Jump Start a Car

Whether it's because you left the lights on or your battery is old, most car owners will be faced with a dead battery sooner or later. If you ever find yourself in such a situation, this article may help you out.

10 Second Summary

1. Open the hoods on both cars, find the batteries, and get out the jumper cables.
2. Connect the red clamps to both batteries' positive terminals.
3. Connect one black clamp to the good battery's negative terminal.
4. Connect the other clamp to some grounded metal on the dead car.
5. Start the working car, then the dead car.
6. Remove the cables once the dead car starts.

Steps

Checking the Battery

  1. Make sure the battery is the problem.
    • Check the headlights. Are they dim or bright? (Note that in some cars you will need to turn the ignition on to test the headlights). If they are dim, it's likely your battery is the culprit. If your headlights are bright, you do not have a dead battery and a jump start will not help.
    • Put the key in the ignition and see whether your dashboard lights up as usual. Test the stereo. In most cases, even with a low battery you should see some dashboard lights and get some sound out of the stereo. If you do not get a flicker out of your dashboard, you may have a problem with your ignition switch.
    • Try to start the car. Does it turn over very slowly, or does it crank quickly? If it cranks quickly, you do not have a dead battery and a jump start will not help. If it cranks slowly, or not at all, you probably have a dead battery.

Jumping the Battery

  1. Open each car's hood and locate the battery. On most cars, it will be near the front of the car on the right or left side, but on some cars the battery is located near the firewall between the engine and passenger compartment. In some cars the battery is located in the trunk. If unsure, check your car manual for location of the battery. Identify the positive and negative terminals.
    • The positive terminal will be marked with a plus sign (+) and will usually have a red cable attached on it.
    • The negative terminal will be marked with a minus sign (-) and will usually have a black cable attached to it.
  2. Park the working car near, but not touching, the disabled car. Park the car in such a way that the distance between both car batteries is as small as possible. Turn off the engine, radio, lights, A/C, fans and all other electrical components. Make sure that all of these things are off in the disabled car, too. Don't let the cars touch at all.
    • If the cars are touching, jumping the battery can cause a dangerous electrical arc between the vehicles.
  3. Put on safety gear (goggles and gloves) if you have it. Inspect batteries for cracks, leaks or other damage. If you find any of these things, do not jump start the car. Call a tow truck instead or replace the battery.
    • It may be necessary to remove the disabled automobile's battery cables from the battery terminals and clean both cables and terminals. Use a stiff wire brush to remove all corrosion. Reconnect the cables to the battery terminals and jump the car.
    • Remove any positive (+) red post protective covers if applicable.
  4. Untangle and unwind your jumper cables. Like your battery, your jumper cables will probably have red and black cables and will have heavy-duty clamps to connect to the battery terminals. You must make sure that the red and black ends of your jumper cables never touch each other once they are connected to the batteries; permitting them to do so can result in serious arcing and/or damage to one or both cars.
  5. Connect the jumper cables in the order described below:
    • Connect one red clamp to the positive (+) terminal of the dead battery.
    • Connect the other red clamp to the positive (+) terminal of the good battery.
    • Connect one black clamp to the negative (-) terminal of the good battery.
    • Connect the other black clamp to a piece of grounded metal on the dead car, preferably the bolt where the thick negative cable from the battery connects to the chassis. If this is not practical, look for shiny metal (not painted or oily) that is attached to the engine. Usually a nut, bolt or other protruding shiny metal will work. You may see a small spark when you connect to a good ground. As a last resort, you may connect to the negative (-) post of the dead battery, but this risks igniting hydrogen gas coming off the battery.
    • Make sure none of the cables are dangling into the engine compartment, where they could be exposed to moving parts.
  6. Start the working car. Let it idle for a few minutes. Do not race the engine, but do rev the engine a little above idle for 30 to 60 seconds. You do this to charge the battery in the dead car, because the starter in the dead car will draw most of the required current (well in excess of 100 amps) from that battery, not through the cables. Common retail jumper cables are not built to pass the current required. Charging the dead battery is a must. If 30 seconds doesn't do it, try charging for the full 60 seconds by keeping the engine at a high idle. A good, clean connection between the battery cables and the battery terminals is essential.
  7. Try to start the disabled vehicle. If it does not start, shut the engine off and disconnect the last connection temporarily while you slightly twist or wiggle each of the four clamps to help ensure a good electrical connection. Restart the working car again. Allow another five minutes for charging before attempting to start the disabled vehicle. If this does not work after a few tries, you may need to have the car towed or the battery replaced.
  8. Remove the jumper cables once the car starts. Do this in the reverse of the order in which they were attached, and don't let any of the cables or clamps touch each other (or dangle into the engine compartment).
    • Disconnect the black clamp from grounded metal on the dead car.
    • Disconnect the black clamp from the negative (-) terminal of the good battery.
    • Disconnect the red clamp from the positive (+) terminal of the good battery.
    • Disconnect the red clamp from the positive (+) terminal of the dead battery.
    • Replace any positive (+) red post protective covers if applicable. These covers help prevent accidental short circuiting the battery.
  9. Keep the recently-disabled car's engine running. Run the car above idle (slightly revved up with your foot on the gas) for five minutes and then on or above idle for 20 minutes before turning it off. This should give the battery enough charge to start the car again. If it does not, you probably have a dead battery or a dying alternator.

Without Cables (Manual Transmission only)

  1. Position the car at the top of a hill, or have people push the car.
  2. Depress the clutch completely.[1]
  3. Put the car in second gear.[1]
  4. Turn on the ignition but don't start the engine.[1] This is also known as key position two. The key is inserted and turned one step to the right. Turning one step further would start the engine, which you don't want to do.
  5. Let go of the brakes. Keep the clutch depressed. You'll start coasting down the hill or moving due to people pushing.[1]
  6. Let go of the clutch quickly when the speed reaches {{safesubst:#invoke:convert|convert}}.[1] The engine should turn and start. If it doesn't, try depressing and releasing the clutch again.



Tips

  • Do not connect the black leads first and the red leads after. If you 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.
  • Don't let the working vehicle leave for at least ten minutes. The dead battery must charge for a while, and sometimes will go dead again (especially if you do not keep the engine above idle).
  • 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.
  • Many jumper cables have instructions with pictures explaining the order to attach the clamps.
  • Buy only high-quality, heavy-duty jumper cables. This is determined by the wire thickness gauge. The lower the gauge number, the heavier the conductor (a #10 conductor or wire is a smaller or thinner than a #8 wire). Do not judge the cable by the overall thickness of the cables alone, as many manufacturers disguise cheap cables simply by encasing a thin conductor with a generous layer of inexpensive plastic insulation. Also remember that the longer the cable, the thicker the wire needs to be.
  • There is no electrocution hazard performing a jump on most cars and light trucks. The voltage in the case of jumping is about 12. 12 volts hasn't fatally electrocuted anyone, however just a small spark near a battery has caused explosions that have caused serious injury or burns. A spark caused by an accidental short circuit is large due to the amount of current or amps, not the voltage.
  • The push/hill start method also works with the car in reverse. Reverse can be easier and requires lower speeds due to the gearing. This also provides an alternative if your car is parked on a hill facing up and you cannot push the car up. You cannot push-start an automatic transmission equipped car, unless you are capable of getting to speeds above {{safesubst:#invoke:convert|convert}}, which isn't recommended since you will not have power brakes or power steering.
  • Extinguish open flames and smoking materials when near batteries. Batteries emit hydrogen gas as a normal by-product of the chemical process to generate electricity. Hydrogen gas is highly explosive.

Warnings

  • Keep your face as far away from the batteries as you can at all times.
  • Never cross the cables while attached to a car battery.
  • A charging or discharging battery creates hydrogen gas, which under certain circumstances can cause the battery to explode.[2] This is why you should try to 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.

Related Articles

Sources and Citations

  1. ↑ 1.0 1.1 1.2 1.3 1.4 http://artofmanliness.com/2008/09/11/how-to-jump-start-a-car/
  2. ↑ http://en.wikipedia.org/wiki/Battery_(electricity)#Explosive_hazards
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