Chevrolet Volt Battery Warranty Details Emerge. Nissan to Follow Suit?

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The battery warranty on the both the Volt and LEAF had been a mystery for a very long time, that is until Chevrolet took the initiative to go first and announce a 8 year/100,000 mile program of coverage.  Nissan, wanting to stay on equal crowd with its closest competitor announced it would be matching that warranty a few days later.

But what is the warranty exactly?   What does it entail?  At what level of degradation would the pack start to be covered under warranty?  Would the pack have to suffer a catastrophic failure to be replaced entirely?

Once again, GM has taken the lead in this regard.

Well, sorta.  There was no fanfare, no announcements, no ‘read the warranty’ button to be found anywhere really.  You have to find your way through the labyrinth to reach it from its Chevrolet Volt homepage (go ahead, give it a try).

GM states that first a dealer service technician will determine if the battery capacity is within the proper limit (given its age and mileage)  to have any service/warranty work done.  This process can apparently take up to 24 hours.

What is a acceptable loss of power? Anywhere from 10-30% loss of the original 16 kWh capacity.  I assume some kind of sliding, pro-rating curve will apply as to which level between 10% and 30% is unacceptable.

If it is determined the car does need warranty servicing, GM (at their discretion) can either use new or ‘factory reconditioned’ components (like replacing individual cells) to repair the pack, or outright replacing the pack with a new (or used) battery.

Also present is the disclaimer about what level of capacity you should expect after work has been done.  The car will be returned “…with an energy capacity (kWh storage) level at or above that of the original battery prior to failure.”

“Your Volt battery warranty replacement may not return your vehicle to a “as new” condition, but it will make your Volt fully operational appropriate to its age and mileage”

So is it good?  Bad?
I rate it as ‘okay.‘  

…but what if Nissan follows GM’s lead again? Is this warranty ok for a BEV like the LEAF that relies on its battery full time?

...et le fine print

36 Responses

  1. Herm says:

    They are talking about replacing individual cells, always a touchy proposition if you put in a new full capacity cell in together with older cells.. the proper way to do it is to cannibalize a pack in a similar life state and use one of those cells/module.. thats why they mention the total kwh will not be returned to new. Rebuilding a pack is done at the factory and will take a while due to testing… lethal voltages are involved.

    Most likely they will just replace 4 cell modules with ones of similar age, tested to a similar capacity level.. exact matching is not needed due to the 20% margin of the LEAF and 50% of the Volt.

    The Battery Management System (BMS) always know exactly the capacity of each module and cell… all the modules should age in step with the others, once one stops matching the others is when you have trouble.

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  2. Herm says:

    Look at the picture Lyle put up over at the Volt blog:


    http://gm-volt.com/wp-content/uploads/2010/05/quigley-dham-volt.jpg

    What do we get?.. pictures of goofy looking smiling llamas :)

      (Quote)

  3. Look at the picture Lyle put up over at the Volt blog:


    http://gm-volt.com/wp-content/uploads/2010/05/quigley-dham-volt.jpg

    What do we get?.. pictures of goofy looking smiling llamas :)   (Quote)

    Well, Lyle is more notorious with the ladies.

    The llamas are classy, (=

      (Quote)

  4. GeorgeS says:

    Herm,
    I would agree w/ what you said. this repair procedure seems fair. Probably when the pack goes past its prorated level of degradation it will because some small percentage of the packs cells have failed. The balancing process undoubtedly will all be monitored by the computer and the computer will tell the tech which cells to replace and I agree it would need to be with a cell of approximately the same coulomb count. This means either the dealer or the factory will have to start cannibalizing packs and storing batteries that are sorted by coulomb count.

    What I question is whether the cell replacement needs to be done at the factory or at the dealer. If it has to be done at the factory I don’t see how they can get it done in the time they are quoting.

    Great article Jay, thanks!!

      (Quote)

  5. Carcus says:

    Statik says: “Anywhere from 10-30% loss of the original 16 kWh capacity.”

    GM says: “…. to as much as 30% of capacity…..”

    Hopefully, Statik is correct in assuming they are basing the warranty off of the 16 kwh original capacity. But GM could be talking about something totally different (i.e. maybe just enough capacity to get you to 28 miles (.7 x 40) AER on the city cycle).

    /more fine print detail is needed

      (Quote)

  6. Loboc says:

    If GM technicians start quibbling about whether it’s at 10% or 30% loss and making poor (customer-wise) judgment calls, it will backfire on GM.

    I’m thinking that anything that goes wrong with a Volt for the first model year will be quickly and professionally solved. It wouldn’t make sense to do otherwise with such a new technology.

    Same goes for the LEAF. Customer service is more important than keeping the profit on one car. In this Internet/connected world, bad service will quickly hit the buzz.

    24 hours will probably be needed for testing. Even if you take a dead conventional battery to Sears, it takes a couple hours for them to determine if it’s the battery or something else. For Volt (or LEAF) a battery testing cycle could take 6 hours or more.

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  7. Loboc says:

    I’m thinking that larger GM and Nissan dealerships will keep a couple reconditioned batteries (fully assembled and tested) in stock for these issues. It would be better customer service to turn it around fast and get the customer back on the road quickly.

    Also, this is where the computer system(s) will help determine what happened. If the customer is not fully charging or is discharging fast (like jack-rabbit starts every time), the computer should have this information in it’s logs.

    It’s the same as now. A dead battery could be caused by a poorly-operating charging system. The battery itself could be perfectly fine.

      (Quote)

  8. GeorgeS says:

    Carcus,
    The devil’s in the details on how the computer will figure it out. I know on my 36 volt ebike pack, if any one of the 10 cells falls below a min value the whole pack gets shut down. This is done to keep from damaging the cell. Since the Volt has so many more cells I doubt if any one cell falling below min voltage would shut down the whole pack. The computer probably just takes the first module out when a cell drops below min, then the second one out when it’s voltage falls below min and so on until “X” number of modules are below at which time the whole pack shuts down. Then it probably compares the entire packs coulomb count and decides if too many cells are falling below threshhold relative to the coulomb count. The entire packs allowable coulomb count would have to be a function of battery age and cell temp.

    JMO

    Fairly complicated indeed!! but the idea is to maintain the health of the cells.

      (Quote)

  9. GeorgeS says:

    Loboc,
    That sounds like a reasonable plan for the dealers. With just a few Volts in service the dealers would probably just have “new” packs on the shelf to use as replacements. As time goes by the factory would have more reconditioned packs available to send to the dealers and they would be sorted by coulomb count. You would get a replacement that comes close to matching the age of your pack.

      (Quote)

  10. Carcus says:

    GeorgeS,

    Is it possible the Volt could have circuitry to rearrange the cells into different modules “on the fly”? i.e. could the volt see 3 or 4 cells dropping and it rearranges them to match in a separate “handicapped module”?

    /I thought I saw this alluded by another poster at gm-volt.com, but I’m not sure I understood what was being said.

      (Quote)

  11. N Riley says:

    Well, Lyle is more notorious with the ladies.The llamas are classy, (=  

    Statik,

    One would be lead to believe you prefer Ilamas to ladies. While the Ilamas are “cute”, they would make terrible dinner companions. LOL

      (Quote)

  12. N Riley says:

    Seems like I remember GM saying that failing cells would be shut down and by-passed. I am sure a threshold would be reached where service would be required. We will not know all the details of the Volt’s or Leaf’s warranties until much later and many of them are on the road.

      (Quote)

  13. Carcus says:

    Okay,

    On cell management I now see another thread (new to me) where the series/parallel arrangement and bad cells are discussed:

    http://gm-volt.com/forum/showthread.php?t=4497&page=2

    One thing I haven’t thought of before — If you had many more smaller cells then you have many, many, many more possibilities of rearranging/eliminating cells in order to preserve the overall health of the pack. This would give an advantage to AC propulsion’s (Tesla’s) pack and might explain why Toyota would be interested in Tesla’s (AC propulsion’s) tech. (?)

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  14. Carcus says:

    Lots of interesting info on modern BMS here:

    http://www.metricmind.com/bms.htm

    In particular, ref. the active thermal management (volt) vs not (leaf), start reading with:

    “Not only manufacturing differences or defects lead to non-uniform cells. If more than one location is used to place all the cells and no active temperature control is deployed, it is practically guaranteed that groups of cells in different locations in a vehicle will have different temperatures……”

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  15. vanuck says:

    This would give an advantage to AC propulsion’s (Tesla’s) pack and might explain why Toyota would be interested in Tesla’s (AC propulsion’s) tech. (?)

    It seems that VW too is interested in Tesla’s type of pack, they hired the pack’s inventor/designer.

      (Quote)

  16. GeorgeS says:

    Cacus, et all,
    I remember that thread but was still somewhat confused at the conclusion re: how Tesla does it.

    Anyway the Volts battery has 18 cells in each module and within the module the cells are arranged 3P6S so 3 cells are in parallel then 6 of those 3P strings are put in series. If one cell goes “open” then the 3P string is probably okay as is no action required. If one cell in the 3P string is just going below the min voltage then I guess GM could either take out that 3P string or ,if they are really able to rearrange down to the cell level, just take out the one cell. Who knows–JMWAG. but fun to think about.

    It still amazes me that Tesla is sticking w/ 18650′s in the S. I wish I knew if they are doing this because that’s “how they do it” or if there really is a sound engineering reason for it. —Lot’s of tradeoffs. I really respect Tesla and hope they make it.

      (Quote)

  17. JEff says:

    Yes.

    ” “Your Volt battery warranty replacement may not return your vehicle to a “as new” condition, but it will make your Volt fully operational appropriate to its age and mileage”

    Is this warranty ok for a BEV like the LEAF that relies on its battery full time?”

      (Quote)

  18. JEff says:

    The llamas are also better looking than that particular woman.

    But I agree with N Riley that the woman would probably make a better dinner companion. (And the llamas might make a better dinner?)

    The llamas are classy,

      (Quote)

  19. GeorgeS says:

    Carcus,
    I don’t think AC propulsion is any part of Tesla anymore. To my recollection they built the first tesla inverter/motor contol unit as analog but Tesla had problems w/ it and totally redesigned it themselves into a digital unit.

      (Quote)

  20. JEff says:

    The was no mention of time to replace cells or the pack. The time given was for testing the battery pack.

    What I question is whether the cell replacement needs to be done at the factory or at the dealer. If it has to be done at the factory I don’t see how they can get it done in the time they are quoting.

      (Quote)

  21. Carcus says:

    I suppose the “how they do it” part is the bleeding edge of battery tech right now, so this is something neither GM nor Nissan nor Tesla will really get into any detailed explanation right away…. and they may not want to talk even after the cars are in customers hands.

    On the Tesla 18650 small cell use — if you have thousands of cells and 10s of thousands of combination possibilities (strong modules/ weak modules/ recovering modules/ trash can — using the imagined high power pcb switching) then you might have the advantage over large cell format systems because of so many more possible combinations to preserve cell life, and if you have to sacrifice a bad cell it’s a tiny proportion of the pack — just take it out of the loop and keep going.

    /I’ve actually read very little about this, so … just random thoughts

      (Quote)

  22. Carcus says:

    Carcus,
    I don’t think AC propulsion is any part of Tesla anymore. To my recollectionthey built the first tesla inverter/motor contol unit as analog but Tesla had problems w/ it and totally redesigned it themselves into a digital unit.  

    No, probably not. I just thought it was AC propulsion’s design which was contracted and now owned by Tesla (??) I really don’t know.

      (Quote)

  23. Carcus says:

    It seems that VW too is interested in Tesla’s type of pack, they hired the pack’s inventor/designer.  

    AC Propulsion is an engineering design firm out of San Dimas, CA. They’ve been described as having their “fingerprints” all over everything in the electric car industry.

    They’ve engineered for Tesla, BMW, VW, and various suppliers. As far as where the licensing/ patents start or stop with all these customers — who knows?

      (Quote)

  24. Carcus says:

    Here, Tesla lists their small cells as having a thermal advantage:
    (related to, but not specific on the liquid cooling)

    “This cooling system design is especially effective because we have chosen to combine thousands
    of small cells rather than several large ones to build an ESS, dramatically increasing the surface
    to volume ratio. For example, with seven thousand 18650 cells the surface area is roughly 27
    square meters. If there were an imaginary set of 20 much larger cube-shaped cells that enclosed
    the same volume, the surface area would be only 3.5 square meters, more than seven times
    smaller. Surface area is essential to cooling batteries since the surface is where heat is removed;
    more is better. Also, because of their small size, each cell is able to quickly redistribute heat
    within and shed heat to the ambient environment making it essentially isothermal. This cooling
    architecture avoids “hot spots” which can lead to failures in large battery modules.

    http://webarchive.teslamotors.com/display_data/TeslaRoadsterBatterySystem.pdf

      (Quote)

  25. Carcus says:

    Here, Tesla describes their small cells as having a thermal advantage of being able to quickly redistribute heat making them essentially isothermal.

    http://webarchive.teslamotors.com/display_data/TeslaRoadsterBatterySystem.pdf

      (Quote)

  26. vanuck says:

    AC Propulsion is an engineering design firm out of San Dimas, CA. They’ve been described as having their “fingerprints” all over everything in the electric car industry.

    …actually I was talking about Martin Eberhard

      (Quote)

  27. GeorgeS says:

    Carcus,

    Do you suppose Tesla really monitors each of the 6831 individual cells individually?? monitoring is one thing but being able to switch each one in and out and rearrange strings seems almost impossible but I’m not an EE so I have not a clue. Only on the outskirts of understanding.

    Thx for the metricmind article. I bookmarked it. Sooo many ways to balance.-GSB

      (Quote)

  28. Carcus says:

    GeorgeS,

    No, I don’t think they do. But could they?

      (Quote)

  29. evnow says:

    GeorgeS,No, I don’t think they do. But could they?  

    .
    Yes the technology is simple – but 6000 switches would be bulky & expensive to implement.

    BTW, there is a guy in the leaf forum reporting that his roadster test drive was cancelled since the roadster battery got too hot in AZ and wouldn’t run. So much for Musk’s bravado.

      (Quote)

  30. evnow says:

    I find this whole thing about 10-30% wierd. Isn’t the whole point of using 50% DOD in the beginning that even at the end of warranty period GM can still gaurantee 8 kwh usable energy so that 40 miles nomical range can be had ? If not, why use 16kwh battery ?

    If 16 kwh goes down by 30% – it is still 11.2 kwh and using 8kwh out of that would be still just 70% DOD.

    GM should be able to warrantee 8 kwh of usable battery (or 40 miles of range) at the end of 8 years.

      (Quote)

  31. DonC says:

    If 16 kwh goes down by 30% – it is still 11.2 kwh and using 8kwh out of that would be still just 70% DOD.
    GM should be able to warrantee 8 kwh of usable battery (or 40 miles of range) at the end of 8 years

    That seems to be exactly what it is doing. The warranty doesn’t kick in if the pack degrades by up to 30%. The problem would be if the pack lost more than 30%. For example, if it degraded by 50% there is no way you could get the promised 40 mile range.

    One nice bit is that GM has always spoken of guaranteeing the 40 mile range at the end of the warranty period. Originally it was 10 years, not it seems to be 8.

      (Quote)

  32. Carcus says:

    Yes the technology is simple – but 6000 switches would be bulky & expensive to implement.

    Perhaps heavy copper and/or extreme copper PCB’s with some sort of specialized transistors to do the switching. With a computer to monitor all the historical voltages, ah’s in and out, temperatures and then put the cells in one of a bazillion different possible series/parallel arrangements. (does that sound expensive? ;) )

      (Quote)

  33. Carcus says:

    If 16 kwh goes down by 30% – it is still 11.2 kwh and using 8kwh out of that would be still just 70% DOD.
    GM should be able to warrantee 8 kwh of usable battery (or 40 miles of range) at the end of 8 years.

    It’s been a long time since we’ve heard anyone from GM say 8 kwh.

      (Quote)

  34. Greg Simpson says:

    I find this whole thing about 10-30% weird. Isn’t the whole point of using 50% DOD in the beginning that even at the end of warranty period GM can still guarantee 8 kWh usable energy so that 40 miles nominal range can be had ?

    The Volt is reported to use 10.4 kWh in CD mode, and I assume somewhat more as a buffer in CS mode. It’s probably a total of around 12 kWh, or 75%.

      (Quote)

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