Is it truly possible to charge an iPhone with a watermelon?

I need to write a paragraph for my Science class about exactly how an iPhone is charged with an iPhone. My teacher explained that once you add salt to the watermelon it makes an electric current. How does the salt charge an ice water soaked watermelon electrically? Is it even possible?

Making a battery out of a fruit is a real thing. Inserting one piece of zinc and one piece of copper into a lemon (for example) creates an electric current. Nails are typically zinc-coated, and coins like a 1p or 2p contain copper, so work as electrodes.

The fruit is not being 'charged' by anything. It is providing an electrolyte in the form of an acid (usually citric) and is firm enough to support the two electrodes. You are simply converting the energy stored in the lemon, the same energy something would obtain from eating the fruit.

I haven't seen a watermelon variant but the saltwater sounds like the electrolyte, which means you could get an electric current from a watermelon too. However in practice you may need thousands of watermelons to charge an iPhone, you couldn't do it with just one (wikipedia estimates over 6 million lemons to start a car).

Each fruit battery produces a finite voltage and current. You would have to place the fruit batteries in series to add up to the proper charging voltage for the iPhone, and then have several banks of these series connected fruit batteries tied in parallel to provide enough current to charge the phone. Theoretically it would work but it would not be to practical. I once used a fruit battery in a class to demonstrate this using an orange and it barely had enough power to light a small LED.