Jump Starting a Dead Battery!

by **Rislar** Wed Jan 20, 2010 9:11 am

It happens to just about everyone eventually. You turn the key in your vehicle only to discover you got a dead battery thanks to the dome light that was left on over night. While you may have a spare tire in your trunk, you probably don't have a spare battery. But thanks to your friend, and a pair jumper cables, you won't have to call AA or a tow truck service to breath life back into your battery. However simply hooking up the jumper cables randomly is not the correct way to successfully jump a car battery and commonly ends up in an unsuccessful attempt at a jump start or even worse. This article will help to explain the do's and don't in jumpstarting a drained battery.

Before you need a Jumpstart

Obviously rule number one if you ever intend to jump start your vehicle is you'll need a set of jumper cables. Jumper cables come in many different grades from the very cheap dollar store quality to professional level. If you don't have a set consider getting a set. While you don't need top of the line professional quality cables to carry around until you might someday need them, try to avoid buying the cheapest set you can find. Typically these cheap sets have less than adequate gauge of wire to carry the current a jump start will draw. This can overheat a wire on a hard to start engine which has been known to melt the cable insulation and burn a few fenders. Also be aware that simply looking at a cable's diameter in the store is not going to tell you much. Its common to see thicker than necessary insulation on cheap cables to give the appearance of heavy gauge wire. Instead look for the gauge of the wire, which should be no less than 4 Gauge (less would have a higher number) for cables under 16 ft. long and rated for a minimum of 400 amps. Also look for the UL Listed symbol. The clamps are another thing to look at. Many vehicles connect to batteries using the side posts of a battery. So your cables should include an extended jaw that has grooves that will conform to theses side posts since that is where you might be doing the jump. The clamps should also have a heavy duty spring to clamp down strongly onto the posts which will lessen the chance of producing sparks during the current draw and increasing the amount of current transferred to the vehicle being jumped.

Something important to note is that there is the small possibility of an explosion during a battery jump.

The reason for this is that Lead Acid batteries do emit hydrogen gas when they discharge. Hydrogen gas is flammable, even explosive when it is concentrated in an area. During a battery jump or even when connecting the cables to the terminals, a small spark "could" ignite the hydrogen gas. But the possibility if this happening is remote because it takes a concentration of hydrogen gas to amount to a dangerous situation and the battery would have had to sit for a long time with little to no air circulation. Though it is a remote chance, there is always the chance so to avoid this kaboom, the key is to connect the cables in the proper order as outlined below.

Jump Starting the Car

So now you need a jump. Your friend offers to give you a jumpstart. You may or may not have a set of jumper cables so if you don't, you'll be borrowing a set. There's a right way and a wrong way to jump start a battery. The first thing to do is get into position. The car that will be just starting your car should be parked front to front with your car so that connect the jumper cables with plenty of slack to spare. Cable lengths vary from 6 feet up to 16 feet or longer. Have a look to see which side of the car your battery and their battery are and park the jumping car accord to the length of your jumper cables and battery positions. Do not allow the vehicles to touch in any way. Turn off the ignition in both vehicles and engage both parking brakes. Automatic transmissions should be in park while manual transmissions should be in neutral. Turn off all accessories and lights in the vehicle receiving the jump.

Raise both hoods and locate the batteries. If the jumper cables will be stretched tight, re-position the boosting vehicle. Also note that when attaching jumper cables make sure that cables do not dangle down into the engine bay where they may come in contact with fans or fan belts.

Start by removing or fold back the terminal covers (if equipped). Clear away any corrosion on the terminals. Note that at this point if one or both terminals on the vehicle getting the jump are seriously corroded, it's a good idea to clean them now so that after a successful jump, the battery will get an efficient charge.

Attaching the Jumper Cable - Start by clamping the RED positive (+) jumper cable clamp to the positive (+) side terminal of the dead battery, also color coded RED. Ensure that both sides of the jumper cable clamp are firmly in contact with the terminal. It sometimes helps to wiggle the clamps so that the teeth dig into the lead terminal.

Secure the other end of the RED positive (+) jumper cable clamp to the RED (+) positive terminal of the good battery. Once again make sure that the jumper cable clamp firmly in contact with the battery terminal.

Next secure the BLACK negative jumper cable to the BLACK negative (-) terminal on the good battery.

Last connect the BLACK negative (-) jumper cable to an unpainted bare metal part such as a bare bolt or bracket on the engine of the dead battery vehicle. This bare metal part should be away from the dead battery and away from the fuel system components such as the carburetor and fuel-injection system parts. Attaching to a bare metal part rather than the negative terminal on the battery will give you a solid ground and also reduce the potential of igniting any buildup of hydrogen gas.

Make a last check to ensure no cable is hanging down into the engine bay and that the clamps are securely connected.

Start the engine on the running vehicle. Bring the engine speed up just above idle but do not race the engine.

Attempt to start the engine on the disabled vehicle. If the dead battery was in relatively good condition and was drained by a light or accessory left on, it should start immediately.

If the dead battery vehicle will not crank over (you might hear a clicking sound), recheck the jumper cable clamps and try again. If the dead battery vehicle still will not turn over, allow the running vehicle to run for a few minutes and supply a charge to the dead battery. Then try again. If the dead battery vehicle turns over but does not start, do not keep trying. This could cause damage to the starter. There may be other issues and you may have to troubleshoot these.

If you do get a successful start, keep the cables connected for about three minutes as both engines run and supply a small charge to the dead battery.

After a few minutes of running, it is time to disconnect the jumper cables. Leave the engines run and begin disconnecting the jumper cables in reverse order. DO NOT allow the cable clamps to touch each other or drop into the engine bay.

1. Disconnect disabled negative terminal (attached to bare metal on engine)
2. Disconnect good battery vehicle negative terminal.
3. Disconnect good battery positive terminal.
4. Disconnect the disabled positive terminal.

After the successful jump, keep the jump started vehicle's engine running for about approximately a 1/2 hour. Keep in mind that an alternator is designed to maintain a fully charged battery and not to fully charge the battery from dead. So once you shut down the vehicle, it may need another jump start so it's a good idea to get it to a suitable location to do so if necessary. Also consider placing the discharged battery on a certified charger for at least 8 to 12 hours to bring the battery up to full charge.