He never gets powers.
hmmm, looks to be the entire point of the books and movie.
http://en.wikipedia.org/wiki/Percy_Jackson_%28character%29Powers/Abilities
* Percy possesses incredible physical strength. He tore a horn off the head of the Minotaur, and was able to bear the weight of the sky, the curse of Atlas.
* Percy has clairvoyant dreams, causing him to watch events in distant locations as an out-of-body experience. This could be the work of Apollo, the God of Prophecy, because he told Percy, "How important dreams could be."
* Percy has a psychic connection with his friend Grover called an empathy link.
* In The Last Olympian, Percy bathes in the River Styx (like Achilles), making him nearly invulnerable except in one weak point (the small of his back) and also granting him increased skill, strength, and puts him into a frenzy in battle.