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2021 Bolt LT - Kinetic Blue
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Discussion Starter · #1 · (Edited)
Hi all,

Here is my story. My wife and I bought our first EV - a 2021 Bolt LT - on February 20, 2021 and immediately fell in love with it. About 4 week ago the service light came on (and went off 12 hours later) indicating a lithium ion battery issue (according to the OnStar email).

The car went into the shop the next week and was diagnosed with a faulty AC pressure sensor which required replacement of the Hybrid Module 2 (HPCM2) which took 6 days to resolve due to shipping delays.

After receiving the car back I did four round trips to work (107 miles each) and determined that I was getting severely reduced range. The last two round trips included carefully controlled speeds (55 mph and 65 mph, respectively) and almost no climate control usage.

I took the Bolt back to the dealer stating the reduced range (stressing the usable capacity is only ~50 kWh instead of 62-64). They came back with the lip service of driving style bringing it down as well as the aftermarket tires (Michelin CrossClimate2) we swapped in after about 600 miles.

I talked to the service advisor and EV tech that I had proof and showed them all the pictures and calculations I took during the two controlled runs. They finally caved and said they would escalate to Chevy corporate for a solution (they had exhausted all their tools for diagnosing what was going on).

Yesterday I charged to 94% and drove to visit family for the day and after the return trip I did another loop around the city to get the battery down to 4%. Here are the journey stats:

Net consumption - 90% (47.1 kWh indicated)
Total travel - 151.1 miles (47.4 mph average)
Efficiency - 3.2 mi/kWh (slightly worse than EPA highway estimate of 3.4 mi/kWh)
Energy usage - 95% driving, 5% climate, 0% battery conditioning
Ambient temperature - 54-56°F
Range impacts -
-15.1 miles (technique)
-5.5 miles (terrain)
-9.1 miles (climate)
-3.1 miles (outside temperature)
-32.2 miles TOTAL

Calculating usable capacity:
47.1 / 0.90 = 52.3 kWh

When I got home last night I plugged the car into the OEM travel charger and a P3 Kill-A-Watt monitor at 12 amps to measure the at-the-wall output to get it back to our standard 90% charge set point. When I plugged it in it was indicating 44 hours until completion (which would be 63.4 kWh added before charging losses), but I would imagine it will only be about 36 hours when it is all said and done (51.8 kWh). I’ll update tomorrow with the results.

I took pictures throughout all the trips to have plenty of evidence, and all we really want is to have the car back to how it performed when we first bought it three months (and 2100 miles) ago.

What is the community’s opinion on how I am addressing this? Are there other avenues to explore to get this car to perform as a brand new car should?

TL/DR - HPCM2 replaced under warranty at 1500 miles and now only have 52 kWh Of usable battery
 

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2021 Bolt LT - Kinetic Blue
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Discussion Starter · #3 ·
After 38.25 hours the battery reached an indicated 99% SOC, here are the relevant stats:
1.44 kW continuous (12 amps at 120v)
54.5 kWh measured at the wall
49.1 kWh added (assuming 90% efficiency)
Calculated capacity: 49.1 / 0.94 = 52.2 kWh

I think this is clear, ample and triple-verified evidence of a capacity limitation.

I also received the VeePeak ODBII reader I order and loaded up Car Scanner Pro. The cell voltages at 99% were between 4.12-4.14 V

If there are any other parameter outputs that would be helpful to know please ask as I captured all of them immediately after unplugging from the charger.
 

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I also received the VeePeak ODBII reader I order and loaded up Car Scanner Pro. The cell voltages at 99% were between 4.12-4.14 V

If there are any other parameter outputs that would be helpful to know please ask as I captured all of them immediately after unplugging from the charger.
You understand the system, and the math, as well as anybody on here. I assume they reset some parameters to default settings in the capacity estimating algorithms, when they replaced the HPCM2 . But after over 500 miles, they should have corrected by now. Even if they are off by 10%, your pack still stinks.

@Telek would be the one person on here who might have a clue.
 

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Someone in my family, with a 2020 Bolt EV, noticed some degradation in range starting last February. It continued until April, where it became alarming.
After some back and forth with the dealer that considered it was due to winter tires and use of heating, a more serious investigation was requested because our computations (based on evident data from the charge station) lead us to estimate the battery capacity to 32 kWh.
The dealer finally looked into this more seriously. Following the detailed battery analysis, they concluded that one assembly within the battery was faulty and needed to be replaced. Due to parts availability issues (about a month), they decided to replace the entire battery (which they could get in 24 hours). Within 48 hours, the car was back on the road.
It took few days until the GOM displayed proper range. The car is now operating as it should.

I'm not saying it's the same but, the new 66 kWh battery in the 2020+ can be prone to issues. If you have evident data, ask for a more detailed battery check. You paid for this nominal autonomy.
 

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Discussion Starter · #6 ·
Looked through the Car Scanner parameters (at 99% SOC as indicated on the MyChevrolet app) and found a few others that may be applicable to my issue:

Hybrid/EV battery pack remaining charge: 90%
Hybrid/EV battery pack system voltage: 396.23 V
Battery - Pack - Capacity Ah Raw 2019+: 191.96 Ah
Battery - Pack - Capacity kWh estimated 2019+: 61.43 kWh
Battery - Pack - State of Charge Displayed: 99.22%
Battery - Pack - State of Charge Raw HD: 90.75%
Battery - Pack - State of Charge Raw LD: 90.98%
Battery - Pack - State of Charge Raw LD 2: 90.59%
Battery - Pack - State of Charge Raw LD 3: 90.59%
Battery - Pack - State of Charge Variation: 0.78%
Battery - Pack - Minimum Voltage: 241.8 V
Battery - Pack - Maximum Voltage: 401.96 V
Battery - Pack - Voltage LD: 396.24 V

Hopefully some of this is helpful. Sorry for such long posts. If you couldn’t tell yet, I’m an engineer.
 

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2020 Chevrolet Bolt
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Looked through the Car Scanner parameters (at 99% SOC as indicated on the MyChevrolet app) and found a few others that may be applicable to my issue:

Hybrid/EV battery pack remaining charge: 90%
Hybrid/EV battery pack system voltage: 396.23 V
Battery - Pack - Capacity Ah Raw 2019+: 191.96 Ah
Battery - Pack - Capacity kWh estimated 2019+: 61.43 kWh
Battery - Pack - State of Charge Displayed: 99.22%
Battery - Pack - State of Charge Raw HD: 90.75%
Battery - Pack - State of Charge Raw LD: 90.98%
Battery - Pack - State of Charge Raw LD 2: 90.59%
Battery - Pack - State of Charge Raw LD 3: 90.59%
Battery - Pack - State of Charge Variation: 0.78%
Battery - Pack - Minimum Voltage: 241.8 V
Battery - Pack - Maximum Voltage: 401.96 V
Battery - Pack - Voltage LD: 396.24 V

Hopefully some of this is helpful. Sorry for such long posts. If you couldn’t tell yet, I’m an engineer.
@Telek would know better, but the "Battery - Pack - Capacity Ah Raw 2019+: 191.96 Ah" is actually quite good, and should correspond to a battery without much degradation at all. As a reference, my new 2020 (purchased 2 months ago) has 189.8 Ah.

The weird number is the difference between "Battery - Pack - State of Charge Displayed: 99.22%" and "Battery - Pack - State of Charge Raw HD: 90.75%." Those numbers should be much closer together, like within one or two percentage points. That makes me wonder if the dealership applied the temporary recall fix which limited charge to ~90%, instead of the final fix...?
 

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Discussion Starter · #8 ·
@liuelson Thanks for the response. I was thinking the same thing and even questioned the service advisor whether the recall software was applied and was told that it was not by both he and the service technician.
 

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Something is wonky here. 90.75% RAW should be 391.5V on the N2 cells in the 2021. I don't see any of the high resolution pack voltages in there, but 396.2 is clearly far off from that. 396.24V should be about 94.9% RAW. You mentioned above that the cell voltages were 4.12-4.14 - that's low.

I suspect there's a cell voltage that is out. Can you grab all your cell voltages ideally with the car off? Just put your foot on to brake to engage the computers and log all OBD2 values starting with ! for a couple of minutes. Pop the log somewhere (remove your GPS values first or send to me directly).

You also never mentioned what the range was like before the HPCM2 replacement. I don't understand why a faulty AC sensor would require that replacement, but ok.

Also

1.44 kW continuous (12 amps at 120v)
54.5 kWh measured at the wall
Is 120V what the kill-a-watt said under load exactly? What about not under load? The 54.5 was measured or calculated?
 

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Discussion Starter · #11 ·
I suspect there's a cell voltage that is out. Can you grab all your cell voltages ideally with the car off? Just put your foot on to brake to engage the computers and log all OBD2 values starting with ! for a couple of minutes. Pop the log somewhere (remove your GPS values first or send to me directly).
I can do that. I’m getting used to the software, so it might take me a day or two.

You also never mentioned what the range was like before the HPCM2 replacement.
I don’t have any detailed notes on range before this, but the GOM never read below 200 miles at 80-90% SOC. The one round trip to my work before the service showed 103.3 miles with 32.6 kWh used (3.17 miles/kWh). I believe I started at 78-80% SOC and ended at 28% (which would indicate a real world range around 198-206 miles. This was on March 5 in southwest Ohio, so it was in the 30’s °F.

Is 120V what the kill-a-watt said under load exactly? What about not under load? The 54.5 was measured or calculated?
120V and 54.5 kW as indicated on the KAW
 

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Discussion Starter · #12 ·
Looking through the parameters I don’t see any starting with a “!”. Should I export all values? And should I just do the recording stationary with the computers active but the car powered off?
 

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Discussion Starter · #14 ·
You can find more info here: Chevy Bolt OBD2 PIDs – All EV Info

I think he means the PIDs that he’s labeled starting with !
Thanks for the help, boltco, I downloaded the CSV file and I’ll record and upload the data tonight. I assume the cell voltage should be closer to 4.20 V (at a true 100% SOC) if the nominal voltage is around 3.65.
 

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Discussion Starter · #16 ·
Ok, I was able to export some data of from the car scanner app. Not sure if I did this right, but here is the CSV file.

I noticed that the gap between the DIC and raw battery inverted and the difference widened as the SOC got lower.

As posted before I had 99.2% (DIC) vs. 90.75% (raw HD) @ 4.13V average
Today I saw 23.92% (DIC) vs. 44.27% (raw HD) @ 3.61V average
 

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Ok, I was able to export some data of from the car scanner app. Not sure if I did this right, but here is the CSV file.

I noticed that the gap between the DIC and raw battery inverted and the difference widened as the SOC got lower.

As posted before I had 99.2% (DIC) vs. 90.75% (raw HD) @ 4.13V average
Today I saw 23.92% (DIC) vs. 44.27% (raw HD) @ 3.61V average
Are you able to collect the data for the PIDs labeled +Cell Voltage #01, +Cell Voltage #02, etc.? There are 96 total.

There's also something weird going on with your *Battery - Cell - Max Voltage and *Battery - Cell - Min Voltage. They shouldn't be exactly the same to so many decimals, and they shouldn't even have so many decimals. I thought those PIDs were only to the nearest 0.02V.
 

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Discussion Starter · #18 ·
I’ll grab a snapshot of the cell voltages. I noticed the same too. Every time I have looked at the cell voltages they have all been within +/- 0.02

Is the best way to grab data in Car Scanner Pro the dashboard screen or the live data function with all variables on one graph? Still trying to figure out the easiest way to get the data requested.

I do feel like we are onto something here with the SOC differential.
 

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Discussion Starter · #19 ·
Here are the DIC vs Raw HD percentages I have so far:

DIC battery (%)Raw HD battery (%)
99.2290.75
30.2049.19
23.9244.27

Here are the voltages I captured last week when the DIC (and MyChevrolet app) was showing 99% SOC:

Cell 01
4.13​
Cell 25
4.13​
Cell 49
4.13​
Cell 73
4.13​
Cell 02
4.13​
Cell 26
4.13​
Cell 50
4.13​
Cell 74
4.13​
Cell 03
4.13​
Cell 27
4.13​
Cell 51
4.13​
Cell 75
4.13​
Cell 04
4.13​
Cell 28
4.13​
Cell 52
4.13​
Cell 76
4.13​
Cell 05
4.13​
Cell 29
4.13​
Cell 53
4.13​
Cell 77
4.13​
Cell 06
4.13​
Cell 30
4.13​
Cell 54
4.13​
Cell 78
4.13​
Cell 07
4.13​
Cell 31
4.13​
Cell 55
4.13​
Cell 79
4.13​
Cell 08
4.13​
Cell 32
4.13​
Cell 56
4.13​
Cell 80
4.14​
Cell 09
4.14​
Cell 33
4.13​
Cell 57
4.13​
Cell 81
4.13​
Cell 10
4.13​
Cell 34
4.13​
Cell 58
4.13​
Cell 82
4.13​
Cell 11
4.13​
Cell 35
4.13​
Cell 59
4.13​
Cell 83
4.13​
Cell 12
4.13​
Cell 36
4.13​
Cell 60
4.13​
Cell 84
4.13​
Cell 13
4.14​
Cell 37
4.13​
Cell 61
4.13​
Cell 85
4.13​
Cell 14
4.13​
Cell 38
4.13​
Cell 62
4.13​
Cell 86
4.13​
Cell 15
4.13​
Cell 39
4.13​
Cell 63
4.13​
Cell 87
4.13​
Cell 16
4.14​
Cell 40
4.13​
Cell 64
4.13​
Cell 88
4.13​
Cell 17
4.13​
Cell 41
4.14​
Cell 65
4.12​
Cell 89
4.13​
Cell 18
4.13​
Cell 42
4.13​
Cell 66
4.12​
Cell 90
4.13​
Cell 19
4.13​
Cell 43
4.13​
Cell 67
4.13​
Cell 91
4.13​
Cell 20
4.13​
Cell 44
4.13​
Cell 68
4.13​
Cell 92
4.13​
Cell 21
4.14​
Cell 45
4.13​
Cell 69
4.13​
Cell 93
4.13​
Cell 22
4.13​
Cell 46
4.13​
Cell 70
4.12​
Cell 94
4.13​
Cell 23
4.13​
Cell 47
4.13​
Cell 71
4.13​
Cell 95
4.13​
Cell 24
4.13​
Cell 48
4.13​
Cell 72
4.13​
Cell 96
4.13​

The average is 4.1303 V (standard deviation of 0.0030 V)

Is there another SOC that would be helpful to get the cell readings?
 

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2020 Chevrolet Bolt
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Here are the DIC vs Raw HD percentages I have so far:

DIC battery (%)Raw HD battery (%)
99.2290.75
30.2049.19
23.9244.27

Here are the voltages I captured last week when the DIC (and MyChevrolet app) was showing 99% SOC:

Cell 01
4.13​
Cell 25
4.13​
Cell 49
4.13​
Cell 73
4.13​
Cell 02
4.13​
Cell 26
4.13​
Cell 50
4.13​
Cell 74
4.13​
Cell 03
4.13​
Cell 27
4.13​
Cell 51
4.13​
Cell 75
4.13​
Cell 04
4.13​
Cell 28
4.13​
Cell 52
4.13​
Cell 76
4.13​
Cell 05
4.13​
Cell 29
4.13​
Cell 53
4.13​
Cell 77
4.13​
Cell 06
4.13​
Cell 30
4.13​
Cell 54
4.13​
Cell 78
4.13​
Cell 07
4.13​
Cell 31
4.13​
Cell 55
4.13​
Cell 79
4.13​
Cell 08
4.13​
Cell 32
4.13​
Cell 56
4.13​
Cell 80
4.14​
Cell 09
4.14​
Cell 33
4.13​
Cell 57
4.13​
Cell 81
4.13​
Cell 10
4.13​
Cell 34
4.13​
Cell 58
4.13​
Cell 82
4.13​
Cell 11
4.13​
Cell 35
4.13​
Cell 59
4.13​
Cell 83
4.13​
Cell 12
4.13​
Cell 36
4.13​
Cell 60
4.13​
Cell 84
4.13​
Cell 13
4.14​
Cell 37
4.13​
Cell 61
4.13​
Cell 85
4.13​
Cell 14
4.13​
Cell 38
4.13​
Cell 62
4.13​
Cell 86
4.13​
Cell 15
4.13​
Cell 39
4.13​
Cell 63
4.13​
Cell 87
4.13​
Cell 16
4.14​
Cell 40
4.13​
Cell 64
4.13​
Cell 88
4.13​
Cell 17
4.13​
Cell 41
4.14​
Cell 65
4.12​
Cell 89
4.13​
Cell 18
4.13​
Cell 42
4.13​
Cell 66
4.12​
Cell 90
4.13​
Cell 19
4.13​
Cell 43
4.13​
Cell 67
4.13​
Cell 91
4.13​
Cell 20
4.13​
Cell 44
4.13​
Cell 68
4.13​
Cell 92
4.13​
Cell 21
4.14​
Cell 45
4.13​
Cell 69
4.13​
Cell 93
4.13​
Cell 22
4.13​
Cell 46
4.13​
Cell 70
4.12​
Cell 94
4.13​
Cell 23
4.13​
Cell 47
4.13​
Cell 71
4.13​
Cell 95
4.13​
Cell 24
4.13​
Cell 48
4.13​
Cell 72
4.13​
Cell 96
4.13​

The average is 4.1303 V (standard deviation of 0.0030 V)

Is there another SOC that would be helpful to get the cell readings?
Although your Bolt isn't subject to the recall, the recall procedure calls for the battery cell voltages to be measured when the SOC is between 30% and 50%. So maybe checking cell voltages around 30% SOC would reveal something? Obviously, right now, there isn't much variance at all, and 4.13 V doesn't seem unusual (nominal pack voltage is 400 V, so 400 / 96 = 4.16 V).

I keep wondering about the large differences between SOC displayed and SOC raw, almost as if the SOC display calculation is off for some reason. Have you tried disconnecting the 12 V battery for a few minutes to reset the computer systems?
 
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