I think it would be doable. for our 85D, I'd charge to full, pre-heat before disconnecting, and do the whole trip in range mode at the 100 or even 90Km/hr. I just started playing with range mode, and it makes a difference in our 85D.
We just recently completed an 850KM trip in the freezing cold -26C (-15F) all on L2 chargers and survived nicely! YouTube