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2024 Rivian R1S — eV has plenty of main battery but shows a 12V warning

CleanGeek210Community StarterApr 16, 20262024 Rivian R1S Dual-MotorSeattle
This started as a small annoyance and I finally decided to track it down. 2024 Rivian R1S Dual-Motor, about 28,000 miles. Traction battery is charged, but a low-voltage warning appeared after the car sat overnight. I know the small battery can still immobilize an EV. What information would you capture before service?
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7 replies

UsedCarTuner681Community StarterCommunity StarterApr 16, 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. Then you'll know the next fork. On “ev has plenty of main battery but,” that was the fork that mattered for me. When does it actually happen? Might be overthinking it, but I'd rather overthink than overspend.
RustBeltDad777Community StarterCommunity StarterApr 16, 2026permalink
Don't clear the alert just to make the screen pretty. Leave the alerts on the 2024 Rivian R1S so service can see what you saw. Then you'll know the next fork. Happy to compare notes if your setup is different. Not trying to scare you — just skip the expensive first guess. Trying not to diagnose from the couch.
WrenchCamperCommunity StarterCommunity StarterApr 16, 2026permalink
Charge curves lie if you don't match starting SOC and temp. Match starting SOC and battery temp if you're comparing 2024 Rivian R1S charge sessions. That's where I'd start. I'd want a dollar figure or a measured spec, not 'should be fine.' If the story changes I'll post the new data.
RustBeltDad777Community StarterCommunity StarterApr 17, 2026permalink
Not convinced that's the whole story. Try a second charger before blaming the 2024 Rivian R1S — site sharing and pack temp change the curve a lot. I'd do that before spending real money. If you share a photo of the worksheet, easier to sanity-check. I've seen both outcomes, which is why I'd test instead of assume. This is the version I'd tell a friend.
TruckDIYer599Community StarterCommunity StarterApr 17, 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. That's where I'd start. On “ev has plenty of main battery but,” that was the fork that mattered for me. This is from a 2024 Rivian R1S in Seattle with 28,000 miles. Happy to compare notes if your setup is different. If your situation is the opposite, ignore me. Parking it somewhere I can hear it better next time.
CleanGeek210Community StarterCommunity StarterApr 18, 2026permalink
OP update: scanned the 2024 Rivian R1S again and still only have the one pending code, no new lights. I'm keeping receipts and dates in one folder.
ProjectMom166Community StarterCommunity StarterApr 17, 2026permalink
Don't clear the alert just to make the screen pretty. Leave the alerts on the 2024 Rivian R1S so service can see what you saw. I'd do that before spending real money. This is from a 2024 Rivian R1S in Seattle with 28,000 miles. Time, temperature, and whether it's in gear are the notes that actually help a shop. Heat soak after errands is the other window.
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