"Balance Required" BMS Alert on Plaid

[Big Earl]

We appreciate the support. Hopefully I'll have an update in the next day or so. I don't feel comfortable charging the car overnight, so after tomorrow's longer driving session I may wait till Friday morning to charge if I won't be awake last enough Thursday, to keep an eye on the on/off charging issue I've had in the past with this car.

By the way, what kind of fluctuations have you seen with your Model 3?

My 3 has been all over the place and seems to go up and down with software updates in addition to fluctuations on long trips.

Here is my stats graph, which unfortunately lost all of the data prior to 60,000 miles.

The car never did get the full 310 miles it was supposed to have. I think it showed 303 at most when new. It is currently hanging out around 280 miles, which seems to be right on track with the rest of the fleet of the same age. Age seems to matter more than miles, as I have 128,000 miles now and some others with similar range have less than half that.

The car performs great, charges faster than it ever has and is a beast on road trips.

 

[WilliamG]

My 3 has been all over the place and seems to go up and down with software updates in addition to fluctuations on long trips.

Here is my stats graph, which unfortunately lost all of the data prior to 60,000 miles.

View attachment 710026

The car never did get the full 310 miles it was supposed to have. I think it showed 303 at most when new. It is currently hanging out around 280 miles, which seems to be right on track with the rest of the fleet of the same age. Age seems to matter more than miles, as I have 128,000 miles now and some others with similar range have less than half that.

The car performs great, chargers faster than it ever has and is a beast in road trips.

Well, your 3 seems great, and overall in line with what you’d expect!

 

[Muzzman1]

So today we heard back from engineering regarding my pack :
"Hi! Engineering replied that they want us to reset the battery management system and monitor. They think this will fix it for you...."
So I was able to capture the time when they did the "reset"

The pack suddenly picked up 22.72kWh at the same SOC.


Soon after they set it to charge to 100% and it stopped at 95% on its own

Based on the 15.28kWh added along with 16% nets a 95.5kWh pack. That's a MASSIVE improvement over the 70.1kWh my pack was showing prior.

After sitting alone for a while the pack settled up to 100%

So my pack went from 259mi to 331.77mi after the BMS reset. I can live with that number (21" Wheel setting) so long as it does not drop much more than that.

Does this mean the problem is gone? Experts?

I guess a few battery cycles will be the only way to tell.

 

[WilliamG]

So today we heard back from engineering regarding my pack :
"Hi! Engineering replied that they want us to reset the battery management system and monitor. They think this will fix it for you...."
So I was able to capture the time when they did the "reset"
View attachment 710195
The pack suddenly picked up 22.72kWh at the same SOC.


Soon after they set it to charge to 100% and it stopped at 95% on its own
View attachment 710196
Based on the 15.28kWh added along with 16% nets a 95.5kWh pack. That's a MASSIVE improvement over the 70.1kWh my pack was showing prior.

After sitting alone for a while the pack settled up to 100%
View attachment 710197

So my pack went from 259mi to 331.77mi after the BMS reset. I can live with that number (21" Wheel setting) so long as it does not drop much more than that.

Does this mean the problem is gone? Experts?

I guess a few battery cycles will be the only way to tell.

My opinion? I think it's BS from Tesla. I reckon it's a temporary band-aid, and I mean temporary. As soon as you drive this down to any lower SoC, this problem is almost certainly going to reappear like it has with my car, even before I charged it again. Now, I want to be wrong about your car, but I have zero faith in either of our battery packs. You can see my latest update here:

2021+ Model S and Model S Plaid Refresh Issues Thread

Question for the veteran tesla owners: Is it normal for these software/firmware updates to be so variable from update to update? Meaning its not as linear as "improvement to improvement" but rather "improvement + setback" which each update?

teslamotorsclub.com

 

[Electric700]

That's good news they might have a path to fixing this though. May be the Model S Plaids just need a software update. I hope it's that simple!

 

[Adri]

That's good news they might have a path to fixing this though. May be the Model S Plaids just need a software update. I hope it's that simple!

It might need a software update to hide and conceal the battery condition.

 

[WilliamG]

Want to see the most f'ed up battery pack ever? Check out mine today after driving it to 9% to see what! Nearly 400mV discrepancy has to be a new record. And I still can't convince Tesla to give me a new battery pack yet. Oh, and then it dropped to 3% SoC over the next 90 minutes, at home, no Sentry. So bad…

 

[mongo]

Want to see the most f'ed up battery pack ever? Check out mine today after driving it to 9% to see what! Nearly 400mV discrepancy has to be a new record. And I still can't convince Tesla to give me a new battery pack yet. Oh, and then it dropped to 3% SoC over the next 90 minutes, at home, no Sentry. So bad…

Yeah, that doesn't look good. Could you post the sane screen after charging?

 

[WilliamG]

Yeah, that doesn't look good. Could you post the sane screen after charging?

Yep. It charged 66.42kWh.

 

[mongo]

Yep. It charged 66.42kWh.

Thanks. Now it's showing 80mV imbalance. The change from 400mV at low SOC is a strong indicator that one brick lost capacity.
Of course, based on V/SOC slope it's hard to say exactly, but the 10% SOC imbalance when charged vs 22% at low charge would support that conclusion.

The BMS may be able to get the 90% SOCs to line up (or some % where the charge slopes intersect), but it won't bring back the capacity.

 

[mongo]

Yep. It charged 66.42kWh.

Oh, one other thing. The weak brick may be the one that hit 100% first. Collecting data during charge (or discharge) would allow plotting the slope of the aberrant brick vs average bricks. Could be it went from -22% to +10% rather than -22% to -10%.

 

[WilliamG]

Oh, one other thing. The weak brick may be the one that hit 100% first. Collecting data during charge (or discharge) would allow plotting the slope of the aberrant brick vs average bricks. Could be it went from -22% to +10% rather than -22% to -10%.

At the end of the day does it matter? I think we’re in agreement I need a new battery pack. I just somehow need to convince Tesla of this. The car only charged to 87% (set to 90%) and then over minutes climbed to 100% (adding about 10kWh while not charging.) I have a less-than 70kWh usable pack.

 

[mongo]

At the end of the day does it matter? I think we’re in agreement I need a new battery pack. I just somehow need to convince Tesla of this. The car only charged to 87% (set to 90%) and then over minutes climbed to 100% (adding about 10kWh while not charging.) I have a less-than 70kWh usable pack.

It probably doesn't matter, just interesting to back calculate the failure mode. If the BMS, for whatever reason, left a balance circuit on and lowered a brick's SOC then the pack would lose capacity but recover later (may take multiples of the fault time depending on software and hardware limits).That would be a reason to wait.
Or, some number of cells could be open circuit (more than 1 would really be interesting). Or a cell could have high leakage. Or a balance circuit could be stuck on.
Or, more esoteric software, the BMS auto calibrates the voltage readings and that was corrupted.

Between simultaneously losing a lot of cells and a BMS error, I might lean toward BMS as that requires less simultaneously failures.

Given the SOC readout jumping to 100%, I think it is most likely that it was the bad brick that hit 100% first (showing it has less capacity). This also means the charging stops based on the lowest brick, but the UI to self adjust based on the highest brick. When a user requests a charge level, they are asking for a minimum level of pack power, so all bricks need that level, even if some end up higher. The UI approach (if it reports the highest brick) is then misleading, but the system was not designed around a partly failed pack.


Probably doesn't matter.

 

[WilliamG]

It probably doesn't matter, just interesting to back calculate the failure mode. If the BMS, for whatever reason, left a balance circuit on and lowered a brick's SOC then the pack would lose capacity but recover later (may take multiples of the fault time depending on software and hardware limits).That would be a reason to wait.
Or, some number of cells could be open circuit (more than 1 would really be interesting). Or a cell could have high leakage. Or a balance circuit could be stuck on.
Or, more esoteric software, the BMS auto calibrates the voltage readings and that was corrupted.

Between simultaneously losing a lot of cells and a BMS error, I might lean toward BMS as that requires less simultaneously failures.

Given the SOC readout jumping to 100%, I think it is most likely that it was the bad brick that hit 100% first (showing it has less capacity). This also means the charging stops based on the lowest brick, but the UI to self adjust based on the highest brick. When a user requests a charge level, they are asking for a minimum level of pack power, so all bricks need that level, even if some end up higher. The UI approach (if it reports the highest brick) is then misleading, but the system was not designed around a partly failed pack.


Probably doesn't matter.

Either way, I’m going to push Tesla for resolution with this car. I have over 20 problems with this Plaid, with of course the battery situation being the largest of them.

 

[SucreTease]

At the end of the day does it matter? I think we’re in agreement I need a new battery pack. I just somehow need to convince Tesla of this. The car only charged to 87% (set to 90%) and then over minutes climbed to 100% (adding about 10kWh while not charging.) I have a less-than 70kWh usable pack.

I don't understand why Tesla is not taking care of this. According to their Battery and Drive Unit Limited Warranty, the battery is warranted to retain a "minimum 70% retention of Battery capacity over the warranty period".

 

[Muzzman1]

To close this case, I was informed today, my pack will be replaced.

 

[aerodyne]

Yeah that sounds official, but Im wondering if anyone has any official methods.

FYI this is my 7th Tesla, and I've dealt with range miscalculations before, especially with my wife's MX 90D, but the plaid is "next level" miscalculating.

I want a definitive official method of recalibration, cause as you can imagine, leaving the car in single digits is not healthy, and getting it down there takes some time.

If Tesla did that, and the logs or your records showed you followed the guidance to the letter, that would not work well for Tesla in arbitration.

It's not your job to calibrate the pack. That's the job of the BMS. If it's not up to the task, lemon law it.

10 years building 18650 cell packs. Time for Tesla to get it right and/or make us whole.

 

[aerodyne]

To close this case, I was informed today, my pack will be replaced.

Sorry, cross posted. Enjoy your new pack, may you never have to worry about it again