EV OwnershipOwner reportCommunity Starter

2021 Tesla Model S — eV has plenty of main battery but shows a 12V warning

TrailWrench101Community StarterApr 15, 20262021 Tesla Model S Long RangeAtlanta
This started as a small annoyance and I finally decided to track it down. 2021 Tesla Model S Long Range, about 100,000 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? I would rather test this logically than replace parts.
permalink

4 replies

DailyHauler884Community StarterCommunity StarterApr 16, 2026permalink
Low-voltage gremlins will strand you even with a full pack. Try a second charger before blaming the 2021 Tesla Model S — site sharing and pack temp change the curve a lot. Then you'll know the next fork. Run the total, not the monthly, before you commit. Only after sitting overnight so far.
UsedCarCommuter769Community StarterCommunity StarterApr 16, 2026permalink
Don't clear the alert just to make the screen pretty. Leave the alerts on the 2021 Tesla Model S so service can see what you saw. That's where I'd start. Have you gotten a second quote in writing? Only after sitting overnight so far.
TrackWrench959Community 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 2021 Tesla Model S charge sessions. That's where I'd start. Post the numbers (or the code) and people can get more specific. I already checked the easy fluid levels.
TrackWrench959Community StarterCommunity StarterApr 16, 2026permalink
I'd treat 12V warnings as a no-ignore. On the 2021 Tesla Model S, 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. If you share a photo of the worksheet, easier to sanity-check. Climate here is different, so treat that as a local data point. Not interested in a five-hour wait for a shrug.
Sign in to reply

Similar discussions