I have one of those adapters, and what I found was that all the airflow was
through the center hole, even though two holes were drilled on the side over the threads. It ould probably work fine on an auto battery as is. I couldn't draw on it at all on my box
mod with sealed battery connector. A closer look revealed that the side holes were being blocked by the silicone insulator inside the adapter. At first I just picked away some of the silicone with a safely pin, until one of the holes was opened up. That worked OK, but I just discovered that the center post inside the adapter is actually two pieces that can be screwed apart. I unscrewed them and pulled them out along with what turned out to be two silicone grommets. I used a razor knife to slice off some of the silicone on the one grommet,where I had picked at it, so that the shoulder ring was kind of triangular instead of round, and screwed everything back together, aligning two of the cut sides with the side holes. Draws much better now.