Something is draining the battery?

It sounds like the BCM is not shutting down which common when it goes bad, but I need to ask was there a CAN scan done? You can get a CAN scanner (Controller Area Network) from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Also, with that big of a drain there with be heat, with the engine cold place your hand on the alternator when the battery is fully charged to see if it is warm, if so, you have found the problem because the alternator has an internal short.

Here is a guide to help you to see what's going on:

https://www.2carpros.com/articles/car-battery-dead-overnight

Here is how to replace the alternator in case you need it. I have also seen the instrument cluster short out and cause this issue as well. Check out the images (below). Please let us know what you find. We are interested to see what it is.