https://www.youtube.com/watch?v=vYtyDX9RTWs
My 2009 370Z after the alternator crapped out, I have replaced it twice and battery twice. The problem persisted, after doing some research it turns out that the PCM (Power Control Module) gets confused about where the throttle valve positioning should be. Also the PCM controls the alternator and tell it when to and not to charge the battery. Most of the computers on the Z have capacitors, they store energy to keep the processors energized with small amounts of energy so they do not loose their memory. I searched YOUTUBE and found this video on how to give your Z and many other cars an enema. Accomplishing this video to the letter fixed my Z. The link above takes you directly the the video. Once you accomplish this and restart your car all the computers reset themselves and you will see the voltage drop and come back up at least once if not twice while the car re-calibrates itself. If by chance the link does not work the title to the video is : How To Reboot Your Car ~ Battery VooDoo.