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BMW i8

Discussion in 'Electric Vehicles' started by Doug_G, Jul 23, 2013.

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  1. Doug_G

    Doug_G Lead Moderator

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    #1 Doug_G, Jul 23, 2013
    Last edited: Jul 24, 2013
    This thread is for discussing the BMW i8. For the i3 please see BMW i3.

    For older posts please see BMW i
     
  2. lloyds

    lloyds Member

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    i8 considering?

    Just a bit curious to see if any MS owners are considering the i8? I personally think it's quite a sexy car, but with a hefty price tag of $125k.
     
  3. SteveW25561

    SteveW25561 Member

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    I was hoping the i8 was going to be my next car: it's certainly stunning, very futuristic and super car looking.

    It's availability was further out than I'd like, but when launched it will turn many heads.

    It's a hybrid so if you're looking for all EV it's not the one, but even though I'm a proud and happy (less than 3 days old) MS85 owner, I can definitely see how the larger market could be more comfortable with a hybrid giving 500 km (310 mi) range and charges the small (7.2kWh, 35km/22mi all electric range) battery in about 3.5h on 110V and overall fuel economy of 94 mpg (2.5l/100km).

    Performance sounds quite strong: 0-60 in 4.5 sec.

    At $125,000, it will be competitive to many buyers to a P85, remembering that many are still uncomfortable with the all-EV concept. Depending on where you stand on the importance of all-EV, we should never discount the mass market appeal of a sexy, long range, efficient hybrid. Since it comes from BMW, it will have the built in respect that Tesla is still building.

    Interesting times ahead.
     
  4. GSP

    GSP Member

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    With only 7.2 kWh, performance in EV mode will be lethargic. Similar to Fusion Energy's EV mode or ancient non-turbocharged diesels. You will need a calendar to measure 0-60 mph. :rolleyes:

    I would much prefer the Model S or even a Chevy Volt.

    GSP
     
  5. brianman

    brianman Burrito Founder

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    Ok, I'll bite.

    Let's start with simple numbers (no buffer, etc. at the top or bottom of the battery).

    Model S85/P85: 265mi. rated @ 85 kWh
    Assume linear: 22.45mi. rated @ 7.2 kWh

    Are you saying that the acceleration of an S85/P85 at 22.45mi. rated is "lethargic"?
     
  6. rabar10

    rabar10 FFE until Model 3

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    #6 rabar10, Aug 11, 2013
    Last edited: Aug 12, 2013
    Apples and oranges. This would be like comparing performance between a lawnmower (with a full 2 gallon tank) and a V6 (with 2 gallons left in its 20-gallon tank).

    It's all about battery discharge rate for EVs. Max electric power (in kW) = discharge rate of the battery (measured in "C") * battery capacity (in kWh). C-ratings are inverse-hour units -- 1C discharge rate means the battery is empty in an hour. 6C rate means it's empty in 10 minutes.

    Then multiply power in kilowatts by .741 to get horsepower, which is more familiar.

    Let's compare i8 capacity and power specs to the Chevy Volt, i3, and Model S:

    - Volt has a 16.5kWh battery but only the middle 10.8 kWh is "usable", giving it a 38-mile electric range. That's 284Wh/mi rated efficiency.
    Max power is 111kW (149hp). Since discharge rate is set from the entire capacity, that's a 6.7C discharge rate when pulling max power.

    - The i3 has a 16kWh battery, and max power of 134hp (or 99.3kW). That's a 6.2C discharge rate.

    - Now for the i8. It has a 7.2kWh battery, giving it a 22.5-mile electric range. (That's 320Wh/mi rated efficiency, which is higher than Volt, and also speculative at this point).
    If we assume the same 6.7C discharge rate as the Volt, then i8 max electric power would be 48.24kW, or 65hp. Not very peppy when in all-electric mode.

    (edit: released specs show i8 has 96kw/128hp motor power)

    - Last data point: Model S 85kWh Performance has max electric power of 310kW (416hp), which is 3.65C discharge rate. Massive battery capacity means that a lower discharge-rate still gives you plenty of max all-electric power.
     
    • Informative x 1
  7. scottf200

    scottf200 Active Member

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    Great post. Goes long with these Tesla numbers:
    Code:
    40kWh*   / 60kWh    / 85kWh    / P85kWh
    6.5s     / 5.9s     / 5.6s     / 4.4s
    235hp    / 302hp    / 362hp    / 416hp
    310lb-ft / 317lb-ft / 325lb-ft / 443 lb-ft
    * - yes 40 kWh is no longer an option but since it still has the 60 kWh battery I would expect it to have the performance of the 60 kWh.
     
  8. MrIanB

    MrIanB Member

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    Don't forget it only seats 2 vs 5 on the MS.

    ian B
     
  9. gnelson

    gnelson Member

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    I wouldn't pay more for a 2 door model with a less powerful electric motor.
     
  10. Discoducky

    Discoducky Active Member

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    The 'prototype' i8 is beautiful, the production i8 might look very different. Also, the fact that it will allow an ICE means it will NOT be optimized for just batteries. I'm only interested in moving tech forward with lower CoG/CoM. The idea of having a motor at each wheel is interesting and brings benefits as well. I dream about an EV supercar and it is NOT the i8.
     
  11. NotTarts

    NotTarts Member

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    I think comparisons with the MS are a bit silly, considering one of a 2-seater sports car and the other is a large 5-seater sedan. 0-60 in 4.3s is pretty disappointing for a car of this class though and I refuse to call it a 'supercar' like some autojournalists want me to.

    The i8's electric motor outputs 129 hp (96 kW) IIRC.
     
  12. Takumi

    Takumi Member

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    People will still buy the i8. They are filling in for Fisker, only this time it's not likely to become orphaned.
     
  13. stephenpace

    stephenpace VIN S00219

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    Just curious, how close do you think the $125k USD will be to the release price? I'm assuming BMW hasn't released official pricing yet, but I've seen a lot of different numbers for this car. For instance, this article projects the price will be around £150,000 which unless they raise the price substantially for the UK, would be $232k USD.

    BMW i8 2013 price and release date | Auto Express

    I agree the car looks great. Not sure I'd want to ride in the rear seats, though:

    BMW-i8-Concept-Rear-Seats-800x533.jpg
     
  14. dsm363

    dsm363 Roadster + Sig Model S

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    Wow. Those are the rear seats? Really a two seater with two emergency rear seats. I agree, it is a cool looking car and will find a market but I doubt dealers will sell this at list price at the start at least.
     
  15. AnOutsider

    AnOutsider S532 # XS27

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    Those seats, striking design and power train keeps yelling fisker karma to me. Perhaps they'll do better
     
  16. lloyds

    lloyds Member

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    I agree that the i8 shouldn't be compared to the MS. They are completely different cars; yet, they do fall into a new generation of technologically advanced cars. This will be quite the 2 seater to sit in my garage next to the MS. :)
     
  17. rabar10

    rabar10 FFE until Model 3

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    Thanks. Makes me think that like the Volt, the i8's battery will have a larger capacity but will be buffered/restricted to 7.2kWh usable. Better for long-term battery health, and then the needed discharge C-rate isn't too large to support that peak motor power.

    Once they add some decent engine power to the mix, it will be the peppiest PHEV around.
     
  18. SwedishAdvocate

    SwedishAdvocate Active Member

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    #18 SwedishAdvocate, Aug 11, 2013
    Last edited: Aug 11, 2013
    I’m guessing the quality, execution and design of the center console graphical user interface will be better. And presumably also the exhaust note (That seems to be important to some folks). And they probably won’t be as vulnerable to fires and/or reviews by owners on Youtube… Or various political attacks in the US for that matter…
     
  19. dennis

    dennis P85D

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    It seems to me that BMW is designing the i3/i8 more for European market needs that US needs. The i3 is characterized as a "city car" that with a optional range extender. The limited electric range of the i8 means that most of the time U.S. drivers will be using the ICE. But its great for Europe where you pay an entry fee to drive you ICE car into a city, but not your electric car.

    I found with the Karma that I am less and less willing to drive it with the ICE running. I want it to be electric all the time. Part of that is the engine noise, and it appears from the first drive article that the i8's engine will also be noticeable:

    The internal combustion engine produces a typical three-cylinder rumble, that gets louder when the engine revs up. The total system output is 266 kW/362 hp with 420 pound-feet of torque and allows you to go from zero to 62 mph in less than 4.5 seconds or go from 50-75 mph in the same 4.5 seconds.

    I have a meeting this week with some BMW marketing folks from Munich who are in the Bay Area interviewing electric car owners about their experiences and wants. I hope to get some insight from them on the i3/i8 positioning for the U.S. market.
     
  20. SwedishAdvocate

    SwedishAdvocate Active Member

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    #20 SwedishAdvocate, Aug 11, 2013
    Last edited: Aug 11, 2013
    Had the engine/exhaust note been finalized at the time of that test drive? The article seems unspecified on that part. (ftr: I’m also in the all electric camp all the way for environmental and human rights reasons.)
     

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