So to start this off I just joined to ask my question after lurking about reading the forums for quite some time trying to resolve my issue. I have an 05 Cayenne, purchased it dirt cheap because of an "electrical drain". Long story short, the electrical drain was no drain, just a bad alternator. I replaced the alternator and figured I was good to go. While I was at it I replaced the battery with a brand new one. All was well until I drove it around for 10 minutes, and then turned it off. I came back out a few minutes later to show my wife that my "investment" was a good one. I turned it back on, start driving and then I get the Battery/Generator failure message on the dash. Now feeling defeated I installed a Bluetooth OBD reader so I could monitor the voltage while driving and let it sit overnight. Started up great the next day and is charging at 14.1v, no warning on the dash. Drove the car around for a while monitoring the voltage and it never changed. Get back home, turn it off, turn it back on and I am immediately at 11.8v not charging at all, but the voltage isn't decreasing either, I drove it around for about 10 minutes and still no decrease in voltage but definitely not charging, just maintaining. I drive back home, turn it off, wait about 30 minutes, go out start it and magically it's working great again, 14.1v, and no warnings. I only get the message after driving it for essentially any amount of time turning it off and then restarting again shortly thereafter. It almost seems like as soon as something is getting warm it needs to cool down before it starts actually charging again. I have tried everything I can think of trying to figure out what is causing the issue from turning the key waiting a moment and then starting, to turning off every accessory before starting but I have come up short. The other thing I have determined is that if I start it and the heater/AC fan motor doesn't turn on that it is going to give me the battery/generator warning. Does anyone at all have any ideas as to what the heck is going on and what I can try to figure it out? Thank you in advance!