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Battery Capacity

Discussion in 'Model S: Battery & Charging' started by GJ79, Oct 27, 2016.

  1. GJ79

    GJ79 Member

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    I have a P85+ and I recently drove the Battery down to 1% and then charged it overnight to 100%. Per Remote S app I added 71Kwh to the Battery. Is there a way to tell how much my battery degraded over time with this information? I am not sure how accurate the 71KwH added from Remote S is.
     
  2. AllenWong

    AllenWong Member

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    The 71 kWh added figure in the Remote S app is directly from Tesla's servers (and so is the rated/ideal miles added). I make no calculations or guesses on that. There is a way that this number could be wrong. And it's if the charge stopped and restarted. But what you stated is quite similar to what others have stated: The charge from 1% to 100% is not exactly 99% of their battery capacity. If I recall someone said he only added 81 kWh when he went from 1% to 100% on his 90D battery.

    I have several guesses on the reasons on why this is:
    1) 100% isn't always 100%. There were times when the charge said 100%, but I was able to get a few more rated miles in by simply waiting.
    2) 1% isn't exactly 1%. I suspect that the Tesla has some "reserve miles" as some drivers reported driving at 0%. And also, the car probably shuts off the car before you fully drain the car to prevent damage to the batteries.
    3) Tesla's servers or your car is reporting inaccurate data.
    4) Battery degradation.

    I think reason 2 is the major one, and here's the math on why I think so: When I charge to 100%, it says that I have 257 rated miles on my P85D. But as I'm charging, I noticed that the rated miles go up by 3.23 rated miles per kWh added. This 3.23 number is pretty consistent whether I add 50 miles or 100 miles. But if you divide 257 rated miles by 3.23, you only end up with 79.6 kWh. So a 100% charge seems to be missing 5.4 kWh. It's very odd. When I look at the press release for the P85D, it says that it has a range of 275 miles. If I divide 275 miles by 3.23, I get 85 kWh. So my conclusion is that the car is hiding a few kWh from our view and that 0% to 100% is more like 5% to 99% of battery capacity. I don't dare test out my theory, though, because I don't want to drive at 0% charge to find out how much the reserve actually is.
     
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  3. GJ79

    GJ79 Member

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    Well I should have added that my 100% currently shows 250 miles.My guess was two as well but I am not sure if the 71kwh probably also considers any looses or so.
     
  4. David99

    David99 Active Member

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    Definitely. Using TM-Spy I can see at the CAN that when the car shows the driver 0% there is actually about 4% left. The car reports the true SoC on the CAN bus. Keeping this 4% safety is of course very important to keep the battery healthy and minimize degradation.
     
  5. AllenWong

    AllenWong Member

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    Can you actually drive and run through the 4% or does it still shut off at around 4%?
     
  6. Matteo

    Matteo Member

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    Hi. There is a battery survey here where you can enter your data if you want. It will show remaining percentage in column S and remaining capacity in column T. After you have entered your data, you can go to the Charts tab and select your username to see how your degradation compares to others.
     
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  7. ChadS

    ChadS Petroleum is for sissies

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    Sorry for the quick diversion, but this is important. The last sentence above is correct; Tesla does reserve some battery capacity (probably the 4% mentioned above) to save the battery from being completely drained, which is harmful.

    However, the suspicion of "reserve driving miles past 0" is decidedly incorrect - you can't drive on that bottom 4%. It wouldn't make sense for Tesla to do that, Tesla has repeatedly said that they don't do that, and a number of owners have run out at exactly 0 - a couple have even run out a tiny bit before that. Yes, some people drive past 0 (which is why this rumor persists), because the battery doesn't store "miles" so Tesla has to guess when it will run out and they try to make that guess conservative. So you might happen to get lucky, but you absolutely can not count on a "below 0 mile driving reserve". There have been several threads on this, please search if you are interested - I hope we don't take this thread further off-topic.

    Getting back on-topic for the OP: Tesla's kWh ratings for their batteries are nominal. Tesla will not say exactly how much is actually usable (I first started asking them back in 2011; back then they would even refuse to say that the 85 number was nominal; they just kept repeating "85" to every question I asked even though it was a senior battery engineer that clearly knew the answer), but your battery very definitely did not provide 85kWh for driving even when new. There have been a large number of calculations and measurements on these forums; but be careful as some of them have been shown to be incorrect. I haven't tried Matteo's link but it sounds like a good place to go. Although even there, you have to keep in mind that your car showing fewer miles than it used to doesn't always mean the miles are "lost" due to battery degradation. Tesla has to estimate how many miles are in there, and the estimate can drift based on driving, charging, and environmental conditions. Charging from near-empty to near-full (as you have done) a few times can help calibrate it a bit.
     
  8. David99

    David99 Active Member

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    No, it's not a usable buffer or reserve. The car will shut down well before it reaches true 0%. That's part of the battery management system to not allow a discharge to zero as it would harm the battery. Now me and several other have successfully driven the car passed 0% on the display. I guess it depends on a few other factors when the car will actually shut down. Sometimes you get lucky, but the 4% is definitely not a usable part of the battery capacity.
     
  9. TheTank

    TheTank Member

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    I have a bit of a story I finally gave up on. My P90DL originally got 438 km at 100% charge or around 393 km at 90%. After about a month it had 360 at 90%. I was told its software and it will be fixed. 1 Year later, its 90% is 365km. I escalated all the way up (hopefully nicely) but eventually they referenced the battery warranty .. I finally agreed to disagree and decided to move on. Having said that, during the discussions, I drove my car down to 0 km left and 0% left. (So it definitely does not stop me at zero) Parked it in my driveway and left the heat blasting and it kept blasting. After 10 mins I put it in Drive and it still drove. I did not drive past the end of the driveway just in case. Then I plugged in and charged up to 100%. It actually stopped at 97%.

    My theory is that maybe the zero point in the algorithm is wrong for my car and it thinks zero is 25-30 km's too high. I was going to try it again and have the heat blast until the car says to stop the heat and then charge fully to see if that would work. Thoughts? I am more curious if that would work than the extra KM's now that SuperChargers are all around us now.
     
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  10. Maarten ST

    Maarten ST Member

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  11. Lanber

    Lanber Member

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    The car protects the battery with the famous anti brick 4kwh, then also it kinda wants to save 3,5-4kwh below 0 and anti brick.

    My 2013 S85 has 75.1kwh useable energy and it is 3.8kwh below 0% and 71.3 from 100% to 0%
    Now those 3.8 you kinda step around with a light right foot and dont tempt faith with, I did however run down 2.3 of them leaving me with 1.5kwh remaining the system estimated. Limiter was then at 40kw. Dont know how much further it would have gone.
     
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  12. wcfinvader

    wcfinvader Member

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    Have I lossed more capacity than I thought?
    tmp_28397-0313170827251774772.jpg
    65.8 kwh used and we started with a full charge 248 rated miles. 4 rated miles left when supercharging started. Is this normal? Per this thread the consensus seems to be that a 85 kWh battery is 75 kWh useable. Mine seems to me quite a bit less. 101,323 miles As of time of this post.
     
  13. apacheguy

    apacheguy S Sig #255

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    @wk057 has a thread that lets you estimate capacity from rated miles.
     
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  14. wcfinvader

    wcfinvader Member

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    248x300=74,400÷1000=74.4 kWh useable per wk057's formula.

    So after 100k miles I've lost only 3 kWh! Very Impressive. Wonder if there was reserve in the battery yet considering there should be 8 kWh leftover if this formula is correct. By the rated miles it would be easy to say there indicated to be 1 kWh left since I started charging with 4 rated miles left.
     
  15. dsnows

    dsnows Member

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    I just bought a 60 D last week from new inventory. It is a 2016 model year. How do I know for sure if the battery is software upgradable to 75? I can't find anything about this in my specific car paperwork or online.
     
  16. wcfinvader

    wcfinvader Member

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    I believe some have looked at the battery label and others have stated that there would be a option online to pay for a upgrade. I have a 85 so I dont know where online they saw it.
     
  17. doubleohwhat

    doubleohwhat Supporting Member

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    Is there an upgrade option in "My Tesla" for your car? If not, call Tesla and they'll sort it out. You can also drop by a service center.
     
  18. dsnows

    dsnows Member

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    I couldn't find the upgrade option on my tesla. I think I will call them to confirm.
     
  19. doubleohwhat

    doubleohwhat Supporting Member

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    The upgrade option on my tesla disappeared and reappeared 2-3 times between me buying my car and purchasing the upgrade. I also had one helluva time getting AP1.0 activated on my car after purchasing via the my tesla upgrade button. So, overall, I'd rate the my tesla upgrades feature as pretty flaky. Better to just call.
     
  20. Rocky_H

    Rocky_H Active Member

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    If it is a 2016 model year, then it is CERTAIN that it is a software locked 75kwh and can be upgraded. The real 60 models had been discontinued for over a year at that point when they re-introduced the software 60 to try to shift people out of the Model 3 queue.
     

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