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Alternator & ChargingDiscussionCommunity Starter

2024 Rivian R1S — fast charging tapers earlier than it used to — second opinion before I spend money

TowDadCommunity StarterJun 28, 20262024 Rivian R1S Dual-MotorWashington DC
On comparable road trips the charge rate now starts tapering sooner. I am trying to separate charger sharing, battery temperature, software changes and actual battery health.
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5 replies

WeekendWrench782Community StarterCommunity StarterJun 28, 2026permalink
I'd treat 12V warnings as a no-ignore. On the 2024 Rivian R1S, I'd get the 12V/DC-DC side checked even if the traction pack looks fine. I'd do that before spending real money. On “fast charging tapers earlier than it used,” that was the fork that mattered for me. This is from a 2024 Rivian R1S in Washington DC. Was this after sitting overnight? If your situation is the opposite, ignore me. Trying not to diagnose from the couch.
PistonDaily566Community StarterCommunity StarterJun 28, 2026permalink
Low-voltage gremlins will strand you even with a full pack. Try a second charger before blaming the 2024 Rivian R1S — site sharing and pack temp change the curve a lot. That's where I'd start. No need to make it theatrical. Worth doing even if the car feels fine right now. Might be overthinking it, but I'd rather overthink than overspend.
TrailBuyerCommunity StarterCommunity StarterJun 30, 2026permalink
Same neighborhood, different next step: Leave the alerts on the 2024 Rivian R1S so service can see what you saw. That's where I'd start. I'd want a dollar figure or a measured spec, not 'should be fine.' If that fails I'll eat the diagnostic fee.
WeekendWrench782Community StarterCommunity StarterJun 29, 2026permalink
Low-voltage gremlins will strand you even with a full pack. Try a second charger before blaming the 2024 Rivian R1S — site sharing and pack temp change the curve a lot. That's where I'd start. When does it actually happen? Worth doing even if the car feels fine right now. That's my plan before I call anyone.
ColdStartWeekend566Community StarterCommunity StarterJun 30, 2026permalink
I hear you, though I'd still want a second check. On the 2024 Rivian R1S, I'd get the 12V/DC-DC side checked even if the traction pack looks fine. I'd do that before spending real money. On “fast charging tapers earlier than it used,” that was the fork that mattered for me. A shop burned me once by skipping that step. If your situation is the opposite, ignore me. If it repeats twice more I'll book time.
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