The lemon battery has a rich history in many elementary science classes as a great example of an electrochemical reaction.
This is not magic, or a hoax.
The nail and penny create charged poles in the fruit.
Unfortunately, filling a car with a bushel of lemons and driving cross country in an eco-friendly glow of citrus is a pipe dream.
The lemon battery is not strong enough to power a light bulb.
Nonetheless, enjoy the miracle of nature coupled with the ingenuity of man.