How to Jump Start a Car the Proper and Safe Way

Posted Tuesday, Nov 20, 2018

So, you climbed into your vehicle and turned the key, but it didn’t start. Now what? Commonly, this condition is caused by a dead battery, but how do you know if that is the problem? First, notice if the dome light illuminates when you enter the vehicle- if it does but appears dim, you have a weak battery. If the engine turns over slowly or you simply hear a clicking sound when you attempt to start the engine, you have a weak/dead battery. If the dome light shines brightly and the engine turns over rapidly, unfortunately, you have some other issue. However, for the sake of this post we’ll assume that you have discovered your battery is the issue. The easiest way to deal with this situation is jump start the car. Hopefully, you carry your own jumper cables in your trunk, but if you do not have any, you’ll have to find someone who does. Once you’ve procured a set of cables it’s time to follow these steps:

jump start1. Find the batteries. Locate the placement of the batteries in each vehicle (the one with the dead battery and the one to be used as the jumper). It’s important to do so because different vehicles have the batteries in different locations. In this way, you can position the jumper car close to the dead car in such a way that you can easily span the distance from battery to battery with the jumper cables.

2. Position the vehicles. Pull the jumper car within 18”- 24” of the dead car so that there is easy access to both batteries, but don’t let the two vehicles touch; then, turn off the engine. In most cases, the cables will reach fine if you face the the two cars towards each other with an 18” gap between them.

3. Safety. Now it’s time to connect the cables, but beforehand, we need to discuss safety. You should wear gloves and wear eye protection when jumping a vehicle. Car batteries have been known, though rarely, to explode when being jumped, and they contain sulfuric acid, which is caustic and can cause injury to skin and eyes. Also, it’s important that you connect the cables in the order described below. Since batteries contain acid (a solution with a certain concentration of hydrogen), they sometimes emit hydrogen gas, which is highly combustible. An ill-placed spark could ignite this invisible cloud and cause an explosion; hence, controlling the position of any sparks is critical. As you read the order of cable connection below, you’ll see that it minimizes the chance of ignition.

4. Connect the cables. As you connect the cables to the batteries, they will eventually become live, so it’s important to keep the cable clamps from contacting one another as you are positioning the cables. This is most easily accomplished by laying the cables on the ground between the two cars while ensuring the four cable clamps are separated. Connect one red cable clamp to the positive post of the dead battery, which will be marked (+) on the battery. Incidentally, it is often coded red in some fashion to match the red cable clamp. Make sure the corresponding black clamp is not touching anything metal on the dead car. Now, connect the other red clamp to the positive (+) post on the jumper battery. Attach the corresponding black cable clamp to the negative post, marked (−) on the battery, of the jumper battery. Now we come to the last clamp to be attached. Since this will close the circuit, this will be the connection that will cause a spark. Knowing that batteries sometimes release combustible hydrogen gas, we want this spark to occur away from the battery somewhere. Hence, you shouldn’t attach the last black clamp to the negative post (−) of the dead battery. Instead, attach it to an unpainted metal part of the car away from the battery, i.e., a nut or bolt connected to the frame or engine block. See the picture from below for an example.

5. Start the jumper. With the two vehicles’ batteries connected, start the engine of the jumper car. Depending on how dead the other battery is, you may need to let the jumper run from a couple of minutes to 15 minutes.

6. Start the dead car. After a few minutes of “charging” the dead battery, it’s time to attempt starting the dead car. If it turns over slowly, allow it to charge a bit longer and try again. If it starts, remove the cable clamps in the reverse order. In this way, you’ll have created a spark with the clamp attached to the nut or bolt away from the battery and will have opened the circuit; there should be no other sparks. Do not turn off the once dead car; let it run for at least 20 minutes. My recommendation is to use those 20 minutes to drive it to an auto parts store. Most will test your battery for free. In this way, you’ll know if your battery had been accidentally drained (by leaving on the dome light, for example) or if it needs to be replaced.

7. Thanks. At this point, you should thank the person who assisted you. Let’s give hospitality a jump start.

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