jvonbokel
John VonBokel
A lot of the supercharger taper is due to pack heating. At 40-50kW the pack isn't going to heat 1/4 as much as it does at 100-120kW. 50kW is actually still under the 0.7C rate that most lithium-ion cells are charged at without liquid cooling.
I always thought the tapering was due to inherent limitations in the amount of charge the cells could safely take based on their current state of charge. If heat were a major factor, I would think Tesla would improve the battery cooling system in order to improve charge times. Also, across multiple Supercharging sessions, the power seems to correlate strongly with SoC. I would think if heat were the limiting factor, the power would correlate more to time since plugging in. However, I imagine my understanding of the battery pales in comparison to wk057's, so I'll defer to him.
That said, either way, I think the lack of taper on CHAdeMO is due to the lower power starting point. On a recent Supercharge session, the taper got down to 50kW only at the 70% SoC level, and 40kW at 80%. Many CHAdeMO stations seem to be rated at 50kW, and are often only capable of outputting 40-45kW. I would assume an S85 could take that rate all the way to 70-80% SoC, and then begin tapering.