We’ve all been there… you left your headlights on, or the interior light on and your car battery is dead.
The two biggest causes of car batteries failing is either leaving your lights on or alternator failure. One of these will probably happen to you at some point in your life.
So you have to know how to jump start a car safely and properly, so that when/if you ever do run into a dead battery in your car you can get back on the road quickly. You don’t always want to have to call out your car breakdown cover, particularly when it is something you can do yourself. Continue reading to find out how!
Preparing your vehicle to jump start a car:
First, you’re going to need a set of jumper cables. They are pretty common, so even if you don’t have a set you should be able to find someone who does. They aren’t expensive, so it’s actually a good idea to pick some up just in case anyways.
Move both cars so that the batteries are close to each other. If you don’t know where your battery is then pop the hood. Make sure that both vehicles are off, and have the parking brake on… you don’t want any accidents.
Make sure that both cars don’t have any accessories running. This means headlights, A/C, heaters, fans, cell phone chargers, radios etc. When you jump start the car it may cause damage to these accessories by pushing too much current through the car’s electrical system… so it’s better to be safe than sorry.
Take a look at the batteries before jump starting. Make sure you know which side is positive (+) and which side is negative (-) before going further. The positive terminal is usually marked red and the the negative is usually black, but check the markings on the battery to make sure.
If your battery is damaged or is leaking… don’t jump start your car. You will need a new battery first, and if you try to jump start it anyways you may cause a lot more unwanted problems. Besides, a damaged battery is not going to hold a charge anyways.
Make sure there isn’t any corrosion on the battery terminals. The terminals themselves won’t hurt you, so you can clean them off with a rag or a brush if you have one.
Time to learn how to jump start a car
Step 1: Connect one of the positive (+) ends of the jumper cables to the positive (+) terminal of the DEAD battery.
Step 2: Connect the other positive (+) end of the jumper cables to the positive (+) terminal of the GOOD battery.
Step 3: Connect one of the negative (-) ends of the jumper cables to the negative (-) terminal of the GOOD battery.
Step 4: Connect the other end of the negative (-) jumper cable to any non-painted metal part of the engine block on the DEAD battery’s car. Why not put it on the negative terminal of the dead battery? Because this could cause an explosion… and explosions are bad.
If you jump start your car by connecting the jumper cables in this order you minimize the chance of the cables sparking and is the safest way to jump start your car.
How do you know if you’ve connected everything right? The dome light in the car with the dead battery should come on when the circuit is complete (all the cables are attached). If the dome light doesn’t come on then you probably either have something connected incorrectly, or your jumper cables are toast.
OK now to jump start the car
Run the car with the good battery for a few minutes and then turn it off. That’s right, turn it off.
Why? Because if you jump start a car with the good battery’s car running, you may actually burn out the alternator on the good car because of too much current being drawn from the electrical system.
So turn off the good car’s engine, and try to crank the car with the dead battery. Most times this will be enough and your car should start.
If that doesn’t work, then you have to start up the good car’s engine. Bring the RPMs just above idle (push the gas pedal just a little bit) to increase the current flow from the alternator. Then try to crank over the bad battery’s car once again.
It can take a few minutes to jump start a car sometimes, so be patient. If you’ve done the previous steps correctly you should have your car running quickly. If you still can’t get enough juice to start the car, try moving the negative (-) cable that is attached to your engine block to the negative (-) terminal on the battery. This should be your last resort, but it may just give you the extra boost you need.
Now to take off the jumper cables
After you’ve jump started your car you need to safely remove the jumper cables off of the batteries.
Disconnect the negative (-) cable from the exposed metal on the engine block first.
Then disconnect the other negative cable from the good car.
Then both of the positive cables.
So you’ve just learned how to jump start a car. As I mentioned above, it’s always a good idea to have a good set of jumper cables in your car/truck in case you have to jump start it. They aren’t expensive and they can really save your butt from time to time.
What if you don’t have jumper cables or can’t find another vehicle to help you?
This one can be tricky. After all, what happens when your battery is dead and you’re not near any other vehicles to help you out? Even worse, what if you’re stuck this way in the winter?
If you have a standard transmission (aka stick shift) then you’re in luck because you can jump start your car without jumper cables using your clutch.
Jumper cables in your trunk are pretty standard emergency equipment, but you may also want to consider investing in a jump starter for your car.
A jump starter will be able to successfully jump start your car without jumper cables. Essentially it’s a battery pack attached to one half set of jumper cables. You hook up your jump starter, flip a switch and hopefully there is enough juice to jump your car.
Be sure to read our reviews of jump starters however, as you don’t want to get stuck with a jump starter that doesn’t have the umph to jump your car. You can check out reviews and get a pretty damn good deal on jump starters over at amazon.com here.
Leave us a comment below about jump starting a car, or even a horror story… I’ve sure got a few, but that’s a different post.
Is there a risk of damaging the computers in either auto, while jump starting one of the autos
Hi Leo,
It’s definitely possible to damage the electronics in the car. If there is a power surge you can even do damage to the computer that doesn’t show up until later. However, if you’re careful to make sure you don’t get any sparks.
Also, after you’ve jumped the car, you can leave both engines running for about 5 minutes, turn both engines off, and then remove the cables in the reverse order that you connected them. This process prevents disconnecting two batteries that have different voltages which is really what causes most electronic problems.
I hope this helps!
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I found some other important tips on boosting the battery http://howtohacklife101.blogspot.com/2011/05/how-to-jump-start-car.html
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Thanks a ton for posting this, I found it very informative, and it clarified the majority of the concerns I had.
It was suggested that, while yes a jump can fry a computer in a car, that while the article says to turn headlights off, TURN THEM ON, before you connect the Jump leads, on both the host vehicle, and the recipient. Because Electricity takes the path of LEAST resistance, Any surge through the car would *FIRST* go through the headlights, as they are on, and the ECU is spared a nasty shock.
Headlights will take more punishment than the ECU, and are usually easier and cheaper to replace if they POP !.
Is there any risk to either car’s electrical system if I try to jump start a car with a cable that plugs into the cigarette lighter socket of both vehicles? I think I posted this question once before but I don’t see any response so perhaps I didn’t submit it correctly. I hope that you can help me.
@Kathy I believe the lighter socket jump starters only work in certain situations because they slowly return power to your battery. If you have a dead battery then this type of jump starter won’t work.
I’d recommend checking out our jump starter reviews for a look at a jump starter that can rescue you in almost any situation.
Thanks!
Where do you attach the negative cable of the dead cars battery if the dead cars battery is in the trunk?
Thank you so much. Step by step directions. You are a lifesaver!