It happened even to the best of us, you leave headlights on all night, or your battery drained for some reason, and you need to jump a car. You never know when you need the know how to jumpstart a car. Be careful of what you hear from random “mechanics”, especially at oil change service. Not that the process is complicated, but for the mechanic illiterate there are some nuances in the process. Doing them correctly might save you hundreds of dollars.
Let’s go through the correct instructions, and I will show how to jump a car in 10 simple steps safely.
1. The first step is to take a car that runs and pull it up to the car with the dead battery, so the jumper cables could reach both batteries. You want to make sure both cars are separated and don’t touch each other. Remember to make sure vehicles are in the park position. You don’t want to risk the car being in the run position. You have to take the keys out of the ignition to protect your vehicles electrical components. For each of your vehicles, you want to find a battery and find with the positive and negative leads.
Check if either of the cars has a positive ground. Many older cars were built to be positive ground, later for a variety of reasons many of those cars were converted to negative ground. It’s important to know which way your car is wired. The easiest and the most accurate way to tell is to look at your battery terminals and cables. Usually, red cable is connected to the positive terminal, black cable is connected to the negative. If negative cable goes to the frame of the car, this is a negative ground car.
2. Now take jumper cables and spread them out. You have one red and one black in each hand. Look at the battery itself, look for a “+” sign near the positive post and a “-” near the negative. Don’t just look at the cable colors!
I would highly recommend getting a good pair of jumper cables, or you could run the risk of shorts. Buy ones that are rated for the size of vehicle/battery you will be jumping. If you have a big motor or you have cold winters, a copper core cable is much better than an aluminum wire. Expect to pay $35-50 for high-quality jumper cables. Some cables are really cheap and often require a lot of “play” to achieve a nice clean connection. Also, use non-zap type jumper leads on EFI cars with an engine management computer, they are designed to prevent the excess voltage from damaging your EMC, it could be a costly repair job if you damage it.
Note that it can be dangerous if the rubber part is missing from one of the handles because it can spark if the metal is exposed and it touches other metal.
3. For a jump to work, it really helps to have good connections. The better the connection, the faster the other vehicle can jump your car. So, one can first make sure the battery terminals on the “dead” battery are clean and tight as bad connections cause the wires to overheat.
If battery poles are filthy, you should remove the corrosion and use dielectric grease to prevent it in the future. I use battery terminal protector pads on all my cars. It’s easy and cheap. It prevents corrosion on the battery post and terminals that cause a bad electrical connection. You can find Battery Protectors at Amazon (affiliate link). Brush-On Oil Based Battery Corrosion Preventative also works well. Also, it is good to clean the battery surfaces of dirt and debris as they can increase parasitic drain.
4. It is safe we start with the “dead” battery car because it’s battery doesn’t have much energy as the good battery. From this point forward we don’t want the jumper cable ends to touch each other.
Take one side of the jumper cable, attach the red positive end to the positive side of the “dead” battery. Make sure you have a good connection right on the battery post. Copper pieces should touch the metal parts of the post. You can wiggle around the connectors to remove rust.
Turn off everything electrical on the dead battery car. Radio, AC/heater, interior light, wipers, etc. It gives the best chance as nothing else is putting a load on the system when you try and start it up.
However, you can switch on the headlights on the “dead” battery car to absorb the sudden surge of electricity that can damage other electronic modules. Also, it would be a good connection test, the brightness of the headlights will tell you if the connection is good or not. If the lights are nice and bright, you know the connection is solid. If you are jumpstarting a car in the rain, keep the connections dry.
Take your ground (black cable end) and just put it on a piece of plastic. You don’t want your ground cable touching any bare metal. Plus then you’ll be grounding it out. You just can leave it there for now.
5. Now go to the good battery, grab both leads as you did before. Don’t touch them together. Take the red one and put it to the positive terminal, take the negative lead and put it onto the negative side of the good battery.
6. Now back to the bad battery – there is the last lead we need to attach. Don’t attach it to the negative battery terminal!
I suggested you read on your car manual to find the ground spot under the “jump start” section where the manual tells you to connect your leads.
In practice, there can be issues like the jumper cables not having enough room for the negative end to reach a good ground rather far apart from the battery. In effect, the ground can be any bare metal part on the car that isn’t a moving part and isn’t attached to an electrical component. Any large metal piece that isn’t painted. Frame bolts, engine parts, etc. can be an extension of your negative battery terminal.
While connecting directly to the negative terminal works fine electrically (and will actually allow the best current flow, as you don’t have the resistivity of all the metal between there and a remote point on the vehicle), it’s bad from a safety perspective. When you make the last connection, there is likely to be a spark due to the difference in voltage between the dead battery and the good battery (which is also being charged by the alternator) in the other vehicle. Lead Acid Batteries produce hydrogen gas when they are charging. Some of the gas could potentially build up under the caps, and if there was a stray spark explode the battery propelling acid all over you. This is why it is proper to use an engine ground instead of the battery negative. Other than causing an explosion, the mighty outcome is actual hard damage of the ECM on modern vehicles.
For safety reasons, there should not be naked flames while jump-starting a car, i.e., cigarettes, liquid burning lanterns, etc., which could ignite gasses from the battery or other flammable parts of the vehicle.
Choose the ground spot and clamp the negative end on that. Make sure you have a good connection.
Inspect to make sure your cables are not near cooling fins, and serpentine belt is on the other side.
7. Then start the donor car and let it run for 2 minutes.
8. Then start the engine of the bad battery car.
9. You want to remove the jumper cables as fast as you can after you turn on your car with the dead battery because it can mess up the alternator.
Before disconnecting the leads is a good thing to switch on several heavy current users such as a blower, rear window heating, etc.; otherwise, the voltage regulator of the dynamo will take a heavy hit suddenly. The portable devices have a kind of dummy load, but you really need to do that on a car to car.
Recommended order for removing the cables:
It should be dead battery’s negative first. Don’t let it touch anything.
Then dead battery’s positive. Make sure jumper leads don’t touch each other.
Then support car’s positive and then support car’s black cable.
It is better to do this job with two people – one hand for each clamp will keep them all wholly separated while disconnecting: two people, four hands, four clamps, zero percent chance of arcing.
If you accidentally let them touch and spark, the donor cars engine will stop and need to be restarted. That short-circuiting also could cause damage to the electronic car systems sensitive to voltage changes.
10. You need to drive the car around for about a half hour or so to make sure the formerly dead battery is charged up again. The battery doesn’t get a full charge with a jump. Your starter uses the juice from the good battery. Once it’s running the alternator charges the bad battery.
Scenario when you turn the key, it just clicks, but the car won’t start, or there is no any clicking noise, can mean a few things. One, your battery is really dead, two, you need a new starter, three, you blew a fuse. Before you give up, make sure you have a good connection on both the positive and the negative terminals on bad and good batteries. As for me, I use a meter to see if I have a good connection. Try connecting your ground to a better spot. A lot of times switching to another ground will start the car. Also, I would check the fuses because usually, they blow out before any damage occurs.
If your battery is nearly dead, there is a quick and simple battery recondition resource that easily brings batteries to life again. It can save your bank account just by reusing your old car battery. For more info on battery recondition, check out our short video review clicking here.
Good advice is using one of the portable car jump starters. It’s great to have it in your car in case of an emergency. You don’t need another vehicle to help you jump-start your car. You can do it yourself. They are really easy to use. The bigger the car, the more power it needs to be jump started. 600 amps should start most cars. But never jump a 12v battery with a different voltage battery though. That could damage it. The same principle applies for a 24v system – you’ll need a 24v booster pack.
Batteries last for 4 years in an average. If you have doubts about your battery health, I would recommend to take the battery out and test it in your local parts store for free. If the alternator and battery are working fine, then once you jump started the car, it will last a long time.