and the answer is 110 miles, 110 miles and 110 miles...
... okay, that's the average distance between supercharger stops on my 4400 mile roadtrip last month. It doesn't really matter how fast I drive, and I drove 88mph fast on some legs in Nebraska, the superchargers don't move.
Try running some simulations in ABRP, abetterrouteplanner.com, and you'll get a sense of range at different speeds, but you'll also find that the fastest trip strategy is to drive as fast as you feel comfortable, I chose 115% of speed limit, and stop and charge at low SOC levels. I chose 13 - 15% SOC. Then you'll see that because of the charging taper, you'll get trip recommendations to charge up to somewhere in the 60 - 70% SOC range. Just looking at my trip, I only needed to charge above 70% SOC, just once, on my westward leg, into a brisk headwind. In other words, you'll find that calculating range based upon speed is something you don't actually use that much, because the Supercharger spacing doesn't change, regardless of speed driven.
Okay, the other thing ABRP gives you is a reference efficiency measured at 65mph. My reference efficiency is 245Wh/mile. On my whole trip, driven 95+% of the time on the highway, I averaged 70mph, with high speeds of 88mph. The efficiency was 274Wh/mile.
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