Looks like all my problems started the day I installed an aftermarket radio. I bought the wire harness adapter so I would not butcher the cars harness. I also installed a factory amp bypass jumper. Radio worked just fine. A few days later I began having the dead battery issue. I would charge it and overnight it dropped below the threshold of starting the car. Not dead, just very weak.
I just spent several hours in front of my computer gleaning tips from others on what to check. Here is what I have done so far:

New battery (less than a month old) First few days, no problem. After that problem came back.

Had alternator and battery tested. Good output, good cells.

Removed aftermarket radio and reinstalled the OEM head unit. Removed the amp jumper and reconnected. Result is the same. Drained overnight.

Checked battery terminals by removing the rubber from the ring and cleaning both sides of the terminal ring. They were fairly clean to begin with but I made them shiny. I used new terminal bolts. Both terminals are tight and secure. Problem continues.

Yesterday I removed the factory radio and amp. I charged the battery with an external charger for four hours. The car started fine. I shut it off then disconnected the power output terminal from the alternator. This morning the car still has a strong charge. Does this mean my alternator is defective? I am a decent mechanic with many years under my belt but this is my first "fancy" car. By that I mean this is the first car I have ever owned with a BCM. Everything else I own is 1988 or older.

If anyone with knowledge will respond I would greatly appreciate it.
Thanks, Mike Myrick

 

Update..........
Just to make sure about the alternator I reconnected it yesterday about 6:00 PM. This morning at 11:00 AM It started perfectly. I just don't know WTF is going on. Perhaps removing the alternator cable reset something on the BCM? I have eliminated the possibility of bad connections, bad cables, bad battery. I suppose if the problem comes back the next step I'll take will be to remove the alternator and have it tested at a parts store. After that I suppose the only thing left would be the BCM?