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Thread: EPA for 60kWh battery rated at 208mi

  1. #41
    Junior Member scole04's Avatar
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    Quote Originally Posted by Alpha View Post
    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 batter, 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...
    +1

    As an ee myself i questioned the logic of adding ballast when overall efficiency is the goal. EPA numbers are what i expected.

  2. #42
    Head Moderator / Administrator doug's Avatar
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    Quote Originally Posted by scole04 View Post
    +1

    As an ee myself i questioned the logic of adding ballast when overall efficiency is the goal. EPA numbers are what i expected.
    Clearly overall efficiency isn't the only goal. (If so the car would look and drive very differently.) It's just one of many, including overall cost and time to market. We don't actually know if they're adding ballast, and while conceptually it may be counterintuitive and offputing, if the car works and performs as advertised it shouldn't really matter. That said, I'd still like to know if they chose to use ballast or not.

  3. #43
    Burrito Founder brianman's Avatar
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    When the NHTSA receives their "off the line" vehicle for testing, regardless of whether they get a 40, 60, 85, or 85 Perf presumably Tesla wants to do whatever they reasonably can to make sure that the NHTSA considers the results applicable to the other 3 flavors. Such accomodations might include specific weight and front/rear balance requirements.
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  4. #44
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    Lets consider they are using less of the same cells then the 85kw Model S

    -they don't need to add ballast, I can't think of a reason why any engineer would ever want to handy cap there own work.

    -for structural support in crash tests they would have three easy options, still install the empty battery cell boxes seen in the main pack, replace empty battery boxes with light honeycomb, just use bracing.

    - each model has lower max speed and lower 0-60 times as you get a smaller pack this is most likely ratio changes in the single speed gear box. They are sacrificing speed for efficiency. Also tesla has only ever mentioned two motors, performance and none performance. So for simplicity each non performance car will likely have the same motors.

    -look at the battery warranties, they also go down with the capacity of the pack, this indicates they most be using the same batteries only fewer. And they are going through much larger cycles. With 85kw you aren't cycling the batteries much day to day for an hours drive. But in the 40kw your using the majority of the capacity to travel the same distance.

    -the software, chargers, algorithms, are so complex and took so many man hours, there is no way tesla tripled their work to use three different battery types. Gear box ratios would take a fraction of the time to impalment.
    Last edited by EcoHeliGuy; 2012-12-10 at 11:01 PM. Reason: Spelling

  5. #45
    Model S Res #7734 SuperCoug's Avatar
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    I know I've seen this several places on these forums but I'm having problems finding this information.

    My question is "How many KWHs does it take to fully charge a 60 KWH car?" or another way to ask it "What is the efficiency of the charger?"

    I will be charging on a 240 volt 50 AMP NEMA 14-15 outlet. I remember reading that 120 volt charging was not quite as efficient since not as much energy is left over for the car once cooling and other overhead processes are taken into consideration.

  6. #46
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    Quote Originally Posted by SuperCoug View Post
    My question is "How many KWHs does it take to fully charge a 60 KWH car?" or another way to ask it "What is the efficiency of the charger?"
    85 kWh S: Range = 265 miles at 38 kWh/100 mi = 100.7 kWh
    60 kWh S: Range = 208 miles at 35 kWh/100 mi = 72.8 kWh
    24 kWh LEAF: Range = 73 miles at 34 kWh/100 mi = 24.8 kWh

    Calculations above performed using EPA efficiency numbers. The EPA ratings are kWh from the wall so includes charging efficiency.

  7. #47
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    Quote Originally Posted by SuperCoug View Post
    I know I've seen this several places on these forums but I'm having problems finding this information.

    My question is "How many KWHs does it take to fully charge a 60 KWH car?" or another way to ask it "What is the efficiency of the charger?"

    I will be charging on a 240 volt 50 AMP NEMA 14-15 outlet. I remember reading that 120 volt charging was not quite as efficient since not as much energy is left over for the car once cooling and other overhead processes are taken into consideration.

    The tesla website (Model S specs page) quotes: "Peak charger efficiency of 92%". Presumably this is the charger itself, not counting the various auxiliaries which will vary according to ambient temperature etc.

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  10. #50
    Nice article. Rather surprised me how interesting it was.

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