GetOffYourGas
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Location: Syracuse, NY

Re: Chevrolet Bolt

Mon Nov 16, 2020 6:16 am

DougWantsALeaf wrote:
Sat Nov 14, 2020 1:20 pm
I just hope this doesn't hurt their sales too much, as they were just gathering steam. It doesn't look like the issue is in the new packs.
One of the theories that I've heard is that as weaker cells age, their internal resistance increases. The BMS software may not account for this properly, causing those weak cells to overcharge, overheat, and start a fire.

Bottom line - I'm not sure we know enough to say whether the new packs are safe or the issue is one of age (hence the new packs aren't old enough to have this problem yet).

I hope GM gets to the bottom of this, but I'm not overly concerned. The recall's solution is to limit the SoC to 90%, which I already do via Hilltop Reserve.
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV (traded for Bolt)
2015 C-Max Energi (302A package)
2017 Bolt Premier
2021 Mini Cooper SE Signature+

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DaveEV
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Re: Chevrolet Bolt

Mon Nov 16, 2020 12:40 pm

GetOffYourGas wrote:
Mon Nov 16, 2020 6:16 am
One of the theories that I've heard is that as weaker cells age, their internal resistance increases. The BMS software may not account for this properly, causing those weak cells to overcharge, overheat, and start a fire.
That seems unlikely to me - what is the max pack/cell voltage that GM charges to?

Monitoring cell voltages and ensuring that bad things don't happen is the #1 job of the BMS - whether that's monitoring for high voltages during charging, or low voltages when discharging.
GetOffYourGas wrote:
Mon Nov 16, 2020 6:16 am
I hope GM gets to the bottom of this, but I'm not overly concerned. The recall's solution is to limit the SoC to 90%, which I already do via Hilltop Reserve.
I'm surprised that this isn't the default setting of the car - both to improve battery life and efficiency so that you have regen available at the start of every drive. It does also improve safety - the higher the voltage of the cell, the more energy there is to be released in the event of a cell failure.

Part of me wonders if the problem is actually outside of the cells, in some of the other components located in the pack, eg in the BMS or charger. If those parts also catch on fire, the cells are close enough that it could cause a cell to catch on fire, though it seems unlikely.

Hopefully GM and LG get to the bottom of this quickly and are able to resolve the issue at minimal cost.

GetOffYourGas
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Re: Chevrolet Bolt

Mon Nov 16, 2020 1:26 pm

DaveEV wrote:
Mon Nov 16, 2020 12:40 pm
GetOffYourGas wrote:
Mon Nov 16, 2020 6:16 am
One of the theories that I've heard is that as weaker cells age, their internal resistance increases. The BMS software may not account for this properly, causing those weak cells to overcharge, overheat, and start a fire.
That seems unlikely to me - what is the max pack/cell voltage that GM charges to?

Monitoring cell voltages and ensuring that bad things don't happen is the #1 job of the BMS - whether that's monitoring for high voltages during charging, or low voltages when discharging.
I'm not sure I follow you. A proper BMS will monitor cell voltages and ensure that bad things don't happen. So why is it unlikely that an improperly programmed BMS could cause this problem? It reads to me like you support this theory more than presenting an alternative. Unless it is the question of aging that you disagree with? But as cells age, those differences could widen, making the BMS ever more important over time. It has to assure that weaker cells don't overcharge or overheat.

So I am not a battery expert by any means, but I do have an electrical background. Could you provide a deeper explanation here? What subtlety am I missing?
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV (traded for Bolt)
2015 C-Max Energi (302A package)
2017 Bolt Premier
2021 Mini Cooper SE Signature+

SageBrush
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Re: Chevrolet Bolt

Mon Nov 16, 2020 1:34 pm

GetOffYourGas wrote:
Mon Nov 16, 2020 6:16 am
The recall's solution is to limit the SoC to 90%, which I already do via Hilltop Reserve.
That is not the recall solution, it is the 'what to do until we figure out the problem and issue a recall.'

Answer me this: if GM has not figured out the cause of the fires yet, why are you confident that the 90% SoC charge will protect you ?
2013 LEAF 'S' Model with QC & rear-view camera
Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

cwerdna
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Re: Chevrolet Bolt

Mon Nov 16, 2020 11:29 pm

SageBrush wrote:
Mon Nov 16, 2020 1:34 pm
That is not the recall solution, it is the 'what to do until we figure out the problem and issue a recall.'

Answer me this: if GM has not figured out the cause of the fires yet, why are you confident that the 90% SoC charge will protect you ?
Correct on the first point.

At about 1:15 into the video at https://my.chevrolet.com/how-to-support ... ltevrecall, they found that of the vehicles they inspected, they were full or nearly full.

There was little or no useful NHTSA documentation the other day but I learned of https://static.nhtsa.gov/odi/rcl/2020/R ... 1-2513.PDF today, which also mentions high SoC. But yes, AFAIK, they don't know the cause yet and the high SoC might be a red herring and just a coincidence as people may just plug in out of habit.

So, for the time being, they're asking people to not charge above hilltop reserve or 90% and they're issuing an update to limit it automatically. There's been plenty of discussion/speculation on https://www.chevybolt.org/ on what they might do as a final remedy to Bolt drivers but that would depend on them knowing the root cause and the cost of the remedy/remedies.

'19 Bolt Premier
'13 Leaf SV w/premium (owned)
'13 Leaf SV w/QC + LED & premium (lease over)

Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

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DaveEV
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Re: Chevrolet Bolt

Tue Nov 17, 2020 1:36 am

GetOffYourGas wrote:
Mon Nov 16, 2020 1:26 pm
I'm not sure I follow you. A proper BMS will monitor cell voltages and ensure that bad things don't happen. So why is it unlikely that an improperly programmed BMS could cause this problem? It reads to me like you support this theory more than presenting an alternative. Unless it is the question of aging that you disagree with? But as cells age, those differences could widen, making the BMS ever more important over time. It has to assure that weaker cells don't overcharge or overheat.
It would be quite the firmware bug that allows cells to get so far out of balance to allow a cell to spontaneously combust. It would take charging the cell well above 4.2V.

If the BMS was not reading a module's voltage properly, it would almost certainly have to trigger some sort of other error code that would shut things down.

I think it's more likely that there's some sort of defect in the separator of the cells which is causing issues, or some other sort of hardware defect. Remember the issue that caused Samsung phones to catch on fire? Or the Boeing 787 battery fires?

cwerdna
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Re: Chevrolet Bolt

Tue Nov 17, 2020 2:33 am

Right... there was https://www.sony.net/SonyInfo/News/Pres ... /06-0825E/ regarding the defective Sony batteries that caused a TON of laptops from many different brands to be recalled.

Or, there could be a short circuit within the pack that might be between the modules or within the modules themselves.

'19 Bolt Premier
'13 Leaf SV w/premium (owned)
'13 Leaf SV w/QC + LED & premium (lease over)

Please don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

GetOffYourGas
Posts: 2122
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Re: Chevrolet Bolt

Tue Nov 17, 2020 5:29 am

SageBrush wrote:
Mon Nov 16, 2020 1:34 pm
GetOffYourGas wrote:
Mon Nov 16, 2020 6:16 am
The recall's solution is to limit the SoC to 90%, which I already do via Hilltop Reserve.
That is not the recall solution, it is the 'what to do until we figure out the problem and issue a recall.'

Answer me this: if GM has not figured out the cause of the fires yet, why are you confident that the 90% SoC charge will protect you ?
What I meant is that the current recall will limit your SoC to 90%, but you knew that. So why are you being pedantic and adversarial about it?

cwerdna addressed your question with some evidence. I am satisfied with the current level of risk I have with the car set to Hilltop Reserve and parked outside.
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV (traded for Bolt)
2015 C-Max Energi (302A package)
2017 Bolt Premier
2021 Mini Cooper SE Signature+

SageBrush
Posts: 5608
Joined: Sun Mar 06, 2011 2:28 am
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Re: Chevrolet Bolt

Tue Nov 17, 2020 9:21 am

GetOffYourGas wrote:
Tue Nov 17, 2020 5:29 am
I am satisfied with the current level of risk I have with the car set to Hilltop Reserve and parked outside.
Funny.

You have NO IDEA what the risk is, because GM has not figured out the cause(s)
And it should be obvious that until the causes(s) are identified, the advice to reduce max SoC as a risk mitigation is a guess at best; a sop to owners like you at worst.
2013 LEAF 'S' Model with QC & rear-view camera
Bought Jan 2017 from N. California
Two years in Colorado, now in NM
03/18: 58 Ahr, 28k miles
11/18: 56.16 Ahr, 30k miles
09/20: 54.3 Ahr; 38k miles
-----
2018 Tesla Model 3 LR, Delivered 6/2018

GetOffYourGas
Posts: 2122
Joined: Tue Dec 20, 2011 6:56 pm
Delivery Date: 09 Mar 2012
Location: Syracuse, NY

Re: Chevrolet Bolt

Tue Nov 17, 2020 11:37 am

Ok, sure. And I have no idea the risk of getting hit by a bus next time I take my dog for a walk. 5 Bolts have caught on fire out of well over 50,000 sold. I'm comfortable saying the risk is low. And I've also taken the necessary precautions to minimize impact if it does. I keep no valuables in the car, and park in my driveway, away from the house.

I'm not sure what else you would have me do, maybe sell the car and buy a Leaf+?
~Brian

EV Fleet:
2011 Torqeedo Travel 1003 electric outboard on a 22' sailboat
2012 Leaf SV (traded for Bolt)
2015 C-Max Energi (302A package)
2017 Bolt Premier
2021 Mini Cooper SE Signature+

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