HomeTips & GuidesCar Battery Extension Cable: How To Pick and Wire This Power Cable

Car Battery Extension Cable: How To Pick and Wire This Power Cable

The car battery extension cable is a specialized battery terminal extender. These copper power cables extend the battery posts to reach external devices like inverters that require a 12V power source.

The extension cables can also bring in power from battery chargers to run your vehicle’s starter motor to crank the engine. 

Let’s look at why you need to install this cable, how to pick the most suitable one, and how to wire it.

Why You Need a Car Battery Extension Cable

You might need this extension cable in the following scenarios.

To Jump Start Another Vehicle

An extension cable will be handy if your neighbor or stranded driver asks for help starting the vehicle due to a dead battery.

This extended wire length makes it possible to share your battery even if the two vehicles are far apart. Picture a scenario where your neighbor’s car is in the garage with limited space to access the hood.

Extension cables enable you to access your vehicle’s battery without moving the car.

To Connect Portable Power Sources

Regular jumper cables might be short. But extension cables are long enough to reach a portable power source like battery chargers and jump starters. You need these mobile power sources if you’re not using another vehicle’s battery to jump-start yours.

To Run Accessories and Appliances

Although some people prefer going offline and being at one with nature when camping, you need some conveniences, like refrigeration.

If your vehicle has a faulty 12V outlet, you can tap power from the battery. This connection requires an extension cable.

An extension cable for the 12V cigarette lighter outlet

An extension cable for the 12V cigarette lighter outlet

Activities like tailgate partying also require 12V powered accessories, or you might need lighting during an outage.

For DIY Projects

A car battery extension cable will be handy to power the tools you need for DIY tasks or restoration projects in your vehicle.

A technician with extension cable clips mounted in his jeans pockets

A technician with extension cable clips mounted in his jeans pockets

Also, you can use this 12V power source to run tools when working on other DIY projects outdoors, especially where you can’t access AC wall outlets.

To Optimize Power Delivery

Some battery chargers and maintainers include short power cables in their packages, meaning you must place them near your vehicle.

Car battery extension cables allow you to install these recharging devices at an optimal position to optimize power delivery to the battery.

A car battery charger with short cables

For Emergency Situations

You can use these extension cables to get power to LED lights or communication devices to reach for help. Similarly, you can use them to run essential equipment if there is a blackout.

How To Choose the Right Car Battery Extension Cable

Consider the following factors to pick the most suitable car battery extension cable.


Length is a primary factor to consider when talking about extension cables. You can get these wires in different lengths, and we recommend getting an exact measurement or slightly longer than what you need. But if price and space are a non-issue, get the lengthiest extension cable available.


Gauge refers to the wire’s thickness, which determines the amount of current the cable can transmit. Therefore, this gauge should match the load or purpose of the car battery extension cable.

Thick, low-gauge battery extension cables

Thick, low-gauge battery extension cables

For instance, if you want to use the wire to power accessories, it should be thick enough to handle the combined load. Otherwise, the red positive wire will heat up because of the increased resistance.


Car battery extension wires must have connectors on either end, and one side should be compatible with your battery terminals. Otherwise, you’ll have to cut these ends and crimp new connectors that match your battery terminals.

The goal is to ensure they create secure joints with the battery for reliable power transmission. You should also check the connectors on the other end to ensure they match the device you want to connect.

Quick connectors can work if you plan to connect and disconnect the extension cable frequently.

Conducting and Insulation Materials

On the conducting side, copper is the best material due to its high conductivity rating. However, the insulating material can differ.

A car battery extension cable

A car battery extension cable

It is challenging to know the properties of all the preferred insulation materials, but you can check the properties of the cable.

For instance, some are extreme-temperature or corrosion-resistant, while others can withstand abrasion. Pick a cable that matches the operating conditions around your application.


The car battery extension cable should be versatile for several applications, including the following.

  • Battery recharging
  • Jump starting
  • Powering accessories
  • Emergencies

Safety Features

Extension cables with safety features like inline fuses and surge protection are better than plain wires because they safeguard the connected components.


This factor depends on the weight and length of the cable. The longer it is, the bulkier it will be. And the heavier it is, the more challenging it will be to move around. Weight is critical if you intend to have the cable in your vehicle throughout.

Generally, though, the extension cable should be compact and lightweight for easy movement on the go. Larger cable sizes are okay if you don’t intend to move with the wire daily.

How To Wire a Car Battery Extension Cable

Connecting this car battery extension cable is one of the most straightforward DIY projects you can undertake. You’ll need the following materials.

  • Extension cable
  • Battery terminal clamps
  • Wire stripper
  • Battery clamp crimping tool
  • Inline fuse (if not included in the extension cable)
  • Heat gun
  • Electrical tape
  • Heat shrink tubing

Follow these steps to install the wire.

Step 1: Unpack the Extension Cord

Unpack and inspect the extension cord to ensure it is an undamaged item and matches the item description. Also, check its current rating to confirm whether that wire gauge is sufficient for the accessories or charging process.

Step 2: Connect the Battery Terminal Clamps

Instead of using crocodile clips in a jumper-style cable, we recommend using battery terminal clamps to make the connection more secure and solid.

But if the extension cable comes with connectors, which you can mount on the existing battery clamps, install them.

Battery terminal clamps

Battery terminal clamps

Step 3: Strip the Wires

Strip about half an inch of the insulation from the black negative and red positive battery cable wires.

Step 4: Connect the Wires

Connect the stranded copper wire conductors to the battery terminal clamps installed earlier. Ensure the red wire goes to the positive terminal and the black wire to the negative terminal.

Step 5: Install the Safety Features

If the cable lacks a fuse or surge protection, we recommend installing an inline fuse to match the load. Mount this fuse on the positive power line near the battery.

Step 6: Insulate the Joints

Wrap the fuse and terminal electrical joints using heat shrink tubing and fire the heat gun to seal these tubings.

Heat shrink tubing wrapped around a connector joint

Heat shrink tubing wrapped around a connector joint

Step 7: Test the Extension Cable

Test the battery cable extension wires by connecting the accessories on the other end. If you need AC power, connect the wires to an inverter and test the system.

Wrap Up

Although unnecessary, car battery extension cables can be a lifesaver. They are handy if you are in an emergency and need power to run accessories or communication devices. 

Also, they can help you if your battery dies and you need help jump-starting.

Contact us for more information if you need this cable and the mounting components. We can ship you the parts at reasonable prices.

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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