Can someone explain to me why they don’t recommend putting car jumper cables on the working battery black terminal to the dead battery black terminal but rather to an unpainted metal surface on the donor car?

Question

Also, how does electricity flow from one car to the other if there isn’t a loop?

In: 26

Answer 1

To answer the second question, you are putting the good battery and the dead battery in parallel using the jumper cables. This will cause 12 volts to appear across the terminals of the dead battery, and allow you to start the other car. (A charging current will also flow *through* the dead battery during this time, but the good battery can supply that no problem.)

Once the other car is running, it’s own alternator will put 12 volts across its dead battery, and hopefully charge it.