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Rumor on Battery improvement

Discussion in 'Rumour Mill' started by Kelvin, May 5, 2017.

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  1. Kelvin

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    #1 Kelvin, May 5, 2017
    Last edited: May 5, 2017
    Eletreck reported an improved battery cell by Jeff Dahn, a top battery scientist partnered with Tesla. He gave a presentation on the improved cell in March. The most important takeaway is this slide.
    [​IMG]
    It shows the new cell can operate between 4.4-3.0v at a C rate of 2.5. After 1200 cycles, the cell degradation is about 5%.

    It pushes the max voltage from 4.1 to 4.4 which yields better energy density. C rate of 2.5 means 0-100% charging in 24 minutes. Assuming supercharging from 0-80% takes about the same time as 80-100%, it indicates 12 minutes 0-80% supercharging. 1200 cycles roughly translate to 480,000 km or 300,000 mi.

    This is nuts.

    So far we know that Model 3 has spec like this:
    $35,000
    320 km / 200 mi
    6s 0-100km / 60 mi
    5 seats, 2 trunks
    4 cents per km for energy(California supercharger rate @5km/kWh)
    $~500 annual maintenance
    Free software update for at least 8 years.
    Better safety, lower insurance cost.

    Assuming Dahn’s improved cell makes it into the wheelbase of Model 3. That adds:

    12 minutes 0-80% Supercharge
    5% battery degradation after 480,000km / 300,000 mi

    Forget about the environment, the car design, autonomy or any other fancy features. There is no way a ICE car can achieve the same economics.

    And, don’t sell your shares.
     
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    • Kelvin

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      Also, if the 100kWh battery pack can charge at average 2.5C, it means 80kWh of energy transfer in 12 minutes, which requires the Supercharger to have at least 400kW of power for 1 stall. So the charger power for 2 stalls should well exceed 400kW.
       
    • krbabu

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      Do we know what range can be expected from the (maximum) 75kWh battery pack?
       
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      No, not yet -- we'll probably get final EPA ratings around the final reveal / delivery event in July. In the meantime, though, we can make educated guesses from several different starting points. Here are a couple that I like:

      1. Start with the Model S 75/75D. The 75 kWh pack has 72.6 kWh usable capacity (per noted Tesla hacker Jason Hughes), and has EPA-rated ranges of 249 (RWD) and 259 (AWD). That gives you rated efficiency of 3.43 mi/kWh and 3.57 mi/kWh, respectively. We know that Model 3 will be lighter, smaller, and (likely) have a better drag coefficient than the Model S, so you can probably add about 10-15% to those numbers, which leads to efficiency in the range of 3.75 - 4.1 mi/kWh. That's about inline with the most efficient EVs on the market (the Hyundai Ioniq currently reigns with 4.0 mi/kWh), and considerably better than the Bolt EV at 3.57 mi/kWh (as it should be). Assuming 72.6 kWh usable capacity (and I all but guarantee that this number will differ from the S, given the new battery chemistry and cell/pack architecture), that works out to 272 - 298 miles of range.

      2. Start with Elon's promise of "at least" 215 miles for the base pack, and Jeff Evanson's statement that the base Model 3 pack will be "less than 60 kWh". Assuming ~55 kWh of usable capacity, dividing 215 miles by 55 kWh yields an efficiency of 3.91 mi/kWh (in the same ballpark as above). For the 75 kWh pack, your efficiency would be slightly less than that due to the increased pack weight. For the Model S, the difference between the 70 and 90 packs is about 0.09, so let's subtract that for the Model 3 75 kWh pack to get 3.82 mi/kWh. Multiply that by 72.6 kWh of usable capacity, and you get about 278 miles, which again falls into the range above. But wait! For which drivetrain do these numbers apply? Well, given that we started with the base model and promise of "at least" 215 miles, and given that AWD will probably add about 10-12 miles of rated range (as it does with the Model S), we can infer that these numbers apply to the RWD powertrain, and that the AWD powertrain would increase the rated range to about 288-290.

      There are many other approaches as well (some of which involve much finer levels of technical detail than what I've written here). That said, as I mentioned at the beginning of this post, there are a lot of unknowns / variables, the two largest of which are (a) the impact of the new cells and chemistry on powertrain efficiency, and (b) the fact that Tesla's nominal pack sizes can often differ greatly from their actual usable capacity (see the Electrek article I linked to earlier), which is why EPA range is what matters most at the end of the day.

      Personally, I'm hoping that Tesla can find a way to crack 300 miles in what they call the 75 kWh pack -- mostly for the psychological impact in the marketplace and my own sense of self-satisfaction. :) Realistically, though, I think the larger pack with AWD will be rated at just under 300 miles -- maybe 290 or 295.
       
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