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Just got my second _replacement_ battery - some graphs showing my degradation trends

Discussion in 'Model S: Battery & Charging' started by pnaecker, Oct 16, 2014.

  1. pnaecker

    pnaecker Member

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    VisibleTesla is cool. Among the other useful things it does is capture data for graphing. It also saves it in a parseable log. (Thanks, Joe.)

    Even though I don't have VT running all the time, it has been running enough since the beginning of the year to produce useful plots of long term battery degradation.

    So last month when I started noticing some change in range at the end of my daily commute, I wrote a few lines of Perl and R and got the following graphs. The graphs simply take the reported State of Charge of the battery and the reported Estimated Range, and divide one by the other to get a normalized range estimate. Then I plotted these values over time. Some events on the timeline.

    October 27, 2012 - Got my car, an S85
    February 25, 2014 - Received a replacement battery
    June 30 - July 16, 2014 - Vacation with the car plugged in
    October 15, 2014 - Received second replacement battery

    Unfortunately, I didn't record the exact date I received firmware updates. But some of them are obvious on the chart.

    I've driven a pretty constant 115 mile round trip daily commute plus a few trips and casual driving. My long term average energy usage is 323 wHr/mi, even though I drive "a little too fast" at times. Pretty happy with the output efficiency, a little less happy with the charging efficiency, but it's not too bad.

    The February 2014 battery replacement was due to a sudden drop in peak output power. The failed component was a contactor (switch) internal to the battery. I happened to have also experienced a battery coolant leak that was the reason I took the car in, but when in the SC explained I saw this other behavior, and they found the failure in testing.

    When I contacted Tesla this week to tell them my battery was failing as indicated by a steep range drop, the reply was: "We checked, and everything is fine." So I sent them these charts and asked the engineers to "please look again". The next day I got an email that they found a problem with my car, "independent of your range concern", and would replace my battery. That very same evening, my car abruptly failed to charge. Although there was no error showing on the console, the remote support folks could see an error when I plugged in the mobile charger while they were logged in - an error they had not encountered before, about an inability to balance the battery modules. The tow truck picked up the car at 7AM the next morning and had it back in my driveway at 7PM. Excellent service. Too bad I needed it. Glad I wasn't stranded (unless you count having to drive an ICE in the non-HOV lane being "stranded"). Worried it might happen again.

    Yes, I got an A battery for each replacement. Yes, I asked for a newer battery this last time, but was told that was not possible and "really not necessary, as this re-manufactured battery had all new components". (I understand a new A battery is not the same as a new D battery, but there was no progress made in that argument.)

    I have no idea why the data is so noisy until April 2014, but I suspect that after that date the firmware improved the reporting of range and SOC.

    I thought the charts might be moderately interesting to others.

    P
     

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  2. apacheguy

    apacheguy Sig 255, VIN 320

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    Very interesting. Assuming you are a Sig? I'll add you to my battery replacement thread.

    Also interesting that they claim the A pack has all new components. Does it charge at 120 kW? Does it display 270+ rated miles on a full charge? If not, then it obviously does not have all new components.
     
  3. kennybobby

    kennybobby Member

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    How many miles on the car/battery? Odometer reading at these events, etc.

    Is your commute on concrete roads with expansion joints, or rough roads with potholes and bumps, etc? The reason i ask is that the contactors are vacuum- or dielectric-gas-sealed units in order to get/keep the contact resistance low and consistent. The coolant leak and faulty contactor make me think a mechanical vibration might be a common root cause.
     
  4. Saghost

    Saghost Active Member

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    If I read this right, you're plotting estimated range against battery SoC? Won't that include variations from your drive in your data?

    Things like HVAC and traffic/driving speed will change your actual consumption, which will cause the car to change its estimate of remaining range for a given amount of energy left in the battery. It's not surprising that estimated range data would show seasonal variations, which is what I think I see in your data.

    Does the dataset you're plotting from include either ideal or rated range information? As I understand it, both of those are straight multiples of the energy the car believes the battery has left, so they might give a feel for degradation independent of weather and driving conditions.
    Walter
     
  5. islandbayy

    islandbayy Active Member

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    I am having a similar issue with the range on replacement battery. Original was a 60 A pack, replacement is a 60 B pack. Pack replaced at almost exactly 34,000 miles. My original pack when car was delivered new was 209 rated miles. Replacement pack blew me away with a range of 211!!! I was ecstatic (as they would not take my money to upgrade me to a 85 pack like I begged for).

    Range remained at 211 +/- 1 mile for about 2,000 miles without fail. At about 2,400 miles on the new pack, I had a sudden almost overnight drop in range to 205 +/- 1 mile. That held for a little while like that. I have had another almost overnight drop to 203 rated.
    I am tracking with temperature. Temperature has had no impact on those numbers so far, as the temps have remained constant.
    At 40,000 miles I'm down to 202.

    Now that we have had a drop in temps, with nights in the 30's, days in the 60's, my rated is about 198-200. BUT, that number is regardless of temps it seems (I know, sounds like I am contradicting myself). What I mean is even when that pack is NICE AND HOT HOT HOT, such as just doing 150 miles on the freeway, and then plugging into a supercharger where I can get my marshmallows out to make smores from the heat being dissipated from the car cooling itself during charging, the range is not going up.

    Now, in comparison, my ORIGINAL 60kWh "A" pack, up until the VERY MORNING of failure, with 34,000 miles on it's clock, and over 150x100% charges, my rated range was 203 Rated Miles. I have treated my new pack no differently then my original.
    I have brought up the issue, and have been told that after reviewing logs, their are no issues. So as long as I still have 84,000 miles left on my battery warranty, I'm just going to keep doing what I'm doing.

    And, I do keep track closely my range. I make a Rated Range video progress report every 1,000 miles for my youtube account.

    Oh, and as requested from someone else a while ago, I have started keeping track how much power goes back "into" the battery during recharge time. While this changes with firmware updates due to how much tesla keeps as reserve, when I got the car back with the new battery, recharge kWh going back in was about 63 from the "Charge Now" screen. That number has dropped to about 55-56 kWh from "Charge Now". I have also run it very very close to shutting it down once since getting the new battery (emergency, had to get kid to hospital, they kindly let me plug into the Spare Ambulance Bay's 14-50 as they only had 2 ambulances and 3 bays, very kind of them), and running that absolutely low, I only got 59 kWh back.


    I hope this date helps... Sorry no graphs or charts, but I watch my range like a hawk. My pack was labeled as "refurbished" on my service invoice, but given the 211 range, and the fact it was a "B" pack I thought it could have been new old stock/ just a spare and that all battery swaps are labeled as refurb's.
    Given the sudden range loss, I deduce that my loss would follow almost exactly what the capacity loss may be if 1 cell, then a second cell were to fail in one of the bricks.
     
  6. pnaecker

    pnaecker Member

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    The car has 55k miles on it now, added more or less linearly during the 23 months. I haven't kept a log of mileage vs date, and I don't think VT has kept one.

    Yes, I made the point with the SC that if the battery does not charge and store like a D battery, then it's not "all newest components". But he wasn't agreeing. He said that there were components external to the battery that would limit the ability to charge at 120kW. Seems reasonable. Except that I am pretty sure I read that someone else received a newer battery to replace their A. Sigh.

    My drive is mostly on freeways, albeit I don't slow down for bumps. So I don't think I would describe my drive as excessively bumpy. Also, I have 19" wheels and very nice, relatively soft tires, so the ride is about as smooth as you get in a MS at speed.

    The VisibleTesla dataset does not include any other measures of range beyond Estimated. It would be ideal if it had logged my odometer reading, but I don't think it has. However, I think it must be logging (where?) my position, so I could theoretically compute a trip-by-trip actual driving distance measure vs SOC. But my energy consumption per mile is quite stable over long periods of time. So while Saghost is correct that there are variations in the estimated range due to local conditions, the chart clearly shows that these variations tend to be small relative to the total. If you look, for example, at the period around 8/1/2014, you will see my range at 50% varied only between 117 and 121. I could plot a moving average, but I think the story is pretty clear from the sample points.

    Also, most of this driving is in Southern California. We are unfamiliar with the concept of "seasons" here, so most of the driving is within a fairly narrow temperature range - certainly everything from July to September, where the dramatic drop occurred.
     
  7. apacheguy

    apacheguy Sig 255, VIN 320

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    Hate to break it to you, but unfortunately whoever you spoke to was dead wrong. We have ample evidence from others, as well as a written statement from Jerome that confirms that the charge rate is limited by internal components to the battery.
     
  8. stopcrazypp

    stopcrazypp Well-Known Member

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    It's possible for the pack to have "all new components" and still be in A-spec. For example if it has "A" components, but new parts (instead of refurbished), it would still be "all new", just not up to the latest specs.
     
  9. pnaecker

    pnaecker Member

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    I'm sure you are correct, apacheguy - I could have continued to argue that I deserved a newer model battery and my car would accept it. But I wanted my car back rather than holding out while I argued up the management chain that I deserved a newer battery. Maybe I should have tried. I understand that other cars that started with A batteries have received upgraded batteries. One thing we have learned from this forum is that there is a lot of variation in how identical situations are handled by the SCs. Truly unfortunate, because it makes Tesla look incompetent and petty.

    Does anyone know if my warranty period "resets" from the date of the new battery?

    My best case scenario is that before too long this battery fails as well, just after the time that there are only "new model" batteries available for replacement.
     
  10. randompersonx

    randompersonx Member

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    The battery has an 8 year unlimited mile warranty. The date should not be pushed out from today, but if you were near the end of the warranty they would probably extend the warranty on the repair by a year. In your case, it most likely would not be extended.
     
  11. apacheguy

    apacheguy Sig 255, VIN 320

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    #11 apacheguy, Oct 17, 2014
    Last edited: Oct 17, 2014
    ok, this could be true if it had all new A-spec cells. Then it would charge to ~270 rated miles, which I doubt. Otherwise, claiming that the pack has all new components is false and misleading.


    Yup. Several early production models have been upgraded to D packs while Sigs, despite protesting at the time of replacement, received refurbed A packs. Not saying Sigs never get upgraded (it has happened), but it does seem rather unfair to me especially given the whole "Tesla treats Sig owners with a lot of respect" nonsense. We are treated the same as the next guy in line who has a VIN in the 40 thousands and doesn't even have a service plan.
     
  12. Electric700

    Electric700 Member

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    Can't Tesla reduce their own costs and make you a more satisfied customer by just giving you a Type D battery? I would think that's the sensible way.
     
  13. ACDriveMotor

    ACDriveMotor Member

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    Only if they sell you the battery. If you can get a free upgrade then I suspect there is concern that some will try to take advantage of that to upgrade perfectly good A packs to D packs.
     
  14. Johan

    Johan Took a TSLA bear test. Came back negative.

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    Are you expecting Tesla to keep replacing your 60kWh batteries as they die off if you keep charging to 100% consistently? Does the battery warranty allow this? Not asking to offend, actually I like that you are pushing the limits of both the technology (battery) but also of Tesla (company).
     
  15. islandbayy

    islandbayy Active Member

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    No, not expecting Tesla to keep replacing my batteries as they die off from charging to 100%. My first battery did not fail from 100% charges, it had a contactor failure.

    Once again, to clarify and simplify my other post, the Problem I'm Having, is that after 34,000 miles, my original factory installed battery, even after my HEAVY use, was still outputting 203 Rated Miles, and that was a Consistent and obtainable real world number.
    My replacement battery, after less then 6,000 miles on my replacement pack, my Rated Range went from 211, and as of yesterday, is down to 200 rated miles.

    Mileage On Pack Rated Range Age/Time in Service
    Original Pack: 34,000 Miles ~203 at Time of Death 1 year 2 Months
    Replacement: 6,000 Miles ~200 Current 3 Months Has been tested in Temp controlled environment as well to rule out colder temperatures (Garage heated to 75*F)

    Can someone who is better at math calculate how much quicker the rate of degradation of my new pack over my old?

    And where my PROBLEM with Tesla lays is that I cant get a straight answer (COMMUNICATION PROBLEMS) on anything. The service center has requested engineering to review things, and they keep saying it's ok. Thats the only answer I get, the battery is OK. Based on 1 year and 2 months living with my original pack, it's NOT ok. I cant get any further information, No logs, no screen shots of the BMS showing it's ok, all I can do is take Tesla's word for it. If I had a 85kW battery with Unlimited Mileage warranty, "OK" would most likely be a acceptable answer FOR NOW. With a 60kW pack with only 125,000 mile warranty, which is not going to last me much more then another 2 years, OK is not a acceptable answer. Normal degradation, what I saw on my original pack, I would have no problems living with and I expected. While my range right now is not much different then what my original pack had at T.O.D, how much further will it have degraded in another month? Current rate is 3.6 miles of degradation/month. In one year my 100% charge would be ~168 at current pace.

    I just want a straight answer, and a bit more then, Your Battery's Ok, to back it up. Once again, service center has done what they can, but my concerns are growing. While the degradation may be within acceptable limits now, how much longer until it isnt?
     
  16. apacheguy

    apacheguy Sig 255, VIN 320

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    Keep in mind that most Leaf owners charge their cars to 100% daily and their battery packs don't die. They might degrade faster, but it certainly isn't "pushing the limits" of what the packs can handle. There are several Leaf owners who charge to 100% regularly and have noticed very little degradation, in fact. If done properly, damage to the cells can be mostly avoided. If it isn't too much for the Leaf to handle, then it certainly shouldn't be too much for a superior battery tech such as Tesla's.
     
  17. WarpedOne

    WarpedOne Supreme Premier

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    Another case of range estimation degradation.
    Nothing to do with battery degradation at all.
     
  18. islandbayy

    islandbayy Active Member

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    That may be, however, would not explain less energy being replenished when recharging. Which is why I would like more information then, It's OK... If nothing is wrong, show me a log. Heck, even my 8 year old laptop has a ware meter telling me the % of original capacity that remains (after 8 years I have 41% of original battery capacity).

    Just point is, Give me some info to put me at ease. Until then, all I have to go by is what is provided, Range display on my car.

    On, one other thing I forgot to mention. Yesterday, after 100% charge, immediately unplugging and driving, my energy bar on the charge screen dropped a ~4% after 1 single mile of driving. It was a instant drop. Driving, then pop... 96%. (% verified through Visual Tesla).
     
  19. qwk

    qwk Model S P2681

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    Who knows how your replacement pack was treated/what the mileage is on it. That is also a big factor.
     
  20. glhs272

    glhs272 Unnamed plug faced villian

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    I don't see anything wrong with the way islandbayy is treating his battery. Sure, charging to 100% every day may mean quicker degradation over a very long period. But, this should not cause the battery to fail.
     

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