I have a question regarding the AC180 wireless charger. If I place a 3/4 inch thick wood shelf directly above it, is it safe to place metal objects on the shelf. If not, what would be a safe distance?
The safest option would obviously be to disconnect the wiring for the QI wireless charging pad, but i believe you may be able to get away with adhering a ferrite sheet to the underside of the shelf to create a magnetic shield. The AC180 wireless charging pad emits a low-frequency magnetic field in the 110–205 kH range which I believe ferrite is designed for. In standby mode the QI charger will periodically send a low power magnetic pulse to see if any compatible devices are nearby. The magnetic force is a lot less than an active QI charger “in use”. I could be wrong but I also thought that QI chargers are designed to disable or shut off if it hasn’t detected a phone nearby in a while. The Bluetti AC180 QI charging pad may also have foreign object detection which means if you place a metal object on top of it, it will sense the magnetic field and turn itself OFF!
Given that it is ok to stack 2 AC180s one on top of the other and operate both, I don’t see an issue when using this logic… 
When not in use, I have stored both of my AC180s on top of each other for years with absolutely no problems at all, though I wouldn’t stack more than 1 unit for longevity.