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Discussion Starter · #1 · (Edited)
PPR / Battery Replacement

Is anyone aware of any type of attempt to have GM address the battery issues associated with the early model Volts if issues were reported prior to warranty expiration? I reported issues with my 2012 battery degradation and loss of range/kwh prior to my warranty expiration, and GM reprogrammed my vehicle to address. I then started receiving the PPR notices after full depletion and sitting for a period of time. I then paid for the PPR update out of my pocket. GM continued to insist that this was normal operations, so I assumed that this was the case. After the latest recall notice, I started reading the forum again and found that this is a widespread issue that their dealers may have been trying to address through software updates. I am curious to know if anything is being done to address, or if I am out of luck...

I just had the new battery balancing recall done. I am not sure if this will resolve, but it sounds like the battery packs had issues.

Thanks
 

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PPR, Propulsion Power Reduced
 
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What damages would you have a class action for? PPR is normal operation. Battery degradation is outlined in the warranty. Battery failures have been replaced under warranty. GM has made software updates available for free to all 2012-2015s to correct cell balancing.
 

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Some older batteries may have "lost some oomph" (nothing but degradation from aging) that may lead to PPR issues, and some have repairable or non-repairable problems, such as cell balancing issues. The PPR and the cell balancing problems are two different issues, and GM has addressed both. Bulletin No. PIC6292C refers to the PPR issue, and GM program #N172130462 deals with the Hybrid Powertrain Control Module (HPCM2) and cell balancing.

The Gen 1 Volt’s 8 yr/100,000 mile battery warranty says: "...the battery may degrade... as much as 30% of capacity over the warranty period" (40% for the Gen 2 Volt and Bolt). For a 2012 Volt, that means the 16 kWh battery may have lost capacity to the point where it is now only a 11.2 kWh battery with a usable window of only 7.3 kWh and an ev range of only 24.5 miles and still be within acceptable warranty standards.

Perhaps GM overlooked the consequences of the effect of degradation on the quantity of power maintained in the Extended Range Mode battery buffer, the buffer between the switch to gas SOC and the hard floor SOC. When the generator output is not enough to meet a Gen 1 Volt demand for power, the motor may "borrow" power from this buffer, which is then recharged when demand lessens.

This buffer holds only 5% of the Gen 1 battery’s full capacity, or less than 1 kWh of power. The buffer of a degraded battery holds even less. While driving with a degraded, depleted battery, if the engine continues to run as you pull into a parking spot and turn the car off to run an errand, the fact that the engine is running may indicate the system has "borrowed" some power and is recharging it back into the battery, i.e., the SOC is not yet back up to the switch to gas SOC. At this point, the degraded battery buffer holds even less available borrowable power. When you then try to start the car, MGA draws power to start the engine, and the SOC may drop too close to the hard floor SOC, triggering a PPR episode (this is why you switch to Mountain Mode to increase the switch to gas SOC to prevent PPRs when you anticipate driving in high power demand conditions such as driving up mountains). That’s why it may be a good idea to wait for the engine to come to a stop (i.e., to let it charge the battery back up to the switch to gas SOC) before shutting off the car if you intend to start the engine again before recharging the battery from the grid.

The PPR problem may thus be the a result of normal battery degradation, not "a faulty battery." The "solution" GM offers for this PPR problem seems to be to program an increase in the switch to gas SOC, increasing the CS Mode buffer of borrowable power above the original 5% so it contains a sufficient amount of the degraded battery’s content. Doing this, however, chops off some of the bottom part of the usable window, so the usable window now contains less than 65% of the degraded battery’s full capacity, and that will show up as reduced kWh Used/ev range numbers ... or, one alternative to the reprogramming is to switch to Mountain Mode whenever you are intending to drive beyond battery range, remain in MM throughout the trip, and switch back to Normal when you are ~14 miles from your next recharging stop.
 

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Some older batteries may have "lost some oomph" (nothing but degradation from aging) that may lead to PPR issues, and some have repairable or non-repairable problems, such as cell balancing issues. The PPR and the cell balancing problems are two different issues, and GM has addressed both. Bulletin No. PIC6292C refers to the PPR issue, and GM program #N172130462 deals with the Hybrid Powertrain Control Module (HPCM2) and cell balancing.

The Gen 1 Volt’s 8 yr/100,000 mile battery warranty says: "...the battery may degrade... as much as 30% of capacity over the warranty period" (40% for the Gen 2 Volt and Bolt). For a 2012 Volt, that means the 16 kWh battery may have lost capacity to the point where it is now only a 11.2 kWh battery with a usable window of only 7.3 kWh and an ev range of only 24.5 miles and still be within acceptable warranty standards.

Perhaps GM overlooked the consequences of the effect of degradation on the quantity of power maintained in the Extended Range Mode battery buffer, the buffer between the switch to gas SOC and the hard floor SOC. When the generator output is not enough to meet a Gen 1 Volt demand for power, the motor may "borrow" power from this buffer, which is then recharged when demand lessens.

This buffer holds only 5% of the Gen 1 battery’s full capacity, or less than 1 kWh of power. The buffer of a degraded battery holds even less. While driving with a degraded, depleted battery, if the engine continues to run as you pull into a parking spot and turn the car off to run an errand, the fact that the engine is running may indicate the system has "borrowed" some power and is recharging it back into the battery, i.e., the SOC is not yet back up to the switch to gas SOC. At this point, the degraded battery buffer holds even less available borrowable power. When you then try to start the car, MGA draws power to start the engine, and the SOC may drop too close to the hard floor SOC, triggering a PPR episode (this is why you switch to Mountain Mode to increase the switch to gas SOC to prevent PPRs when you anticipate driving in high power demand conditions such as driving up mountains). That’s why it may be a good idea to wait for the engine to come to a stop (i.e., to let it charge the battery back up to the switch to gas SOC) before shutting off the car if you intend to start the engine again before recharging the battery from the grid.

The PPR problem may thus be the a result of normal battery degradation, not "a faulty battery." The "solution" GM offers for this PPR problem seems to be to program an increase in the switch to gas SOC, increasing the CS Mode buffer of borrowable power above the original 5% so it contains a sufficient amount of the degraded battery’s content. Doing this, however, chops off some of the bottom part of the usable window, so the usable window now contains less than 65% of the degraded battery’s full capacity, and that will show up as reduced kWh Used/ev range numbers ... or, one alternative to the reprogramming is to switch to Mountain Mode whenever you are intending to drive beyond battery range, remain in MM throughout the trip, and switch back to Normal when you are ~14 miles from your next recharging stop.
Thank you, Wordptom, for this incisive analysis.
 
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Discussion Starter · #7 · (Edited)
Thank you! I get it. I was just curious. I believe that GM updated the software well after purchase that redistributed the buffer, taking away usable kwh to accommodate the degradation. Mine was highlighted with an update that changed my usable kwh overnight with an update, at about 3/4 of my warranty life. I get the concept, but I always understood (maybe in error) that the buffer was to maintain the usable kwh as the battery degraded. I feel they should have been more upfront with the updates and what they were addressing, or maybe I should have looked more into them before allowing the dealer to perform the updates. Dealer support and their explanations have always been lacking. I still like my Volt, and always have.

And I tried to remove the "Class Action Lawsuit" from the thread title immediately after posting, but it would not let me update.

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I offer this additional information for this discussion regarding the cell balancing issue, including the benefit of performing a number of full charge/depletion cycles following the procedure. This was posted in a recent thread by another forum participant:

Posted by forum member JuneBug: "I saved this from the Facebook Volt forum:

Jaryd Carvell->Hi friendly neighborhood Volt tech here! As I have tried to explain to so many people in this group. The recall (GM Program #:N172130462 Issued: Mar 28, 2019) is to correct your vehicle from improperly balancing the cells over time. The balance of those cells is part of what is used to calculate the GOM. When they reprogram the module 2 things happen. The vehicle starts to properly balancing the cells again, and the battery capacity learned values are reset. Over the course of multiple charge/discharge cycles the cells properly balance, and then the module relearns the capacity and the GOM adjusts accordingly. If your GOM goes up or down it means that the car had not been properly balancing the cells for quite some time. This process happens much slower without full discharge/charge cycles and so some people the adjustments happen much quicker than others. Also not all vehicles have the same cell imbalance. Even with the bad software some vehicles were staying close to properly balanced and others were quite a bit off. If yours was one that was close to correct, not much will change after the recall. If your cell balance was off, the more it's going to change after the recall. This is why some people noticed almost no change and others have had a change in the GOM. This is also why some people have seen the change quickly and some it took a while. Complete discharge/complete charge cycles will accelerate this learning process. Oh and one more thing, the 2013-2015 volts have 9 battery temp sensors but really only need 6. There is also software included in the recall that allows the vehicle to ignore up to 3 of the redundant temp sensors if they fail, rather than having to replace them. So there are multiple reasons to have this recall performed."
 

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Again, wordptom, thank you for such useful information! I'm going to check if this recall was performed on my Volt during it's annual NYS inspection in June of this year. From memory, I don't think that it was done.

EDIT: The update wasn't performed, but, I do have the letter advising me to have the update done...offer good until 6/30/2021.
 

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PPR / Battery Replacement

Is anyone aware of any type of attempt to have GM address the battery issues associated with the early model Volts if issues were reported prior to warranty expiration? I reported issues with my 2012 battery degradation and loss of range/kwh prior to my warranty expiration, and GM reprogrammed my vehicle to address. I then started receiving the PPR notices after full depletion and sitting for a period of time. I then paid for the PPR update out of my pocket. GM continued to insist that this was normal operations, so I assumed that this was the case. After the latest recall notice, I started reading the forum again and found that this is a widespread issue that their dealers may have been trying to address through software updates. I am curious to know if anything is being done to address, or if I am out of luck...

I just had the new battery balancing recall done. I am not sure if this will resolve, but it sounds like the battery packs had issues.

Thanks
Only a class law action will make GM act. I am initiating a class action myself and if you all want to it join it ask me how
 

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Only a class law action will make GM act. I am initiating a class action myself and if you all want to it join it ask me how
Please keep us posted on your progress, Ken.
 

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Please keep us posted on your progress, Ken.
Yes let us know. Got another PPR today limiting speed to under 30. This should not be. Plus I only have 8509miles on warranty left
 

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Yes let us know. Got another PPR today limiting speed to under 30. This should not be. Plus I only have 8509miles on warranty left
I honestly would be concerned, having experience with battery failure. It starts with an occasional PPR, then a bunch of regular PPR's, then PPR all the time, then... a CEL and no more forward motion.
 
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