Vacilo in this context means a
Have you ever made a call you knew you probably shouldn't? In "2%", the singer does just that, making a desperate call with only 2% battery left. He knows the odds are stacked against him, admitting there's a 98% chance the person on the other end will say no. Filled with regret for letting someone go, he's having a terrible night, even punching walls in frustration.
He worries he's being annoying and interrupting a much better evening, but he can't help himself. His message is a last-ditch effort fueled by saudade, a deep feeling of longing. Even if his phone dies, he hopes the call makes the other person's heart race and reminds them: "You know where to find me."