Which Jumper Cable Goes on First?

The first connection should be the red positive (+) cable to the positive terminal of the dead battery. Then attach the other red clamp to the positive terminal of the good battery, the black clamp to the negative terminal of the good battery, and finally the remaining black clamp to an unpainted metal ground on the disabled vehicle, away from the battery. This sequence reduces the risk of sparks and protects sensitive electronics.

The correct connection order

The following steps outline the standard, widely recommended sequence (used by major roadside-assistance and safety agencies) for connecting jumper cables safely and effectively.

1. Turn both vehicles off; set Park (or Neutral with parking brake) and switch off accessories and lights.
2. Attach the red positive (+) clamp to the positive terminal of the dead battery.
3. Attach the other red positive (+) clamp to the positive terminal of the good battery or booster pack.
4. Attach the black negative (−) clamp to the negative terminal of the good battery or booster pack.
5. Attach the remaining black negative (−) clamp to a solid, unpainted metal ground on the engine block or chassis of the dead vehicle—well away from the battery and fuel system.
6. Start the good vehicle and let it run for a minute or two; then try starting the dead vehicle.

Connecting positive leads first and finishing with a chassis ground keeps any potential spark away from the dead battery, where hydrogen gas may be present, and establishes a stable circuit for modern vehicle electronics.

How to disconnect after the engine starts

Disconnecting in the reverse order prevents electrical surges and keeps sparks away from the battery.

1. Remove the black clamp from the grounded metal point on the previously dead vehicle.
2. Remove the black clamp from the negative terminal of the good battery.
3. Remove the red clamp from the positive terminal of the good battery.
4. Remove the red clamp from the positive terminal of the previously dead battery.

This reverse sequence breaks the circuit safely and reduces the chance of accidental short circuits or arcing near the battery.

Why the order matters

Lead-acid batteries can emit hydrogen gas, which is flammable. Making the final connection on a remote ground point keeps any spark away from the battery top. The staged order also stabilizes voltage and limits sudden inrush currents that could stress control modules and sensors.

Modern vehicles contain sensitive electronics, AGM or EFB batteries, and sometimes battery monitoring sensors on the negative terminal; following the recommended sequence helps avoid damage and diagnostic trouble codes.

Safety checklist and common mistakes

Before and during a jump-start, these precautions help protect you and both vehicles.

• Verify both systems are the same voltage (most passenger vehicles are 12V; some heavy-duty or older vehicles differ).
• Consult the owner’s manual for designated jump points—many modern cars and hybrids provide remote positive posts and ground studs.
• Wear eye protection and avoid loose clothing near belts and fans.
• Keep cable clamps from touching each other and clear of moving parts.
• Do not connect the negative clamp to the dead battery’s negative terminal; use a clean, unpainted metal ground instead.
• If cables or terminals are corroded, clean enough surface to ensure solid metal-to-metal contact.
• If the dead battery is cracked, leaking, or badly swollen, do not attempt a jump—have the vehicle serviced.

These steps reduce fire risk, prevent short circuits, and improve the chances of a successful, safe jump-start.

Special cases: hybrids, EVs, and modern start-stop cars

Some vehicles require special handling for jump-starts. Always check the owner’s manual first, as the wrong connection point can damage costly components.

• Hybrids: Use the designated 12V jump posts, often in the engine bay; do not access high-voltage orange cables.
• EVs: You cannot jump the high-voltage traction battery, but many EVs can jump-start (or be jump-started for) their 12V systems via specified posts.
• Start-stop/AGM batteries: Follow the manual’s jump points; some vehicles have battery monitoring sensors on the negative post that you should not clamp directly.
• Portable jump packs: Follow the same order (red to dead positive first) and observe pack instructions and polarity indicators.

Using the manufacturer-recommended posts and procedures helps avoid damage to battery sensors, DC-DC converters, and high-voltage systems.

Quick FAQ

These quick answers address common jump-start questions that arise at the roadside.

• Can I put the black clamp on the dead battery’s negative terminal? No—use an unpainted metal ground away from the battery to minimize spark risk.
• Should both cars be running during hookup? No—connect with both off; start the good vehicle only after the cables are attached correctly.
• How long should I let the good car run before trying to start the dead one? Typically 1–3 minutes; very depleted batteries may need longer.
• What gauge cables should I use? Thicker cables (lower gauge numbers like 4 or 6 AWG) deliver more current and work better in cold weather.
• What if my car still won’t start? The battery could be failing, terminals may be loose, or there may be starter/alternator issues; seek professional help.

Following these guidelines improves safety and reliability when dealing with a weak or discharged battery.

Summary

Connect the red positive cable to the dead battery’s positive terminal first, then red to the good battery, black to the good battery’s negative, and finally black to a metal ground on the dead vehicle. Remove in reverse order. This method minimizes sparks, protects electronics, and aligns with established safety guidance for modern vehicles.

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.

Does it matter which jumper cable comes off first?

Yes, you must remove jumper cables in the reverse order from how you connected them to prevent sparks and damage to the car’s electrical system. The general rule is to disconnect the black negative clamps first, in reverse order of connection, and the red positive clamps last. This sequence helps to keep any potential sparks away from the battery, which may be releasing flammable hydrogen gas as it charges.
 
Safe Disconnection Steps:

1. Turn off the engine: of both vehicles. 
2. Disconnect the black negative clamp: from the dead battery’s chassis (or negative terminal). 
3. Disconnect the black negative clamp: from the good battery’s chassis. 
4. Disconnect the red positive clamp: from the good battery’s positive terminal. 
5. Disconnect the red positive clamp: from the dead battery’s positive terminal. 

Why the Order Matters

• Safety First: Disconnecting in reverse order prevents accidental short circuits, which can cause damage to the vehicles’ electronics or create sparks. 
• Hydrogen Gas: Car batteries can produce flammable hydrogen gas, especially when accepting a charge. Sparks can ignite this gas, leading to an explosion. By ensuring the last connection (and initial disconnection of the negative clamp from the chassis) happens further from the battery, the risk is reduced. 

Do you take the red or black cable off first?

You take the black, negative cable off first to prevent electrical shorts and dangerous sparks. Disconnecting the negative cable first isolates the vehicle’s body and engine, so if your wrench touches the positive terminal and a metal part of the car, it won’t complete a circuit and create a spark or short-circuit.
 
Why the negative cable comes off first 

• Prevents shorts: The black, negative cable is connected to the vehicle’s frame and body. If you remove the positive (red) cable first and then touch the wrench to the positive terminal and the metal chassis, you create a short circuit.
• Avoids sparks: Disconnecting the negative cable first prevents the possibility of a spark when you work on the positive terminal. Sparks can be dangerous, especially around the hydrogen gas that batteries can produce.

Steps to safely disconnect the battery

1. Turn off the engine: and make sure all lights and accessories are off. 
2. Identify the terminals: (red for positive, black for negative), which are usually marked on the battery itself. 
3. Disconnect the black, negative cable: first by loosening the clamp and removing it from the terminal. 
4. Set the negative cable aside, ensuring it doesn’t touch the battery. 
5. Disconnect the red, positive cable: second. 

This video demonstrates the correct order for disconnecting and connecting a car battery: 57sHelpful DIYYouTube · Feb 27, 2016
For connecting the battery: Always do the reverse order, connecting the positive (red) cable first, and then the negative (black) cable last.

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.