How to Use Jumper Cables Safely and Correctly

Connect the cables in this order: red to the dead battery’s positive (+), red to the donor battery’s positive (+), black to the donor battery’s negative (−), and black to an unpainted metal ground on the car with the dead battery. Start the donor, wait a few minutes, then start the dead car; remove the cables in reverse order and let the revived engine run for at least 20–30 minutes. Always follow your vehicle’s owner’s manual and avoid connecting the final black clamp to the dead battery’s negative post.

What You Need and Safety Checks

Before attempting a jump-start, confirm that both vehicles use compatible 12-volt systems and that the dead battery isn’t damaged. Modern cars often have specific jump points that should be used instead of the battery terminals to protect electronics and ensure a safe connection.

The following items and checks help ensure a safe and effective jump-start.

• Heavy-gauge jumper cables (4–6 gauge, good insulation, clean clamps), ideally 10–20 feet long.
• A donor vehicle (or portable jump starter) with a healthy 12V battery; avoid trucks with 24V systems.
• Owner’s manuals for both vehicles to locate official jump points and warnings.
• Eye protection and gloves; remove dangling jewelry/watches.
• A clean, stable area away from traffic; engage parking brakes and place transmissions in Park or Neutral.
• A quick battery check: do not jump a battery that is cracked, leaking, frozen, or visibly swollen.

Having the right tools and confirming system compatibility reduces risk to you and to the vehicles’ electrical systems.

Step-by-Step: Correct Connection Order

The sequence below minimizes sparks near the battery and reduces the chance of short circuits or damage to electronics. Make sure both ignitions are off and accessories are switched off before connecting.

1. Position vehicles nose-to-nose (but not touching) so cables reach comfortably. Engage parking brakes and switch off both ignitions and accessories (lights, HVAC, infotainment).
2. Locate positive (+) and negative (−) terminals or the marked jump-start posts. Verify polarity marks carefully.
3. Attach the red (positive) clamp to the dead vehicle’s positive (+) terminal or designated positive jump post.
4. Attach the other red clamp to the donor vehicle’s positive (+) terminal.
5. Attach the black (negative) clamp to the donor vehicle’s negative (−) terminal.
6. Attach the final black clamp to a clean, unpainted metal surface on the engine block or chassis of the vehicle with the dead battery—well away from the battery and fuel lines. Use the manufacturer’s recommended ground point if one is provided.
7. Ensure cables are clear of fans, belts, and other moving parts.

This order keeps any incidental sparking away from the dead battery—where hydrogen gas may be present—and ensures a controlled, safe circuit.

Start the Car and Disconnect Safely

Once the cables are connected, bring the donor system online first, then attempt to start the disabled vehicle. Avoid extended cranking to protect both starters and electronics.

1. Start the donor vehicle and let it idle for 2–5 minutes. Lightly raise RPM to 1,200–1,500 to boost alternator output.
2. Try to start the dead vehicle for up to 5–10 seconds. If it doesn’t start, wait 60–90 seconds and try again. Repeat a few times as needed.
3. When the dead vehicle starts, let both vehicles idle connected for another 1–2 minutes to stabilize voltage.
4. Disconnect in reverse order: remove the black clamp from the grounded metal on the formerly dead vehicle; remove the black clamp from the donor negative (−); remove the red clamp from the donor positive (+); remove the red clamp from the formerly dead positive (+).
5. Keep the revived vehicle running for at least 20–30 minutes or drive 15–30 minutes to recharge the battery. Have the battery and charging system tested soon after.

Disconnecting in reverse order prevents live clamps from touching grounded metal and reduces the risk of short circuits or voltage spikes.

Common Mistakes to Avoid

Many jump-start mishaps stem from rushed connections or overlooked warnings. Avoid these errors to protect your vehicle and yourself.

• Reversing polarity (red to − or black to +), which can cause severe electrical damage.
• Clamping the final black lead to the dead battery’s negative post, which increases spark and explosion risk.
• Jumping a frozen, cracked, leaking, or swollen battery—call for service instead.
• Letting clamps touch each other or metal surfaces while connected.
• Routing cables near fans, belts, or hot exhaust components.
• Using a 24V source on a 12V system, or allowing vehicle bumpers/frames to touch.
• Jumping or using an EV/hybrid as a donor unless the owner’s manual expressly permits it.
• Attempting a jump in poorly ventilated or hazardous environments.

Taking an extra minute to check polarity, cable routing, and battery condition can prevent injuries and costly repairs.

Special Notes for Modern Vehicles

Newer cars often have sensitive electronics and specific jump-start provisions. Following manufacturer guidance is essential.

• Use the designated positive and negative jump posts under the hood when provided; avoid direct-to-battery connections if advised.
• Start-stop systems with AGM/EFB batteries can be more sensitive; follow the manual’s jump procedure exactly.
• Hybrids and EVs: do not use them as donor vehicles; many allow jump-starting their 12V system from an external source only. Check the manual.
• Portable jump starters are a safe, convenient alternative; ensure the unit’s clamps go to the correct posts in the same order as above and follow the device instructions.
• If your vehicle specifies a “memory saver” or cautions about surges, consider a quality jump pack with surge protection.

Automaker-provided jump points and instructions are designed to protect modules, sensors, and the alternator while delivering adequate current.

Troubleshooting If It Still Won’t Start

If the engine doesn’t crank or start after several attempts, targeted checks can help determine next steps.

• No crank, no lights: recheck clamp connections and ground point; ensure good metal contact and clean off corrosion.
• Starter clicks but won’t turn: wait longer with donor running; the dead battery may be deeply discharged or sulfated.
• Cranks but won’t start: may be fuel/ignition related; jumping won’t resolve that—seek diagnostics.
• Try shifting to Neutral and starting; a faulty park/neutral safety switch may be at fault.
• If it starts but dies immediately, the alternator may be failing. Don’t rely on repeated jump-starts—test/replace components.
• Blown main fuses or loose battery cables can also prevent starting; inspect if accessible and safe.

Persistent no-start issues after a proper jump usually indicate a failing battery or charging/starting-system problem requiring professional service.

Why the Ground-Last Clamp Matters

Connecting the final black clamp to a remote, unpainted metal ground on the disabled vehicle keeps any sparking away from the battery, where hydrogen gas may accumulate during charging. This reduces explosion risk and is the connection pattern recommended by most manufacturers and roadside-assistance organizations.

Summary

Use jumper cables in this order: red to dead (+), red to donor (+), black to donor (−), black to a solid ground on the dead vehicle—then start the donor, wait a few minutes, start the disabled car, and remove cables in reverse order. Keep the revived engine running to recharge, and consult your owner’s manual for designated jump points and model-specific cautions. Avoid damaged batteries, reversed polarity, and connecting the last clamp to the dead battery’s negative post. If the car won’t stay running, have the battery and charging system tested promptly.

What is the correct way to use jump leads?

One end of the red jump lead should be connected to the flat battery’s positive terminal. The lead must not touch any vehicle metal. Attach the red lead’s other end to the boosting battery’s positive terminal. Take the black lead and connect one end to the boosting battery’s negative terminal.

Is there an order for putting on jumper cables?

Make sure you have followed these steps in proper order: red clip from booster cable to positive terminals, then black clip from booster cable to negative terminals. Once all connections are made, start up your working vehicle and let it run for a few minutes before attempting to start your dead battery’s engine.

In what order should I jump start?

To jump-start a car, the jumper cable connection order is crucial for safety. Connect the red clamp to the positive terminal of the dead battery first, then the other red clamp to the positive terminal of the working (donor) battery. Next, connect the black clamp to the negative terminal of the working battery, and finally, connect the other black clamp to an unpainted metal surface on the dead car’s engine block away from the battery. Disconnect the cables in the reverse order.
 
Connecting the Jumper Cables

1. Red to Dead Battery: Connect the red (positive) clamp of the jumper cable to the positive terminal (+) of the car with the dead battery. 
2. Red to Donor Battery: Connect the other red (positive) clamp to the positive terminal (+) of the car with the working battery. 
3. Black to Donor Battery: Connect the black (negative) clamp to the negative terminal (-) of the car with the working battery. 
4. Black to Ground: Connect the final black (negative) clamp to an unpainted metal surface on the engine block of the car with the dead battery, away from the battery itself. 

Starting and Disconnecting

1. Start the Working Car: Start the engine of the vehicle with the good (donor) battery and let it run for a few minutes. 
2. Start the Dead Car: Try to start the engine of the car with the dead battery. 
3. Disconnect in Reverse Order: Once the dead car’s engine is running, disconnect the cables in the following reverse order: 
   • Black clamp from the engine block. 
   • Black clamp from the donor vehicle’s negative terminal. 
   • Red clamp from the donor vehicle’s positive terminal. 
   • Red clamp from the dead battery. 

This video demonstrates the proper way to jump start a car: 58sAAA Connect Video Hub | Auto Club GroupYouTube · Sep 23, 2024
Important Safety Tips

• Ensure both cars are turned off and the parking brakes are engaged. 
• Make sure the cars are close enough to reach but not touching. 
• Avoid contact between the positive and negative cables to prevent sparks. 
• If the dead car doesn’t start after a few tries, there may be a more serious issue requiring a mechanic. 

What is the proper order to attach jumper cables?

To properly connect jumper cables, attach the red clamp to the positive (+) terminal of the dead battery, then the other red clamp to the positive (+) terminal of the good battery. Next, connect the black clamp to the negative (-) terminal of the good battery, and finally, connect the last black clamp to an unpainted metal part of the dead car’s engine block or chassis, away from the battery.
 
This video demonstrates the entire process of jump-starting a car: 50sCars.comYouTube · Oct 11, 2024
Step-by-Step Connection

1. Red to Dead Battery: Opens in new tabConnect one red (positive) clamp to the positive terminal of the dead battery. 
2. Red to Good Battery: Opens in new tabConnect the other red (positive) clamp to the positive terminal of the good (donor) battery in the working vehicle. 
3. Black to Good Battery: Opens in new tabConnect one black (negative) clamp to the negative terminal of the good (donor) battery. 
4. Black to Engine Block: Opens in new tabConnect the other black (negative) clamp to an unpainted, unmoving metal component on the dead car’s engine block or chassis. This creates a grounding point and keeps any sparks away from the battery, which can produce flammable gases. 

You can watch this video to learn more about safely connecting the cables: 1mEich VolkswagenYouTube · Jul 7, 2017
After Connecting

1. Start the Working Vehicle: Start the engine of the vehicle with the good battery and let it run for a few minutes to charge the dead battery. 
2. Start the Dead Vehicle: Attempt to start the engine of the vehicle with the dead battery. 
3. Charge the Battery: Once the dead vehicle is running, allow both cars to run for at least 30 minutes to give the alternator time to charge the battery sufficiently. 

Disconnecting the Cables
Disconnect the cables in the exact reverse order of how you connected them to prevent sparks and damage to the electrical system.