Help! SOC Variability After Yellow HV Battery Error

[gramorris]

On Friday while road tripping from the UK to Spain I got the yellow HV battery error at a Tesla Supercharger. I believe this was the first 400v charger I’d been to.

The error cleared after 2hrs of turning the car off and on again while waiting for assistance. Interestingly it cleared after I force quit the phone app - logically maybe the app pinging the car was stopping it from fully shutting down.

I didn’t watch the charge as I had no reason to but we were in the car with it turned on and ended the session at a displayed 62% charge.

We then continued our journey as that seemed the best course of action at this point but over this leg of the journey the cars charge didn’t fall for the first stretch, which I didn’t immediately notice. But after 109kms the charge had only fallen 13% and the consumption was showing 4.3mi/kWh - clearly impossible for a gen 1 fully packed GTS riding on 21s at 120km/h

This is also reflected in the app:

So by my reckoning I’ve got ~15% of unaccounted charge and either the car overcharged or lost track of the charge on the Tesla charger and corrected itself or the car now thinks it’s got more charge than it has.

Has anyone got experience of this or knowledge as to the behaviour of the BMS that might reassure me I can get the family back to the UK safely?

I’ve attached diagnostics from eFlow too including the errors that were triggered. The errors unfortunately are timed 13 mins after the completion of the charge, so not helpful.

Thanks.

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[Bennachie]

Dont find that consumption, that, implausible on a road trip. Decent steady speed running etc.

 

[gramorris]

Dont find that consumption, that, implausible on a road trip. Decent steady speed running etc.

That’s 60% higher than I’ve ever been able to get. The 3.0m/kwh you can see on the left would be my record.

You’ve really got a fully loaded Taycan on 21 missions at 70-80mph to do 350+ miles on a full charge?

 

[daveo4EV]

probably a bad cell - dealer service visit for diagnosis

 

[gramorris]

probably a bad cell - dealer service visit for diagnosis

I had considered that but the cell voltages don’t show any obvious issues and the range to charge looks fine too currently (60% / 140miles)

I’m working on the assumption the BMS got or is out of kilter but open to other possibilities. Is there a way I could identify cell issues outside of the cell voltage check?

 

[tonycolin]

what year is your car?

 

[r553]

Keep track of your range after charging. Sudden loss of range was what clued me into my battery going south. They put a re-manufactured battery in my car. It took about a month all together. The replacement battery is supposedly a 2023 with improved design. I am certainly getting improved range (~280 miles) now after 80% charge. Good luck.

 

[gramorris]

what year is your car?

2024.

I’ve ran the car down to 12% and I’m going to let the BMS recalibrate before doing an AC recharge.

The range for charge level has been in the correct bounds so I’m leaning towards the car errored during the charge and lost track of the level it had before correcting on the out of bounds run.

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