super helpful, thanks. Yeah, separate contactors and BMS...this is why i'm trying to avoid separate packs. I live in southern california, so hoping to skip coolant heating, but have also been thinking about at minimum designing cooling loop in which I can easily add heater later, in case I move back to a cold place. I will keep messing with the design to see if I can maintain the single batter pack approach, but I may give up and take on more complexity, we'll see.
On a related note, I have been looking for guidance on battery box enclosure design, but not finding much. Easiest thing for me will be to design a sheet metal box that can be folded and welded. I think 18 gauge (1.2mm thick) steel sheet is reasonable to create a rigid box that will hold all the components. BUT, this is going in a car, so I'm thinking about crash and impact safety. My gut tells mem that 18 gauge steel is too thin for attaching mount points and other fasteners that may be needed on the enclosure. Eyeballing videos online from Electric Classic Cars and Zero EV, I think they're using thicker sheet metal. Any guidance on how to select a sheet metal thickness, or other considerations in enclosure design?