I took out my 2015 March built Model S 85D for supercharging after a long time, just to test chargegate.
Guess what? I can’t use this car for road trips anymore. It took 1hr 20 minutes to charge from 15% to 90% and it barely stayed at ~60kW charge rate before dropping down to 50s and then settling around 30s.
I have about 52k miles on it and have only supercharged it maybe 20 times or less in about 5 years.
The only good news is that it doesn’t suffer from batterygate as 100% is still pretty good at 265 miles while new was 273 or thereabouts.
Try it again some time. I have 270k miles and I'm heavily affected by the reduced charge speed. I do get 90kW for the first few minutes but it drops quickly down. At 50% I get just over 50 kW. But that's only on good days. Often it's lower. After a day of lots of driving, I go to a supercharger and I only get around 50-60 kW maximum. This is a repeatable behavior. After busy days the charge rate is just sh*t. During the day when I top off at a supercharger, the rate is normal. Maybe the car knows I just want to top off before I go to sleep and I'm not on a road trip so it allows only a limited rate.