open circuits. The latter is the most devastating in this case.

An open circuit will only make it impossible to jumpstart the car because there is no continuous path for electrical current to flow through. But if there is a short to ground, an enormous current will flow through the cable.

Like reversed polarity, a short to ground will cause the jumper cable to melt and possibly damage your car’s electrical systems.  

How to Prevent Jumper Cables from Melting

There is nothing you can do if your jumper cables have melted. Safely discard them and buy a new set. Fortunately, you can avoid this situation by doing the following:

1. Connect Jumper Cables Correctly

As mentioned, reverse polarity is one of the most common causes of jumper cable melting. To avoid this scenario, learn how to correctly connect your jumper cables.

The two batteries are connected in parallel. That is positive terminal to positive terminal and negative terminal to negative terminal. But how do you do it? Here are the steps:

  1. Connect one end of the red jumper cable to your car’s battery positive (+) terminal and the other end to the positive battery terminal of the other vehicle.
  2. Attach one end of the black jumper cable to the negative battery terminal (-) of the donor car. Connect the other end to your car’s bare metal on the chassis.
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Don’t connect the black jumper cable directly to the negative battery terminal of your car. As stated, attach to bare metal on the chassis to avoid possible explosion when the jumpstarting goes wrong.

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2. Store Jumper Cables Properly to Avoid Damage

Your jumper cables are sensitive to environmental elements. Moisture can cause the clamps to rust, while high temperatures can melt the insulation or cause the copper to split.

Store your jumper cables safely, preferably in a protective bag. Also, clean them regularly, especially after use, to remove any dirt.  

3. Buy Quality Jumper Cables

Invest in high-quality jumper cables. Cutting corners can leave you stranded by the roadside if your cheaply sourced jumper cable melts.

High-quality jumper cables have the right conductor thickness and proper insulation. They are less likely to melt when you use them to jumpstart your car. Given their importance, it is worth every penny investing in jumper cables.

4. Avoid Loose Terminal Connections

Loose connections can cause your jumper cable to melt. Ensure a snug fit by double-checking the connections.

Tap the jumper cables with your hand. And if they are loose, tighten them before connecting the batteries together.

Factors To Consider When Buying Quality Jumper Cables

Jumper cables can all look the same, two long red and black wires with clamps at either end. That, however, doesn’t mean they have the same quality.

If you are shopping for a high-quality cable, consider the following factors:

1. Cable Rating

Cable rating refers to the thickness of the conductor inside the insulator. The thicker the conductor, the more reliable it is for jumpstarting your car, but it comes at a higher price.

Lower-value ratings of 1 or 2 gauges are the best. These heavy-duty jumper cables can waistband current that flows through them when jumpstarting your vehicle. Higher-value ratings of 9 or 10 are often used by small compact cars.

Most jumper cables used by everyday drivers range from 4 to 6. They are not as expensive as heavy-duty ones and are still reliable.

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2. Cable Insulation

You should be protected from the electric current that flows through the conductor. As a result, you need a jumper cable with thick insulation. These also protect the conductors from eternal elements, improving the lifespan of the jumper cables.

Jumper cables with thick insulation can be stiff and expensive, but they are the best for safety, reliability, and durability.

3. Cable Length

The longer the jumper cable, the better it is. A short one makes it connect to the two cars when jumpstarting your vehicle.

A 10-foot-long jumper cable should be sufficient for most situations. But if you have more on your budget, buy 25-foot-long ones for any eventualities.

4. Conductor Material

Jumper cables made of copper are the best choice, but they are more expensive. Solid copper is the most efficient conductor of electricity.

Aluminum conductors are also an option, but they are not as efficient. It will take longer to jumpstart your car and may overheat. Consider thicker aluminum jumper cables to avoid melting your cables.

5. Clamp Design

The design of your jumper cable clamps determines whether you get a snug fit or a loose connection. The golden rule is buying clamps with toothed alligator clips for a firm grip on the battery terminals.

The handle of your clamps should also be sturdy and well-insulated for your safety and ease of use.


Is it safe to use melted jumper cables?

No. Melted jumper cables are unsafe and can cause electrocution or short circuits. The risk of the jumper cables touching each other or the car chassis is high. This can damage the battery and vital car electricals. Discard melted jumper cables and invest in high-quality replacements.

What is the cost of a quality jumper cable?

The cost of jumper cables depends on length, rating, and conductor material. One that ticks all the boxes will be more expensive than others. You can buy them for as low as under $25 or as high as over $200. It all depends on your budget and your car type.

Can you jumpstart a dead car battery without jumper cables?

Yes. You can still jumpstart your car without jumper cables. The first option is push start, which requires a friend to push you to crank the engine. Alternatively, you can call roadside assistance for help.

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What happens if you hook your jumper cables up wrong?

Hooking jumper cables incorrectly has far-reaching consequences. The jumper cables will begin melting, and damage to car electricals and electronics can be severe. Ensure you don’t reverse the polarity when jumpstarting your car.

Is it bad if jumper cables spark?

Yes. Sparking is often a result of loose connections. But if it happens because you touched them together, it indicates they are in good condition. However, you should avoid shortening your jumper cables and use recommended methods for testing them.

Why don’t you connect both negatives when jumping a car?

You are advised not to connect both negative battery terminals directly to avoid an explosion from the dead battery. Instead, connect the other end of the black jumper cable from the donor car’s negative battery terminal to the bare metal on the chassis of the car you want to jumpstart.

Do you turn off the car before disconnecting the jumper cables?

No. Your car may not start again if you shut down the engine immediately after jumpstarting. Just disconnect the jumper cables with the engine running, disconnecting the negative (black) cable and then the positive (red) one.  

Final Remarks

If your jumper cables melt, they might be connected in reverse. Other possible causes include low-quality jumper cables, wiring faults, loose connections, and wrong conductor material.

Invest in high-quality jumper cable. Consider the cable length, rating, conductor material, and clamp design. These features ensure the reliability, durability, and safety of jumper cables. Also, store your jumper cables properly after use to avoid damage.

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