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Discussion Starter · #1 ·
Hiya! I wanted to share this research I put together using 333K data points from real live Bolts across the US. The first plot is onboard rated range vs. external temperature, and the bottom one is a moving average of range estimate vs. odometer. Happy to answer any questions.

The full write up is hosted on Recurrent's website where the focus is on the used EV market. I'm curious what data current or potential future Bolt drivers would want to see and would love to chat with any recent Bolt owners about their buying experience.

Thanks!!

36301

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Thanks for posting. On the second chart, I am thinking a person can see the approximate battery degradation, right? Something like 10-15% at 100k miles? Also, in the first chart the range reduces at high temperatures for the 60kwh packs and not the 66kwh packs. Any idea why?
 

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After 95,000 Miles on 2017 Premier

36321




Also 170 Amph


Looks almost perfect .. 5.6% oops..mean 9% or so degradation based on 60kWh battery


EXCEPT .. and I need to get a screen capture but I noticed today when I halfway floored it that Max cell went to 3.8 and Min cell went to 3.4 ...big difference and I dont know if that has ever been discussed on the forum.. when looking for bad cells are we looking just at "idle" ...cruising or hard acceleration ... ?


Can a large Voltage drop on 1 cell under hard acceleration an indication of a cell going bad ????


Other than that "back in my mind thought".. it seems like the pack at least currently is holding up well.


Getting 250-260 Miles driving around town all day long even with the 9% degradation (no ac)
 

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After 95,000 Miles on 2017 Premier

View attachment 36321



Also 170 Amph


Looks almost perfect .. 5.6% oops..mean 9% or so degradation based on 60kWh battery


EXCEPT .. and I need to get a screen capture but I noticed today when I halfway floored it that Max cell went to 3.8 and Min cell went to 3.4 ...big difference and I dont know if that has ever been discussed on the forum.. when looking for bad cells are we looking just at "idle" ...cruising or hard acceleration ... ?


Can a large Voltage drop on 1 cell under hard acceleration an indication of a cell going bad ????


Other than that "back in my mind thought".. it seems like the pack at least currently is holding up well.


Getting 250-260 Miles driving around town all day long even with the 9% degradation (no ac)
Thanks for sharing this info. What was your charging habit with the car? ie- charged to 100% every night, never charged over 70% unless travelling, charged only when the car got to 20%, etc.
 

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Thanks for sharing this info. What was your charging habit with the car? ie- charged to 100% every night, never charged over 70% unless travelling, charged only when the car got to 20%, etc.
Brad I drive the car hard , driving UBer/Lyft ..zipping from on location to another. I use Fast Chargers all the time and charge to 100% every night .(other than a couple months during the first recall)
 

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Discussion Starter · #6 ·
Thanks for posting. On the second chart, I am thinking a person can see the approximate battery degradation, right? Something like 10-15% at 100k miles? Also, in the first chart the range reduces at high temperatures for the 60kwh packs and not the 66kwh packs. Any idea why?
That is what I suspect, but I'm hesitant to make that call without knowing the actual age, rather than just odometer as a proxy.

In terms of the difference between the high temp range in 60 kWh vs. 66 kWh - I'm not exactly sure. Could be the way the newer ones are cooled, or the way the range is calculated. I'll poke around and see if there are any details available that I may have missed.
 

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In terms of the difference between the high temp range in 60 kWh vs. 66 kWh - I'm not exactly sure.
I believe it was a simple design/materials change to the cells, so everything else in the battery pack assembly is the same, with the exception of the software.

It's kinda like many computer parts. There's always a little improvement that makes the new one faster or more efficient or have a higher capacity. Sometimes the new version costs more but often the new one costs the same or less. If you look at the standard industrial 18650 cell you will find the same exact cell size with high capacities that are nearly double the lowest capacity. -Samsung 18650 Batteries - IMR Rechargeable Lithium Ion - 18650 Battery Store
Pouch cells, like those in the Bolt are a little different because there's a huge variety of cell sizes available, often custom made, and a variety of cell designs and material formulations designed for reaching certain design goals, like; charge/discharge rate, operating/storage temperatures, capacity, etc.
 

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Hiya! I wanted to share this research I put together using 333K data points from real live Bolts across the US. The first plot is onboard rated range vs. external temperature, and the bottom one is a moving average of range estimate vs. odometer. Happy to answer any questions.

The full write up is hosted on Recurrent's website where the focus is on the used EV market. I'm curious what data current or potential future Bolt drivers would want to see and would love to chat with any recent Bolt owners about their buying experience.

Thanks!!
I'd love to have a 1:1 conversation with you about this. I love data, but we have to be very careful how and what is collected and how to interpret it. It's pretty easy to draw incorrect conclusions.
 

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Ok, a few things here.

After 95,000 Miles on 2017 Premier. Also 170 Amph
Looks almost perfect .. 5.6% oops..mean 9% or so degradation based on 60kWh battery
You can't use that to calculate degradation. It's very difficult to do this unless you've been tracking it the whole time. Also, temperature and other factors change the reading.


EXCEPT .. and I need to get a screen capture but I noticed today when I halfway floored it that Max cell went to 3.8 and Min cell went to 3.4 ...big difference and I dont know if that has ever been discussed on the forum.. when looking for bad cells are we looking just at "idle" ...cruising or hard acceleration ... ?
Do NOT use Max and Min cell voltages for anything. They are limited to 0.02V accuracy and often delayed. They are not real-time. They're only useful for the tech's to do a replacement analysis.

Can a large Voltage drop on 1 cell under hard acceleration an indication of a cell going bad ????
You can't monitor while driving. The adapter takes at least 6 seconds to scan all cell voltages, more often 10-15. So if you're driving, the current draw when it scans cell 1 is different than when it scans cell 30 which is different than when it scans cell 90. You can only monitor while the car is in a "steady state" and ideally has been for at least 10-30 minutes.

Best time to get cell readings is before you drive when the car has been off for a while. Hold your foot on the brake (turns on the computers) and don't turn on the car. Scan for a minute. Then turn the car on.

Only other thing you can do is blast the heater on full and monitor for a few minutes to see how the cells react under ~7kW of draw.
 

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Ok, a few things here.



You can't use that to calculate degradation. It's very difficult to do this unless you've been tracking it the whole time. Also, temperature and other factors change the reading.




Do NOT use Max and Min cell voltages for anything. They are limited to 0.02V accuracy and often delayed. They are not real-time. They're only useful for the tech's to do a replacement analysis.



You can't monitor while driving. The adapter takes at least 6 seconds to scan all cell voltages, more often 10-15. So if you're driving, the current draw when it scans cell 1 is different than when it scans cell 30 which is different than when it scans cell 90. You can only monitor while the car is in a "steady state" and ideally has been for at least 10-30 minutes.

Best time to get cell readings is before you drive when the car has been off for a while. Hold your foot on the brake (turns on the computers) and don't turn on the car. Scan for a minute. Then turn the car on.

Only other thing you can do is blast the heater on full and monitor for a few minutes to see how the cells react under ~7kW of draw.
OK ASSUMING a Full 60 kWh battery new.. Then my Stats show 9% degradation Batt Cap Est 54.3%


I also did another spread test as you indicated full 100% ..waited a couple hours and I am stil getting the very nice .020 spread...so it is pretty accurate going down the road as well.
36360







I'm not so sure about Hard Acceleration ... I'd be willing to put a few bucks on the dark horse that Hard Acceleration CAN display ..give you an idea of not only the weakest of cells but how weak ...


It seems logical that a weak cell will not hold up as well under stress (hard acceleration" as a stronger cell. (that's my science ;))


I'm sure it can be measured ...would you know how to measure that ? To add that to PIDS
 

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OK ASSUMING a Full 60 kWh battery new.. Then my Stats show 9% degradation Batt Cap Est 54.3%


I also did another spread test as you indicated full 100% ..waited a couple hours and I am stil getting the very nice .020 spread...so it is pretty accurate going down the road as well.
View attachment 36360






I'm not so sure about Hard Acceleration ... I'd be willing to put a few bucks on the dark horse that Hard Acceleration CAN display ..give you an idea of not only the weakest of cells but how weak ...


It seems logical that a weak cell will not hold up as well under stress (hard acceleration" as a stronger cell. (that's my science ;))


I'm sure it can be measured ...would you know how to measure that ? To add that to PIDS
You will need OBDLink MX and use only one PID for weakest cell you know about and even then there will be 3-6 seconds delay from processing to refreshing on the screen.....and you will have to set quickest pulling your app is allowing you without crashing the connection between obd2 and app.. if you have figured out weakest cells in stationery way....there is no need for under heavy load measurements.
 

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Discussion Starter · #13 ·
I'd love to have a 1:1 conversation with you about this. I love data, but we have to be very careful how and what is collected and how to interpret it. It's pretty easy to draw incorrect conclusions.
I'd love to have a 1:1 conversation with you about this. I love data, but we have to be very careful how and what is collected and how to interpret it. It's pretty easy to draw incorrect conclusions.
I sent you a DM!
 

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You will need OBDLink MX and use only one PID for weakest cell you know about and even then there will be 3-6 seconds delay from processing to refreshing on the screen.....and you will have to set quickest pulling your app is allowing you without crashing the connection between obd2 and app.. if you have figured out weakest cells in stationery way....there is no need for under heavy load measurements.
Yes, I know which cell is the weakest ...I'm wondering aloud is , we can get an idea of HOW weak a particular cell is by putting it and all the cells under the stress of hard acceleration.

Which under my observation is that under hard acceleration/stress the weak cells "weakness" is magnified.. that the spread between the weak cell and other cells WIDENS


That is a very sound and reasonable line of thinking

I just need to need to record that data


I have Veepeak...does OBDLink MX display something Veepeak doesn't?
 

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Yes, I know which cell is the weakest ...I'm wondering aloud is , we can get an idea of HOW weak a particular cell is by putting it and all the cells under the stress of hard acceleration.

Which under my observation is that under hard acceleration/stress the weak cells "weakness" is magnified.. that the spread between the weak cell and other cells WIDENS


That is a very sound and reasonable line of thinking

I just need to need to record that data


I have Veepeak...does OBDLink MX display something Veepeak doesn't?
I think the issue will be the ability to record that data quickly enough. There's a polling rate with ODB where a few seconds may pass between reading the first cell voltage and the last cell voltage. Unless you can find a way to provide a constant power drain on the battery for that period time, your cell voltages may vary by the time you've recorded them. It would be difficult to sustain a constant power draw for several seconds literally accelerating on the road, and any slight variation (even 1 kW difference) might change your voltage readings. Maybe using a dynamometer might work. Otherwise, people have suggested using the AC (Lo temp) or heater (Hi temp) for a constant 7 kW draw.
 
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