Alternator charging the battery and the battery drain are two issues, IMO. There are posts with suggested procedures to seek out the source of the battery drain. Essentially, you take the fuse out of the fuse box, one by one, until you identify the source of the problem. A multi-meter is quite cheap. I just bought one for under $20. With a quick search, you should be able to find posts from people who have already gone through this process. Alternatively, you can ask a dealership to diagnose. It will take a minimum of one hour, likely many more, to do a good job so that will be $$ expensive.

The drain could come from any module but again, the navigation system is a common source. Perhaps you can start from there first.

Good luck.