How to Jump-start a Car Like a Pro

You can jump-start your vehicle with confidence by following this advice and using a good set of jumper cables.

| December 11, 2009

Jump start a car battery

Although electrical shock is a possibility when jump-starting a car, you also need to be careful so that the battery doesn’t explode, spraying acid onto everyone and everything nearby.


If your car won’t start, you may want to jump-start it so you can drive it to a mechanic or recharge the battery. But before you attempt to jump-start a car, you need to determine if the battery is really the problem. If the headlights or other lights still work, the battery isn’t dead, and jump-starting won’t help. Jump-starting the vehicle is also not the answer if the motor cranks, although the battery may be partially drained if the engine turns over sluggishly a few times.

Before you connect the jumper cables, get ready by following these steps:

  1. Park a running vehicle near the car with the dead battery, but not so close that the two vehicles are touching.


  2. Put both vehicles in park (or neutral for vehicles with manual transmissions), and be sure both parking brakes are on.


  3. Turn off both vehicles and anything that would use electricity: fans, lights or audio equipment.


  4. Remove any corrosion from the battery posts (the short metal rods coming out of the battery) or the bolts that attach wires to the battery. Special metal brushes are available for this, but you probably don’t carry one in your vehicle, so do your best to brush or scrape off the corrosion.


  5. Check the dead battery for leaks or cracks. If the battery is damaged in any way, don’t try to jump-start the vehicle.


  6. If the battery is not the sealed type (see the Image Gallery for examples of different types of batteries), pry off the caps (or unscrew them) and make sure the battery has enough water in it. It’s rare to have to add water to modern batteries, but the water level should be up to the bottoms of the holes that the caps fit into. If it doesn’t have enough water in it, add distilled water. Do not try to jump-start the battery if the liquid in it is frozen or the water level is too low.


Car batteries contain acid, so you can get an acid burn if you touch the liquid inside the battery. It will also eat holes in clothing. Wear safety goggles and gloves.

Connecting the Jumper Cables

Your vehicle’s owner’s manual should have information on jump-starting (or tell you not to jump-start it). If you can’t find the battery easily, the manual will tell you where to attach the jumper cable clamps.

Don’t allow the clamps to touch each other while you are connecting them to or disconnecting them from the batteries.

Batteries create hydrogen, which can build up and, if ignited, explode. (Do not smoke while jump-starting a vehicle.) When an electrical circuit is being closed, there is a possibility of creating a spark. This procedure for connecting jumper cables minimizes sparks near the batteries:

jan steinman
12/28/2011 7:02:14 PM

I'm not sure I go along with #4. The only argument I've ever seen for not connecting to the negative battery posts of both vehicles is the hydrogen gas explosion argument. Yet I've never actually heard of a hydrogen gas explosion from jumping. If you connect the negative to the body or frame, you may not have a good connection to the alternator, which is what you want supplying current to the dead vehicle. It is very common for engine-body resistance to develop over time, or for engine grounding straps to be broken. Battery-to-battery works better for me, whereas I've had several problems with battery-to-frame.

12/17/2009 1:25:04 AM

A word on safety: The "metal rods" sticking out of the battery are made of lead. After cleaning or scraping the corrosion off, wash your hands, and the tool you used. I've seen people use a pocket knife to do the job, and later use the knife to slice some fruit! Also a solution of a little baking soda in warm water does wonders in neutralizing and dissolving the acidic corrosion.

12/16/2009 8:24:15 AM

Another bad idea is after letting the car helping you to jump start is after it has run for 3 minutes is letting it continue to run when you try to start your dead car. Doing so can burn out either alternator diodes, Turn the source battery car off before trying to start the dead car. If it is the battery it will start immediately. Also you risk your car computer burn out from the spark of connecting the batteries together.

tom roberts
12/11/2009 3:54:41 PM

The diagnostics here are not entirely correct. With a weak battery, the lights (even headlights)and radio can still come on, but the battery won't have enough "juice" to kick over the starter.

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