How To Jump-Start Your Car

Booster cables (or jumper cables) are handy emergency electrical cables that can get a car with a weak or nearly dead battery going when nothing else can. However, they must be used properly to work safely.

At one time or another, you have probably used booster cables to jump-start your car. For example, you may have stopped at a restaurant and left the headlights on. When you returned to your car, it wouldn’t start. The headlights had drained the battery of the power it needed to turn the starter motor fast enough to start the engine.

Or, on a hot day in bumper-to-bumper traffic, you may have whiled away the tedium with the radio and air conditioner going full blast. When you got home and parked, you had no reason to suspect there was a problem. But in the morning, when you tried to start the car, it was unresponsive. A combination of small problems, perhaps a slipping alternator belt or an already weak battery, and that stop-and-go commute that never permitted the battery to fully recharge, created an emergency (the car won’t start and you need to get to work on time).

Jump-Start Car

Or, on a cold winter morning, you may have switched on the ignition and heard an anemic, half-hearted attempt by the starter motor to crank the engine. The cold had sapped the battery of its starting power.

Common emergencies such as these call for a boost, a quick jolt of auxiliary power to get the engine started. Once it’s started and you’re on your way, the alternator or generator will recharge the battery, assuming it’s in good condition.

If you are a member of an auto club and you face a battery emergency within its service area, you can phone for emergency service. (Some car manufacturers also provide similar road service.) Tow trucks are equipped to boost batteries. Or you can haul your own booster cables from the trunk and have someone give you a boost.

What To Do

1. There’s a right way and a dangerously wrong way to jump-start a battery. Do it incorrectly, and you can ruin your battery. You can also cause it to catch fire or even to explode with the force of a small bomb.

To do it safely, the booster cables must be correctly attached. Just as important is the order in which the boosting battery’s negative and positive terminal posts are attached to the negative and positive terminal posts of your battery. The positive cable is usually colored red and the negative cable is usually black, both with alligator clamps at each end. However, check your owner’s manual before making a determination.

Batteries are potentially dangerous to work around, although the newer no-maintenance types are sealed, eliminating some of the danger. Batteries produce highly volatile and explosive hydrogen gas. They are also the source of skin- and eye-burning sulfuric acid. And even a weak battery can be discharged (if you accidentally short its two terminals) with enough electrical energy to give you a jolt. Fully charged batteries pack enough electricity to severely injure.

When boosting your battery, use simple precautions. Don’t smoke or have any open flame near the battery. If you can, boost in an open area rather than in an enclosed place like a garage. Remove any metal jewelry or other metal objects that might brush the battery’s terminals and cause the battery to short and discharge. If you are using any metal tools, work on only one terminal, whether the negative or positive, at a time to avoid shorting the battery and risking an electric shock. Never permit the boosting vehicle to come in contact with your own. Although your car and the booster’s car may be positioned bumper-to-bumper, particularly if booster cables are short, absolutely do not let the bumpers touch.

2. Inspect the terminal posts and the cable clamps (which are fastened to the posts) for corrosion. Excessive corrosion acts as an insulator, impeding the flow of current from one battery to the other.

Remove as much corrosion as you can. Mechanics use a small scrub brush and a mixture of water (about a quart) and baking soda or ammonia (a cup of either mixed with the water). Since it’s unlikely you’ll have either ammonia or baking soda on hand, use anything abrasive to rid battery posts and their clamps of corrosion, such as sandpaper. Even sand mixed with radiator water can be applied with a toothbrush or with a handy rag. Clean one terminal at a time.

Also, inspect the battery post clamps. They should be tightly connected. If not, tighten the clamp with an adjustable wrench or vise-grip pliers.

3. Have the booster position his or her car so that the booster cables, which vary in length, reach from one battery to the other. Usually this means that cars must be positioned with their “battery side” closest together or positioned front bumper to front bumper.

4. Turn off both cars’ ignitions, lights, radios, anything that uses battery power.

5. Follow the attachment procedure exactly, and remember that when you are hooking or unhooking a clamp, you must be careful not to let its opposite clamp touch anything metal on the car.

6. First, clamp one of the red (positive) cable clamps to the positive terminal of the booster car’s battery. (A plus sign [ + ] or the abbreviation Pos near the terminal will identify the positive posts.)

7. Clamp the same cable’s opposite end to the positive terminal of your battery.

8. Clamp one of the black (negative) cable clamps to the booster battery’s negative terminal post. (The negative has a minus sign (-) or the abbreviation NEG near it.)

9. Finally, clamp the same cable’s opposite end to a piece of unpainted metal, like a part of the car (not the grill or the radiator).

10. With booster cables in place, get into your car. Put the key in the ignition and shift into Neutral or Park. Then, when you’re behind the wheel and ready, signal the other driver. He or she will start the other car’s engine and accelerate to modest speed. As the engine revs up, turn the key in your ignition. The boost your battery will get from the other battery should crank and start your engine.

Jump-Start Your Car

11. Let both engines idle as you remove the booster cables.

12. Follow the removal procedure exactly. First, remove the negative clamp from the metal you clamped it to.

13. Remove the negative clamp from the booster’s battery.

14. Remove the positive clamp from your battery.

15. Finally, remove the positive clamp from the booster’s battery.

16. Drive your vehicle for at least twenty minutes (on a highway, if possible) to give the alternator or generator a chance to recharge your battery. A little speed recharges your battery quicker. Avoid street traffic. At a stoplight or in stop-and-go traffic, the engine might die before your battery has the power to restart it.

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Filed Under: Cars & Vehicles


About the Author: Vincent Carreno is a cars enthusiast who loves all things about cars and the automotive technology. He is also the chief editor at a local magazine which shares new, exciting and informative articles about troubleshooting car problems.

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