"Balance Required" BMS Alert on Plaid

[Muzzman1]

So my plaid IC gives me a grand total of 300 miles with 19" wheels at 100%
According to the HV section in the "Dyno Mode" page my total pack energy is 73kWh.
Needless to say there's something amiss.

I noticed there's an alert indicating that "Balance required" in the BMS.
Normally this alert is hidden, but lucky for me it is visible through the "dynotest" screen.
FYI, that alert has been consistent for the last 4 days.

That being said, are there any HV experts out there with a definitive method to balance the pack so I can get some realistic estimates on my Plaid.
Should be 396 EPA

 

[DerbyDave]

Open up a service ticket thru the app and upload your logs. They will likely take care of it over the air.

 

[Muzzman1]

Open up a service ticket thru the app and upload your logs. They will likely take care of it over the air.

Yeah, I did. Day 1 getting the car. It's been over a week and nada. Appt is Sept 20. Rather not wait that long.

 

[DerbyDave]

Wow, they usually call or text me with a day on a service request thru the app, letting me know what they found by reviewing logs, and ordering any parts required for mobile service, or if they can't handle it, parts for regular service. Balancing does not sound like anything urgent, except your range is down.

 

[Big Earl]

Yeah, I did. Day 1 getting the car. It's been over a week and nada. Appt is Sept 20. Rather not wait that long.

In the meantime, if you haven’t already, run it down to single digits and let it sit parked and asleep for several hours. Then charge it mostly full and let it sleep for several more hours. It might take a few cycles as the BMS adjusts.

 

[Muzzman1]

In the meantime, if you haven’t already, run it down to single digits and let it sit parked and asleep for several hours. Then charge it mostly full and let it sleep for several more hours. It might take a few cycles as the BMS adjusts.

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.

 

[WilliamG]

In the meantime, if you haven’t already, run it down to single digits and let it sit parked and asleep for several hours. Then charge it mostly full and let it sleep for several more hours. It might take a few cycles as the BMS adjusts.

I'm having the same issue. This fix does not work for this particular Plaid battery issue, as I've done this several times now with no luck. My Plaid is rated for 298 miles right now after sitting for two days at 100% to try and rebalance (per Tesla), and realistic range is in the 200 range, even at 283Wh/mi.

 

[KalJoMoS]

Tesla’s suggestion was - for pre refresh BMS - to run the SoC to 5% and let it sit for few hours and then to charge to 100% and leave it for few hours again for balancing the cells. This is best done on road trip, I managed to get app. 5% back on my last trip but I never charged it to 100% nore stayed at low SoC for hours. It is not instant gain on the battery, you will notice the change after few balancing attempts. I did this in April and the change was seen around June. To be successful, the balancing charging must be different than your regular every day behaviour.

 

[WilliamG]

Tesla’s suggestion was - for pre refresh BMS - to run the SoC to 5% and let it sit for few hours and then to charge to 100% and leave it for few hours again for balancing the cells. This is best done on road trip, I managed to get app. 5% back on my last trip but I never charged it to 100% nore stayed at low SoC for hours. It is not instant gain on the battery, you will notice the change after few balancing attempts. I did this in April and the change was seen around June. To be successful, the balancing charging must be different than your regular every day behaviour.

Realistically speaking your particular situation isn’t going to be an issue on a brand new car where it’s reading 20-25% less battery than normal as it is on mine and @Muzzman1 .

 

[Adri]

Realistically speaking your particular situation isn’t going to be an issue on a brand new car where it’s reading 20-25% less battery than normal as it is on mine and @Muzzman1 .

20-25% less charge on a brand new car sounds like a new battery to me..

 

[WilliamG]

20-25% less charge on a brand new car sounds like a new battery to me..

Agreed. I just need to go through the motions with Tesla until something happens.

 

[Electric700]

You shouldn't have to charge to 100%. They told me the batteries now automatically balance even if set to 90%, which they recommend as the maximum you should set your vehicle to for normal use.

 

[WilliamG]

You shouldn't have to charge to 100%. They told me the batteries now automatically balance even if set to 90%, which they recommend as the maximum you should set your vehicle to for normal use.

That’s correct, - at least it correlates with what the technician said to me. That said, what’s the largest imbalance that’s even possible to correct on a ~100kWh battery pack? At some point surely there’s too much of an imbalance to fix without a new HV battery?

 

[mongo]

That’s correct, - at least it correlates with what the technician said to me. That said, what’s the largest imbalance that’s even possible to correct on a ~100kWh battery pack? At some point surely there’s too much of an imbalance to fix without a new HV battery?

Indeed, from tear downs on older packs, the BMS can only bleed high groups, and that slowly. The cells are highly uniform and the BMS only needs to deal with the slight difference in self-discharge. If a cell fails or a group has abnormal leakage, the system cannot compensate and that group will limit the pack more and more at either the high (low self discharge) or low (high self discharge) end of the SOC.
A failed cell will also cut pack capacity by 1/(number of cells in parallel).

 

[WilliamG]

Indeed, from tear downs on older packs, the BMS can only bleed high groups, and that slowly. The cells are highly uniform and the BMS only needs to deal with the slight difference in self-discharge. If a cell fails or a group has abnormal leakage, the system cannot compensate and that group will limit the pack more and more at either the high (low self discharge) or low (high self discharge) end of the SOC.
A failed cell will also cut pack capacity by 1/(number of cells in parallel).

Do you know what the threshold is for inability to balance?

 

[mongo]

Do you know what the threshold is for inability to balance?

I know how to calculate it, it's group voltage/ resistance which gives the additional current draw it can use to drain the high group(s) (if only one group in the whole pack is low, it must drain every other one).
This does not map out to an SOC difference directly though.

The SOC reading issues are a result of drift between the cells and the BMS approximation of their level. The discharge/ charge cycle provides widely spaced voltage points and a large well measured number of Ah to determine the pack SOC.

In the event the car stops at >5%ish SOC or stops charging at <95ish%, the issue is either one group is out of balance and hit the voltage limits first or the SOC approximation was wrong. Imbalanced groups will repeatedly cause this condition (since the BMS has limited control and the condition will probablykeep getting worse), wheread an erroneous SOC calculation should recover quickly.
More stuff on the topic :
Explaining Changes post-firmware 2019.16 Regarding Range Loss | wk057's SkieNET

 

[MP3Mike]

That being said, are there any HV experts out there with a definitive method to balance the pack so I can get some realistic estimates on my Plaid.

I think in general charge it to 90% and then let it sleep for days, or a week based on how far out of balance your pack is. Make sure there is nothing waking it up. (Don't check on it in the app, make sure no third-party apps, TeslaFi/etc., are waking it up.)

My guess is even if it does balance itself, it will just go out of balance again after use. (In other words I suspect you have a bad brick and the pack needs to be replaced. But I guess we will see.)

 

[Muzzman1]

I think in general charge it to 90% and then let it sleep for days, or a week based on how far out of balance your pack is. Make sure there is nothing waking it up. (Don't check on it in the app, make sure no third-party apps, TeslaFi/etc., are waking it up.)

My guess is even if it does balance itself, it will just go out of balance again after use. (In other words I suspect you have a bad brick and the pack needs to be replaced. But I guess we will see.)

Question is, how do we get tesla to admit that a new pack is in order?

 

[MP3Mike]

Question is, how do we get tesla to admit that a new pack is in order?

I'm not sure, the warranty pretty much only covers failures and/or 30+% degradation. So if you charge it to 100% and it reports ~277 miles of range you would qualify for a pack replacement. I would say open up an executive escalation, but that got removed because it was abused/used too much...

I would hope that they step up and just replace it once you have brought the pack in to balance by letting it sit, and then show it just goes out of balance again during normal use.

If they don't then you may just have to abuse the pack to get it to fail and/or degrade sufficiently. Charge it to 100% often and do lots and lots of launches, especially at a low SoC. That should really stress the "bad" brick(s) and possibly cause them to fail. (We may know more in a couple months once Munro gets their Plaid and tears it down.) Just expect it to leave you stranded when it does finally decide it has failed.

How many people have reported this problem? Is it just three, with one of them reporting it was resolved? (edit: scratch that the third person said it has reoccurred, so it was only temporarily balanced.)

 

[Muzzman1]

That's what scares me. The car has 1000 miles on it, and this is not covered. This is the 5th car I've taken delivery from Tesla and I've had severe degradation on my Model X, but that was after 30k miles.
This one is crap with 20 miles.
How is this NOT covered is absurd.
I am going to abuse it to cause failure. I am going to do my best because TBH this car has the same range my 85D had on the dash just about!
I had ordered a Plaid + for the range and settled for this, now Im stuck back with my 2015 MS range.