How do I jump-start a car with a spare battery?

I made a huge mistake and left my car lights on all night. My battery is completely dead now and my car is older. I have a spare battery in my trunk, so I’m wondering if you know how to jump-start a car with a spare battery?

Melanie Krieps Mergen · Updated on
Reviewed by Shannon Martin, Licensed Insurance Agent.
Leaving the car lights on happens to the best of us—not to worry! 
The good news is you can jump-start a car with a spare battery. You’ll want to make sure you have a set of jumper cables handy and about 30 minutes to spare after you’ve hooked everything up.
Not sure how to jump-start a car with a spare battery? Here’s how:
  • Step 1: Buy or use a spare 12V battery
  • Step 2: Grab jumper cables
  • Step 3: Clasp a red clip to the positive (+) terminal of the flat battery, then clasp the other red clip to the spare powered battery’s positive (+) terminal
  • Step 4: Clasp a black clip to the negative (-) terminal of the spare powered battery, then clasp the other black clip to the flat battery’s negative (-) terminal
  • Step 5: Start your car
  • Step 6: Let your car run for at least 30 minutes
  • Step 7: Disconnect the cables in reverse order
Before jump-starting your car: Be sure to verify that both batteries are in good condition, and remember to keep best safety practices in mind.
Pro tip: You can also purchase portable jump-starters from most auto parts or hardware stores, often for between $50 and $100.
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Jerry partners with more than 50 insurance companies, but our content is independently researched, written, and fact-checked by our team of editors and agents. We aren’t paid for reviews or other content.

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