I've considered that, just as a project to feed my curiosity as much to power the rig. I hope competition puts some downward pressure on prices and 75 Ah 12V LIFEPO4 can be had for around $500 in the near term. I don't mind spending that or slightly more if that means I get a 7 or 10 year warranty and roughly 3000 cycles out of it.

I have one question on the portable systems that one builds. I know on a permanently mounted dual battery setup, we need to ground the aux battery. If I were to do it I would just run the negative cable to the same chassis ground where my starter battery is grounded. But suppose I have a lithium battery in a removable box. I realize that the DC to DC is going to be grounded via the starter battery and linked up to the aux battery in the box but is that all that is required? Do I need to create a chassis ground for the portable unit on top of that?