I will try to explain the procedure needed to start a car with jumper cables. The process is not that simple as it looks on the first sight. There are a few things you need to consider. If you follow this protocol, everything should go as planned.
First check if the car does not start because of the battery. If the engine cranks when you turn the key, the problem is not the battery and jump-starting will not do any good. If you determine that the battery is the problem then you will need another car with good batteries and jumper cables. Here is how the procedure goes.
Turn of the engine of the booster car. That is the car with good batteries that we will use to start the car with the empty battery. On the car that you are trying to jump-start you must turn of all the electrical equipment and turn the switch for engine starting off. Connect positive terminal (+) of both batteries with one of the jumper cables. For the positive terminal, or the plus terminal, use the red jumper cable. The positive terminal is usually slightly bigger than the negative. Never connect the batteries when the booster car is running.
Then put one end of the jumper cable (black) on the negative terminal (-) of the booster cars battery. Connect the other end of the black cable to an metal part of the other cars engine. If you cannot connect to a metal part, put it to the negative terminal of the other battery (-). You should do this only if there is no other way.
You must also make sure that jumper cables do not touch any moving parts of the engine. If you have completed all these steps, then you can start the engine of the booster car. You should then rev the engine. Now you can try to start the engine of the other car. If you are not successful after about 15 seconds, you must wait at least a minute before trying again. When you have successfully started the other cars engine, you should leave both running for 2-3 minutes. Before you disconnect the cables from the other car you should turn the heating of the rear window on. This will prevent high current jumps. After that, you can disconnect the jumper cables in reverse order of attachment: negative, negative, positive, positive.
Starting the engine with jumper cables should be used only when there is no other option. Make sure you follow the correct procedure when starting the car. If you do not, big voltage jumps can occur. These jumps can damage cars electronics.