Yes—the order of jumper cables matters for safety and success

Yes, the order you connect and disconnect jumper cables absolutely matters. Connecting in the wrong sequence can cause dangerous sparks, damage sensitive electronics, or fail to start the car. The safest, widely recommended method is: red to dead battery positive, red to good battery positive, black to good battery negative, and black to an unpainted metal ground on the disabled vehicle—then remove the cables in the reverse order after the engine starts. Below is a clear, step-by-step guide, plus the reasoning, safety tips, and exceptions for hybrids and EVs.

Why the sequence matters

Modern vehicles carry flammable hydrogen gas around the battery area and pack dozens of electronic control modules. The connection order is designed to minimize sparks near the battery and prevent voltage spikes. Making the final connection away from the discharged battery (to a chassis ground) helps avoid igniting any gas and reduces the chance of damaging electronics if clamps arc.

Before you begin

Verify both vehicles use 12-volt, negative-ground systems (most do), park them close but not touching, set parking brakes, and turn off accessories. Check both batteries for cracks, leaks, or swelling; do not jump a visibly damaged or frozen battery. Consult each vehicle’s owner’s manual for any model-specific jump points or instructions—many newer cars have dedicated under-hood posts.

How to connect cables in the correct order

The following steps outline the recommended, safe connection order that most automakers and roadside services advise for 12V systems. Follow them carefully and keep the metal clamps from touching each other at all times.

1. Red clamp to the positive (+) terminal on the dead vehicle’s 12V battery or designated positive jump post.
2. Red clamp to the positive (+) terminal on the good (boosting) vehicle’s battery or positive jump post.
3. Black clamp to the negative (–) terminal on the good vehicle’s battery or negative jump post.
4. Black clamp to a solid, unpainted metal ground on the dead vehicle—such as a designated ground post or a sturdy engine/bracket bolt—away from the battery and fuel system.
5. Start the good vehicle and let it run 1–3 minutes at a fast idle (about 1,500–2,000 RPM) to send charge to the dead battery.
6. Attempt to start the dead vehicle. If it doesn’t start within 10 seconds, stop, wait 30–60 seconds, and try again.

This sequence reduces spark risk near the discharged battery and allows the donor vehicle to stabilize voltage before the start attempt. If the dead vehicle doesn’t crank after several tries, there may be a deeper issue (battery failure, corroded terminals, blown fuse, bad starter) that jump-starting won’t resolve.

How to disconnect cables safely (reverse order)

Once the disabled vehicle starts, you must remove cables in the reverse sequence to avoid arcing and voltage spikes.

1. Remove the black clamp from the grounded metal point on the formerly dead vehicle.
2. Remove the black clamp from the good vehicle’s negative terminal/post.
3. Remove the red clamp from the good vehicle’s positive terminal/post.
4. Remove the red clamp from the formerly dead vehicle’s positive terminal/post.

Keep clamps from touching and ensure cables are clear of belts and fans. Let the revived vehicle run for at least 15–30 minutes or drive to allow the alternator (or DC-DC converter in hybrids) to replenish the 12V battery.

Safety and best practices

These precautions lower risk to people and electronics, especially on vehicles with sensitive modules, stop-start systems, and battery monitoring sensors.

• Wear eye protection and gloves; batteries can vent gas and acid.
• Confirm polarity: positive to positive, negative to negative/ground. Reversed polarity can instantly destroy ECUs and fuses.
• Use the chassis ground on the dead car for the last connection unless your manual specifically instructs otherwise.
• Avoid jump-starting a damaged, leaking, or frozen battery; replace it instead.
• Keep cables and clothing clear of moving parts (fans, belts) and hot components.
• If either vehicle has a designated jump-start post, use it—don’t bypass the battery monitoring sensor on the negative terminal.
• Do not connect a 12V system to a 24V or 6V system.
• Portable jump packs follow the same order: red to positive, black to chassis ground on the dead vehicle; then power on the pack as directed.

Following these best practices greatly reduces the chance of sparks, component damage, or injury, and it improves the odds that the jump will work on the first try.

Special cases: hybrids, EVs, and modern systems

Not every vehicle should be jumped or used as a donor the same way. Here’s what to know about newer technologies.

• Hybrids (HEV/PHEV): Most have a standard 12V battery that can be jump-started at under-hood posts. Never attempt to jump the high-voltage traction battery. Check the manual for exact locations and cautions.
• Electric vehicles (EVs): Many allow you to jump their 12V battery from an external source, but most manufacturers advise against using an EV to jump-start another car due to DC-DC converter limits. Always check the manual.
• Stop-start/AGM/EFB batteries: Use the specified jump posts and avoid bypassing battery sensors. Incorrect connections can trigger charging system faults.
• Remote batteries (trunk/rear seat): Use the designated under-hood jump posts instead of clamping directly to a distant battery.

Because designs vary, the owner’s manual remains the definitive guide. When in doubt, use a portable jump starter or call roadside assistance.

Troubleshooting if the car still won’t start

If the correct procedure doesn’t succeed, these checks can save time and prevent damage.

• Clean clamps and terminals; corrosion impedes current flow.
• Verify solid metal-to-metal contact on the ground point.
• Try a longer charge period (3–5 minutes) before cranking.
• Listen for clicks: repeated rapid clicking suggests insufficient voltage; silence could indicate a bad starter or blown main fuse.
• If jump-starting repeatedly fails, the battery may be sulfated or the charging system faulty; test or replace the battery and check the alternator.

Persistent no-start conditions usually point to a dead battery beyond recovery or another electrical/mechanical fault that needs diagnosis.

Key takeaways

The connection and disconnection order isn’t a formality—it’s a core safety practice. Use red-to-dead, red-to-good, black-to-good, black-to-ground; then remove in reverse. Ground the last connection away from the dead battery, confirm polarity, and follow vehicle-specific guidance for hybrids, EVs, and cars with smart charging systems.

Summary

Yes, order matters when using jumper cables. Connect red to the dead car’s positive, red to the good car’s positive, black to the good car’s negative, and black to a metal ground on the dead car—then disconnect in the reverse order. This sequence minimizes sparks, protects electronics, and improves the chance of a successful start. Always check your owner’s manual for model-specific procedures and heed safety precautions.

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. 

What happens if you attach jumper cables in the wrong order?

Connecting the Leads in the Wrong Order
Connecting the Cables incorrectly (positive to negative or vice versa), Reversing the order can cause a spark, which may lead to battery damage or even an explosion.

Does it matter in what order you attach jumper cables?

Yes, the order of connecting and disconnecting jumper cables matters for safety to prevent sparks, short circuits, and explosions from the hydrogen gas a dead battery can produce. The recommended order is to first connect the red (positive) cables to both batteries, then connect the black (negative) cables to the working car’s negative terminal and the dead car’s unpainted metal chassis. For disconnection, reverse the process by removing the black negative cables first, then the red positive cables. 
This video demonstrates the correct and incorrect ways to connect jumper cables: 1mStan CravensYouTube · Oct 9, 2018
Connecting the Cables (The Right Way)

1. Red to Dead: Connect the red clip to the positive (+) terminal of the dead car’s battery. 
2. Red to Donor: Connect the other red clip to the positive (+) terminal of the donor (working) car’s battery. 
3. Black to Donor: Connect the black (negative) clip to the negative (-) terminal of the donor car’s battery. 
4. Black to Ground: Connect the other black clip to an unpainted, unpainted piece of metal on the dead car’s engine block or frame. This is the final connection, which helps prevent sparks near the dead battery. 

Disconnecting the Cables (Reverse Order) 

1. Black from Dead: Disconnect the black clip from the ground point on the dead car. 
2. Black from Donor: Disconnect the black clip from the negative (-) terminal of the donor car. 
3. Red from Donor: Disconnect the red clip from the positive (+) terminal of the donor car. 
4. Red from Dead: Disconnect the red clip from the positive (+) terminal of the dead car. 

Why the Order Matters

• Safety: Connecting the final negative cable to a metal ground point away from the battery minimizes the risk of a spark igniting hydrogen gas from the battery. 
• Electrical Safety: Following this sequence helps prevent short circuits and potential damage to the cars’ electronic components. 
• Explosion Prevention: The last connection is made away from the batteries to prevent any sparks from igniting any potentially explosive gases. 

Which clamp do you take off first?

When working with a car battery, you should take off the black, negative clamp first to prevent sparks and potential damage to electrical components. The negative terminal is the “ground” side, and disconnecting it first creates a safe way to work on the positive terminal without causing a short circuit if you accidentally touch it to the car’s metal body. 
Why disconnect the negative terminal first?

• Safety: Disconnecting the negative cable first eliminates the risk of an electrical surge or short circuit. 
• Preventing damage: If the positive terminal’s cable touches the car’s metal frame while you’re working on it, and the negative cable is still attached, it can cause sparks, damage sensitive electronics, or even start a small explosion. 

Steps to disconnect a car battery:

1. Turn off the car ignition: and ensure all lights and accessories are off. 
2. Locate the negative terminal: (usually marked with a minus sign and a black cap). 
3. Loosen the clamp: securing the negative cable to the terminal. 
4. Twist and lift the clamp off: the terminal. 
5. Wrap the red, positive terminal: or cover it with a plastic cup to prevent accidental contact. 
6. Then, loosen and remove the red, positive terminal clamp .