2016 fatboy
Not sure if it's the same for the Fatboy, but right behind the battery, sitting vertically was the fuse box (I think it was the fuse box, didn't open it.). Right under it was the capped off accessory plug. It's a 6-pin Deutsch connector. I have ordered this setup to build a proper converter to it, which will wire to my new fuse box I'm installing to manage the Innov K1 camera system, as well as other things I have planned, like LED lights, USB connectors front (for me) and back (for the wife).
I didn't take a picture, sorry. And I'm at work right now, so... Attaching a picture of roughly where it was on my bike, not sure which bike this is in the picture, but should give you the idea.







