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EPA for 60kWh battery rated at 208mi

Discussion in 'Model S: Battery & Charging' started by Adm, Dec 7, 2012.

  1. arg

    arg Member

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    Are we sure this is comparing apples-to-apples here? It's always been slightly curious that there's only one EPA number for the 85kWh - you might expect the Performance and standard models to give different results (due to the 21" tyres at least - and it would be surprising if the powertrain has no effect at all).

    Maybe the '85' number is for a performance with 21" wheels while the '60' is on the 19".

    Another variable is the reserve capacity. It's reasonable to expect the top-end reserve (difference between standard charge/range charge/theoretical max charge) will scale in proportion to the pack size since the limits correspond to cell voltages, and so that wouldn't affect the relative range. On the other hand, the bottom-end reserve (2 months anti-bricking allowance after reaching 'empty') should relate to the vampire load and so should be a fixed number of kWh rather than a percentage of the pack [if I've analysed it correctly, that should actually give worse range for the 60kWh rather than better, but at least it's an example of a factor that doesn't scale - perhaps there are others].

    There's also the question of whether the reduced performance of the 60kWh means that it ends up doing less work during the EPA test. I can't find enough detail about the test cycles to say if this is an issue or not.
     
  2. ahimberg

    ahimberg Member

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    that was my thought exactly, 19" tires is probably part of the difference here.
    Maybe firmware updates/tuning have made all cars better too, so when the 85 gets re-tested next year it will improve too?

    Does give me more confidence that the 60 will be usable with the supercharger network, too (and that one won't have to drive 50mph to be able to make it between stops)
     
  3. mklcolvin

    mklcolvin #P-5058

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    #23 mklcolvin, Dec 7, 2012
    Last edited: Dec 7, 2012
    That's good news. We might be able to actually get to 230 miles (ideal range). I haven't been able to wrap my head around the ideal/range? info from the dashboard. Which is more accurate?
     
  4. stopcrazypp

    stopcrazypp Well-Known Member

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    The weight would be the same if they went with the plan when they announced the car (which is the same amount of cells in both the 60kWh and 85kWh versions, with the 60kWh version using the less energy dense cells). I guess they decided to just use less of the same cells in the 60kWh pack. The 40kWh pack will definitely weigh less than the 85kWh because even using the lowest cells available (2200mAh) that pack will still have significantly less cells than the 85kWh version (~5000 for 40kWh vs ~7600 for 85kWh).

    The caveat here is that some of this bump in efficiency may have to do with the different tires, improvement in the charger (which Elon has said they were targeting for improvement when the 89MPG figure came out for the 85kWh version), and general software updates for the newer version.
     
  5. rcc

    rcc Model S 85KW, VIN #2236

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    I was under the impression that the battery packs are the same size, weight and weight distribution in all models so that the same safety design and crash testing (and suspension design and tuning) applies to all models. If that's the case, I bet the efficiency difference is due to some combination of two things:

    1) the EPA 5-cycle testing includes a new test that attempts to measure efficiency under aggressive driving conditions (and higher speeds and lower speeds). Both 85KwH versions of the Model S accelerate faster than the 60 KwH version so it's reasonable to assume that the 85KwH S's will burn more power and therefore get a lower mpge under hard acceleration.

    2) it's possible that the 60 KwH version was tested using the new acceleration profiles released in the 4.0 software update. I think there's a good chance that smoother acceleration is more efficient.

    I bet the majority of the difference is due to #1 above.
     
  6. drees

    drees Active Member

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    Exactly this.

    You will notice that on Tesla's new range estimator that the difference between 19" and 21" wheels is nearly exactly the same ratio as the difference in efficiency between the 60 kWh and 85 kWh cars.

    The battery pack between the 60 kWh and 85 kWh is supposed to consist of the same number of cells, so weight difference between the 2 should be minimal (no more than 100 lbs) and thus have a negligible effect on overall efficiency.

    I would expect the 40 kWh car to post nearly identical numbers to the 60 kWh car.
     
  7. Ceilidh

    Ceilidh Member

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    Wow. Happy about this rating. Now if Tesla could just throw them into the production line a little early that would make a great new year...

    Cheers.
     
  8. doug

    doug Administrator / Head Moderator

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    Right still some open technical questions I've been curious about and hoping Tesla will answer soon.


    • What's the difference in mass?
    • Which type can how many cells did they end up using?
    • Did they end up adding ballast mass?
    • Did the center of mass change?
    • Did the suspension setup change?
    • How is handling affected?
     
  9. rcc

    rcc Model S 85KW, VIN #2236

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    Ok, I sit corrected :).

    Seriously, the tires make that much of a difference? Wow.
     
  10. qwk

    qwk Model S P2681

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    +1

    This info interests me too. None of it is a trade secret, so why Tesla doesn't publish it is beyond me.
     
  11. Rodolfo Paiz

    Rodolfo Paiz P85 "Plug and Play"

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    +1. Precisely.
     
  12. aviators99

    aviators99 Model S - R140

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    As a data point for the 85, in the 3 days I've had it, I have been getting nearly EXACTLY the EPA range. I do not drive as aggressively as many here, but probably have done 2 or 3 "demo" drives per day where I demonstrate max 0-60 acceleration.
     
  13. rolosrevenge

    rolosrevenge Dr. EVS

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    Right behind you...
  14. 100thMonkey

    100thMonkey Member

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    being someone who is hours from signing paperwork on a non-P 85, it would be very nice to have a complete handle on an apples to apples comparison showing the differences in MPGe of the 60kW vs P85kW and the non-P 85kW. do we not have an MPGe for the non Performance 85kW? I'm sure I'm not the only one thinking that if the 60 kW is truly that much more efficient, that it narrows the temptation gap between the 60 and 85. I'm still feeling like range is like hard drive space, it's hard to have too much, you pay more for it up front but it's so much cheaper than running out down the line and having to trade in/up later.

     
  15. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    No surprise there. Sticky tires are, well, sticky. I had a set of A001-R tires once that required acceleration to go down Simon Fraser University hill.
     
  16. Jason S

    Jason S Model S Sig Perf (P85)

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    Could be all the cars got a little more efficient due to a software change and the 60 is the first to show it because of testing.

    Edit: although tires could make all the difference in this case.
     
  17. NotTarts

    NotTarts Member

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    I'm fairly certain it isn't the tires, or anything other than the weight and possibly motor power. Tesla themselves predicted the efficiency differences due to weight in their range estimates (@ 55 mph):

    85 kWh = 300/85 = 3.52 mi/kWh
    60 kWh = 230/60 = 3.83 mi/kWh
    40 kWh = 160/40 = 4 mi/kWh

    That they added an extra 5 kWh to the battery in the top model to reach the claimed 300 mi shows this. If the 85 kWh model had the same efficiency as the 40 kWh model, it would have a 'Tesla range' of 340 mi. That's a huge difference.
     
  18. Zextraterrestrial

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    well mine charges to 315mi Ideal EPA range, explain that ....~ 340 Tesla range miles?
     
  19. NotTarts

    NotTarts Member

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    The standard charge has a max ideal range of 300 mi (AFAIK). Turning on 'Range' mode gives you an extra 5% of capacity which is where the extra 15 miles comes from.

    Elon has said in the past that (paraphrasing) "more batteries, more power" (in regards to the power output), which suggests that the lower models do use fewer cells. It wouldn't make sense to use different chemistries or energy densities for each model anyway as that would require Panasonic to manufacture unique cells at low-volume, which doesn't work financially.
     
  20. Alpha

    Alpha Member

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    #40 Alpha, Dec 9, 2012
    Last edited: Dec 9, 2012
    Come on! The 65kWh battery has to be lighter! (and the 40kWh battery lighter still.)

    Adding significant ballast to the smaller batteries screams ridiculous to any good engineer (which Tesla has in spades, starting with Elon!!)
    I understand the idea of not having to perform additional crash tests. But I'm sure that they *are* doing the additional crash tests (not to mention computer simulations!) They have the resources!!

    Putting a significant amount of dead weight into the battery just for convenience is just not right -- the Model S already has pretty much a lower center of gravity than probably any ICE car in the same class, so easing up on that center of gravity by say, half a ton would still end up with a handling profile while maybe slightly worse than the heavier battery, still well above or on par with any ICE competition.

    Once the first 60kWh models start getting delivered, this question should be answered once and for all.
    I'm hoping this happens before I have to finalize...
     

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