We got home with temperatures in the low 20's, line voltage about 252.6 and of course the Mini E won't charge, not even one blink or click.
After turning on almost everything in the house, the line voltage drops to 250.0 and bingo! It started charging and did not stop. I was expecting to need to get it down to 249, since recently 249.2 was not far enough down. Sounds like 249 to 250 is the threshold when temperatures are a bit below freezing.
I heard from a reputable source that the AC Propulsion safety limit (maybe there is another more official term? Jason, can you comment?) should be 264 volts. That gives plenty of margin past the ANSI spec of 252 max. To bad it doesn't hold in the cold.