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Hello - I recently purchased a used 2017 Chevy Bolt Premier with ~14,000 miles from a Chevrolet certified dealership. The estimated range showed much lower than the 238 quoted range so we asked about battery capacity. They ran diagnostics and showed us that the battery pack capacity was showing 174 Ah. They noted that the maximum expected capacity is 185 Ah and minimum capacity within warranty period is 111 Ah. Therefore, we concluded that the battery pack was fine.

We have been driving for ~2-3 weeks and are already starting to see an increase in the range estimates abut were curious about the battery capacity. So we performed the following tests:
- Charged battery to 100%
- Drove until 3 bars appeared on the dash display (15% battery remaining)

Data after test as shown on dash and central displays:
- Energy used = 37.1 kWh
- Distance = 156.8 miles
- Average = 4.2 mi/kWh

If the above, data is correct, I am calculating:
- Battery capacity = 37.1 kWh / 0.85 = 43.6 kWh
- Range = 156.8 / 0.85 = 184.5 miles

Can anyone please let me know if I am doing something wrong with the calculation or test because 43.6 kWh is a significant decline from the expected 60 kWh battery capacity? Is this something we should look into and worry about?

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I'd say it looks fine. I rounded your numbers to 40kwh (2/3 battery) and 165 miles. So 165 x 1.5 = 247.
 

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because 43.6 kWh is a significant decline from the expected 60 kWh battery capacity?
Welcome to the forum. Does look low. Your method should be a good indication. But, you're still outside the level that would trigger the warranty. A bad cell tends to get worse with time. But there's also a chance that the battery needs to go through a few charge cycles if it's trying to recalibrate from some other event.
 

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I'd say it looks fine. I rounded your numbers to 40kwh (2/3 battery) and 165 miles. So 165 x 1.5 = 247.
Your math stinks. Op used 85% not 66%. And what have miles got to do with anything? They are looking for battery capacity.
 

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I'd say it looks fine. I rounded your numbers to 40kwh (2/3 battery) and 165 miles. So 165 x 1.5 = 247.
Range looks accurate, but the battery definitely doesn't look fine. After 40 kWh, the meter should be showing 7 bars. It is showing 3: an indication that the battery has lower capacity.

Mike
 

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You might have a low battery cell. You can check if you use Torque Pro or maybe talk the dealer into it. Sometimes dealers are reluctant to do the test, or don't know what to do. It makes it easier if you're armed with your data from Torque Pro.
 

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If the above, data is correct, I am calculating:
- Battery capacity = 37.1 kWh / 0.85 = 43.6 kWh
Yup. That is bad! Unfortunately, not bad enough to get a warranty replacement. Get Torque Pro, and Telek's PIDs. I suspect you have one or more bad cells.


Did they show you the Battery Cell State of Charge Variation number? That number is not to exceed 6.5%.

 

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Your math stinks. Op used 85% not 66%. And what have miles got to do with anything? They are looking for battery capacity.
Well, rounding off the numbers.

  • Energy used = 37.1 kWh just about 66% of 60 kWh, or 40kWh used
  • Distance = 156.8 miles about 165 using the above rounded 40kWh

So if 165 miles used 40kWh, or 66% of the charge, another 33% would be 247 miles.
 

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Range looks accurate, but the battery definitely doesn't look fine. After 40 kWh, the meter should be showing 7 bars. It is showing 3: an indication that the battery has lower capacity.

Mike
Yeah, I missed that part. It's rather important.
 

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Keep driving it until it gets very low. And even push it to the point (just stay around a charger or your home where you can push the car back) when the battery refuses to propel the car.
Then recharge it all the way and see how much it took.

I am not sure how well battery management is in here, maybe it needs to be reset. Maybe GM could do it... or do it yourself - definitely going low will trigger the process.
Based on the gauge level, you are talking about no more than 45 kWh capacity (assuming some error on the 3 bars).

Good thing is that if that is the cell dying, it will get worse quickly enough, but your warranty is 8 years.
So... be rested.
 
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Good thing is that if that is the cell dying, it will get worse quickly enough, but your warranty is 8 years.
So... be rested.
I wouldn't rest too much. You may want to park outside.

October 21, 2020 NHTSA ID NUMBER: 11365622
Components: ELECTRICAL SYSTEM
NHTSA ID Number: 11365622

Incident Date July 30, 2020

Consumer Location TEMECULA, CA

Vehicle Identification Number 1G1FX6S07H4****

Summary of Complaint

CRASH No

FIRE Yes

INJURIES 0

DEATHS 0

I BROUGHT THE CAR TO THE DEALER ON 2 SEPARATE OCCASIONS WITH CONCERNS OF A FAULTY BATTERY. THE BATTERY SUDDENLY STOPPED CHARGING FULLY. HOWEVER, I WAS TOLD BY THE DEALER TWICE THAT THE BATTERY WAS FUNCTIONING PROPERLY AND THERE WAS NOTHING THEY COULD DO. I OPENED A CLAIM WITH GM REGARDING THIS INCIDENT, ASKING THEM TO REPLACE THE BATTERY, SINCE IT WAS STILL UNDER WARRANTY, AND THERE WAS CLEARLY AN ISSUE. AFTER MONTHS OF BACK-AND-FORTH, GM CLOSED MY CASE STATING IT WAS NORMAL DEGRADATION OF THE BATTERY. ONE WEEK AFTER THEY CLOSED MY CASE, THE BATTERY SPONTANEOUSLY CAUGHT FIRE WHILE CHARGING IN MY GARAGE OVERNIGHT. IT TOTALED 2 VEHICLES, CHARRED EVERYTHING IN MY GARAGE, AND CAUSED SUCH SEVERE SMOKE DAMAGE THAT ALMOST EVERYTHING IN MY HOME WAS A TOTAL LOSS. THE FIRE DEPARTMENT DETERMINED THE FIRE ORIGINATED FROM THE TRUNK AREA, WHERE THE BATTERY IS. MY FAMILY IS DISPLACED WHILE REPAIRS ARE BEING DONE TO MY HOME, AT A TUNE OF APPROXIMATELY $200,000 AT THIS POINT. WE LOST APPROXIMATELY $105,000 IN CONTENTS, AS WELL AS THE 2 TOTALED VEHICLES ($75,000).
 

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I wouldn't rest too much. You may want to park outside.

October 21, 2020 NHTSA ID NUMBER: 11365622
Components: ELECTRICAL SYSTEM
NHTSA ID Number: 11365622
Good point! I know that investigation is not complete but some of us have been speculating that if you have some bad cells, the BMS may overheat trying to balance something that is "unbalanceable". Weber Auto gave us a clue to that when he said that the BMS can overheat when it encounters a situation where balancing is not possible. In a case like this, I think I'd park outside for sure!

Mike
 

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Welcome to the forum. Does look low. Your method should be a good indication. But, you're still outside the level that would trigger the warranty. A bad cell tends to get worse with time. But there's also a chance that the battery needs to go through a few charge cycles if it's trying to recalibrate from some other event.
Thank you! The warranty triggers below 60% of capacity right? So below 36kWh?
 

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Yup. That is bad! Unfortunately, not bad enough to get a warranty replacement. Get Torque Pro, and Telek's PIDs. I suspect you have one or more bad cells.


Did they show you the Battery Cell State of Charge Variation number? That number is not to exceed 6.5%.

Thank you for the reply! Dang, bummer about the warranty...

I will look into Torque Pro and Telek's PIDs, thanks for the link.

Yes, the Battery Cell State of Charge Variation appears to be 25%. I've attached the photo from the dealer, sorry for the poor quality. Would a bad cell be covered under warranty?
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Thank you! The warranty triggers below 60% of capacity right? So below 36kWh?
Correct. But there is absolutely no chance of any Bolt having 40% degradation yet. Any Bolt with capacity reduced this much has had one or more bad cells. This will trigger a warranty replacement of one or more battery sections. As I mentioned, find out what the Battery Cell State of Charge Variation number was. If they found you Ah number, they should also have this number. It must not exceed 6.5%.

1605215774246.png 1605215839327.png
 

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Yes, the Battery Cell State of Charge Variation appears to be 25%. I've attached the photo from the dealer, sorry for the poor quality. Would a bad cell be covered under warranty?
Absolutely. Make sure they replace all modules with bad cells. We have a member on here who had to go back twice, as they tore the whole battery apart, and replaced one section, only to figure out weeks later they had missed one!!
 

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Thank you! The warranty triggers below 60% of capacity right? So below 36kWh?
That's my understanding. But this is from normal degradation where all cells are dropping. This takes years and yours is most likely one cell causing trouble. Look back at @GJETSON's post where there's other scenarios for battery being covered.
 

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Absolutely. Make sure they replace all modules with bad cells. We have a member on here who had to go back twice, as they tore the whole battery apart, and replaced one section, only to figure out weeks later they had missed one!!
Thank you again for the replies, they are really helpful!

Excellent, we will go to the dealer to get the cells replaced. That is good to know about making sure they replace all modules with bad cells. Is it best to ask they show the Battery Cell State of Charge Variation less than 6.5% to confirm this?
 
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