How to Safely Use Jumper Cables to Start a Car

The proper way is to connect red to the dead battery’s positive, red to the donor battery’s positive, black to the donor battery’s negative, and the final black to an unpainted metal ground on the disabled car; then start the donor, wait a few minutes, start the dead car, and remove cables in reverse order. This sequence minimizes sparks near the battery and protects sensitive electronics. Below is a detailed, step-by-step guide with safety checks, troubleshooting tips, and special notes for hybrids and modern vehicles.

Before You Begin: Safety and Compatibility

Jump-starting is generally safe if you follow the right order and use suitable equipment. Modern cars often have battery sensors and remote jump posts that you should use instead of the battery terminals themselves, and there are important caveats for hybrids and EVs.

The following points outline critical safety checks and compatibility considerations before you connect anything:

• Confirm both vehicles use 12-volt systems; do not jump between different voltages (e.g., 24V truck to 12V car).
• Inspect batteries: do not jump-start a battery that is cracked, leaking, heavily corroded, or suspected frozen (bulging case, ice present).
• Park safely: both vehicles in Park (automatic) or Neutral (manual), parking brakes on, ignitions off, accessories and lights off.
• Avoid hazards: keep clamps from touching, remove loose jewelry, wear eye protection, and work in a well-ventilated area away from flames or smoking.
• Use designated points: many cars (BMW, Mercedes, some hybrids) have under-hood positive posts and a marked chassis ground—use them instead of the battery terminals if provided.
• Battery types: AGM/EFB stop‑start batteries can be jump-started with standard cables; still follow the same sequence. Vehicles with an Intelligent Battery Sensor on the negative terminal should use the specified ground point, not the negative post.
• Hybrids/EVs: you can usually jump-start their 12V battery from another vehicle or a booster pack using the provided posts. Do not use an EV to jump-start another vehicle unless the manufacturer explicitly allows it.

If any safety or compatibility check fails, do not proceed—have the vehicle towed or the battery professionally serviced.

Step-by-Step: Connecting and Starting

Follow this precise sequence to reduce the risk of sparks, reverse polarity, or damage to electronics. Read each step before you begin so you can move smoothly and safely.

1. Position the vehicles close enough for the cables to reach, but do not let the vehicles touch. Turn both ignitions completely off and set parking brakes.
2. Locate the positive (+, usually red) and negative (−, usually black) terminals or the under-hood jump posts indicated in the owner’s manual.
3. Attach the red (positive) clamp to the disabled vehicle’s positive (+) terminal or positive jump post.
4. Attach the other red (positive) 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 (negative) clamp to a clean, unpainted metal ground on the disabled vehicle—such as a solid engine block bolt or labeled chassis ground—away from the battery and moving parts.
7. Start the donor vehicle and let it run for 2–5 minutes. Lightly raise engine speed to around 1,500–2,000 RPM to help push charge to the dead battery.
8. Attempt to start the disabled vehicle. If it doesn’t start immediately, wait another 2–3 minutes and try again. Limit cranking to 10 seconds at a time with 30–60 seconds of rest between attempts.
9. Once the disabled vehicle starts, let both vehicles run for about a minute to stabilize voltage.
10. Disconnect in reverse order: remove the black clamp from the disabled vehicle’s ground, then the black clamp from the donor negative, then the red clamp from the donor positive, and finally the red clamp from the disabled vehicle’s positive. Keep clamps from touching metal or each other.
11. Keep the revived vehicle running and drive for 20–30 minutes to recharge, or connect a smart charger to fully restore the battery.

This order keeps sparks away from the battery (where hydrogen gas can collect) and helps protect sensitive electronics. If clamps get hot or you see arcing, stop and reassess your connections.

Why the Ground Connection Matters

Connecting the final negative clamp to a remote ground on the disabled vehicle, rather than its battery negative post, reduces the chance of igniting hydrogen gas that may vent from the battery during charging. It also helps avoid upsetting battery sensors and can provide a more stable path for current, protecting onboard electronics.

Troubleshooting and When to Stop

If the car doesn’t start or you notice unusual behavior, the issues below can help you decide your next steps safely.

• Single click or rapid clicking: the disabled battery is very low. Let the donor run longer, ensure solid clamp contact on clean metal, and try again.
• No dash lights or sounds: check for poor connections, blown main fuses, or a completely failed battery; inspect ground points and terminals.
• Engine cranks but won’t start: this points to fuel/ignition issues rather than battery charge; jump-starting may not resolve it.
• Sparks, smoke, hot cables, or sulfur smell/swelling: stop immediately, turn off vehicles, and carefully remove cables in reverse order. Seek service.
• Alarm/immobilizer light remains on: you may need to lock/unlock the vehicle or follow the owner’s manual procedure to re-enable starting.
• Needs frequent jump-starts: have the battery load-tested and alternator/charging system checked; repeated deep discharges can ruin a battery.

If two or three attempts fail, avoid repeated cranking to prevent damage. Consider a tow or professional diagnosis.

Special Cases: Hybrids, EVs, and Stop-Start Cars

Most hybrids and EVs use a conventional 12V battery to power electronics and contactors. You can typically jump-start that 12V system using the manufacturer’s designated posts and a donor vehicle or booster pack. However, many EV makers advise against using your EV to jump-start another vehicle—check the manual. For cars with stop-start systems and intelligent battery sensors, use the provided ground point rather than the battery’s negative post to avoid tripping sensors or causing measurement errors.

Gear Checklist and Best Practices

Having the right equipment and habits makes jump-starts safer and more effective.

• Heavy-gauge jumper cables (4–6 gauge, 12–20 feet) with clean, tight clamps.
• Safety glasses and insulated gloves.
• Portable lithium jump starter as a backup, charged and sized for your engine.
• Battery terminal brush and paper towels to clean corrosion and ensure good contact.
• Optional: dielectric grease on terminals after the jump to help prevent corrosion.

Quality cables and a maintained booster pack can turn a risky roadside task into a quick, controlled procedure.

Aftercare: Protecting Your Battery and Alternator

After a successful jump, fully recharge the battery with a smart charger if possible; short trips and idling won’t fully replenish a deeply discharged battery. Check charging voltage with the engine running—typically 13.8–14.7 volts indicates a healthy alternator. Clean and tighten battery terminals, and test the battery if it was fully drained; older or deeply discharged batteries may need replacement. Investigate root causes such as interior lights left on, parasitic drain, or cold-weather weakness.

Summary

To jump-start with cables: connect red to the dead positive, red to donor positive, black to donor negative, and black to a clean ground on the dead car; start the donor, wait a few minutes, then start the dead car and remove cables in reverse order. Use designated jump points, keep sparks away from the battery, and recharge the revived battery promptly. If problems persist or safety concerns arise, stop and seek professional help.

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.

What is the correct order to attach jumper cables?

It goes like. This red to the dead. Red to the good black to the good. Then under the hood. Now let’s watch as Brian from Henderson Auto puts all of that into action.

Which car do you hook up first with jumper cables?

When jumping a car, you should always connect the red jumper cable first to the positive terminal of the dead battery to prevent sparks that could ignite gases and cause an explosion. The positive cable is then attached to the positive terminal of the good battery, and the black (negative) cable is attached to the negative terminal of the good battery, and finally, the other black cable is connected to an unpainted metal surface on the frame or engine of the dead car.
 
Connection Steps

1. Red clamp to the dead battery Opens in new tab: Attach the red (positive) clamp of the jumper cable to the positive (+) terminal of the dead car’s battery. 
2. Red clamp to the good battery Opens in new tab: Attach the other red (positive) clamp to the positive (+) terminal of the good car’s battery. 
3. Black clamp to the good battery Opens in new tab: Connect one black (negative) clamp to the negative (-) terminal of the good car’s battery. 
4. Black clamp to a metal surface on the dead car Opens in new tab: Connect the remaining black (negative) clamp to an unpainted, unmoving metal part of the engine block or chassis of the car with the dead battery. This provides a ground and is the last connection, keeping any spark away from the dead battery. 

After Connecting 

1. Start the good car’s engine .
2. Let the good car run for a few minutes to allow power to transfer to the dead battery.
3. Attempt to start the engine of the car with the dead battery.
4. Once the dead car is running, run both engines for about 15 minutes before disconnecting the cables.

Important Safety Tip: Always disconnect the cables in the reverse order they were connected, ending with the black cable from the metal surface on the dead car.

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.