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So I'm a little confused... are batteries going to be replaced if they are .070 or .030 volts off from the rest of the pack? Or are they just going to replace individual cells?
 

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So I'm a little confused... are batteries going to be replaced if they are .070 or .030 volts off from the rest of the pack? Or are they just going to replace individual cells?
There is no way to replace an individual cell. There are 288 cells in a Bolt pack. Every three are spot welded together into a cell group (called 3p, or in parallel), so if one was bad you would need to replace all three. However, you can't replace just three because each group of three is permanently assembled into a module with eight or ten 3 cell groups in series in each one (called 8s3p or 10s3p). And you can't just replace a module because there are two modules permanently connected in a section, 5 sections in all. GM would replace a section, or two, or the entire battery. It depends on how many bad cells you have, in which sections.

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or at least these two.







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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.
I have one cell that is consistently .3V lower than all other cells, but the dealer says it’s “normal.” I escalated to GM customer care today - waiting for a call back. This is not normal, right?!
 

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I have one cell that is consistently .3V lower than all other cells, but the dealer says it’s “normal.” I escalated to GM customer care today - waiting for a call back. This is not normal, right?!
0.3v (300 millivolts) sounds really bad... like "starting Tchaik 4 without clearing the spit valve" bad. Could you post a screenshot of your app?
 

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I have one cell that is consistently .3V lower than all other cells, but the dealer says it’s “normal.” I escalated to GM customer care today - waiting for a call back. This is not normal, right?!

It now depends on the average cell voltage. Your lowest cell must be 0.070 V below the average.

 

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I'll assume that 95 cells are between 4.110 and 4.080, since 30mV difference is not uncommon. And there is one cell at 3.800v. Average would be 4.092. Delta is 292mV. 292 > 70, so GM will replace a module.
(note: if there's a second bad cell in another module, then I believe they'd replace the whole pack).

I would just print-out the picture in post #1 of this thread. Also, print-out your screen shots showing the 0.3v cell difference.

The dealer should perform test procedure "Hybrid/EV HighVoltage Battery Reduced Range Analysis" per DocID 5406681. If they ask for a "diagnostic fee," let them know that this test is covered as labor 5031139 by the propulsion warranty... maybe print-out https://static.nhtsa.gov/odi/tsbs/2019/MC-10168233-9999.pdf and highlight that statement on page 5, in case it's necessary.

Since the dealer already turned you away once, you may want to have this done at a Bolt-savvy dealer. In my metro area, if I search on Cars.com for 2020 Bolts within 50 miles of me, I find that half of the Bolts for sale are all at one dealer... that's usually the one to go to. Many Chevy dealers are pretty clueless about Bolts.
 

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I'll assume that 95 cells are between 4.110 and 4.080, since 30mV difference is not uncommon. And there is one cell at 3.800v. Average would be 4.092. Delta is 292mV. 292 > 70, so GM will replace a module.
(note: if there's a second bad cell in another module, then I believe they'd replace the whole pack).

I would just print-out the picture in post #1 of this thread. Also, print-out your screen shots showing the 0.3v cell difference.

The dealer should perform test procedure "Hybrid/EV HighVoltage Battery Reduced Range Analysis" per DocID 5406681. If they ask for a "diagnostic fee," let them know that this test is covered as labor 5031139 by the propulsion warranty... maybe print-out https://static.nhtsa.gov/odi/tsbs/2019/MC-10168233-9999.pdf and highlight that statement on page 5, in case it's necessary.

Since the dealer already turned you away once, you may want to have this done at a Bolt-savvy dealer. In my metro area, if I search on Cars.com for 2020 Bolts within 50 miles of me, I find that half of the Bolts for sale are all at one dealer... that's usually the one to go to. Many Chevy dealers are pretty clueless about Bolts.
Thank you for the quick and detailed response!!!! The dealer is the biggest in the area with a supposedly quite experienced head tech, but I'm not a fan.
 

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Yes, I think GM may be the only manufacturer I've heard of doing sub-pack maintenance at local shops. It's impressive also because they would have to train auto mechanics to work around 200 volt DC.
No. Nissan's been doing it for ages.

2012 SL with range collapse - My Nissan Leaf Forum got a module replaced. Seems Nissan Leaf Electric Car Reports Own Battery-Cell Failure Via Carwings also did (I've actually met Rob and rode along in his '11 Leaf back when it was the latest (and first) model year).

There have been a few other Leaf cases which involved the dealer having to open up the pack casing.
 

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No. Nissan's been doing it for ages.
I guess that most of the defects I read about in LEAFs are due to degradation below the 8-bar warranty, so of course they get a whole pack. While none of the defects for Bolts are due to degradation, so nobody gets a new pack.
 

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I guess that most of the defects I read about in LEAFs are due to degradation below the 8-bar warranty, so of course they get a whole pack. While none of the defects for Bolts are due to degradation, so nobody gets a new pack.
The first handful of Bolts with defective cells got entirely new packs. This was partly so GM could look at them, and partly because they never thought they would be dealing with so many bad packs.
 

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That’s one of the articles I found & printed out for the dealer.
If a dealer takes an interest in your case, it would be great if they wanted to learn about these issues that can affect Bolts. Unfortunately, some dealers don't have that interest. In some ways, the warranty booklet doesn't even matter to them: if a customer says something needs doing under warranty, they just call GM, and if GM says it's covered under warranty, then great. The dealer doesn't need convincing, because they don't think it's their decision. However, they do sometimes need coaching, so that the question they ask to GM gets a "yes."

Just trying to lower the bar, so you don't get too frustrated if they show no interest in articles!

Another approach would be to call Chevy's EV Concierge Monday. You could tell them that you independently established that your pack's cell-group voltage variation is 292mV, and ask them to call your dealer and advise that Range Analysis 5406681 should be performed and is covered under Voltec:

Contact our dedicated customer support team, Chevrolet EV Concierge 1-833-EVCHEVY available Monday through Friday from 8:00am – 7:00pm EST
 

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If a dealer takes an interest in your case, it would be great if they wanted to learn about these issues that can affect Bolts. Unfortunately, some dealers don't have that interest. In some ways, the warranty booklet doesn't even matter to them: if a customer says something needs doing under warranty, they just call GM, and if GM says it's covered under warranty, then great. The dealer doesn't need convincing, because they don't think it's their decision. However, they do sometimes need coaching, so that the question they ask to GM gets a "yes."

Just trying to lower the bar, so you don't get too frustrated if they show no interest in articles!

Another approach would be to call Chevy's EV Concierge Monday. You could tell them that you independently established that your pack's cell-group voltage variation is 292mV, and ask them to call your dealer and advise that Range Analysis 5406681 should be performed and is covered under Voltec:
Update! Stevens Creek Chevrolet in San Jose, CA ran diagnostics on my car todayand confirmed that a portion of the battery section has died, and they have ordered parts to replace it. I assume this means they are replacing a module not the entire battery.
 

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I would have expected Stevens Creek Chevrolet to get it right the first time. Is this the dealer that you originally went to that said a cell .3V lower than all other cells is “normal” ??
 
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