Which jumper leads go on first?

Connect the red positive (+) lead first: attach one red clamp to the dead battery’s positive terminal, then the other red clamp to the donor battery’s positive terminal; next attach the black negative (–) clamp to the donor battery’s negative terminal, and finish by clamping the remaining black lead to a clean, unpainted metal ground on the disabled vehicle—away from the battery. This sequence reduces the risk of sparks and battery explosions.

The correct connection sequence

Following the proper order protects both people and vehicle electronics. Before you begin, park the cars nose-to-nose or side-by-side so the cables reach, set both vehicles to Park (or Neutral for manual), apply parking brakes, and switch everything off.

1. Open both hoods and locate the designated jump-start points (often marked with + and –). If your car has remote jump posts, use those instead of the battery terminals.
2. Attach the red (+) clamp to the dead vehicle’s positive (+) terminal or positive jump post.
3. Attach the other red (+) clamp to the donor vehicle’s positive (+) terminal or jump post.
4. Attach the black (–) clamp to the donor vehicle’s negative (–) terminal or negative jump post.
5. Attach the remaining black (–) clamp to a solid, unpainted metal ground on the dead vehicle (such as an engine lifting eye or chassis ground stud), well away from the battery and fuel system.

This order keeps the final connection—most likely to spark—far from the dead battery, where hydrogen gas may be present, and helps protect sensitive electronics.

Starting up and removing the leads

Once connected, bring the dead battery back to life step by step. Patience and the reverse order on removal are key to avoiding damage.

1. Start the donor vehicle and let it idle for 2–5 minutes to send charge to the dead battery. Lightly raising the donor engine speed to ~1,500 rpm can help, if safe.
2. Try starting the dead vehicle. If it doesn’t crank, wait another 2–3 minutes and try again.
3. After the dead vehicle starts, let both engines run connected for 2–3 minutes. Optionally switch on the blower fan or rear defroster in the revived car to help buffer voltage spikes.
4. Disconnect in reverse order: remove the black clamp from the grounded metal on the revived vehicle; remove the black clamp from the donor negative; remove the red clamp from the donor positive; remove the red clamp from the revived vehicle’s positive.
5. Keep the revived engine running for at least 20–30 minutes or drive to allow the alternator to replenish the battery.

Reversing the sequence when removing helps prevent short circuits and sparks near the battery, reducing safety and electronics risks.

Why the order matters

Car batteries can emit hydrogen gas. Making or breaking a connection directly at a battery can cause sparks that ignite that gas. Connecting the last clamp to a grounded metal point away from the battery moves any sparking far from where gas accumulates. It’s a long-standing safety practice endorsed by roadside-assistance organizations and many automakers.

Vehicles with special considerations

Modern vehicles often have specific jump-start provisions. Check the owner’s manual before connecting cables, especially on newer, hybrid, or luxury models.

• Remote jump posts: Many cars hide the battery but provide under-hood jump posts. Use these instead of clamping onto the battery directly.
• Start/stop systems (AGM/EFB batteries): Use the designated posts and correct polarity; avoid cheap, unregulated boosters that can over-voltage sensitive systems.
• Hybrids and EVs: You typically jump only the 12V system via marked posts. Never attempt to jump the high-voltage traction battery. Follow the manual strictly.
• Portable jump packs: Match the pack’s instructions; many “smart” packs handle sequencing automatically. Ensure the pack is rated for your engine size.
• 24V systems (some trucks/commercial vehicles): Do not use a 12V donor on a 24V system. Use a compatible source or professional help.

Because electrical architectures vary, the safest approach is to follow the vehicle-specific guidance, which may supersede generic instructions.

Common mistakes to avoid

Simple errors can turn a routine jump-start into an expensive repair—or a safety hazard. Avoid these pitfalls.

• Reversing polarity (mixing up + and –), which can fry electronics instantly.
• Letting clamps touch each other or loose metal while connected.
• Clamping to painted, rusty, or oily surfaces that prevent a good ground.
• Jumping a frozen, swollen, or physically damaged battery—risk of explosion.
• Revving the donor excessively; brief, modest RPM increases are sufficient.
• Disconnecting as soon as the engine fires; give the revived battery time to stabilize.

Taking an extra minute to double-check polarity, clamp placement, and secure footing for each clamp dramatically improves safety and success rates.

If it still won’t start

Persistent no-start after proper connections usually points to deeper issues. Work through these quick checks before calling for help.

• Re-seat all clamps for solid metal-to-metal contact and try again after 3–5 minutes of charging.
• Look for severe corrosion on terminals; clean if you can do so safely.
• Check interior lights or accessories left on that might have deeply discharged the battery; a longer charge may be needed.
• Listen for a single click (possible starter/solenoid) versus nothing at all (possible battery/cable/fuse issue).
• If immobilizer/security lights flash, consult the manual; some systems need a key cycle or lock/unlock reset.
• If jump-starts fail repeatedly, the battery may be beyond recovery or there may be alternator or cable faults; seek professional service.

When in doubt—especially with hybrids/EVs or vehicles packed with electronics—roadside assistance can prevent further damage.

Safety reminders

Basic precautions reduce risk during every step of a jump-start.

• Wear eye protection and avoid open flames or smoking near batteries.
• Keep jewelry and loose clothing away from moving engine parts.
• Ensure vehicles do not touch each other while connected.
• Use quality, adequately rated cables; thick-gauge cables carry current more safely.
• Always confirm the + and – markings before clamping.

Safety-first habits protect you and your vehicle while ensuring an effective jump-start.

Summary

Put the red positive clamp on the dead battery’s positive terminal first, then red to the donor positive, black to the donor negative, and finally black to an unpainted metal ground on the dead car. Start the donor, then the dead car, and remove cables in the exact reverse order. Follow your vehicle’s manual, use designated jump points, and prioritize safety to avoid sparks and electrical damage.

Which jumper lead goes on first?

Here’s the correct order for your jumper cables: RED to DEAD: Connect the red clip to the positive terminal on your dead battery. RED to DONOR: Connect the red clip to the positive terminal on the donor vehicle’s working battery. BLACK to DONOR: Same car!

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.

Do I connect black or red first?

When connecting jumper cables to a car with a dead battery, always connect the red/positive cable first to the positive (+) terminal of the dead battery, and then to the positive terminal of the working battery. The negative (black) cables should be connected last, with one to the negative terminal of the working battery and the other to an unpainted metal surface on the dead car’s engine block or frame to complete the circuit.
 
This video demonstrates how to safely connect jumper cables to a car battery: 51sStan CravensYouTube · Oct 9, 2018
Step-by-Step Guide to Connecting Jumper Cables:

1. Turn off both vehicles: Opens in new tabEnsure the ignition keys are in the off position in both the car with the dead battery and the donor car. 
2. Connect the red (positive) cable to the dead battery: Opens in new tabAttach one red clamp to the positive (+) terminal of the dead battery. 
3. Connect the red (positive) cable to the donor battery: Opens in new tabAttach the other red clamp to the positive (+) terminal of the good battery on the donor vehicle. 
4. Connect the black (negative) cable to the donor battery: Opens in new tabAttach one black clamp to the negative (-) terminal of the donor vehicle’s good battery. 
5. Connect the black (negative) cable to the dead car’s frame: Opens in new tabAttach the final black clamp to an unpainted, unmoving metal part of the engine block or frame of the car with the dead battery. A slight spark may occur, which is normal. 

Why this order?

• Red first: Connecting the positive (red) cable to both batteries first creates a complete circuit without completing the negative side. 
• Last connection to metal: The last black clamp is attached to an unpainted metal surface on the dead car’s frame, not the negative terminal. This minimizes the risk of sparks, as the battery releases hydrogen gas that could cause an explosion. 

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.