Learned some big charging lessons this weekend. Took a 260 mile trip from Philadelphia, PA to Hancock, MA in my S 60. Left Philadelphia with 200 miles of range. After 90 miles I stopped in Paramus, NJ to charge and have lunch. Since I planned to be there a while to eat, I charged fully. Normally, I could easily have driven the remaining 170 miles with a full pack, except perhaps in really cold weather. Well, I didn't make it and had to stop again in Kingston, NY to charge more.
I paid very close attention to charging and energy use for the remainder of the weekend and observed some things that caused me to plan the return trip differently.
The first thing I noticed was that the charging display no longer shows volts and amps. It now shows kWs. That seemed more logical, but I was initially confused by the new numbers. Superchargers have gotten much faster since my last road trip. I added 200-300 miles of range per hour instead of the old 130 (ish) m/range/h I was used to. That seemed ideal, once I adjusted to the new display and charging speeds. Overall I am thrilled with the higher output.
However, the second thing I learned was, there seems to be a penalty for quickly charging to full. I usually drive the speed limit, 55-65 mph, and typically average 250-300 kW/hour. However, after a fast, full charge, I used double the juice for several miles. I suspect that charging more than twice as fast puts more heat in the batteries so the car uses more energy to cool the pack, thus reducing range. Hadn't counted on that and ultimately got the dreaded "reduce speed to 50 mph" message. Luckily, my trip was proximate to New York city where there are many Superchargers, so I didn't have to spend hours at a destination charger to complete the journey. A short Supercharge close to my destination did the trick.
So thing one and thing two add up to thing three, which I tried on the way home. I charged fully the night before I left at the very nice Supercharger in Lee, MA, close to my hotel. I departed in the morning with a full, but cool pack. Made a short stop in Newburgh, NY and a second short stop in Cranbury, NJ. I got excellent range on all legs of the trip. Plus, I probably stopped for 20 minutes or less each time. A full charge takes 60-70 minutes as charging slows for the last 10-20%, so I spent at least 30 fewer minutes stopped, drove faster than usual, and still got better than average rated range, rather than poorer than average. That's a win-win.
I hope my conclusions are valid. I feel confident they are but I'm fine if smarter minds can poke holes in my logic. I just want to learn the best strategies as our cars and the chargers evolve. I can find no other significant variables. For example, I had a sudden temperature drop and unexpected uphill climb rob me of range at the tail end of my first road trip for Thanksgiving of 2013. Summer temps in the 80s don't seem to deplete range like freezing temps do and there was little elevation change or other obvious difference in this equation. Maybe a hot pack will be a good thing in winter, but I'm not counting on it and will proceed with caution. Hope I learned the right lessons.