How to Use Jumper Cables to Start a Car

Dead batteries are an inconvenience at best—and at worst they can leave you stranded and waiting for help in dangerous conditions. Jumper cables are standard issue in nearly any roadside assistance kit you can buy because they're one of the most useful items to have in your car.

In this article, we'll take a look at how to connect jumper cables, how to use jumper cables, and other ways to jump a vehicle when another car isn't available.

How do jumper cables work?

Jumper cables or booster cables work by transferring electricity from an energy source to a dead battery. Most often, they are connected between a car with a working battery and car that won't start because of a dead battery. Jumper cables can, however, be attached to portable chargers, or any other appropriate source of electricity, in order to charge batteries.

What precautions should be taken when using jumper cables?

When it comes to how to jump start a car with cables, there are some important things to keep in mind to prevent damage to both the dead battery and the live battery. 

• Check for Similar Voltages—Make sure that the two batteries have similar voltages. Drastically uneven voltages could damage a vehicle's electrical system.

• Pay Attention—Matching the clips to their appropriate charges (positive or negative) is crucial, but the order in which you make the connections is also important. Improper connections can lead to sparks flying in an oily engine compartment, which is dangerous.

• Inspect for Damage—Jumper cables tend to spend a majority of their life bumping around in the trunk. Before using your jumper cables, make sure the cables aren't frayed and that the clips are free from rust.

How should jumper cables be used?

Below is a step-by-step guide to properly connecting and jump starting a dead battery using another vehicle. Always remember the precautions listed above. To reduce the chance of accidents, be sure your vehicles are parked in a safe, out-of-the-way location. Also, be sure the vehicles are not touching.

Step 1: Connect the Positive (+) Cable

Start by connecting the red positive clamp to the positive battery post on the dead battery. Connect the other end to the positive battery post on the jumper battery in the working vehicle. Remember to always connect positive to positive.

Step 2: Connect the Negative (-) Cable

Connect the black negative clamp to the jumper battery in the working vehicle. Move to the nonworking vehicle and find a large, metal component in the engine compartment. Then, connect the final black negative clamp to the metal component. Connecting the negative clamp to the dead battery can lead to sparks flying, which is a fire risk.  

Step 3: Start the Working Vehicle

With the cable connection complete, it's time to start the working vehicle. Allow it to idle for five to ten minutes.

Step 4: Start the Nonworking Vehicle

Start the nonworking vehicle. If you're still having difficulty getting the vehicle to start, you may need to let the idling vehicle charge the battery for a longer period of time. Once the vehicle with the dead battery has started, let it run for at least 30 minutes in order to give the alternator ample time to charge the battery.

How to choose a portable jump starter?

Although a bit pricey, portable jump starters are also fantastic resources to have available in your vehicle, should you run into battery problems. These portable power banks are as versatile and varied as any other high-tech product, but they all work in similar ways. Fully charge your portable jump starter at home and keep it in your vehicle, ready to help when you need it.
When choosing a portable jump starter, here are some key features to consider:

• Extra Ways to Connect—Many portable jump starters come equipped with a full range of ports and connection options. Look for USB and USB-C ports, as well as 12V outlets, as these can help charge a range of devices on the go, not just your dead car battery.

• Air Compressors—Some portable chargers also come equipped with air compressors to help you inflate flat tires.

• Emergency Lights—Onboard emergency lights give you great peace of mind if you are stranded at night or in situations where visibility is low. 

• Power Rating—Consider the vehicle you plan to use with the portable jump starter. Smaller vehicles with lower-voltage batteries may be able to get by with portable jump starters with lower power, but larger vehicles will require portable jump starters with more power.

 

What are the recommended jumper cables to keep in your trunk?

Having a reliable set of jumper cables on hand can make all the difference during a roadside emergency. When choosing a set, look for cables that are long enough to reach between vehicles and thick enough to deliver adequate power. Here are three great options to consider:

Lifeline AAA Four-Gauge Jumper Cables

Available through AAA, these cables are designed for dependable, everyday emergency use. The insulated clamps are compatible with most battery types, and the compact 12-foot length makes them easy to store in your trunk. While lighter-duty than some aftermarket options, they’re a practical choice for smaller vehicles and routine roadside situations; especially for drivers who prefer AAA-branded gear.

Energizer Four-Gauge Jumper Cables

A reliable, all-around option, these heavy-duty cables provide strong power transfer for cars, SUVs, and light trucks. The thicker 4-gauge construction helps ensure consistent performance, while the 20-foot length offers flexibility when vehicles can’t be parked close together. Durable insulation also helps keep the cables flexible in colder temperatures.

TOPDC Four-Gauge Jumper Cables

These cables offer a balance of durability and versatility, making them a good fit for a wide range of vehicles. Copper-coated clamps provide a secure connection, and the longer length helps in real-world scenarios where positioning is less than ideal. They’re especially useful for drivers who want a more heavy-duty option for larger vehicles or colder climates.

Frequently Asked Questions

Do cars come with jumper cables?

Most new cars do not include jumper cables as standard equipment; manufacturers more often supply tire repair kits or battery-saving systems instead. Check your owner’s manual or the trunk (under the spare or in a side panel)—some models and aftermarket accessory packages still include a set. If you don’t have cables, keep a compact set in the trunk, or consider a portable jump starter for convenience.

What size jumper cables do you need?

Pick cables by gauge (thicker wire = lower gauge) and length. For most passenger cars, a four-gauge or six-gauge cable that’s 10–20 feet long is a practical choice: Four-gauge moves current more efficiently for quicker starts, while six-gauge is lighter and cheaper. If you drive trucks, SUVs, diesel vehicles, or often help others, choose a thicker cable (two-gauge or equivalent) for reliable power transfer.

What is the best gauge for jumper cables?

If you want one set that covers almost everything, go with two-gauge or four-gauge. Two-gauge is the most robust and works well for heavy-duty vehicles, while four-gauge is a great all-around compromise for most cars and light trucks. Avoid thin eight- or 10-gauge cables for modern vehicles since they’re slow to deliver current and may struggle in cold weather.

Can you jump-start your car if the battery is completely dead?

Often, yes—a “completely dead” battery can frequently be brought back long enough to start the engine if the cells still hold some charge and you use proper cables or a jump starter. If the battery has a failed cell, is swollen, cracked, or registers near zero volts, jump-starting may not work, and the battery should be replaced. Always consult your vehicle’s owner’s manual before attempting a jump, and don’t jump-start high-voltage hybrid or electric systems (follow the manufacturer’s service instructions).

What should you do if your car still won’t start after using jumper cables?

First, double-check the cable connections and try again, allowing a minute or two for charge transfer before attempting to start. If it still won’t start, the problem may be the starter, alternator, a blown fuse, a bad battery cell, or an electrical fault. At that point, call roadside assistance or arrange a tow to a shop for diagnostics. If you frequently depend on others for a boost, consider a portable jump starter or replacing an aging battery.

Can you jump-start your car in cold or wet weather?

Yes, but take extra care: Cold reduces battery capacity, so thicker cables and a longer charging interval help, and a warm engine compartment improves chances of success. Avoid standing in deep water and keep all connections dry; if the battery case is cracked or leaking, don’t try to jump it. If conditions are hazardous, call roadside assistance rather than risking slips, sparks, or exposure.

Do jumper cables go bad?

Yes, clamps can corrode, insulation can crack, and internal wires can fray, all of which reduce performance and can be unsafe. Inspect cables periodically (especially before a trip), and replace them if the clamps don’t grip firmly, the insulation is brittle, or any wiring is exposed.

How do you properly store and maintain jumper cables so that they last?

Coil cables loosely (avoid tight kinks), and store them in a dry, cool place inside a protective bag or the vehicle’s cargo area to prevent moisture and UV damage. Wipe terminals clean, lightly coat clamps with dielectric grease to prevent corrosion, and inspect the insulation and clamps regularly. Replace the set if you find exposed wires, brittle insulation, or badly corroded clamps. Testing them occasionally by using or checking continuity will ensure they work when you need them.

What safety precautions should you take when using jumper cables?

Wear eye protection and gloves, park the booster vehicle so that cables reach without stretching, and turn off all electronics in both vehicles. Connect clamps in the proper order (positive clamp to positive terminal on both batteries first; negative clamp to a grounded metal point on the dead car away from the battery) to minimize sparking near the battery. Don’t let clamps touch each other, and don’t lean over the battery while connecting. Follow your owner’s manual, and when in doubt, call professionals.

What is a portable jump starter, and when does it make sense to buy one?

A portable jump starter is a compact battery pack with jumper-clamp leads (and often USB ports and lights) that can start your vehicle without another car. It makes sense if you frequently drive alone, travel remote routes, own a vehicle with an aging battery, or simply want faster, safer self-recovery. When choosing one, pick a unit with enough peak or cranking amps for your engine size, safety features (reverse-polarity and spark protection), and a reputable warranty.