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Car Booster Cable: Definition and Connection Steps

If your car has a damaged battery, the solution is to replace it. But if you drain the battery, it will be low on charge but not damaged. A car booster cable can help you start the car to recharge the battery. 

Let’s look at the characteristics of these booster wires and how to connect them when jump-starting vehicles with dead batteries.

What Is a Car Booster Cable?

Also known as a battery jumper cable, a car booster cable is a thick wire containing two conductors and crocodile clips on each end. These cables enable you to connect batteries in two cars when parked side by side without removing them.

Car Booster Cable Characteristics


Booster cables are dual-conductor wires with crocodile clips on each end. Each wire has two clips, making them four total, and these components enable you to connect the conductors to the battery lugs or posts.

A set of crocodile clips

A set of crocodile clips

Another critical part of this cable is the insulation. Unlike most car wire harnesses, the jumper cable is usually exposed to the elements when linking the batteries.

Therefore, the insulation must resist water, moisture, abrasion, corrosive liquids, mechanical impacts, etc.

The most suitable material to provide these insulation properties is EPR (Ethylene Propylene Rubber).

Inside this insulative material are two stranded copper cables that maximize the wire’s flexibility.

Some jumper cables feature a synthetic semi-conducting tape between the copper strands and the EPR insulation for voltage stress relief.


Although car booster cables feature voltage ratings, the critical upper limit is the current rating.

Thick conductors with low gauge ratings can handle more current when transmitting power to the dead battery.

A person holding a car booster wire with thick, low-gauge cables

A person holding a car booster wire with thick, low-gauge cables

For instance, 2-AWG jumper wires can transmit about 165 amps at 35kV. Such ratings might be insufficient for large vehicles, but the cable will work.

Remember, these wires are intended for short-term use, meaning you can pass high electrical currents without damaging the link.

But you should always pick a thick, heavy-duty jumper cable to ensure maximum durability.


Connecting the battery terminals in reverse is dangerous because it can damage the battery or even make it explode. It can also damage your vehicle’s electrical system. You can imagine how expensive that repair bill will be.

To avoid these mistakes, car booster cables have color-coded wires to indicate the positive and negative lines.

Red and black color-coded wires and alligator clips that form the car booster cable

Red and black color-coded wires and alligator clips that form the car booster cable

The red wire’s crocodile clips should always connect to the terminals labeled + on both batteries. The black wire’s crocodile clips should terminate at the terminal labeled – on the donor battery.

How To Jump Start a Vehicle Using a Car Booster Cable

Before getting to the wiring part, you must bring the vehicles close to each other.

The one with a dead battery can’t move, so drive the “helper” car near the other to closely position the batteries in their hoods. After that, turn off the engine. Ensure both are off.

Cars parked next to each other for jumpstarting

Cars parked next to each other for jumpstarting

Step 1: Prepare the Battery Terminals

Open the hoods of both vehicles and remove any plastic covers over the battery terminals. Clean these terminals using vinegar and baking soda if they have salt residues.

Give the chemicals a few minutes to dissolve the salt, then rinse them. Wipe the terminals to have a dry working area.

Step 2: Wire the Batteries

Connect the car booster cable to the batteries, starting with the red wire. Attach the red wire alligator clip to the terminal marked + on the dead battery.

After that, connect the other red end to the + terminal on the donor vehicle’s battery.

Next, link the black wire’s alligator clip to the donor battery, then finish up with the negative connection to the dead battery end.

A vector image showing how to connect a jumper cable between two vehicles

A vector image showing how to connect a jumper cable between two vehicles

Take note of this last part. Don’t connect the clip to the dead battery’s negative terminal. Instead, link it to an unpainted metal component or surface on the vehicle’s engine. Look for brackets, bolts, or screws on the engine.

Follow this connection order to prevent electrical faults.

Step 3: Start the Cars

Start the vehicle with the donor battery and let it idle for 2-3 minutes. It is crucial to have this engine running because the alternator will provide the extra power to start the other car. Also, it will prevent battery drain.

Connected car booster cables, ready for engine starting

Connected car booster cables, ready for engine starting

After 2-3 minutes, start the car with the dead battery and let it run for 10-15 minutes to recharge its battery.

If the car fails to start, you must look deeper into the problem because it could be a wiring, starter relay, or starter motor issue.

Step 4: Disconnect the Booster Cables

Unhook the alligator clips in reverse order, beginning with the one connected to the engine block. Drive or rev the “dead battery” car for about 15 minutes before turning off the engine.

What Next After Boosting the Dead Battery?

You’ll have to observe the “dead battery” vehicle for some days because a deeper issue might be causing the power drain.

If it does not misbehave, it was a simple accidental battery drain. But if the issue reoccurs, the battery might be on its way out, or the car might have an internal electrical issue.

What If You Don’t Have a Donor Car?

What you need is the power source, not the car. Therefore, you can use a jump box because it can power any 12V device, including an engine starter. If you have this battery pack, hook the car booster cables to its terminals using the order above, then start your car.

After starting, leave the box connected for 10-15 minutes, then remove the clips in the reverse order.

Remember to keep this box recharged to avoid damaging the batteries and have enough power to start the engine next time.

Potential Issues That Can Arise With Wrong Booster Cable Connections

  • Incorrect positive (red) and negative (black) cable connections will make the vehicle fail to start.
Vehicle jumpstarting during winter

Vehicle jumpstarting during winter

  • Failure to attach either cable’s crocodile clips won’t complete the circuit, making the vehicle fail to start.
  • Connecting the black jumper cable to the dead battery’s negative terminal can cause sparking, which is dangerous because it can ignite flammable substances.

Wrap Up

Car battery booster cables are convenient vehicle tools because you never know when you might experience starting issues, especially during winter. These cables are affordable, so buying one shouldn’t dent your pocket.

You can get the cable in different lengths and gauges to match specific vehicle needs. Contact us if you need a set, and we’ll recommend some for your consideration.

I am Lillian Yang, having been a sales manager for over 10 years.

I have received many positive reviews from customers. They have praised our excellent service, on-time delivery, and high-quality cable assemblies.

For your projects, please provide cable assembly files/images/smples, etc., so that I can send you a quotation within 24 hours.

Contact me now and let’s get started on building your wire harnesses!

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