Sudden drop in range while driving

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Jan 21, 2021
I have a 2019 VW e-Golf SE with 10,500 miles that I have owned for 2 years (trouble-free...until recently). Two months ago, the car experienced a sudden drop in battery range while driving. The battery was charged ~60% full, and within seconds, the range monitor dropped from 80 miles to 5 miles of range, the battery gauge dropped to the red, and the message screen displayed "limited battery performance, switching to turtle mode" alert, and the power dropped to reserve power (turtle mode). We drove the car home in turtle mode. The next morning, I started the car with no problems, the range monitor/battery display was back to 60%/80 miles and I was able to charge the car normally.

The car has performed normally until last week when the battery display/range dropped again while sitting at a red light at a busy intersection. Same display of "limited battery performance, switching to turtle mode" and we had to pull the car off the side of the road. I shut down the car, restarted it, and the battery gauge and range were back to normal and I drove it home.

I scanned the car for codes using an OBDLink onboard scanner, and it showed no fault codes detected. The car is now sitting at my local VW dealership:-(

My guess is that this is a problem with the Battery Management System similar to the recall in the 2014-2016 e-Golfs (recall #16V138000). Any ideas or suggestions would be greatly appreciated!
Check all cell group voltages. (There are 3 cells in parallel per “cell” in OBD data). Maybe there is a bad cell?
Thanks for the suggestion. I will try to do that. I suspect that that there is actually nothing wrong with the batteries themselves because when the car recovers from these episodes and is acting normal, the range is still ~180 miles in city driving (typical for this particular car). For some reason, the computer thinks that the battery is depleted when it's not.
Update: The VW dealership inspected the car and scanned for fault codes. All physical connections (that they looked at) were fine and there were no fault codes stored. They contacted VW "Central HQ" to run the symptoms by them. VW Central recommended 2 software updates, one of which is specifically for the battery management system. Basically, this is all they could do since there are no codes and (of course) the car is running fine while it's at the dealership. I'm hopeful that these software updates will fix the problem. At the same time, I can't help wondering why VW does not make it known to e-Golf owners that software updates are available.
Good point about software updates for the rest of our cars. VW is very stingy with software updates.
Hmm, i would like to ask my VW service, if they could flash me the new FW. Maybe it solve this phenomena about 50 %of SOC, which i mentioned in my thread...
On the other side, when i bought my egolf, i ask about FW updates and claimed me, that they do it only in case of any problems... Without problems, they dont do it. From some POV i understand such approach, on the other side, generally with updates are things optimized...

It there in OBD11 possible to find sw version of BMS? that ve could compared, who has which version?
So i communicated with VW. They will upgrade me FW for HV battery. Now should be version 350, the new one should be 400. Even that is not free of charge i will go to it.
You have a 2019 car and the HV electrical system is still covered under warranty (at least in USA) - this should cost you nothing.

It would be great if you could tell us cell voltages. I use Car Scanner most of the time but also sometimes OBDEleven.