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Is the max range reduced or did they just change the charging profile? I requested a buy-back quote from GM and yesterday they called me to ask some questions including whether I wanted a trade-up or a buy-back. I requested buy-back and they said fine. So I'm guessing the they wouldn't have offered that if there truly was a fix that didn't reduce range?
Just because the initial people you're speaking with said fine, doesn't mean anything. They're just filling out the form. Once the internal people review, it'll most likely be denied unless your state lemon laws dictate that they must do it.
 

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I did manual testing - running the battery down, etc. The numbers seem to roughly match the TorquePro capacity readings. Last year, similar analysis led to the suspicion my 2019 had more than 60 kWh capacity and that was eventually borne out by TorquePro when Telek added support for 2019s. When I started to see my numbers climb back up a month ago, I thought it could be a winter thing but they seem to have stalled out. We'll see.
Send me a list of all your cell voltages from an android device ideally.
 

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FWIW, I have noticed that since I started limiting my charge to 60% to 70% my deltas have gone way down. My cell match at low battery is also much better. It almost seems to me that this is healing something.
You are misunderstanding what is simply a result of the shape of the voltage curve. The voltage delta of cells will always be closer together toward the center of SoC.. It simply means that near the center of SoC, a 0.XXX volt difference represents a much larger difference in SoC than it does near the ends
 

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A few things.

The cell min/max PIDs that they are using are rounded to 0.02V. So a 0.08V delta could be 0.06 or 0.10V.

Also, the BMS will balance to within 0.03V of actual real cell voltages.

Ergo, if you see 0.08V or more, that means the BMS has failed to balance and the cell(s) is/are definitely dead.

But, this MEANS NOTHING. This is exactly the same that it was before. There is no indication of improved processes here. Also, cells that can lead to fire do NOT NECESSARILY SHOW UP this way. They can look perfectly fine from a voltage perspective, then they catch fire. Dendrites are a huge pain. They can cause a minor impact which can show up with voltage, or they can cause a major short and burn up within an hour or two.

Boeing spent 3 years on this, and their solution was to put their batteries in a fireproof box and hope for the best. Multiple studies have also concluded this.

The only promising technology that I've seen is high frequency impedance measurements, and neither the existing BMS nor the external balance tool can do this currently. Alternately you can use improved cell separators which are much more resistant to dendrites, but that's obviously not an option.

So all they can do is enhance their ability to watch for voltage differences which indicate that a cell needs to be replaced - they can't even measure impedance of every cell. This is a mostly different problem than when the cell might catch fire.

Also I don't know why the OP is talking about 6-7 hours for a recall fix as a sign of commitment - that's ONLY when the cell needs to be replaced, which they expect less than 1% to be done. I've already heard back from owners who have had this fix applied - it's just 15 minutes for the software flash and that's it.
All I can say is hang in there with your work on TorquePro. It will be really interesting to see how this all plays out.

FWIW, LG has responded in other cases that Lithium plating may not cause a fire issue. They claim that dendrite growth is not a "done deal" if plating is found. Is this just CYA or do they actually know something?

I think if one is to accept using Lithium Ion batteries at all, one may need to accept that minor dendrite failure is a fact of life that may not always lead to a spectacular failure. A lot of this is in the statistics and what a failure will lead to. Obviously it's a lot bigger deal at 30,000 feet with 200 people on board. As an engineer, I just don't know how to respond without seeing all of the data.

At this point, I'm going to trust GM until I see a reason not to. Hey, we are Beta testers after all. lol
 

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Thats not what a BMS does. Its a pack voltage leveling system. Since you have multiple batteries running in series, Some will have slight differences in resistance, so they will charge/discharge faster than others. The BMS prevents over/under charging for the series section. Its 9 modules in series. Each module is 32 cells in a series parallel to make 40 volts.

What the bms fix is to be extra sensitive when left plugged in and at 100% and in "trickle charge" mode. We used to call this "sparkle charge" mode in the lead acid days, and its the most dangerous time for the pack. So the fix should just react quicker to cells getting to 100% before others, which means the battery should reach 100% a wee bit slower (because all cells need to reach the finish line at the same time). And the fix should prevent stop the pack from just sitting there slowly drawing current.

A charger has 2 ways of dealing with a full pack. One is "trickle charge" to keep the pack at 100% forever. This can be dangerous as some cells are at 100%, and some are not, and its possible to over charge some cells. The other mode is charge to 100% and then cut off. In this mode the pack will slowly self discharge till the charger is reset. Odds are the Fix monkeys with these two modes.
It never ceases to amaze me how, 4 years in, people speak very certain about things and are incorrect :p

It's probably already been mentioned, but there are 10 sections in 5 modules. 8 of the sections have 10x3 cells, 2 of them have 8x3 cells. There are 288 cells in total. The modules split between the two halves of the battery, so each have one section in each half. So the voltage changes depending on the module, and it's 3.65V nominal, not 3.60V.

Also, there is no trickle charge mode, and no float charge mode. This never happens with lithium ion, or at least should never happen. All charging specifications typically cut off at 5% of full charge current and are very explicit about this. The Bolt is no different, although it does go a bit lower to compensate for not being able to charge at full voltage (4.17V limit instead of 4.20V). It cuts off at about 3.5% from my measurements. Float or trickle charging lithium ion is a fantastic way for the cell to swell and burst.

So the fix has nothing to do with this, nor the sensitivity when it's fully charged. It's almost certainly ONLY enhanced monitoring of voltage differences between the 3-packs of cells during usage, to watch for anomalous changes that aren't typically caught by the idle-time balancing voltage delta monitoring.

But ultimately the 3-pack of the cells is what kills us. It's very difficult to notice a problem with one cell before it gets out of hand. Since they don't have impedance measurements per cell, there's not a lot that can be gleamed from just the cell pack voltage.

Also, fires may not have anything to do with voltage deltas, so there's that problem as well.

For the record - the BMS's only ability to balance is a passive drain of high cells. Although I have yet to ever catch this in action, it only can drain high cells. When a cell is failing, it's falling low, and the BMS can't do anything about that. So the BMS doesn't help a dying cell, it just tries to keep overperforming cells from getting stressed out due to higher current situations. The car's thermal management system is barely adequate, and temperature gradients in cells exponentially accelerate degradation. That's what's ultimately trying to be avoided here.
 

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You are misunderstanding what is simply a result of the shape of the voltage curve. The voltage delta of cells will always be closer together toward the center of SoC.. It simply means that near the center of SoC, a 0.XXX volt difference represents a much larger difference in SoC than it does near the ends
That could be true but it is not in this case. The reduced delta is also present at a high SOC. At any rate, the delta at low battery is the only thing that matters anyway.

The delta at full charge is basically meaningless. This is only meaningful if the cell capacity is balanced. In the end what matters is that a "weak", undercharged, cell is not prematurely causing a low battery condition.

What I am seeing is a delta range that has dropped from over 30mv to about 5mv at about the same cell voltage. I really don't know why.
 

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I can speculate two possibilities when it comes to "advanced diagnostics" as a "fix":

Scenario 1
Previous cell diagnostics were not good enough to detect when a cell (or multiple cells) went bad and the BMS continued to charge those cells which damaged them further and caused fires. In this case, the "fix" is more akin to a "smoke alarm" fix: the advanced diagnostics can tell when cell(s) go bad and will not continue to try to charge them. In this case, IF your battery pack suffers from this problem, you're likely to get a message that the propulsion system has failed and the car won't charge/drive... thus preventing a fire by continued charging causing further cell damage.

Scenario 2
Previous cell diagnostics were not good enough to compensate for weaker cells and the previous software was actually the cause of the cell damage. In this case, if the advanced diagnostics are able to better balance the pack without causing further damage to accumulate in weaker cells, it may result in cells not going "bad" in the first place. And if cells are bad beyond balancing, the diagnostics may disable the vehicle like in Scenario 1.

The important distinction here is that scenario 1 simply detects an existing problem and disables the vehicle while scenario 2 could actually prevent cell problems AND may disable the vehicle if cells are "beyond balancing repair" via the BMS. I wish we knew which of the above is true or if neither (and it's some scenario 3), what that is. But this is GM... so I suspect we'll never know the details.

Mike
Neither of these are the case.

Lithium ion doesn't catch fire because the cell is weak or overused. They catch fire due to damage or dendrites. While continuously forcing a near dead cell to perform can drastically increase dendrites, the BMS was already way more than sensitive enough to brick your car if a cell was underperforming.
 

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I find it very, very hard to believe that GM will allow out-of-warranty batteries that fail the diagnostics to stay out in the wild where they can cause a fire, or become unusable with no recourse. I can say from experience that it is highly likely that GM will either voluntarily, or involuntarily, extend the warranty on the battery, possibly to "lifetime".
Everyone keeps conflating weak batteries with fires.

They have very little to do with each other.

If your battery has advanced degradation, it's not likely going to catch fire. This is the warranty area.

I can agree, however, that regardless of warranty status or age of the car, if GM's "advanced" monitoring software detects the situation that they believe can lead to a fire, the owner will be informed and the car will have to go in for service. Whether or not GM charges for this is up for debate.
 

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A few things.

The cell min/max PIDs that they are using are rounded to 0.02V.

So all they can do is enhance their ability to watch for voltage differences which indicate that a cell needs to be replaced - they can't even measure impedance of every cell.
Are all the PIDs you list for our cell groups only good to two decimal places? If so, am I just fooling myself by setting them to three decimal places?

When you say they can't measure impedance of every cell, do you mean the individual cells, or the parallel cell groups. I am certain they can't distinguish the paralleled cells. But I would think they could determine the impedance of parallel cell groups from watching the voltage sag under load?
 

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Is anyone else concerned about GM possibly down-playing known flaws, like they did with the ignition scandal a few years ago?
I actually really doubt it. This isn't something to #### with. They are going all-electric, and if they screw this up, it will cost tens if not hundreds of billions of dollars over the next decade.

They have to believe that this software fix is actually going to solve the problem.
 

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It never ceases to amaze me how, 4 years in, people speak very authoritatively about things and are completely incorrect :p

It's probably already been mentioned, but there are 10 sections in 5 modules. 8 of the sections have 10x3 cells, 2 of them have 8x3 cells. There are 288 cells in total. The modules split between the two halves of the battery, so each have one section in each half. So the voltage changes depending on the module, and it's 3.65V nominal, not 3.60V.

Also, there is no trickle charge mode, and no float charge mode. This never happens with lithium ion, or at least should never happen. All charging specifications typically cut off at 5% of full charge current and are very explicit about this. The Bolt is no different, although it does go a bit lower to compensate for not being able to charge at full voltage (4.17V limit instead of 4.20V). It cuts off at about 3.5% from my measurements. Float or trickle charging lithium ion is a fantastic way for the cell to swell and burst.

So the fix has nothing to do with this. It's almost certainly ONLY enhanced monitoring of voltage differences between the 3-packs of cells, to watch for anomalous changes that aren't typically caught by the idle-time balancing voltage delta monitoring.

But ultimately the 3-pack of the cells is what kills us. It's very difficult to notice a problem with one cell before it gets out of hand. Since they don't have impedance measurements per cell, there's not a lot that can be gleamed from just the cell pack voltage.

Also, fires may not have anything to do with voltage deltas, so there's that problem as well.
Welp you seem to have deeper knowledge of the pack. So when left plugged in for say weeks, what is the mechanism to keep the pack at 100%? My work uses the "cut off and never turn on till reset" charger. In this mode the charger does not monitor the pack once 100% charge has been reached. Its not uncommon to come back to a dead "device" after a few weeks even if it was left on the charger, because the charger does not reset.

So how does the bolt handle keeping the pack at 100%?
 

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What is interesting is, '17 and '18 models would presumably have more risk, the damage has had longer to fester. So why would they target '19 models first? It could be as simple as picking a smaller sample size so they can verify the results, or perhaps they need more time to test something else that might be contained in the update.
Risk has nothing to do with age. It's much more likely to do with what happened during manufacturing, which is where I suspect they have narrowed down the scope to.

Similar to the 2020+ getting the software update eventually (why not?) it's probable that the 2017-2018 are actually less likely to have the problem, hence why they were not focused on first.
 

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2019 has different hardware than the 2017-2018. Im speculating the 2019-2021 has the same hardware. But if you have an obdII scanner, the "feed" or whatever is different for interpreting the 2019+ vs the 2017-2018.
Not necessarily hardware. We'd need someone with access to the hardware to do a teardown to know for sure.

PIDs change based on software differences, not hardware ones.
 

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Are all the PIDs you list for our cell groups only good to two decimal places? If so, am I just fooling myself by setting them to three decimal places?

When you say they can't measure impedance of every cell, do you mean the individual cells, or the parallel cell groups. I am certain they can't distinguish the paralleled cells. But I would think they could determine the impedance of parallel cell groups from watching the voltage sag under load?
Individual cells are 12-bit resolution, most other things are either 2 decimal places or 0.02V.
 

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So we should plan to get to the dealership with less than 30% charge? I guess the test procedure will ensure you leave with at least 30% charge, LOL!
 

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Welp you seem to have deeper knowledge of the pack. So when left plugged in for say weeks, what is the mechanism to keep the pack at 100%? My work uses the "cut off and never turn on till reset" charger. In this mode the charger does not monitor the pack once 100% charge has been reached. Its not uncommon to come back to a dead "device" after a few weeks even if it was left on the charger, because the charger does not reset.

So how does the bolt handle keeping the pack at 100%?
Generally speaking self discharge of lithium ion is very, very low. Somewhere around 1% loss a month. If your packs are draining faster than that at work, it's likely because their internal BMS never turns off, so they have parasitic drain.

But, at least based on what I've seen, there's a hysteresis mechanism used in the Bolt. So let's say that 4A to the pack is minimum charge current. Once the BMS calculates that 6A current could be drawn, it will re-engage charging until the 4A limit is reached.

I'm somewhat making up those numbers. I'd have to go check to see the actual minimum cutoff that the Bolt uses (I know I have it somewhere). But I have next to no logging having the car plugged in at full for a while to measure the re-engagement limit.
 

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So we should plan to get to the dealership with less than 30% charge? I guess the test procedure will ensure you leave with at least 30% charge, LOL!
Just tell your dealer to plug you in while waiting so that you have a full charge when you pick it up.
 

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That could be true but it is not in this case. The reduced delta is also present at a high SOC. At any rate, the delta at low battery is the only thing that matters anyway.

The delta at full charge is basically meaningless. This is only meaningful if the cell capacity is balanced. In the end what matters is that a "weak", undercharged, cell is not prematurely causing a low battery condition.

What I am seeing is a delta range that has dropped from over 30mv to about 5mv at about the same cell voltage. I really don't know why.
Disagree about the full charge delta - not at all meaningless. A bad cell will show up with the delta across the entire range, including at full, getting worse after you go below about half.
 

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Just tell your dealer to plug you in while waiting so that you have a full charge when you pick it up.
They did last time but I think the L2 was only 16A so it would take forever. The dealer is not too far from my house, so it's just easier to drive it back and charge at home. Would be great if they have 25KW DC chargers though.
 

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Generally speaking self discharge of lithium ion is very, very low. Somewhere around 1% loss a month. If your packs are draining faster than that at work, it's likely because their internal BMS never turns off, so they have parasitic drain.

But, at least based on what I've seen, there's a hysteresis mechanism used in the Bolt. So let's say that 4A to the pack is minimum charge current. Once the BMS calculates that 6A current could be drawn, it will re-engage charging until the 4A limit is reached.

I'm somewhat making up those numbers. I'd have to go check to see the actual minimum cutoff that the Bolt uses (I know I have it somewhere). But I have next to no logging having the car plugged in at full for a while to measure the re-engagement limit.
No my devices do not have a self discharge. They are "on" and monitoring sensors and stuff in the device. The complaints from users is they do not "run forever" when left on the charger like a laptop does. So it sounds like the Bolt bms does have a charger reset mechanism.
 
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