I have to say, I had an interesting experience driving to and from Mammoth last week. For those of you used to cold weather driving, this may be old news. This was my first trip to serious cold weather. Most of us who visit Mammoth come from warm climates, and have no experience with dealing with these issues.
First, my range usage was much higher than predicted. I used evtripplanner and calculated for the correct weight, using a speed multiplier of 1.1. I used a temp of 45 degrees, but it was really about 32 for the drive up, and colder once I made the climb up the hill. I did not use the climate control at all, just the heated seats. There were some headwinds for the first half of the trip, which would account for my heavy usage then, but little for the second half. My understanding was that evtripplanner speed multiplier uses 1.0 for "average" speed found on the route, not the posted speed. I did a steady 74 mph the entire trip (minus the town crossings of course). That's a nice comfortable speed, and even though I have a radar detector, it is less stressful to keep a steady safe speed that they don't care about, and remain relaxed. Anyway, my energy usage from Lone Pine to Mammoth more approximated a speed multiplier of 1.2. Maybe a little less. Perhaps the biggest factor was the cold. Was it that the battery had to work harder to keep warm?
While in Mammoth, it was COLD. One day, the high was only 9 degrees. I arrived with about 42 miles remaining, and got an warning message that I was in low power mode and should charge soon, which I did. I hardly drove while there, mostly because it dumped 14" my first day there and the roads sucked and I didn't want to put my chains on. Even so, people were sliding all over the place, even with chains. Being Christmas, few of the private roads were maintained. I have to admit though, when I did drive, my Model S handled the ice beautifully. I kept the car in energy saving mode, and lost very few miles while parked. Maybe 7 miles/day. I was relieved for that.
The next big issue for me was the return trip. By the time I left Mammoth, the temperature was up to a downright balmy 32 degrees. I still got a warning message stating something to the effect of "power may be limited" and that regenerative braking was not available. I assume this was due to a cold battery. I've never seen this before, and do not frequent the cold weather forums. The disappointing nature of this was that most of the regeneration for the drive home is immediately upon leaving Mammoth. I got no regeneration for the first 30+ minutes of the trip, at which time, I got a slow return of this feature. Since I do not have easy access to charging, I cannot pre-warm the battery or the cabin. Once the SC is live, I could plug in there for a few minutes, but that takes up time. As long as I have enough miles to get going, I might as well skip the regen, and drive to Lone Pine and spend the time there. Half a dozen of one, 6 of another I guess.
