The only change I would make is to make the battery cages from lighter steel or aluminum. The original cages were a bit beefy consisting of 3/16” angle to support 130+ lbs of AGM batteries on each side. My new Lion batteries are about 45 lbs per side. Mounting the lithium batteries outside will work for people that live in a temperate climate and occasionally visit cold climates.I'm really digging like your updated battery setup. Was set on having the batteries inside due to cold weather issues but after seeing your insulation/warmers I'm now thinking otherwise. Is there anything you would change in the design of the warmers/insulation?
Was able to score 6 of the same lion batteries you've got. Those would take up major interior space which I need for our toys!
Btw, where's your goto for the baltic birch? I'm in the Bay Area Peninsula and it's difficult to find larger sheets.
Sources for Baltic birch include hardwood and cabinet supply shops. I shop mostly at The Hardwood and Hardware store, TH&H, in San Diego. I recommend paying a few dollars more for the quality birch ply. My shop offers both including a cheaper Imported birch ply that typically contains voids when cut but will work in projects where the edges are not exposed.