TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Software limited batteries as they degrade

Discussion in 'Model S: Battery & Charging' started by chris5639, Jul 26, 2016.

  1. chris5639

    chris5639 Member

    Joined:
    Jul 8, 2016
    Messages:
    49
    Location:
    Dallas
    There's been a lot of discussion about being able to charge the new model 60 to 100% because it has a 75 kWh battery software limited to 60 kWH. However, anyone care to speculate on how the software would behave as the battery degrades? Does the software simply continue to limit to 60 kWH (huge benefit to consumer) or would it limit to a fixed % of total current available (degraded) capacity? The first method seems too good to be true but then again we are already seeing the big benefit of being able to charge the new 60's to 100% daily as well as the full speed charging from superchargers.
     
    • Helpful x 1
  2. kort677

    kort677 Active Member

    Joined:
    Sep 17, 2015
    Messages:
    1,910
    Location:
    florida.
    what degradation? tesla's have minimal degradation, it isn't a leaf
     
    • Helpful x 1
    • Dislike x 1
  3. chris5639

    chris5639 Member

    Joined:
    Jul 8, 2016
    Messages:
    49
    Location:
    Dallas
    All Lithium-based batteries degrade due to time and amount of time they sit at high and low SOC. It is the reason why Tesla recommends not charging to 100% all the time and why there's a feature to set the charging limit right from the dash.
     
  4. Buddy

    Buddy Member

    Joined:
    Jul 3, 2016
    Messages:
    382
    Location:
    Riverside County
    That's a great question. I'm commenting on here incase someone ever finds an official answer.

    Hoping for option number 1.
     
  5. chillaban

    chillaban Member

    Joined:
    May 5, 2016
    Messages:
    580
    Location:
    San Jose, CA
    But in a Tesla such degradation is negligible at best. It seems to be in the ballpark of 3-5% degradation over the course of 50,000+ miles and flattens out at that point. And even then, it's not at all clear whether that's degradation or changes to the pack capacity estimation algorithms over the course of time.

    It might make your 70 to 75 unlock feel less worth it, but I can't imagine a 75 degrading into a 60 (20%+) over the usual course of ownership. As someone else said, this isn't a Leaf….
     
    • Informative x 1
    • Dislike x 1
  6. ElectricLove

    ElectricLove Member

    Joined:
    May 28, 2013
    Messages:
    365
    This is a very interesting discussion! When TESLA started out I advocated for them to always limit the usable capacity to 80% of total capacity and then unlock additional % as degradation occurs (thus holding customer usable energy at a near constant until significant degradation has occurred... Perhaps minimum 10 years before anyone would even have any degradation)... Of course they didn't do that...

    Now with these new "60" they have the opportunity to do the same! They can fix the capacity and keep it there until the actual degradation is beyond the buffer... Meaning a 60 that is really a 75 would not have any degradation at all to its range for upwards of 10 years (range degradation, not battery degradation)...

    I think it would make sense for TESLA to do it this way and the software is actually simpler this way (just set a limiter for max in/out of pack vs. generating an algorithm that degrades as the total degrades), but which way they did it is anyones guess until we line up a bunch of 60's and test them!

    If you could take a batch of 60's that are really 75's and get the usable SOC out of diag mode you can likely answer this question... Are they all fixed to the same number? Or are they all varied by the same degree that their total capacity is varied? (rarely do two teslas have identical capacities, even just off the production line that is many thousands of battery cells and each is organic and varies a bit)...
     
    • Like x 2
  7. ElectricLove

    ElectricLove Member

    Joined:
    May 28, 2013
    Messages:
    365
    Any owners in the Phoenix area that want to meet up and answer this question? Or a batch of people who will be at TMC Connect? Maybe we can get a Tesla-tech who can get the service passwords without tearing down the dash like I would have to do?
     
  8. chris5639

    chris5639 Member

    Joined:
    Jul 8, 2016
    Messages:
    49
    Location:
    Dallas
    Sure but that has to do with Tesla's having thermal management for their batteries. The original leafs relied on passive cooling. Also, with the larger capacity, most Tesla owners rarely have to charge to 100% to get where they need to go. With the much lower 24-30 kWH batteries of the Leafs, I'm willing to bet owners have to charge to 100% more often.

    However, my original post wasn't about the rate of battery degradation nor a debate about whether Tesla batteries degrade better or worse than another make and model. It was about when that degradation happens, be it 5 years or 10, how would software limiter behave. As a software engineer myself, I can imagine different implementations.
     
  9. kr200

    kr200 Member

    Joined:
    Apr 5, 2013
    Messages:
    31
    Location:
    Ontario Canada
    My 40 was limited to 68% of the 60kwh battery. In other words it would degrade at the same rate as a 60 that never charged over 68%. I expect the new 60 and 70 do the same.
     
    • Informative x 1
  10. ElectricLove

    ElectricLove Member

    Joined:
    May 28, 2013
    Messages:
    365
    kr200; if that was the case we should expect similar behavior with the new one... Sure does seem silly though, it would be an added feature/benefit to eliminate degradation (or delay its effects) for these owners, and it would take literally nothing from TESLA to do that...
     
  11. MP3Mike

    MP3Mike Active Member

    Joined:
    Feb 1, 2016
    Messages:
    1,650
    Location:
    Oregon
    Other than once your battery pack degrades to the point that it won't get you where you are going Tesla would have nothing to sell you. With them giving you 80% of the current state of your 75 kWh pack they can always sell you the remaining 20%. So I can't see them giving you the extra 20% for free, even if it is little bit by little bit over time. (If they were to do that they would have to prorate the upgrade to 75 kWh as time passed...)
     
    • Informative x 1
  12. chillaban

    chillaban Member

    Joined:
    May 5, 2016
    Messages:
    580
    Location:
    San Jose, CA

    Right. I had this concern while they sold the 70 and the 75, and it's one of the reasons why as an owner of a software-locked 70 I wouldn't consider paying the unlock to turn it into a 75…..

    But for 60 vs 75, that 20% is such a big difference that unlocking even 18% of it during your course of ownership is compelling.
     
  13. GarrickS

    GarrickS Member

    Joined:
    Apr 5, 2016
    Messages:
    66
    Location:
    Inglewood, CA
    That sounds terrible. You are saying we should be carrying around unused battery weight just for the appearance of less battery degradation. I'd rather have that useable capacity the whole time.
     
  14. ElectricLove

    ElectricLove Member

    Joined:
    May 28, 2013
    Messages:
    365
    It isn't for the "appearance", it is to sell a vehicle with a guarantee that your range will be the same today as it will 5 years from now, maybe even 10 years from now...

    The only reason you are taking the stance of having the capacity is that is the way TESLA went with it, if they didn't do it that way you'd likely agree with the alternative, biggest reason being that it protects the batteries from the very issue we are discussing... degradation... Using less of the capacity will have less degradation and b/c TESLA built their program with a minimum range in mind rather than minimum capacity it would have simply pushed the actual battery capacities higher more quickly... Of course the consequence is more cost to an already expensive vehicle... I don't think anyone buying one is too concerned with price though (I'm not), so not sure if that would have hurt them in the end (an extra $1K per every battery sold)...

    Oh well, they didn't do it that way and don't appear to be doing so in the software limited vehicles either... So I'm wrong by default anyways! (no way to prove me right... Unless you look at battery degradation in a Chevy Volt and compare to a TESLA Roadster/S/X)
     
  15. supratachophobia

    supratachophobia Active Member

    Joined:
    Sep 24, 2014
    Messages:
    1,997
    Location:
    Columbus, Ohio
    Owners who purchase the 60kw car will never see battery degradation not have worry about it. The only issue I can see is if they decide in 3 years to upgrade to 75, and all of the sudden, the max charge they thought they would get is off by 15 miles.
     
  16. MP3Mike

    MP3Mike Active Member

    Joined:
    Feb 1, 2016
    Messages:
    1,650
    Location:
    Oregon
    Why do you think that? Do you have any proof or a statement by Tesla? I suspect that they will have degradation just like everyone else. (Just like the S40s that were limited 60 kWh packs.)
     
  17. jaguar36

    jaguar36 Member

    Joined:
    Apr 10, 2014
    Messages:
    868
    Location:
    NJ
    Tesla's absolutely have battery degradation, just look at the data.

    I would speculate that the software limited packs range will degrade based on the overall battery degradation. Keep in mind that Tesla wants people to buy the 75, not the 60. The margins on the 75 are vastly higher than on the 60. They also really want people to pay for the upgrade later, since its pure profit. By only degrading the unused capacity it lessens the incentive to upgrade.

    Until someone has a new 60 for a few months though we won't actually find out.
     
    • Informative x 1
  18. supratachophobia

    supratachophobia Active Member

    Joined:
    Sep 24, 2014
    Messages:
    1,997
    Location:
    Columbus, Ohio
    Why? Why would Tesla use a software algorithm to degrade the max rated range? If the battery is only using 60 out of 75 kwh, then the battery never actually suffers any of causes of battery degradation to begin with.
     
  19. chillaban

    chillaban Member

    Joined:
    May 5, 2016
    Messages:
    580
    Location:
    San Jose, CA

    FWIW, the trendline on the data shows that by ~80k miles, there's an average of 4 or 6% degradation depending on whether it's the 70 or 85kWh pack, respectively.

    So except for the 70 -> 75 unlock (6.66% capacity gain), you would still be getting a good 15% of additional range by opting for the unlock even at 80k miles, given the worst case scenario for the unlock purchaser.

    And honestly, I expect the majority of folks going for the unlock to do so within the first 20k or so miles because it tends to be a buyers' remorse type of expenditure (e.g. their finances improved compared to their expectation at time of purchase). By the time a car has 80k miles, I would imagine instead of paying $10k for a software unlock you would be better off putting that $10k towards trading in your Tesla for a new one.
     
  20. MP3Mike

    MP3Mike Active Member

    Joined:
    Feb 1, 2016
    Messages:
    1,650
    Location:
    Oregon
    Because they have to be able to unlock the extra 15 kWh, they can't just give it to you.

    And they probably don't have a software algorithm to degrade the battery, the algorithm simply maps the range of the battery you are allowed, 0-80%, to be displayed as 0-100%. Which is very simple, take the actual battery charge level and increase it by 25% before displaying it. (Just multiply the charge level by 1.25.)
     

Share This Page