I have a 2016 Buick Enclave that the battery has a current draw that kills the battery in a few hrs. I can pull the ( battery #3 fuse ) and it won't drain but I cant find any information on what that fuse controls, any ideas?
A little embarrassing having to lift the hood and pull a fuse all the time.

As a 2016 it should still be under warranty. Possibly give a call to your local GM dealer, & talk to a service advisor, they will probably know more about BAT 3 fuse & circuitry.
Has any additional aftermarket electronics been installed?

No additional aftermarket electronics been installed. Bought it used and don't know if it is covered, will check with dealer.

Just being thorough: Have you checked for dome lights on and accessories (especially laptop computers) plugged into power ports etc.?

I have checked for dome lights and other accessories,nothing on that I can see

Your bumper to bumper is 4 years(from in service date) or 50K miles, so if you are under 50K miles, you are covered by the bumper to bumper warranty....after that you have a 6yr/70K Powertrain warranty.....

So start pulling fuses and the circuit breaker......

I have over 60,000 miles but thanks for the diagram that will help.

I've seen bad window switches cause this. Do they all work? That drain could really be anywhere not the easiest way to narrow it down yourself, if you're comfortable with a meter & tools is to pull the bolts on the fuse block so you have access to the rear and check each incoming wire. You'll need to isolate each wire to check them but at least then you have a wire color to bounce off the wiring diagram. Should narrow down the problem location.

Yes all the window switches work.

A couple of ideas for testing:

1. Mark then pull all of the relays. Check if battery is dead in the proper amount of time. If it is then you've narrowed down the potential causes. If not, then you've also narrowed down potential causes.

2. Find a 10+amp (continuous) battery charger with some kind of gauge. Disconnect battery. Connect charger to battery cables while being careful that they don't touch each other and anything else. Watch the gauge for the largest impact from removing and returning fuses and relays one at a time.