Originally Posted by Red_Chili
What is the inrush (startup) current for these fridges? That wiring looks ultra light duty!
My Engel MT45 inrush isn't huge (~5A), but it's also not nearly as smart with the under voltage protection. I have a 12AWG running about 12 feet from the battery to my outlet. Lowest I ever ran it was 2 days in the summer without starting the truck. The battery was at 11.7V (measured by my ham radio, so very unscientific). The fridge was still running and cold, although the engine cranked s-l-o-w.
FWIW, 18AWG wire is 6.5 milliohms per foot, so 6 feet is around 40 milliohms. If the fridge is 10A inrush, that's 0.4V of drop. I can't disagree that 18AWG is maybe light. Going to 12AWG or 14AWG would help, yielding V drops of about 0.10V and 0.15V respectively (assuming 10A inrush). I'd be surprised if the inrush is that high, but maybe it is and the UVL is just that sensitive. Suppose your battery is brand new and at 60% SOC, so sitting at about 12.2V and it's hit with a start-up, dropping to 11.8V. I dunno, seems sorta high still.