Jump Your Battery

A battery has a negative (-) terminal and positive (+) terminal. Each terminal will be labeled with the appropriate symbol and most wires will be color coded—red (or yellow) for positive (+), black for negative (-). On top post batteries, the positive (+) post is larger than the negative (-) post. Always pay close attention to the color of the cables and the negative (-) and positive (+) symbols on the battery or post, and be aware the order in which you connect the cables to the batteries does matter, so make sure you follow the correct sequence to avoid the discharged battery exploding and potentially causing injury, death or disfigurement.

Steps

  1. Get a working vehicle. Bring it to the disabled vehicle.
  2. Verify that both the dead battery and the rescue battery have the "same" voltage. Car batteries are usually twelve Volts. Trucks/tractors may operate on a twenty-four volt system, sometimes two twelve volt batteries combined to make a twenty-four volt system. Do not attach 12V to 24V.
  3. Position the vehicles so that the car batteries are close enough to each other for your jumper cables to reach each one. Make sure the cars are not touching.
  4. Turn off both engines. Open the hood of each of the cars.
  5. Turn off the headlights, wipers, radios, and all accessories on both cars. Unplug anything charging in the cigarette lighter. They waste power and might even be damaged by surges of power.
  6. Untangle and unwind the jumper cables. The jaws of the cable clamps are designed to bite into the soft metal of the battery clamps that are attached to the battery terminal posts.
  7. Visually check both batteries for cracks, leaks, and damage. If any of these exist, stop. Call a tow truck, do not attempt to jump the car, do not even connect the cables.
  8. Connect a red clamp "first" to the positive (+) post on the dead battery. Then connect the other end with the red clamp to the positive (+) post on the good battery.
    • Remember, the order in which you attach the clams does matter, so follow these steps exactly.
  9. Connect a black clamp to the negative (-) post of the good battery.
  10. Connect the only remaining clamp (a black clamp for the car with the dead battery) to a solid piece of unpainted, grounded metal on the dead car. Do not connect this clamp to the negative post of the dead battery—do this only as a last resort. (See tips for suggestions on what metal parts to clamp to.)
  11. Start the working vehicle. It will charge its own battery and the dead one.
  12. Let it idle for approximately five minutes before trying to start the other car. Never race the engine. If a "fast" idle is not enough to charge the dead battery then it's not going to charge.
  13. Try to start the disabled vehicle. If it doesn't start, wait another five minutes for a little more charging, and try again. Repeat until the disabled vehicle starts.
  14. Remove the jumper cables from the vehicles in the reverse order from when you attached them. Remove the clamp from the ground of the recently disabled vehicle, black and red from the good battery and finally the red from the formerly dead battery.
  15. Keep the recently disabled vehicle engine running a little above idle for at least twenty minutes to charge the battery.



Tips

  • It may be necessary to remove the disabled automobile battery cables from the battery terminals and clean both the connectors and the terminals. Use a stiff wire brush to remove all corrosion. Reconnect the cables to the battery terminals try jumping the car again.
  • When looking for a good ground for that last clamp, look for shiny metal around or on the engine. Painted, oily, or rusted metal will not work. Nuts, bolts, or other protruding shiny metal is best. There may be some sparking when you connect to a good ground. It's strongly recommended not to clip the last clamp to the dead battery (which would be an obvious choice) as the sparks that may fly when you complete the electrical circuit could ignite the hydrogen gas coming off the battery.
  • Remember that batteries are not always in the same place. Some vehicles have the battery under the hood, some behind the cab, and some are even in the trunk.
  • Look at your jumper cables. Many will have instructions with pictures explaining the order to attach the clamps.
  • Don't let the working vehicle leave for at least ten minutes. The dead battery must charge for a while, and sometimes the charging car will knock off and need another jump (especially if you do not keep the engine above idle).
  • Some car manufacturers have designated jump start connectors located somewhere other than the actual battery, a red connection place for positive and a bolt sticking out of the frame nearby which is unpainted and is used for the negative ground connection. Presumably this is to lessen the risk of accidental battery gas ignition and less trouble than finding the actual battery buried beneath the plastic engine covers that some modern vehicles have.
  • Do not use cheap jumper cables with thin wire. Use good, heavy-duty jumper cables.

Warnings

  • Never cross the cables while attached to a car battery.
  • Tell people to back off. Batteries can explode if you don't do the job right.
  • Keep your face as far away from the batteries as you can at all times.
  • Double check all connections before starting the good car. Make sure all clamps are securely connected to the right posts.
  • A charging or discharging battery creates hydrogen gas, which under the right circumstances will cause the battery to explode. This is why one must avoid connecting two batteries directly to one another (all four clamps on battery posts). Use this as a last resort when the primary method fails and you have taken proper safety precautions. Make sure you stand clear. There may be sparks which can cause an explosion.
  • Use safety: if goggles or gloves are available, put them on before you begin. Have anyone not wearing safety equipment stand clear of both vehicles.
  • Don't connect the black leads first and the red leads afterward: If you would do that and accidentally drop the red cable onto the car's frame, a massive short-circuit will form, possibly welding the clamp to the chassis.

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Sources and Citations

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