If you can’t open your car with the remote, the engine won’t start, and no indicator lights are on, the battery is probably dead. In this case, jump starting with jumper cables can help. But be careful: mistakes can cause expensive damage to the electrical system.
Step by step to a running engine
- If the vehicle is on a busy road or in a blind spot, first put on a high-visibility vest and secure the accident site with a warning triangle.
- Check the operating instructions for the vehicle in question to see whether jump-starting is permitted or whether the battery needs to be replaced immediately. Vehicles with a start-stop system and some hybrid and electric cars are not suitable for this.
- As car batteries are particularly prone to failure in winter, check that the cable is sufficiently flexible, as the insulating material hardens in cold weather. In addition, the terminal clamps must be completely covered with plastic and only have bare metal at the tips to prevent short circuits.
- Drive the donor vehicle with the bonnet as close as possible – ideally directly in front – of the broken-down vehicle. Switch off the ignition of both vehicles to protect the electrical systems. Alternatively, a battery charger can be used.
- Now connect the red cable first to the positive terminal of the flat battery, then to the positive terminal of the fully charged battery. Then connect the black cable to the negative terminal of the donor battery. The other end of the black cable should be connected to the specified ground point on the broken-down vehicle (see operating instructions) or to an unpainted area on the engine block. Important: Do not connect to the negative terminal of the recipient battery – otherwise there is a risk of sparks!
- Once both cables are connected correctly, start the engine of the donor car. After a few minutes, try to start the broken-down vehicle. If this does not work, wait one minute and try again. After the third unsuccessful attempt at the latest, stop the jump start, switch off both vehicles and call for professional help, as further attempts to start the vehicle may cause damage. However, if the broken-down vehicle starts, leave both vehicles running for a few minutes. Switching on larger consumers such as the fan or lights in the recipient vehicle also helps to avoid voltage peaks and thus protects the on-board electronics.
Safe procedure after successful jump start
When removing the cables, proceed in reverse order:
- First disconnect the black cable from the broken-down vehicle, then from the donor vehicle. Then remove the red cable. The engines should continue to run during this time so that both batteries can recover from the jump start. There is also a risk that the broken-down vehicle will not start again after being switched off.
- Once the cables have been removed, the consumers that were previously switched on can be switched off again.
When continuing your journey, drive carefully and watch out for error messages. If problems occur, electronic assistance systems such as power steering may fail. The battery should now be fully recharged as soon as possible. This can be done either with a suitable charger connected to a domestic power socket or by driving for a longer period on roads that are as clear as possible, ideally country roads.
There are links to jump-start tips that can also be printed out as a PDF file. However, if you are unsure about how to jump-start your car, it is best to call a qualified mechanic. If the problem occurs again, the battery may be defective or too old and need to be replaced. In either case, calling the breakdown assistance hotline of an automobile club can help.