Battery draining overnight

My favorite way to troubleshoot battery drains is to use a small bulb like a dash light. Get one with leads. Unhook your positive battery cable and put one wire on the unhooked battery cable and the other one to the positive battery post.

If you have a drain, the battery will light up. Unhook stuff till the light goes out.
I tried this when my alternator was hooked up and it was glowing bright. When I disconnected the alt, it went out completely