Guide: How to Jump Start a Car

Difficulty: Easy Time Required: 10–15 minutes

A dead car battery is frustrating but easily fixable with jumper cables and another vehicle. Jump starting provides enough power to start your engine, allowing your alternator to recharge the battery as you drive. This essential skill gets you back on the road quickly whether you left your lights on, have an old battery, or dealt with extreme cold weather. Follow these steps carefully—correct cable order matters for safety.

What You'll Need

Materials:

• Jumper cables (at least 10–12 feet long, 4–6 gauge wire)
• Another vehicle with a working battery (same voltage—typically 12V)
• Flashlight (if jump starting in the dark)
• Clean rag or paper towel (to wipe battery terminals if corroded)
• Owner's manual for both vehicles (to locate batteries)

Prerequisites:

• Access to both car hoods
• Ability to identify positive and negative battery terminals
• Both cars turned off completely
• Both cars in Park (automatic) or Neutral (manual) with parking brake engaged
• Basic understanding of car battery safety

Step-by-Step Instructions

Step 1: Position the working car near your dead car

Park the working car close enough that jumper cables reach both batteries comfortably—typically 18 inches to 3 feet apart. The cars should not touch each other. Both cars must be in Park (automatic) or Neutral (manual) with parking brakes engaged. Turn off both cars completely, including all lights, radio, and accessories.

Step 2: Open both hoods and locate the batteries

Pop both hoods and secure them with hood props. Find the battery in each car—it's a rectangular box with two terminals (posts) and thick cables attached. In some cars, the battery is in the trunk or under a cover. If you can't find it, check your owner's manual. Most modern cars have clearly labeled jump start points under the hood even if the battery is elsewhere.

Step 3: Identify positive and negative terminals

Each battery has two terminals: positive (+) and negative (−). The positive terminal is marked with a plus sign (+) and usually has a red cover or red cable attached. The negative terminal is marked with a minus sign (−) and usually has a black cover or black cable. Never confuse these—connecting cables incorrectly can damage your car's electrical system.

Step 4: Attach the first red cable to the dead battery's positive terminal

Take one red jumper cable clamp and attach it firmly to the positive (+) terminal of the dead battery. The clamp should grip the metal terminal securely. If the terminal is corroded (white/green buildup), wipe it with a rag first for better connection. This is cable connection 1 of 4.

Step 5: Attach the other red cable to the working battery's positive terminal

Take the other end of the red cable and attach it to the positive (+) terminal of the working battery. Ensure a firm connection. At this point, both red clamps are connected: dead battery positive and working battery positive. This is cable connection 2 of 4.

Step 6: Attach the first black cable to the working battery's negative terminal

Take one black jumper cable clamp and attach it to the negative (−) terminal of the working battery. Ensure a solid connection to the metal terminal. This is cable connection 3 of 4. Never attach this black clamp to the dead battery's negative terminal.

Step 7: Attach the final black cable to an unpainted metal surface

This is the most important step: attach the remaining black clamp to an unpainted metal surface on the dead car's engine block—NOT to the negative terminal of the dead battery. Look for a metal bracket, bolt, or engine component away from the battery. This grounding point prevents sparks near the battery, which could ignite hydrogen gas. This is cable connection 4 of 4.

Step 8: Start the working car and let it run for 2–3 minutes

Start the engine of the working car and let it run for 2–3 minutes at normal idle. This allows the working car's alternator to charge your dead battery slightly. You can gently rev the engine to 1,500–2,000 RPM if you want to speed up charging. Keep the working car running during this entire process.

Step 9: Start the car with the dead battery

With the working car still running, try to start your car. Turn the key or press the start button. If it doesn't start immediately, wait another 2–3 minutes and try again. If it still doesn't start after 3–4 attempts, your battery may be completely dead or you may have another issue. If it starts successfully, let both cars run for 1–2 minutes before disconnecting cables.

Step 10: Remove cables in exact reverse order

Remove cables in the opposite order you attached them: first, remove the black clamp from the metal ground on the formerly dead car; second, remove the black clamp from the working battery's negative terminal; third, remove the red clamp from the working battery's positive terminal; fourth and last, remove the red clamp from the formerly dead battery's positive terminal. Keep clamps from touching each other or any metal while disconnected.

Common Mistakes to Avoid

• Connecting cables in the wrong order: Always connect red to dead positive first, red to working positive second, black to working negative third, black to metal ground last. Wrong order can cause sparks, electrical damage, or battery explosion. Remove cables in exact reverse order.
• Attaching the final black cable to the dead battery's negative terminal: While this works, it creates a spark risk directly at the battery. Batteries release hydrogen gas, which is explosive. Always connect the final black cable to unpainted metal on the engine block instead—it's safer.
• Letting cable clamps touch each other or metal surfaces: Once cables are connected to a battery, the other end is live with electricity. If clamps touch each other or metal surfaces before being properly connected, you'll create sparks and could damage electrical systems.
• Jump starting a frozen or cracked battery: If your battery is frozen solid (only happens in extreme cold) or has visible cracks, do not jump start it—it can explode. If the battery case looks swollen or damaged, call for professional help instead of jump starting.
• Assuming the battery is fine after one jump start: If your car needed a jump, you have a problem: old battery, failed alternator, or parasitic drain. Drive for 20–30 minutes to recharge the battery, then have the battery and charging system tested at an auto parts store (free service) to identify the issue.

Pro Tips

• Keep jumper cables in your trunk permanently: Buy quality 10–12 foot jumper cables with 4–6 gauge wire for $20–40 and store them in your trunk. Cheap thin cables don't carry enough current. You'll use them to help others as often as you need them yourself.
• Consider a portable jump starter: Battery jump packs ($60–100) let you jump start your car without another vehicle. They're rechargeable, fit in your glove box, and usually include USB ports to charge phones. Ideal for remote areas or if you park in garages where other cars aren't accessible.
• Drive for at least 20 minutes after a jump start: Your alternator needs time to recharge the battery. Drive on highways or main roads—not just around the block. Avoid turning on heavy electrical loads (AC, heated seats, stereo) until you've driven 15–20 minutes.
• Check battery terminals for corrosion monthly: White, blue, or green buildup on battery terminals reduces connection quality and can prevent starting. Clean terminals with baking soda and water solution, then apply terminal protector spray to prevent future corrosion.
• Know your car's battery location before you need a jump: Some cars hide batteries in trunks or under seats. Many European cars have positive jump points under the hood even when the battery is elsewhere. Check your owner's manual now so you're not searching in an emergency.

Related Skills

Now that you know how to jump start a car, expand your automotive and home maintenance capabilities with these related guides from Your Life Manual:

• How to Check Your Car's Fluids
• How to Change a Tire Safely
• How to Use Basic Hand Tools
• How to Build a Simple Emergency Kit