Roughly one week's worth of experience this now and fairly encouraging.
About 3000 watts of electrical energy are being applied each day. Roughly 1,000 Watts from the short solar days low on the horizon, which means 2000 Watts out of and through the batteries.
The batteries are in a soft sided thermal cooler of decent quality. 8 days worth of cycling has them at about 80° in this sealed soft-sided cooler. That surprised me. But there it is. A red cooler.
Last evening at 9 it was 36 degrees outside, quickly dropping 230 and below all night. This morning inside that cooler it was 40°. Safe for the batteries. Had I flipped on the $30 Walmart heating pad that snake through the batteries probably it would have been 60 degrees not 40 degrees inside this morning. Had I flipped it on for only a couple of hours. Or, had I filled the two hot water bottles with very hot water it would have been probably 70°.
Also, Oh my goodness a 15 or 20 mile-an-hour Tailwind reduces energy requirement by 50% and a headwind increases it by 50%.