Thanks for submitting us your great question!

The simplest way to think about the way a car cell phone charger works is to imagine the charger as a wire that connects your car battery to your cell phone, allowing electrochemical energy to be transferred from your car battery to your cell phone battery. This process is easily accomplished by simply connecting the two batteries, because the battery in a car is a higher voltage power source (~12 V) than a cell phone battery (~ 3 - 4 V). This means that the electrochemical energy is flowing from a higher energy state to a lower energy state (you can visualize this by imagining electrons flowing down an "energy hill" with the car battery at the top and cell phone battery at the bottom).

Certainly there are additional aspects associated with this process, such as the fact that the cell phone charger has to have internal circuitry that "steps down" the car battery voltage from 12 V to the appropriate voltage required by the specific cell phone battery you would like to charge (this is why cell phone chargers are rarely universal). Also, the exact way that batteries generate and store the electrochemical energy that is being transferred is quite a complex process, but I think that the following webpage gives a great introduction to these concepts:

I hope that this answers your question, and please feel free to send us any additional questions that you think of. Have a nice day!