Jump Starting a Dead Battery
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 AAA 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
Before you need a
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.
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
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
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 battery was old it may not start immediately
.... see step 10.
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
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.