How to jump start a car

Warning: there are things that can go wrong when you jump start a car that can be hazardous or even deadly. Do not attempt to jump start a car unless you are aware of these precautions.

That said, in most cases, it's pretty easy. From About.com's auto repair site:

The first thing to be right about is the order to connect the cables:

Attach one end of one cable to the dead battery's positive terminal.

Attach the other end of the same cable to the positive terminal of the battery in the starting vehicle.

Attach one end of the other cable to the negative terminal of the battery in the starting vehicle.

Attach the other end of that cable to the engine block of the car with the dead battery. Look for unpainted metal surfaces and be sure it will clear anything moving when the car starts. Do not attach the negative cable to the dead battery itself.

Got that? Dead + / Live + / Live - / Dead engine block. Some jumper cables will have those numbered.

Edmunds.com has a jump-start page with instructions and video

Step Five
Make a final check to confirm that the jumper cables are not near any moving engine parts, and start the booster car. Let it idle for several minutes, depending on the state of the dead battery. If the dead battery is new and was drained by the lights being left on an extended period of time, it will probably start immediately. If it is an old battery or it has sat for a long time (more than a month) it will probably take awhile to charge it sufficently.

Prevent Blindness America has a page of precautions when jump-starting a battery:

1. Check your battery for cracks, corrosion, and loose wires every time you change your oil.

2. Always wear a pair of splash-proof polycarbonate goggles when jump-starting your battery. Your goggles should have a Z-87 label on the frame. This means your goggles are certified use during auto repairs.

3. Never smoke or use anything that may spark when working on your battery. Car batteries contain hydrogen and oxygen, two gasses that could ignite and explode.

Mr. Fixit has a page

Once the car has started run it at fast idle for a few minutes. Assuming that its charging system is up to snuff, this will charge the battery sufficiently to restart the car after the next step. To make sure that you aren't injured I recommend that you now turn off both engines so that you can safely remove the cables without getting tangled in the moving parts like fan blades and belts. Remove the cables in the reverse order that you used to hook them up, taking the ground cable clamp from the engine metal first. After removing the cables immediately re-start the car. If you feel comfortable removing the cables with the engine running have a care about loose clothing and fingers and keep the cables away from moving parts.

"Black and Decker VEC026BD 400 Electromate JumpStarter / Inflator" (Vector)

"Freeplay Energy FC1CG Freecharge Weza Foot-Powered Portable Generator" (Freeplay Energy)

"Black & Decker Simple Start Battery Booster #BB7B" (Vector)

"Xantrex 852-2000 XPower Powerpack 600HD Portable Backup Power Source" (Xantrex Technologies)

Comments

[dan]

Seem it might be a good idea to print on the inside of the hood of cars some basic information, like
- how to jump start the car
- what kind of oil should go in the car
- what else?...

[Tim]

"Attach the other end of that cable to the engine block" is a little confusing. You can attach the cable to any ground -- the "unpainted metal surfaces" mentioned. Pretty much any bolt head you can get the cable to hook to should work.

@dan: most of that stuff should be in the user manual. Usually you can skip to the back of the manual for the spec tables.

[Dave New]

The idea of attaching the last connection to something away from the battery, of course, is to avoid the spark that nearly always results. Setting off a spark at a battery terminal can invoke the wrath of the Hydrogen gas gods, producing a nasty flashback.

One thing I'm not crazy about, though, in the given instructions (although I understand the wish to connect things with all mechanical parts idle), is the idea of connecting a good battery to a dead one, without the engine and charging system already running in the 'donor' vehicle.

Depending on how good the 'good' battery is, there is the possibility of running both of them down to the point where neither vehicle will start, if you wait to start the good battery/engine combo after connecting the whole mess together.

Considering that the instructions seem to think it's OK to dis-connect (carefully) the cables on running engines, I wouldn't consider it too much of a stretch to advise folks to leave the good engine/battery running while (carefully) making the initial connections, just to keep from stranding themselves along with the person they are trying to help.

Of course, even if you do everything correctly, there is a chance of blowing the diodes in your alternator, due to the outrageous surge current pulled by the dead battery when you connect it up. Because of this, even though officers usually carry jumper cables in their vehicles, in most circumstance, they will refuse to jump-start a stranded motorist. Something about getting tired of replacing alternator diode rings in their squad cars, it seems.

[jhritz]

I will add that if your battery is not starting your car after a cold soak, it may be time to replace it. OEM batteries are designed to start the car at 0 degrees F. Most OEM batteries are good for 5 years on average. If you're getting slow or no crank after it sits overnight, its time for a load test. Much better to be stranded at your nice warm house than in a random spot. Weather like we're having is cold, but doesn't really require a block heater for a reliable start if the battery is in good shape.

[Juno888]

One thing I'm not crazy about, though, in the given instructions (although I understand the wish to connect things with all mechanical parts idle), is the idea of connecting a good battery to a dead one, without the engine and charging system already running in the 'donor' vehicle.

[Jessa]

I had to jumpstart a guy's car last night, who said he knew how to jumpstart cars. He did the attachments of the cables and hooked up his negative to my positive, and his positive to my negative. I started revving and stopped as soon as I noticed smoke and the smell of burning rubber. My car has started fine since then but could this have done any permenant damage? At the moment the cables are fried but that is all that appears to have been damaged.

[Stone]

One thing to be wary of is that many cars will use the red rubber boot on a terminal cable for postive and black for negative. I spotted in a car the other day where both cables were black. Fortunatley there are postive (+) and negative (-) markings on the battery. As long as you keep the same color of clamp on the same type of post (postive + to positive+ and negative - to negative or chasis ground) you'll do okay.

[Edward Vielmetti]

Car Talk has a nice PDF on the topic which would be excellent to print out two sided and stick in your glove compartment.

http://www.cartalk.com/content/features/roadside/jumpstart.pdf