I built a power breakout box that lives in my rooftop tent. The power cord runs to my fuse block in my trailer, through a solar cable gland in the roof of my trailer.
It has 3 cigarette sockets, and 3 dual usb qc sockets. We use it to power two cpaps, and charge two phones and my daughters tablet, as well as run the USB powered light in the rooftop tent. It's worked very well so far.