How to use jumper cables
Sooner or later it happens to all
drivers, a dead battery. It could have been you left your lights on or
the battery just failed, but now the only thing to do is to boost your
car with jumper cables to get it going. Assuming you have them, or can
flag down someone who does, do you know how to use them? It can be
dangerous both to you or your car if they are not used properly. What
you are doing when you connect jumper cables is to temporarily borrow
electrical power from a good battery to get your engine started and
then hopefully the running engine can generate power to recharge your
dead battery. To begin with you need a pair of good jumper cables. The
clamps must be in good condition and have enough force to clamp onto
the battery terminals and not fall off. The cable should be of
sufficient capacity to carry the amperage to operate the starter.
A good jumper or booster
cable set has a wire gauge (thickness) of 4, 6 or 8. Avoid
jumper/booster cables with higher gauge numbers (thinner wire). These
CAN work but are not recommended.
See Q & A below.
basics are quite simple if you take a minute to look under your hood
now and not have to find things when it dark and rainy outside. Open
the hood and locate your cars battery. The battery for most cars and
trucks is visible and easily found. A fairly large black box with 2
large cables attaching to either the top or the side. If your car is a
GM most likely the battery connections are located on the side of the
battery. The battery has 2 posts that the car’s cables attach to. The
positive is the largest of the two. Many times it has a red cover but not
always. The negative is smaller and may not have a cover at all. Some
late model cars have the battery located out of sight but provide a
positive post for jump starting when needed; it will have a red cover
over it and most likely will be labeled for jump starting.
jumper cable clamps are most
times colored black and red.
It is common
practice when jump starting the car to match the color of the jumper
cable clamp to the color of the battery terminal. Consider the black
cable to be the ground, or negative, and the red
cable to be the positive.
it to connect the cable clamps is a sequence that matches the polarity
and is safe for the person making the connections. Batteries produce an
explosive gas called hydrogen and if sparks are made close by an
explosion can occur spraying battery acid in the eyes of the people
The first thing is to bring the vehicle with the good
battery close enough that the jumper cables will reach. Open the hoods
of both vehicles and locate the batteries and which terminals are
which, look for a plus sign on the battery case (+), this is where you
connect the red
positive jumper cable. The negative battery terminal will have a minus
sign (-). Shut the engine off on the vehicle that is providing the jump
start, this will lessen the risk of damage to the electrical system
should the cable gets connected wrong.
out the cables on the ground stretching from one vehicle to the other.
While connecting cables, make sure the unconnected clamps are not touch
moving parts or a bare metal part. You
are going to match the colors, red to red, black to black.
- The first connections are the red clamps on each end of the cable to the
positive terminal each
vehicle’s battery. This first cable connection is safe to do as no
sparks will occur. Make sure the clamps are tightly on each terminal;
give them a little wiggle when connected to make sure they don’t fall
- Now the second cable connection. This is the important one and must be done
in this sequence only. Make the first connection of
the black cable to the negative terminal of the good battery while
holding the other black cable clamp in your other hand. The other end
of the cable must go to a heavy metal bracket or part of the engine block away from the battery and any
moving parts. This is important so as to not create a spark near the
battery. You may get a small spark when making the last connection as
power travels from the good battery to the car with the dead battery,
If you have left your lights on the headlights may go on now, if so
turn them off. If the jumper cables are of good quality and the battery
in the boosting vehicle is sufficient for your car, you can turn the
key and start your car immediately.
- When the engine is running
steady you may remove the jumper cable in reverse order, the clamp you
put on the metal bracket first, then the other end of the black cable.
Then remove the red cable.
If the engine does not crank
over and start as usual, but cranks over slowly or clicks, the cable
clamp connections may not be good; wiggle them. If that doesn’t do it,
then you must leave the cables connected and allow the running booster
vehicle to charge your battery. If your battery is in good shape this
may only take 5-10 minutes before you can try again. Even with very
cheap jumper cables, if you leave them connected long enough you should
be able to charge the battery sufficiently to start the engine.
A printer friendly version of this article is available here.
you get a large flash when you make the last connection you probably
have the polarity wrong and you need to recheck the battery connections.
you cannot get past a clicking but the engine won’t turn over, one of
the vehicles may have loose battery cables and is not transmitting the
current to the car’s system. You should not be able to twist the cable
connections by hand; if so tighten them. With the jumper cables connected temporarily turn on the
headlights of the vehicle with the dead battery to see if they light up
as usual. If you have good connections the headlights should be bright;
if not recheck the connections for tight.
- If you remove the cables and the car you just jump
started stalls soon after, you likely have a charging problem, that
will be why the battery went dead to begin with.
- If after doing all of the above and the engine will
not crank over you may have serious electrical problems or a bad
Q ) What color cable to connect first?
A ) Red cable first.
Q ) How long to leave the cables connected after the car is started?
A ) You can remove them immediately or you can leave the cables on as
long as you need to be sure it is running steady and not going to
stall, you won't damage anything.
Q ) How long do you leave the cables connected before you can start the
A ) If the cables are of good quality you can start the car immediately.
Q ) Why does it spark when I connect the jumper cable?
A ) You should only get a small spark, that is because the good battery
you connected is actually charging, or putting electricity into the
dead battery . If you get a large flash you have connected the cable
incorrectly and need to recheck your connections.
Q ) How long will it take for the dead battery to recharge after it has
been jump started?
A ) If the battery and the charging system is in good working order you
should be able to restart the engine after 30 minutes of running.
Q ) Can I leave the jumper cables on to charge the battery?
A ) Yes you can.
Q ) The jumper cables get very hot or smoke when I try to start the car
with the dead battery?
A ) 2 Possibilities here.
1) If it smokes when you try to start the car with the dead battery,
your jumper cables are too small a gauge (wire thickness) and
cannot handle the current. Heavier gauge cables is recommended, but you
can still jump start the car if you start the car providing the jump
and let it run for several minutes to charge the battery of the dead
2) If the cables start to smoke as soon as you connect them, the cables
are attached wrong. Remove them immediately and recheck the connections.
Q ) Can I jump start a car with just a battery sitting on the ground?
A ) Yes you can, just connect the cables to the battery like it was
installed in a car.
Q ) Can a car with a small battery jump start a car with a big battery?
A ) Yes it can, but it is best to leave the cables connected for
several minutes with the jumping car running to charge the battery in
the dead car before you try to start it.