Great job! Very clean, well organized. For those planning on doing something similar, they'll find your pictures and videos very helpful. With all this cold weather we've had lately, it's a perfect time to test everything.
One observation. Got to wonder if such a high wattage heating pad is necessary. 78w (6.5ah) is quite a high draw---especially if you're boondocking and trying to conserve. Realize you're trying to heat your 100ah lifepo4 cells indirectly, by heating the exterior plastic case. No doubt there's some inefficiencies at play here.
We've found 4, 24w 80x100mm silicone heating pads (wired parallel/series) have the capability to heat our 200ah lifepo4 battery pack to 60f with an ambient of 0f. I'd guess they could probably maintain the cells at 35f with an ambient of -15f. Since the 4 pads are wired parallel/series they only consume 24w total (2a at 12vdc). This is a portable, completely self-contained battery with everything located inside an uninsulated Group 24 battery box. In cold weather we typically keep our lifepo4 cells at a constant 50f 24/7 so we can safely do .4c charges and .6c discharges at any time. We've found at 15f ambient, the heating pads (thermostat controlled) only draw approx. .75ah while keeping the cells at 50f. That's approx. the same overall draw as our inverter's parasitic, no-load draw.
