Looking at the account of the cross-country travel is informative. A number of superchargers were skipped in the interests of minimizing the total charging time. The time taken to deliver a kWhr increases as the battery reaches its capacity. It's better to start with a battery that's lower, and charge it only with enough to ensure making the next station.
Tesla's aim is to place stations every 150 miles or so. In the cross-country trip there were a few intervals of over 200 miles. They were probably the result of skipping stations. I'm going to assume that pretty soon there will be stations every 150 miles on major routes.
Lets say cars are only charged to 90% of their capacity as a day-to-day maximum and use the EPA range (208 235 for the 60 and 85KWhr battery respectively. After a 150 mile trip, the 60 kWhr car will be down to 32 miles, 18% capacity. That's close enough for me, let's use that 32 miles as a buffer and restore the battery to 90% capacity.
The 85Kwhr battery will retain 40% of it's capacity after 150 mile trip starting at 90%. to give the same buffer of 32 miles at the end of the next leg, we'll have to start with 182 miles, 69% of capacity.
At the end of the second leg, both cars will be down to 32 miles. The 60 kWhr battery will have to be charged from 15% to 90% whereas the 85 KWhr will only need to be charged from 12% to 69%. What's the difference in these two times?
My guess is that it will take longer to put 150 miles in the 65 than the 85 kWhr battery when both are pretty low, but I don't know how much longer. Some might prefer to use the bigger battery to gain a bugger buffer. Sometimes the bigger battery could be used to skip chargers. The average charging time for the cross-country route was 38 minutes. I'd rather not do that every 150 miles - every 2 hours in good conditions.
Yes, I know I have stated elsewhere that I need a city car, not a GT. But it's hard to spend $70K on a car that dictates frequent long breaks on any substantial trips. Maybe it's worth the extra $10K to reduce the length and frequency of such breaks.
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