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Wh/mile -- difference between 60kwh and 85kwh batteries

Discussion in 'Model S: Battery & Charging' started by schoendp, Jan 23, 2013.

  1. schoendp

    schoendp Member

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    I know there aren't many 60kWhs on the road yet, but I am curious as to what Wh/mile they are getting.

    Looking at past threads on the 85kWh battery from Rod/Barbara and others, it appears the EPA rating comes out to approximately 307 wh/mile (this comes from assuming 95% of the battery pack is available for use, which leaves 80.75kWh. If you divide this by 265, you get 305 wh/mile - very similar to 307 wh/mile estimated by Rob/Barbara).


    However, when you do the same type of math on the 60kWh battery, you get a much lower Wh/mile average for the EPA rated range. For example, if you again assume that 95% of the battery is available for use, that leaves 57kWh. If you then divide this by the EPA rating of 208, you get 274 wh/mile. This is significantly lower than the 305-307 you get for the 85kWh battery.


    Does this inherently mean the 60kWh battery uses about 10% less energy to operate (on average)? Is this due to the fact that horsepower/torque is lower? Can we expect the 40kWh to use even less energy, average?


    Any insights would be greatly appreciated.
     
  2. rolosrevenge

    rolosrevenge Dr. EVS

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    I think that the 60 kWh pack weighs significantly less, so there's that. Also with less power comes less I^2*R losses in the internal electronics, so the efficiency is boosted slightly more through that.
     
  3. gg_got_a_tesla

    gg_got_a_tesla Model S: VIN P65513, Model 3 Res Holder

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    I'm seeing the following in my 60; Trip A's today's driving and Trip B lifetime (with some spirited runs in the first couple of days):

    ImageUploadedByTapatalk1358970360.590939.jpg
     
  4. schoendp

    schoendp Member

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    gg - what type of driving do you do (city/highway)? Also, do you think Trip A is a real world experience that would think could continue over the life of the car?
     
  5. rcc

    rcc Model S 85KW, VIN #2236

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    And is the 60KW battery really lighter? There's been mixed guesses but no concrete data. I think yours is one of the first 60KW production vehicles to hit the road. Congrats, btw!!
     
  6. gg_got_a_tesla

    gg_got_a_tesla Model S: VIN P65513, Model 3 Res Holder

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    It would be about 5 miles in the city and the rest on the highway. This is definitely more the way I'd drive daily and may be considered a real-world experience. A caveat is that I didn't have to use climate control at all today except for my seat heater (at setting 3). Should be different in peak summer or in much colder climes.
     
  7. giants2001

    giants2001 Member

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    I had the day off today and decided to drive down to Monterey, Pebble Beach. I wasn't quite sure exactly how much extra driving I would do when I got there, so before I left I set to Max charge and it went from 188 rated to 197 (expecting 210?). I left San Jose and drove through Santa Cruz via Highway 17/1. There is a little bit of elevation gain on highway 17, so I took a snap shot of my 30 mile average. What goes up must come down.
    photo (4).JPG

    I arrived at Pebble Beach with 115 rated left and 156 projected. Total distance traveled was 85.5 miles using an average of 304 wh/mi. Although the weather wasn't the greatest, we still had a blast driving around 17 mile, taking in the sights.
    photo.JPG

    I figured we had plenty of range to make it back to San Jose the same way we came, but instead decided to check out the Gilroy SC on the way back and see what type of charge rate I could get. And its free, so I couldn't pass that up! Got there with 67 rated/ 65 projected miles left (132 miles traveled). I averaged 306 wh/mi.
    When I first started charging the display read 72mi/hr, 75amps, 309V. At the end it was reading 102mi/hr, 120amps, 341V. After 1 hour I left with 175 miles on a standard charge.
    Before SC-
    photo (2).JPG
    After SC-
    photo (3).JPG
     
  8. Todd Burch

    Todd Burch Electron Pilot

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    See this.

    All speculation, but my guess is that the EPA profile possibly floors it or accelerates aggressively, and with its higher performance the 85 ends up using more energy.

    But honestly I have no idea. I had been under the understanding that the 60 and 85 were the same weight (or similar), with the 85 using the most advanced battery chemistry. But it could be that they both have the same chemistry, and the 85 just has more cells (weight).
     
  9. aronth5

    aronth5 Long Time Follower

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    Interesting comment from the article
    "Improved battery chemistry? An unofficial source at Tesla hinted to me that the chemistry of the 60-kWh battery is different--and better--than that of the 85-kWh battery."

    One possible explanation which I think is highly unlikely is that Tesla is using the newer Panasonic NCR18650B 3400mah batteries in the model 60. If that was the case I would think we would have already heard about it.
    So I put that in the "maybe" column for the Model X.
     
  10. Todd Burch

    Todd Burch Electron Pilot

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    Yes, I doubt the 60 has more advanced chemistry than the 85. In the past we'd always heard it was the other way around.
     
  11. apacheguy

    apacheguy Sig 255, VIN 320

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    I could swear I remember reading the same thing. That the 60 and 85 have the same number of cells and therefore same weight. The 85 pack just has a higher energy density per cell.
     
  12. GSP

    GSP Member

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    Perhaps the more advanced chemistry in the 85 kWh packs stores more energy per cell, but is less efficient than the older chemistry in the 60 kWh packs.

    GSP
     

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