My battery will drain overnight unless it's unplugged, what could be the problem

Sounds like you have whats called "parasitic draw" This is a fancy name for something staying on when everything should be off.Unless you have a firm grasp of electrical knowledge - your going to need a good Tech. You can check the basics like phone chargers and dome lights staying on. Make sure all your fuses are good too. But I have a feeling you'll be looking for a short somewhere. Good luck

copy and paste the link,watch the video...................................................................................... How to Test and Find a Parasitic Battery Drain … www.youtube.com/watch?v=zdIKNnwEjIs