I’ve got a BT3400 v. 2.2 and its OEM fan has been quiet, but I bought two of the Delta fans off of Ebay just to have as spares, as Wolf has suggested.

I also bought the LiteOn 5.5A 12v power brick and while I don’t use it regularly, it was fairly cheap to get ($12 shipped?) My inner hole on the barrel connector is slightly over sized, so if I jiggle it when the charger is running, it’ll disconnect, but I just don’t move the charger once things are charging.

Chris