A dead car battery is one of the most common roadside emergencies — and one of the easiest to handle if you know the correct procedure. Jump starting a car in the wrong order can cause sparks, damage expensive electronics, or in extreme cases cause a battery to explode. The correct cable attachment order is: positive first, negative last on both connections.
Key Takeaways
- Cable connection order: Red (+) to dead battery → Red (+) to good battery → Black (-) to good battery → Black (-) to engine ground (NOT dead battery)
- The negative cable connects to a metal ground point on the dead car's engine — NOT the dead battery terminal
- Run the good car's engine for 5-10 minutes before attempting to start the dead car
- Modern vehicles with complex electronics should ideally use a battery tender instead of traditional jump starts
- NHTSA recommends carrying jumper cables or a portable jump starter in every vehicle
Step 1: Position vehicles Pull the good car nose-to-nose with the dead car (or side-by-side if the engine bays are close enough). Do not let the vehicles touch each other — this can create an unintended ground connection.
Step 2: Identify battery terminals Locate the batteries in both vehicles. Identify the positive (+) terminal (usually red cover) and negative (-) terminal (usually black cover).
Step 3: Connect RED cable to dead battery's POSITIVE terminal Attach one red (positive) jumper cable clamp to the dead battery's positive (+) terminal.
Step 4: Connect RED cable to good battery's POSITIVE terminal Attach the other red (positive) clamp to the good battery's positive (+) terminal.
Step 5: Connect BLACK cable to good battery's NEGATIVE terminal Attach one black (negative) clamp to the good battery's negative (-) terminal.
Step 6: Connect BLACK cable to ENGINE GROUND on dead car Attach the other black (negative) clamp to an unpainted metal surface on the dead car's engine — a bolt on the engine block or a metal bracket away from the battery. NOT to the dead battery's negative terminal.
Why not the dead battery terminal? Connecting negative to the dead battery terminal last creates a spark risk near the battery, which can emit hydrogen gas. Connecting to an engine ground moves any spark away from the battery.
"The sequence of jumper cable attachment is specifically designed to prevent sparks at the most dangerous location — near the battery. Hydrogen gas emitted from charging batteries is flammable. The engine-ground connection for the final negative cable directs any spark to a safe location." — AAA Battery Safety Guidelines, 2024
Step 7: Start the good car Start the vehicle with the good battery. Let it run for 5-10 minutes to charge the dead battery through the cables.
Step 8: Attempt to start the dead car Try starting the dead vehicle. If it doesn't start after 30-60 seconds of cranking, let the good car charge it for another 5-10 minutes and try again.
Step 9: Disconnect cables in REVERSE order Remove cables in the exact reverse of connection order:
Step 10: Keep the revived car running Drive the revived vehicle for at least 30-45 minutes to allow the alternator to recharge the battery. If possible, have the battery tested — a battery that needs jumping may need replacement.
A portable jump starter (lithium battery pack with clamps) is safer than traditional jumper cables because:
Cost: $40-$100. Recommended to keep in your trunk.
What order do you connect jumper cables? Red (+) to dead battery → Red (+) to good battery → Black (-) to good battery → Black (-) to engine ground on dead car (NOT to dead battery's negative terminal).
Why do you connect the negative cable to the engine block instead of the battery? Batteries emit small amounts of hydrogen gas while charging. Connecting the negative cable to the engine block (away from the battery) moves any potential spark away from the hydrogen gas — reducing fire/explosion risk.
How long do you need to charge before starting? Let the good car run with the cables connected for 5-10 minutes before attempting to start the dead car. Longer if the battery was completely dead.
Can jump starting damage my car? Incorrect cable connections can damage vehicle electronics. Modern vehicles have sensitive computer systems. When done correctly, jump starting is generally safe. Frequent need for jump starting indicates a failing battery that should be replaced.
What if the car won't start after jump starting? The battery may be too damaged to accept a charge, the alternator may not be working, or another electrical issue may exist. Call roadside assistance.
How do you disconnect jumper cables? Reverse the connection order: Black from engine ground (dead car) → Black from negative (good car) → Red from positive (good car) → Red from positive (revived car).
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