It seems like one of two things:
1. You have a loose Wire somewhere. When you floor it, the Engine moves a little more than usual and a wire may be disconnecting from the Alternator. Check all the Plugs at the Alternator and Grounds and make sure they are tight. Make sure that the Grounds are not white. If loose, then fix the problem. It Ground has white stuff on it, unscrew and clean it then put it back.
2. Your alternator may be going bad. If all the wiring is secure, then take your alternator in for a checkup.
Patel