Battery draining overnight

Only when the engine is off.
Understanding this^^^ will be key to setting up trouble free circuitry.

Depending on how/when the fans will be running, may want to connect their power wire to a terminal stud from the alternator output.*
What I should’ve said is that the fans are connected to the large stud on the starter relay (this is where my alternator wire goes) and will only turn on when the key is to the on position and engine is up to 185. So as you have taught me, they draw from the alternator.