How to Jump a Car When Your Battery Is Dead

Few car problems are as maddening and disorienting as a dead battery. With the right equipment and knowledge, you may never be stranded again.

under the hood how to charge your car battery
Editor's Note: In this limited series, Under the Hood, we'll share do-it-yourself tips for drivers who want to wrench their own cars, no matter their skill level.

The dreaded dead battery: one of the most common "user error" issues car owners suffer. You slip into the driver's seat (if you can even unlock the door) and turn the key, but instead of the expected 'purring engine' soundtrack, you're greeted with… silence. And horror. Your day's itinerary flashes in front of your eyes. Suddenly, you're stranded and helpless.

Thankfully, drained batteries are less common in the days of automatic lights and other clever tech fail-safes built into modern cars. But, knowledge is power, and whether you need just enough juice to get to an auto shop and replace a dead battery or just need to start the car after leaving your dome light on, here’s what you should know about jumpstarting.

First, Know Your Battery’s Age

Separate from battery issues and jumpstarting techniques, it’s generally important to know when your current car battery was installed. Batteries lose capacity as they age, so this info could, in theory, save you from any issues in the first place. The typical car battery has a lifespan of three to five years, so make sure to keep track of its performance once you cross the three-year threshold.

Keep Jumper Cables Handy

(Purchase any supplies and tools from eBay Motors or your retailer of choice.)

under the hood how to charge your car battery

Even if you haven't yet had the pleasure, dead batteries are super common. Stowing the right equipment alongside your car jack could make you a hero to strangers in need. You'll find jumper cables for sale at most big box stores and automotive parts stores, and of course, online. The issue is that many jumper cables are cheaply made, meaning they could fry after a single use or, worse yet, not function at all. It's worth buying quality cables with a proper gauge, or thickness. The lower the gauge number, the thicker the cable; the thicker the cable, the more electricity it can handle; bigger engines need lower gauge wires. Most vehicles will do perfectly well with 4- or 6-gauge cables, but if you have a big truck or similar, looks for 2-gauge.

How to Use Jumper Cables

under the hood how to charge your car battery

If you're stranded without cables and have successfully flagged down a cable-owning good samaritan or called someone you know, positioning their car correctly is the first step. Jumper cables need to reach from their car battery to yours with some slack left over, so have them park quite close, either nose-to-nose with or directly parallel to your car.

Remove any battery cover and visually inspect your battery for disconnected wires/terminals or corrosion. Before connecting any cables, carefully wipe away any corrosion using a cloth of some kind, taking care not to touch the terminals with anything made of metal. Identify the positive and negative battery terminals – these are almost certainly marked with a + and -, respectively. Once you're ready, do the following:

  1. Turn off the ignition in both cars.
  2. Connect the red, positive jumper cable to the positive terminal of your battery and then the other end of the same red cable to the positive terminal of the other battery.
  3. Connect the black, negative cable to your dead battery, followed by the negative terminal of the other battery.
  4. Now, turn on the 'donor' car, and after it runs for about five minutes, try starting your car.
  5. If it does start, leave it running and carefully disconnect the cables. If it doesn't start, re-check cable connections and leave it for another several minutes before trying again.
  6. If your battery is totally shot and still won't start, ask for a ride.

    How to Use Portable Jump Starters

    If you live in a lightly populated area or simply insist on being self-sufficient, you may want to invest in a portable jump starter that can restart your battery on its own power. These work exactly like external cell phone battery packs but store more energy and come with jumper cable attachments. The process is essentially the same for all these types of jumpers and much simpler than connecting to another car. Typically, you'll connect the cables to your dead battery, turn on the device and start your car right up. (Pro tip: be sure to keep your portable jump starter charged, or you risk learning a painfully ironic lesson.)

    No Cables but Big Confidence? Roll it Down the Hill

    under the hood how to charge your car battery

    First, know that we don't necessarily recommend anyone do this, but it can be an effective method if you have the wherewithal. It'll only work with manual transmissions, and for perhaps obvious reasons, it can be risky. Presuming you’re on an incline and there aren't obstacles or other cars/pedestrians in the way, put the car into second gear and while pressing in the clutch… push your car down the hill. Once you reach about 5-10 mph (no need to Marty McFly this situation), quickly release the clutch. The engine should roar to life. This move is called "popping the clutch," and it's the automotive equivalent of CPR. Basically, the engine uses its own sudden movement to start itself. At least in theory.

    How to Keep Your Battery Going Strong

    The typical car battery has a lifespan of three to five years; exactly how long yours will last depends on several factors. One of the best ways to maintain the life of the battery is by regularly checking the terminals for signs of corrosion and cleaning them up if any develops. Running a bunch of accessories (supplemental lights, a/c, power accessories) will also make your battery work harder. Lastly, it can help to exercise good driving habits, so don’t push it too hard (too often). But like any product, there are many types of batteries: some more robust and longer-lasting than others. So choose wisely, and keep on truckin'.

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