More on my dead battery in my "04" Bonneville GXP .
Every thing is leading to the Alternator regulator being bad ( I think it never shuts off) also the voltage runs at 15.64 volts with a average load .
So is there a easy to change the alternator ? It looks like the radiator and the fan group needs to removed

I have replaced the battery with a new tested good one ,Replaced the Alt.
All battery connections are clean and tight .
There are no ather things hooked up (radar det, cell phone chargers or GPS).
All this work was completed last Friday night ,The car started Sat but was dead on Monday morning!It'* been cold but not that cold.

Try pulling some fuses at night, then put them back in the morning. If the car is not dead then you have narrowed down where the problem is. I would try the ELC first.

I had a similar experience many years ago. Come to find out I had a trunk light switch that was defective and the bulb stayed on when the trunk was closed. It'* amazing how much just a little ole light bulb can pull down a battery.

pull fuse 15 right side under dash, is for int lights and pwr ant, door locks

This is a GXP Model and does not have fuses under the dash. And an old thread. I believe the owner has it fixed now.