How to Use Jumper Cables to Start a Car, Safely and Correctly

Park the cars close without touching, turn everything off, then connect cables in this order: red to the dead battery’s positive (+), red to the donor’s positive (+), black to the donor’s negative (−), and black to a metal ground on the dead car. Start the donor, wait a minute or two, try starting the dead car, then remove cables in reverse order. Drive 20–30 minutes to recharge. Below is a step-by-step guide, safety checks, and troubleshooting for modern vehicles.

What You Need and Safety Checks

Before you begin, gather the right tools and make sure conditions are safe. A few quick checks can prevent damage or injury and help the jump go smoothly.

• A quality set of jumper cables (8–12 feet or longer, thick-gauge clamps with good insulation)
• A donor vehicle with a healthy 12-volt battery (similar size helps)
• Eye protection and gloves (recommended)
• Owner’s manuals for both vehicles (to confirm jump-start points and any model-specific cautions)
• Clear, stable area away from traffic; both vehicles in Park (automatic) or Neutral (manual) with parking brakes set

If you notice a swollen, frozen, cracked, or leaking battery—or smell strong sulfur/rotten egg odor—do not attempt a jump. Call roadside assistance. Never smoke or create sparks around batteries.

Step-by-Step Jump-Start Instructions

Follow these steps in order to minimize risk and get the best chance of a successful start. The sequence matters, especially where you place the final ground clamp on the disabled vehicle.

1. Position the vehicles: Park nose-to-nose or side-by-side close enough for cables to reach, but keep the vehicles from touching. Turn off both ignitions and all accessories (lights, HVAC, audio), and set parking brakes.
2. Locate battery terminals and jump points: Identify positive (+, often red) and negative (−, often black) terminals. Many modern cars provide dedicated jump posts under the hood—use those if present.
3. Inspect for hazards: Check for corrosion, damage, leaks, or loose terminals. If you see serious corrosion or damage, don’t proceed.
4. Connect the red (positive) cable to the dead car’s positive (+) terminal or designated positive jump post.
5. Connect the other end of the red (positive) cable to the donor car’s positive (+) terminal.
6. Connect the black (negative) cable to the donor car’s negative (−) terminal.
7. Connect the other end of the black (negative) cable to a clean, unpainted metal ground on the dead car—such as a solid engine bracket or chassis ground point—away from the battery. Avoid moving parts. Note: If your car has a battery monitoring sensor on the negative terminal, do not clamp onto the sensor; use the manufacturer’s specified ground or jump stud.
8. Start the donor car and let it run for 1–3 minutes. Lightly raise engine speed to ~1,500–2,000 rpm to help charging.
9. Attempt to start the dead car. If it doesn’t start, wait another 2–3 minutes with the donor running and try again. Avoid cranking for more than 10 seconds at a time; let the starter rest 30–60 seconds between attempts.
10. Once the dead car starts, keep both engines running. Carefully remove cables in reverse order: remove the black clamp from the dead car’s ground, then the black clamp from the donor’s negative, then the red clamp from the donor’s positive, and finally the red clamp from the dead car’s positive. Ensure clamps don’t touch each other or metal while removing.
11. Let the revived car run or drive for 20–30 minutes to recharge. If available, check charging voltage (typically ~13.8–14.7V while running). If it stalls or won’t hold charge, have the battery and alternator tested.

This sequence reduces the risk of sparks near the battery and gives your weak battery time to accept charge before cranking. Taking it slow can make the difference between success and a repeat failure.

Why the Ground Connection Matters

Attaching the final negative clamp to a chassis or engine ground on the dead car keeps any spark away from the battery, where hydrogen gas may be present. Many manufacturers explicitly recommend this. If your vehicle provides a dedicated negative jump stud, use that. Some vehicles with battery sensors may instruct negative-to-negative terminal connections—always follow the owner’s manual if instructions differ.

Common Mistakes to Avoid

Small errors can cause big problems. Keep these pitfalls in mind before and during the process.

• Reversing polarity (mixing up + and −), which can blow fuses or damage electronics
• Letting cable clamps touch each other or metal surfaces once connected
• Clamping to painted, oily, or moving parts, which prevents a good ground or creates hazards
• Ignoring the owner’s manual on vehicles with battery monitoring sensors or special jump posts
• Jumping a visibly damaged, frozen, or leaking battery
• Using an incompatible power source (e.g., 24V system on a 12V vehicle)
• Skipping safety basics: cars touching, transmissions not secured in Park/Neutral, or no parking brake

Avoiding these mistakes helps protect sensitive electronics and ensures a safer, quicker jump-start for both vehicles.

Troubleshooting If It Still Won’t Start

If the engine won’t crank or starts and dies, these checks can help isolate the issue before you call for help.

• Recheck connections: Ensure solid contact on clean metal, especially the ground on the dead car.
• Give it more time: Let the donor run 3–5 additional minutes to feed the dead battery before another start attempt.
• Try a different ground point: Move the negative clamp to a better, unpainted engine or chassis bolt.
• Assess the donor: A weak donor battery or failing alternator may not supply enough current.
• Look for corrosion: White/blue crust can block current; clean carefully if needed.
• Check immobilizer/security: A flashing key or lock icon could prevent starting; use the correct key fob and try again.
• Consider the starter or main fuse: No crank with good power may point to a bad starter, relay, or blown fuse.
• If it starts but dies quickly: The alternator might be failing; get a charging system test.
• Use a jump pack or call roadside assistance: A quality lithium jump starter can help when another vehicle isn’t available.

Persistent failure typically indicates a battery at end-of-life or a charging/starting system fault; professional testing will pinpoint the cause.

Special Cases and Modern Vehicles

Newer systems and alternative powertrains warrant a few extra notes. Check your manual for vehicle-specific instructions.

• Start-stop/AGM/EFB batteries: Safe to jump, but use the designated posts. Replacement and charging procedures may differ from standard flooded batteries.
• Hybrids: You can usually jump the 12V system using the under-hood posts, but never attempt to jump or access the high-voltage battery. Follow the hybrid’s manual strictly.
• EVs: Many EVs have a 12V battery for accessories; some allow using an external 12V source to “wake” the car. Do not attempt to jump the traction battery. Consult the manual.
• Battery monitoring sensors: Avoid clamping directly onto the sensor at the negative terminal; use the specified ground or negative post.
• Cold weather: Batteries deliver less power; allow extra charge time and ensure solid metal-to-metal connections free of ice.
• Manual transmissions: If safe and legal, push-starting can be an option for some older gasoline manuals, but jump-starting is usually easier and safer.

Respecting these nuances protects sensitive electronics and avoids damage, particularly in vehicles with advanced battery management systems.

Environmental and Etiquette Tips

A few practical steps can keep everyone safer and make the process smoother for both drivers.

• Use hazard lights and reflective triangles if you’re roadside; choose a safe shoulder or parking lot.
• Wear gloves and eye protection; stow cables neatly to avoid engine-bay snags.
• Thank your helper and return borrowed cables promptly; consider carrying your own set or a jump pack.
• Recycle failing batteries at auto parts stores or municipal facilities; most accept them at no charge.

Preparedness and courtesy go a long way—good equipment and safe habits make jump-starts quick and drama-free.

Summary

To jump-start a car with cables: connect red to dead (+), red to donor (+), black to donor (−), and black to a solid ground on the dead car; start the donor, wait, start the dead car, then remove cables in reverse order and drive to recharge. Use proper jump points, avoid sparks near the battery, and follow your owner’s manual—especially on vehicles with battery monitoring, hybrids, or EVs. If repeated attempts fail, the battery or charging system likely needs professional attention.