Jump starting a car battery correctly is critical for your own safety.

If you are a licensed driver, you have probably found yourself jump starting a car at some point if you have been a driver for very long.

Connecting the cables incorrectly or letting the clamps touch each other or other metal on your vehicle could cause dangerous sparks and explosions that could seriously burn you and damage your vehicle.

Always check your owners manual of your vehicle before performing any maintenance under the hood.

Some newer vehicle instructions will say NO jump starting a cars battery.

Others might give different instructions for connecting jumper cables.

Why a car battery dies

Car batteries can die for many reasons some of the most common reasons for a dead battery are:

Leaving headlights on (probably #1 reason)

Bad alternator

Old battery and corrosion on the terminals that hasn't been cleaned.

To read how to clean a car battery click here.

A car battery should last from 3-5 years

If your car battery dies within the first year you bought it,
(aside from leaving headlights or other electric equipment on)
take it back to where you bought it.
Car batteries should have at least a one year warranty.

What to look for in quality jumper cables

Every car should be equipped with a good set of jumper cables in its emergency roadside kit.

The thicker the cables the better the chance they will work when jump starting a car battery. It will be worth an extra $10-25 if the thicker cables get your battery started when you're stranded.

Very cheap, thin jumper cables may not be able to carry enough electric current to start your car, and in some cases they may get too hot from the current that is going through, ruining the cables and possibly causing sparking, a fire or explosion.

In the picture below two sets of jumper cables are side by side. Notice the orange and black jumper cable is thicker than the red and black. The orange is a 6 gauge, the red is an 8 gauge.

Realize the lower the gauge number, the thicker the cable will be. It is said you should have at least 6 gauge jumper cables.

Also beware, some manufacturers will put thick rubber insulation around thin, high gauge wire, making you think you are getting better quality than what it actually is.

Pick up the jumper cables and feel how heavy they are. If they don't weigh much, it has thinner wire (higher gauge).

The longer the cables are, the thicker the wire (lower gauge) must be to deliver the same amount of current as in shorter cables.

Think: "Long and Thick" Will do the trick, "Short and Thin" could lose or win.

The Long, thick, and short, thin cables will work safely on small cars but the thin cables won't work safely on larger vehicles.

Before jump starting a car,
Make sure the amps needed to start the jumped vehicle aren't less than what the cables can hold.

If the car you're jumping is only a 4, maybe 6 cylinder "Short and thin" (8 gauge) should work. Anything larger needs "long and thick" (6 gauge or lower).

Other factors to look for are the quality of the clamps. The bigger, thicker the clamps, the more current (amps) they will carry.

The handles of the clamps should be well insulated.
If the clamps are very shiny and light weight, there is a good chance they are only copper coated. Having solid copper clamps is best.

Also read the label to be sure you are getting the quality you are looking for.

Safety when working with car batteries

Remember a car battery is full of sulfuric acid as well as hydrogen and oxygen gases.
Wearing safety goggles could save your sight if an explosion occurred while jump starting a car.

People who work with car batteries regularly also wear ear protection. Hearing has been damaged or lost from the intense, loud sound when a battery has exploded.

Wearing gloves when working with car batteries is also recommended to keep the acid off your hands, and to keep from touching the lead posts of your battery

Although there is always a chance of a battery exploding when Jump starting a car, it is only slight and will be minimized even more by following correct procedure for connecting and disconnecting the cables.

The dead battery has more risk of exploding because when a battery is discharged it releases hydrogen gas by the battery terminal posts.

Before jump starting your car battery, check your battery.

If there are any cracks or damage to the battery DO NOT attempt to jump it.

If the weather is below freezing make sure the battery is not frozen.
Do this by by removing the caps and making sure no ice is in the cells.

An older battery or a discharged battery is more likely to freeze because there is more water and less acid in the battery cells.

Because of the "Freezing-Point Depression" phenomenon, the freezing point is lower with acid mixed with the water.

Jump starting a car with a frozen battery is very likely to explode.

Also remember the fluid will expand when it freezes possibly causing a crack in the battery even if you can't see it.
It will be safer for you to buy a new battery if your battery has frozen.

If your battery has corrosion on the posts it should be cleaned off first to insure a good connection.
A wire or bristle brush would work, or buying a can of soda pop and pouring it over the post, then rinsing and drying works well too.

Be sure the problem is a dead, discharged battery. If you try to start your engine and the lights and other electrical equipment come on, then the problem is not a dead battery.

Connecting jumper cables correctly

Once you have found a booster car, make sure the booster car battery is close enough to your dead car battery so the cables can reach each post.
But don't have the cars touching.

Before jump starting a car battery, All electrical equipment should be turned off in each vehicle and the engines should be off.

Below is the order to connect the cables
When jump starting a car.

Step 1.
Connect the positive cable to the dead car battery positive post
(should be red with a positive + sign)

Notice the negative clamp is clipped to the cable, this is so it won't fall and make a connection to metal on the vehicle.

Step 2.
Connect the other positive clamp to the booster car battery positive post.

Again, the negative clamp is clipped to the cable so it won't touch metal on the vehicle.

Step 3.
Connect the negative clamp on the booster car battery negative post.

(should be black with a negative - sign)

Step 4.
Look for a shiny, unpainted metal part connected to the body of the car to be jumped, away from the battery or moving parts .

In the picture you see there is a small screw a few feet from the battery on the echo to be jumped.

Connect the negative clamp to something like this screw on the vehicle needing a boost, as in the picture.

*Although I have successfully used this screw seen above, on the strut tower of this Echo for jump starting it,

I have also been told that using a metal part directly connected to the body of the vehicle for the last negative clamp hinders the current flow when jump starting, because the wire used to connect the body to the engine is usually thinner than the wires connected to the engine block.

Therefore it is best to use a metal part connected to the engine block.
Since my Echo has a plastic cover over the engine as seen in the picture on the left, I find no metal to connect the clamp to on the engine.

You see two screws in the picture on the right. The screw by the red arrow is fastened to the air filter hose, without being directly connected to the engine. This would not make a good connection.

The screw I circled in green, however, is connected to the engine block, where the air filter hose and engine meet.

Though it is a tight squeeze, this would be the best choice in this vehicle for the last negative clamp connection.

Step 5.

With everyone standing away from the cars, start the engine of the booster car.

If all you had to use were thin, cheap jumper cables, wait several minutes for the battery to charge with the booster car running, then start the disabled car.

With thick, heavy duty jumper cables the dead battery will probably start up right away.

Pushing the gas pedal of the dead battery car will help charge the battery.

Step 6.

Remove the cable clamps in the opposite order you connected them.

First remove the negative clamp from the metal part on the jumped car.

Second remove the negative clamp from the booster car battery post.

Third remove the positive clamp from the booster car positive battery post.

Fourth and last, remove the positive clamp from the jumped cars positive battery post.

Step 7.
Before you turn off your car, after the battery is jumped, Drive for at least 10-20 minutes on a road like a freeway that you don't have to stop while driving. This will give the battery the charge it needs so it won't die after you turn off the engine.

After jump starting a car battery

Cleaning your cable clamps with some baking soda and water will neutralize the acid that got on them and prevent corrosion.

top of page

More to come on jump starting a car

Return to car maintenance from Jump starting a car