How To Connect Jumper Cables Properly

As a driver, one of the more common problems that you will need to learn how to troubleshoot is a dead battery. This is usually a common occurrence during wintertime or near summertime, when the weather brings in a sudden drop or increase in temperatures. Or, you might have left an accessory turned on, such as your dome lamp or headlamps. A discharged battery will make it difficult or even impossible to start the car.

In these events, a manual or standard  transmission vehicle has an advantage, because you can push start them and the motor will turn over with the right combination of speed and gear. However, automatic vehicles use a torque converter to transfer power from the engine to the wheels, and you cannot use push-starting to get the motor running.

It’s important to learn how to properly use and connect jumper cables. Otherwise, improper use might result in explosions. Or, you can even damage your car’s onboard computer.

For this instructional, we will refer to the car with the good battery as car #1, and the car with the flat battery as car #2.

  • Drive car #1 as close to car #2 as possible, such as their front bumpers are near each other. However, make sure that the cars don’t touch in any way, as this might cause a short-circuit.
  • Turn off car #1’s engine. Set both to Park. Or if either is a manual transmission car, set them to neutral. Turn off all accessories on car #1.
  • Switch on the air conditioning or heater on car #2. This will help minimize or absorb any shock that a surge in power will bring to car #2’s electrical system.
  • If car #2’s battery is not the no-maintenance type, open the vent caps and cover them with a clean cloth. You might want to refill the battery with distilled water later on.
  • Connect the red terminals first. Use the red jumper cable. Clamp the one on the dead battery first, and then the red terminal on the good battery.
  • Next, connect the negative terminals. First connect the black cable on any unpainted metal surface on car #2’s engine bay. This will act as ground. Connect the other end to the negative terminal on the good battery.
  • Make a visual inspection of the cables, making sure these are not loose in any way.
  • Start the engine on car #1. Lightly step on the gas to increase RPM to about 1,500. This way, the alternator will be charging the battery and giving enough voltage to charge car #2’s battery momentarily.
  • Start car #2’s engine. As soon as the engine starts, turn off the A/C or heater.
  • Let both engines run for about five minutes, to give the dead battery enough charge.
  • Disconnect jumper cables. First disconnect the black terminal on car #1, then the ground on car #2. Then disconnect the red terminal on car #2 and then the red terminal on car #1.

Note that car #2 will probably not start or the engine would sputter out if the battery is totally dead. Jumpstarting will only work if there is even a little bit of charge capacity left on the battery. Also, frozen batteries are likely to explode when you try to jumpstart the car. For your safety, wear goggles and gloves when working on your car’s electrical system.


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