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Discussion Starter #1 (Edited)
[Edit: after a couple of drives and recharges, projected range was 250 miles this morning, with a max of about 290 and min of about 210. If this is in the real world ballpark I’m in good shape.]

My new to me certified pre-owned 2017 Bolt came with range problems. The dealer tech initially said there wasn’t a problem, but on further investigation caused, I think, by the recall, they found a bad cell and replaced that by replacing its module.I haven’t had it back long enough to know if the range is acceptable, but at least the battery has been thoroughly tested and “refurbished” (if you will). They also did the software update to limit charging. I’ve attached a photo of the receipt FYI.
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Would kind of explain why charging to full (4.10 volts) resulted in the car catching fire (>4.17 volts).
 

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Would kind of explain why charging to full (4.10 volts) resulted in the car catching fire (>4.17 volts).
What do you imagine happens to a cell at 4.17 volts? It shouldn't burn at 4.2 volts. Probably would be fine at 4.4 volts, except for accelerated degradation.

12-29-18-1.jpg

The problem isn't the high cells. It is the low ones, indicating dendrites, and internal shorting causing self-discharge, and heat.
 

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What do you imagine happens to a cell at 4.17 volts? It shouldn't burn at 4.2 volts. Probably would be fine at 4.4 volts, except for accelerated degradation.

View attachment 31968

The problem isn't the high cells. It is the low ones, indicating dendrites, and internal shorting causing self-discharge, and heat.
That would explain why GM is limiting charge to 90%. ?!?
 

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Yes. Trying to charge a badly shorted cell will generate tremendous heat...enough to turn it into a road flare.
So you would recommend everyone to charge to 100% daily to ensure the cell voltages never gets too low?!?
 

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So you would recommend everyone to charge to 100% daily to ensure the cell voltages never gets too low?!?
I think you're misinterpreting what he's saying.

The damaged cells would show lower voltage despite BMS's efforts to charge them up. If those were kept forced up to higher voltages, then they would be at a higher risk of failure due to stress. So stopping the charge at a lower level would lessen the stress, and thus reduce the risk.
 

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So you would recommend everyone to charge to 100% daily to ensure the cell voltages never gets too low?!?
No. If the problem is failing cells, as opposed to a balancing problem, would suggest getting them out of your car. Nothing is going to resuscitate a bad cell. Charging and discharging them will only continue their degradation. Doing so less, may reduce the degradation, and chance of fire. But the only real solution would be to replace them.
 

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Thanks for sharing. Interesting the paperwork says spec variation should be no more than 0.07 volts. The service manual stated 0.03 volts.
If my Bolt showed a 0.07 volt variation, I would not be parking it in my garage. It would be at the dealership.
 

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What I find interesting is the number of people that have packs that are obviously failing, they take the car into the dealer, and no codes are found.

I hope after the final "fix" is released, when something is wrong, and the car is hooked up to GM's diagnostic equipment, a big old "THIS BATTERY IS BROKEN" shows up in some way. 😁
 

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What I find interesting is the number of people that have packs that are obviously failing, they take the car into the dealer, and no codes are found.

I hope after the final "fix" is released, when something is wrong, and the car is hooked up to GM's diagnostic equipment, a big old "THIS BATTERY IS BROKEN" shows up in some way. 😁
The diagnostics they use are showing the big voltage spread, and the Battery State of Charge Variation is working. I think the untrained techs are the problem.

They don't need more info in the shop. It needs to show up on the dash in the car.
 

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The diagnostics they use are showing the big voltage spread, and the Battery State of Charge Variation is working. I think the untrained techs are the problem.

They don't need more info in the shop. It needs to show up on the dash in the car.
Yeah I'm really surprised that the battery management system isn't programmed to show some indications or faults if the voltage spread under some specific conditions (resting for x amount of time) exceeds some value, or if 1 or 2 cells are much lower than others.

Seems like this is not done on the Bolt, Kona, Leaf, etc. Is it really that hard to program this? Or is it not hard but they are concerned about false positives from transient voltage readings?
 

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The diagnostics they use are showing the big voltage spread, and the Battery State of Charge Variation is working. I think the untrained techs are the problem.

They don't need more info in the shop. It needs to show up on the dash in the car.
Having never seen how Chevy's diagnostic system works, I don't know what the answer is. I'm sure the data is there, but it seems like the modus operandi in the repair world is if there is not a code, there is not a problem. There have been numerous instances of people with bad cells, the dealer says no codes, and sends them home. Only for them to return later and get a replacement. Seems like a code isn't being thrown at all, so an untrained technician doesn't even have a chance to start down the correct path.

It would be cool if someone in this situation was allowed to actually see what is reported when the vehicle was hooked up for the first time.
 

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Having never seen how Chevy's diagnostic system works, I don't know what the answer is. I'm sure the data is there, but it seems like the modus operandi in the repair world is if there is not a code, there is not a problem. There have been numerous instances of people with bad cells, the dealer says no codes, and sends them home. Only for them to return later and get a replacement. Seems like a code isn't being thrown at all, so an untrained technician doesn't even have a chance to start down the correct path.

It would be cool if someone in this situation was allowed to actually see what is reported when the vehicle was hooked up for the first time.

We have seen the service manual description of what to look for, and shop printouts of the results, on this forum. And still some shops ignored what they had printed out to show the customer, telling them there is no problem, and the forum members had to go back and point at the shop's own data.
 

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We have seen the service manual description of what to look for, and shop printouts of the results, on this forum. And still some shops ignored what they had printed out to show the customer, telling them there is no problem, and the forum members had to go back and point at the shop's own data.
Yeah, I admit I haven't dug into every case and I may not be remembering details correctly, but it seems like there are several instances where there were no "codes" reported despite obvious (to the customer) problems. Just like what was stated at the top of the ticket in this thread: No codes present. Seems like many shops stop after the first sentence, i.e. no codes, no problem.

Luckily in this case, despite there being no codes, someone did further analysis.
 

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My new to me certified pre-owned 2017 Bolt came with range problems. The dealer tech initially said there wasn’t a problem, but on further investigation caused, I think, by the recall, they found a bad cell and replaced that by replacing its module.I haven’t had it back long enough to know if the range is acceptable, but at least the battery has been thoroughly tested and “refurbished” (if you will). They also did the software update to limit charging. I’ve attached a photo of the receipt FYI.
View attachment 31963
Wait hold up - the dealer was able to replace a single module on your pack??
 
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