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Charge-off 90kW vs. 120kW

Discussion in 'Model S: Battery & Charging' started by Owner, May 7, 2014.

  1. Owner

    Owner Active Member

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    The detailed data from the charge-off last month and Tesla's responses are available now:

    Charge-off 90kW vs. 120kW | Tesla Owner

    And coincidentally, I saw the Atlantic ocean today making it cross-country in the Tesla.
     
  2. dsm363

    dsm363 Roadster + Sig Model S

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    I still feel like I should be upset :)

    Nice work and great to see Tesla respond to it as well.
     
  3. Seven7

    Seven7 Member

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    Wow, excellent write up and test! Thank you!
     
  4. ken830

    ken830 Model S (Res#P12,447)

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    Thanks for the work in organizing, executing, and summarizing the Charge-off!
     
  5. bluetinc

    bluetinc Member

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    Would you mind expanding a bit on the "points when each car reached its respective 20% range? (52 miles for the original design, 49 miles for the newer design)" comment by Tesla. If they feel the 20% point is different for the two Batteries, do they feel the 90% range is the same or different? That comment just seems to open up a long list of questions without a explanation of what they mean.

    Thanks Peter
     
  6. wts13

    wts13 Member

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    Now how about when we get 135kW? :D

    Would also be interested in seeing tests like this done with 60's
     
  7. wraithnot

    wraithnot Model S VIN #5785

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    Thanks for posting this. An actual side-by-side comparison under the same conditions is definitely better than trying to compare data collected at different times and at different locations.
     
  8. Owner

    Owner Active Member

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    Thanks everyone for the notes of appreciation. And thanks to my two testers who helped with the article too.

    The original 4 minute difference between the two batteries referred to a 20-90% charge range. So a simple test to do that would be to drain each car to that exact amount (for that a car) and then fill each car up until it reaches 90% or a non-range charge.

    Instead of doing that exact test, I extrapolated the data for the 20-90% numbers for the newer battery.
    If you do it exactly as the numbers per each battery, the battery A looks worse because its 20% number is lower by 3 miles and its 90% includes the long taper.

    Its a bit odd that the 90kW battery with twice as much mileage has a better range and less degradation than my battery, which has since got worse as i am now on the other coast. I got a 10% hit on the Roadster battery too in the first year or so and then it stabilized.

    hope this is clear, it does get confusing if you try to slice the numbers both ways.
     
  9. apacheguy

    apacheguy Sig 255, VIN 320

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    Very nice and thorough blog post. However, I'm still confused regarding the taper. From 10% SOC my car maintains > 88 kW rate of charge for exactly 14 minutes, which seems comparable to the numbers you guys saw. However, when I overlaid my charge curve on top of wraithnot's this is what I came out with:

    taper.png

    You'll notice significant differences in the taper between 40-60% SOC. The B pack began its taper from 90 at 45% compared to my 35%. So a couple questions for you:

    1. Do you have a % SOC value corresponding to the point at which the A pack began to taper?
    2. How long did it take to go from 10% to 80% for both batteries?

    Perhaps not all A batteries are created equal. My 100% charge on 5.8 was 245 rated with 25,000 on the odo.
     
  10. malcolm

    malcolm Active Member

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    Great result.

    Thanks for all the work you've put into this.
     
  11. Owner

    Owner Active Member

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    1. Battery A began to taper at 100 miles.
    2. The 10-80% charge difference (based upon the "standard" way) was 4.5 minute difference between the two batteries. Mine came in 5 minutes, the other 120kW at 4 minutes.

    I've never done this by pure SOC as that number seems more granular than the mileage number and harder to record.

    There are also so many other variables involved in all of this. I've done seven tests on my own, you'll find them on my blog.
     
  12. apacheguy

    apacheguy Sig 255, VIN 320

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    Interesting, at 100 rated miles (40%), my A pack is down to 79 kW.

    I just did a test of my own today at the new SJC SpC to get at the differences I see in the 40-60% range. I was interested mainly to see if anything had changed in 5.9 (previous data points were on 5.8). Here was the result:

    taper.png


    Oddly enough the first two data points, which admittedly are difficult to see on the graph above, matched exactly the numbers I saw on 5.8, but then there clearly was something that caused a power sag. The fact that it shot straight up to 90 kW from the get go indicates to me that there weren't any environmental factors affecting the supercharge session as the battery did not require a conditioning period.

    Misc factors:
    I was on a dedicated supercharge slot (4a). 4b does not exist.
    All numbers were read directly from the REST API.
    Exterior temp was mid 60s.
    C/C disabled throughout the test.
     
  13. Kraken

    Kraken Member

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    #13 Kraken, May 8, 2014
    Last edited: May 9, 2014
    As a fellow tester, I believe you are missing a big point:

    Environmental factors (and other factors) are the BIGGEST thing affecting these differences in charging. These are more important than A or B battery. Your statement of where it starts showing environmental factors aren't a factor is actually quite misguided. It isn't where it starts, but how it performs in the middle (when the battery is chugging through the hard work of charging) that makes a difference. We assume temperature is a big one, and it likely is a factor (and there is probably a sweet spot, instead of COLDER or HOTTER is better). Additionally, things like humidity and other environmental factors could be huge for all we know. Other things like how much use the car just went through could be a huge factor too. These seem to have a greater affect than the charging pattern than the battery type. Thus, when we eliminated more of the variables (impossible to eliminate all of them), we saw very much more of what Tesla told us we should expect to see, and less of what you see when you overlay two different tests from two completely different locations/times/dates/temperatures/etc.
     
  14. Todd Burch

    Todd Burch Electron Pilot

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    #14 Todd Burch, May 9, 2014
    Last edited: May 9, 2014
    Thanks for the great test! Makes me feel even more comfortable with having an A pack.

    A note on the supposed battery degredation: This continues to support the argument that we're generally not seeing real degredation when we see significantly smaller rated max range. I'm convinced that charging and driving patterns affect the indicated range a lot, and indicated range simply cannot be used to predict degredation. We've seen several examples where high mileage users who typically use more of their pack and likely range charge more frequently show higher indicated range.

    I think folks need to stop relating indicated range to degredation. I know it's the only thing we've got, but range calculation is just too complex to be considered highly accurate.
     
  15. apacheguy

    apacheguy Sig 255, VIN 320

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    Can you elaborate on that? It has always been my experience that if the battery is not properly conditioned (i.e. cold soaked, hot from a long, grueling drive) it will back off from the highest rate of charge at the beginning until it is ready to accept more power at which point it will match the expected power curve. I have never seen or heard of the opposite happening in relation to environmental factors.

    I think the power sag was most likely caused by fluctuations in the grid. I'll have to go back and run another test at any rate.
     
  16. Owner

    Owner Active Member

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    Anyone remember this? Rated Range Results | Tesla Owner

    That there really wasn't any clear indication between simplistic driving patterns and rated range.

    There has to be some correlation between battery degradation and rated range. But maybe we need to have a lot more miles on the cars.

    One very relevant data point to support Todd's assertion is that I have now added 6K miles driving cross country since this test. My rated range has gone up by 3 miles. Not a lot but does show that a few full range charges probably have an effect on the number.

     
  17. Todd Burch

    Todd Burch Electron Pilot

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    I'm sure there is a correlation, but with so many variables, the error in range estimation far exceeds the amount of degredation, and the degredation gets swallowed up by the other errors. We expect to have just a few percent degredation after a year of driving. I think the error in range estimation is several times this.
     
  18. tomas

    tomas Traded in 9 rep bars for M3, used to be somebody!

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    #18 tomas, May 10, 2014
    Last edited: May 10, 2014
    Thx for the test...

    My perception from all of the charging curves posted plus the charge-off plus my experience is that if you need 185 rated miles between charges (70% charge), the 90 and 120 kW capable batteries would be closest charging from 10 to 80%. That means for a trip to have almost equivalent charging times, you need chargers 185 miles apart (generally true) and you need to be comfortable going down to 10%. I don't like driving on edge of range, and would much prefer to go 20 to 90%, or even 15 to 85% in order to get my 185 miles, but that has negative impact on charge time.

    Personally, I'm encouraged by the test, but it has borne out that I have a battery that charges at an inferior rate, despite the fact that the difference can be minimized through a great deal of effort and assumption of ideal circumstances.

    I'm still looking forward to the battery upgrade program Tesla has indicated they'll provide when battery production is less constrained.... and still hopeful there will be some economic accommodation in it for the "A" owners who will have lived with additional charging time for years.

    PS I'm also finding that several range charges have increased 100% rated range... from 250 to 255 to 256... maybe there's more.
     
  19. apacheguy

    apacheguy Sig 255, VIN 320

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    I started a poll earlier this week that aimed to gauge interest in a refurbished pack upgrade option. The idea is that production constraints would no longer be an issue as no new deliveries come with refurb packs. Also, it would enable TM to offer an upgrade path at considerably less cost and, considering the responses I received, I think it would play out very well among A pack owners who are unsatisifed with their current situation:

    Poll: A pack owners: Refurbished Pack Upgrade?

    As a token of appreciation to TM's early adopters I think it would be nice of them to waive the labor costs and merely charge the difference in mileage between the packs.
     
  20. Todd Burch

    Todd Burch Electron Pilot

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    Since Tesla will need to implement a pack buyback plan and a strategy for either refurbishing packs or converting them for stationary energy storage use, maybe those interested in the upgrade could be the guinea pigs for the new Tesla buyback program.
     

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