Does persistent cell imbalance == module issue?

[jpsd]

According to ScanMyTesla, one of my HV battery modules is always 4-10mV under the rest of the pack.

Could this indicate an issue (e.g., Condition X or Z)?

Other potentially relevant data:
- 2013 Model S 85kwh
- 98,000 miles
- Original battery
- PN 1014114-00-B

 

[Fierofiend]

Module 3 and 10 are always low on mine. It hasn't seemed to change over time.

 

[aerodyne]

Module 2, String 1 is always low on mine. Average about 10-20 mv low when at rest.

2015 with 40k, almost never out of chill mode.

Suspect a bad cell as one out of 74 would drop the voltage by about 50mv.

 

[jpsd]

Module 2, String 1 is always low on mine. Average about 10-20 mv low when at rest.

2015 with 40k, almost never out of chill mode.

Suspect a bad cell as one out of 74 would drop the voltage by about 50mv.

Yes, could be a few bad cells. Do bad cells drop out entirely, partially, or both?

All six strings of Module 7 and two strings of Module 10 run 4-10mV under the rest of the pack.

 

[sorka]

It's not enough to be bad cells. Odd thing is your difference narrows at lower SOCs to 4mV or so but at 95% the difference is more like 9mV.

If you had a bad cell, it would be more like 50mV less than the rest in the 3.7 volt range.

 

[aerodyne]

All six strings of Module 7 and two strings of Module 10 run 4-10mV under the rest of the pack.

Could be a bad BMS board. Maybe a replacement pack in your future, hopefully, under warranty

 

[jpsd]

It's not enough to be bad cells. Odd thing is your difference narrows at lower SOCs to 4mV or so but at 95% the difference is more like 9mV.

If you had a bad cell, it would be more like 50mV less than the rest in the 3.7 volt range.

Interesting. Would Service Center address this…or just tell me to get lost?

 

[jpsd]

Could be a bad BMS board. Maybe a replacement pack in your future, hopefully, under warranty

Warranty expires 9/5. Any tips for getting a remedy from Tesla? Rated range is now 230 miles after 98,000 miles (13-14% degradation).

 

[jpsd]

Interesting. Would Service Center address this…or just tell me to get lost?

I wonder if this is the “Condition X” identified in the batterygate petition? In Condition X, a module/brick is perpetually drained (albeit slowly), by the BMB. @wk057 was unaware of any real-world examples.

 

[aerodyne]

Interesting. Would Service Center address this…or just tell me to get lost?

The service center would never say that. Instead, they state your pack is "Fine" or "Performing as designed". Probably both, if they charged you for a diagnosis.

 

[aerodyne]

Warranty expires 9/5. Any tips for getting a remedy from Tesla? Rated range is now 230 miles after 98,000 miles (13-14% degradation).

Pray for a module to shut down before then? Or not...

 

[sorka]

The service center would never say that. Instead, they state your pack is "Fine" or "Performing as designed". Probably both, if they charged you for a diagnosis.

If you don't have any active errors, they'll just tell you everything is fine.