Which cable do you connect first: red or black?

Connect the red (positive) cable first, then the black (negative). When disconnecting, remove the black (negative) cable first, then the red. For jump-starting a vehicle, attach the final black clamp to a clean, unpainted metal ground on the disabled car—never directly to its negative battery terminal—to reduce the risk of sparks near the battery.

What the cable colors mean—and why order matters

In 12-volt automotive systems and most consumer batteries, red denotes the positive terminal (+) and black denotes the negative (−) or ground. Connecting in the correct order limits the chance of a short circuit and minimizes sparking around the battery, where hydrogen gas can accumulate. Reversing polarity or causing a short can damage electronics, melt cables, or cause injury.

How to jump-start a car safely

Following the right sequence protects both vehicles and reduces risk. The steps below assume you’re using traditional jumper cables and a donor vehicle with a healthy 12-volt battery. Always consult both vehicles’ manuals—some hybrids and EVs have specific jump-start points and restrictions.

1. Park the vehicles close but not touching. Turn off ignitions and accessories, set parking brakes, and put transmissions in Park (automatic) or Neutral (manual).
2. Identify the positive (+, red) and negative (−, black) terminals on both batteries. Remove terminal covers if present.
3. Attach the first red clamp to the dead battery’s positive (+) terminal.
4. Attach the second red clamp to the donor battery’s positive (+) terminal.
5. Attach the first black clamp to the donor battery’s negative (−) terminal.
6. Attach the second black clamp to a clean, unpainted metal ground on the disabled vehicle (engine block or designated ground point), away from the battery and moving parts.
7. Start the donor vehicle and let it run for 2–5 minutes. Lightly revving to ~1,500 rpm can help charge the dead battery.
8. Try starting the disabled vehicle. If it doesn’t start, wait a minute and try again. Avoid cranking more than ~10 seconds at a time.
9. Once the disabled vehicle starts, keep both vehicles running. Disconnect the cables in reverse order (see the quick sequence below), ensuring clamps don’t touch each other or metal.
10. Let the revived vehicle run for at least 15–30 minutes or drive to allow the alternator to replenish the battery.

This sequence minimizes sparking near the battery and helps ensure enough charge transfers to start the disabled vehicle without stressing electrical systems.

Disconnecting after a jump: the reverse order

Removing the cables in the correct reverse order further reduces spark risk and prevents accidental short circuits.

1. Remove the black clamp from the grounded metal on the formerly disabled vehicle.
2. Remove the black clamp from the donor battery’s negative (−) terminal.
3. Remove the red clamp from the donor battery’s positive (+) terminal.
4. Remove the red clamp from the formerly dead battery’s positive (+) terminal.

Keeping the clamps separated and away from metal throughout the removal process helps avoid accidental arcing and component damage.

Replacing or installing a car battery

When swapping a battery, the rule flips between removal and installation to maintain safety and protect the vehicle’s electronics.

1. Turn off the vehicle, remove the key, and wear eye protection and gloves.
2. To remove the old battery: disconnect black (negative) first, then red (positive). Remove any hold-downs and lift the battery out carefully.
3. Clean terminals and tray; check cables for corrosion or damage.
4. To install the new battery: connect red (positive) first, then black (negative). Tighten clamps securely—snug, not overtightened.
5. Reinstall terminal covers and hold-downs; confirm the battery is secure and cables are not strained.

Disconnecting negative first prevents tools from shorting the battery to ground. Connecting positive first on installation minimizes accidental grounding while the circuit is open.

Using a battery charger or portable jump starter

With a plug-in battery charger

Most smart chargers specify connection order to detect polarity and charge safely. Always follow your charger’s manual.

1. Ensure the charger is unplugged and the vehicle ignition is off.
2. Connect red clamp to the battery’s positive (+) terminal.
3. Connect black clamp to the battery’s negative (−) terminal or a recommended chassis ground.
4. Select appropriate battery type and charge rate; then plug in and turn on the charger.
5. When finished, turn off and unplug the charger before removing clamps—black off first, then red.

Unplugging before removing clamps prevents live leads from sparking and allows the charger to complete shutdown safely.

With a portable jump starter (power pack)

Portable boosters simplify the process but still require correct polarity and order to avoid damage.

1. Power off the pack and verify it’s adequately charged.
2. Connect red to the battery’s positive (+) terminal.
3. Connect black to a solid chassis ground or the battery’s negative (−) terminal if the manufacturer allows.
4. Power on the pack and attempt to start the vehicle.
5. Power off the pack before removing clamps—black off first, then red.

Many packs include reverse-polarity and spark protection, but correct connection remains essential for safety and reliable starting.

Safety essentials and common mistakes to avoid

Working around lead-acid batteries involves electrical current, acid, and flammable gases. A few precautions go a long way.

• Wear eye protection and gloves; remove metal jewelry that could bridge terminals.
• Keep sparks, flames, and cigarettes away from batteries.
• Never let red and black clamps touch each other or the same metal surface.
• Double-check polarity before clamping; look for + and − symbols, not just cable color.
• Do not jump-start a leaking, cracked, swollen, or frozen battery—replace it instead.
• Use designated jump posts on vehicles that provide them (common on hybrids and some EVs); consult the owner’s manual.
• Avoid using an EV to jump-start another vehicle unless the manufacturer explicitly permits it.
• If the engine doesn’t start after several attempts, stop and investigate—there may be deeper electrical or fuel-system issues.

These practices reduce the chance of injury, component damage, and fires while improving your odds of a successful start or installation.

Summary

Connect red (positive) first and black (negative) second; when disconnecting, remove black first, then red. For jump-starts, attach the final black clamp to a solid, unpainted metal ground on the disabled vehicle. Follow the reverse order to remove cables, and always consult the vehicle and equipment manuals for model-specific guidance.

What is the proper order to hook up a car battery?

And tighten it all the way down connect the positive. First. So your red one right there you got to remove that red cap let’s remove that. And then we’ll go ahead and connect the positive.

Do you put on black or red first?

When you connect jumper cables, you start with the positive or red cable. Disconnecting starts with the negative. Whether you’re changing a car battery or jump starting one, stay safe and protected. Make sure you put on safety glasses and take off any jewelry.

Which one goes first, black or red?

Always make sure red goes to positive and black goes to negative. Sparks during connection: Sparks can occur if the clamps aren’t properly grounded or if there’s a short circuit. To avoid this, always attach the black clamp to a metal part away from the battery.

Do I connect positive or negative first?

When installing a car battery, you should connect the positive terminal first, then the negative terminal. The reverse is true when disconnecting: always disconnect the negative terminal first, then the positive. This safety procedure minimizes the risk of sparks and short circuits by preventing your tools from accidentally touching the car’s grounded chassis when the final connection is made.
 
Connecting the battery: 

1. Positive first: Attach the red (positive) cable to the positive battery post.
2. Negative last: Connect the black (negative) cable to the negative battery post.

Why this order matters:

• Safety: The engine block and car body are at ground potential. If you connect the negative terminal first and then accidentally touch your wrench to the car’s chassis while connecting the positive terminal, a direct short circuit will occur. 
• Preventing shorts: By connecting the positive terminal first, the negative connection is not yet made, so any accidental contact with the car’s frame by your tool will not create a dangerous spark or short circuit. 

For disconnecting: 

1. Negative first: Disconnect the negative terminal first.
2. Positive last: Disconnect the positive terminal last.