Home generalConnect jumper cables correctly to the car battery - that's how it works

Connect jumper cables correctly to the car battery - that's how it works

  • preparation
  • Connect jumper cable
  • Use jump aid

Does not jump the car, it may sometimes need some jump start. What you should consider in the jump-start and how to properly connect a jumper cable to the car battery, you will learn in this guide.

Although our cars are becoming ever more reliable, it is not unusual for a car to break down at an unfavorable time: an empty starter battery is still cause number one - according to the Auto Club Europa (ACE), around 28% of all vehicle breakdowns were due to a drained power storage system.

Especially in winter, the difficulty lies in the fact that the cold additionally reduces the capacity of an already aged battery. In addition, the engine oil is viscous in the cold, so the starter must overcome a greater resistance. As a result, it often happens that the car does not even start. The longer the vehicle has not been moved, the higher the risk of an empty car battery; unlike a modern lithium-ion battery in a smartphone, the self-discharge of a car battery is not to be underestimated. Even modern vehicles can be moved to jump start with a jump lead. However, car owners must pay attention to some hints so that the sensitive electronics are not damaged.


For the so-called foreign start a vehicle with an empty starter battery no tool is required.

You need this:

  • Booster cables
  • another vehicle with an intact battery

Or alternatively:

  • Jump Start Device

Tip: The connections of many car batteries become dirty or oxidize over the years. This creates contact resistances, which reduce the voltage and make starting even more difficult. Using a cloth or a wire brush (oxide layer), the poles of the battery should be cleaned for preparation.

Connect jumper cable

First, the jump-start in the conventional variant with the "donor car" is described, which has a functioning, charged car battery.

Step 1: If electric appliances are still switched on in the vehicle that is not ready to drive, they should now be switched off.

Step 2: The starter battery is visible in almost all vehicles in the engine compartment. Before the actual jump start, you must first find the car battery.

Step 3: Drive the second vehicle close to your car so that the length of the jumper cables is sufficient in any case.

Step 4: Connect the positive terminals of the car batteries of both vehicles with each other through the red cable.

5th step: Connect the black cable to the negative pole of the battery of the second, still running car. The other side of the cable should never be connected to the negative pole of the battery of the vehicle to be started - here, explosive gases may have formed. Better: Clamp the cable to the engine block or another bright metal in the engine compartment (ground point).

Step 6: Start the engine of the still running vehicle. This also increases the voltage applied to the car battery, which simplifies the jump start.

Step 7: Try to start the engine of the vehicle that needs the jump start. If the attempt to start is unsuccessful, wait at least 10 seconds to retry.

Step 8: When the car has started, the engine has to run for a while to charge the battery. The jumper cables are removed in reverse order, starting with the black cable.

Use jump aid

The jump start device is a large battery to which a jumper cable is already connected. The practical device replaces the second vehicle and an external jumper cable.

To start your car with the Jump Start device:

Step 1: Just as when starting with a second vehicle, all electrical consumers must first be switched off so as not to burden the car battery additionally.

Step 2: Locate the vehicle battery. In almost all cars, the starter battery is located in the engine compartment, less often in the bottom of the trunk or under the back seat. In case of doubt, the operating instructions provide information.

Step 3: Then attach the red positive cable to the positive pole of the battery.

Step 4: Then clamp the black negative cable to a bare metal in the engine compartment to ensure ground contact.

Step 5: Many jumpers have different voltage ranges. Here you have to set 12 V, only some classic cars have a 6 V on-board voltage.

Step 6: Now press the starter. If the vehicle does not start, wait at least 10 seconds before trying again. During this time, the car battery can recover a bit.

Step 7: If the car has been started successfully, switch off the start aid. The clamps are removed in reverse order starting with the black clamp. The engine should be run for a while to allow the low battery to charge a little.

If the jump start attempt is successful, you should clarify what was causing the glitch. With a service life of several weeks, it is quite due to the usual discharge of the battery that not enough energy was available for starting. With a shorter service life, however, it is advisable to have the starter battery or, if necessary, the charging system of the vehicle checked. In a specialist workshop, the remaining capacity of the battery can be determined, also charge controller and generator can be tested. This short check prevents you from having to start again soon.

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