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Old 08-06-2006, 05:41 AM   #41
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Assuming a CdA=~.41-.42, the roadster will consume ~2.806kwhr at ~48mph. For some reason they didn't use that and fudged the highway mpg conversion, instead of ~135mpg it should be 265mpg equivalent EPA highway. And their street should be ~530mpg, with the combined being 39somethingmpg, or just about 400mpg, like they stated in the paper. And the range at ~75mph should be over 300 miles, @50mph it's over 700 miles, and in the city, well over 1000miles...
If my rusty physniks is correct anyway.

Borked it... I think CdA is more like .57m^2@125wh/km and .49m^2@110wh/km, but I'll think on it. Tesla gives those two figures in wh/km, 110 and 125, so until I can figure out what they're factoring in to change those, the CdA's still in the air.
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 08-06-2006, 05:44 AM   #42
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ahhh but you forget the parasitic losses that are a funtion of time - the slower you go the more the power overhead eats into the battery capacity. Besides have you ever tried to go 700 miles at 25 miles an hour?
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Old 08-06-2006, 07:21 AM   #43
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Ah, yup. Gotta have the AC, and radio, and lights, etc... 700 miles in LA traffic would suck. But it should absolutely own any other vehicle in it's price range. And if you can hit it at 50mph w/o much else to pull current, I think 600-700 miles of driving is doable.

Edit - No clue where I got these numbers from... :?
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I think if i could get that type of FE i would have no problem driving a dildo shaped car.
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Old 08-06-2006, 12:21 PM   #44
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600-700 miles might be over estimating a bit. I'd think 400 miles may be in grasp with a very good driver.

But maybe I'm wrong. Can't wait for these cars to be put on the roads so we can get some real world figures.
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Old 08-06-2006, 02:48 PM   #45
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If it does have a ~.41 CdA, then the instantaneous force on the car at 48.3mph is .5(1.2kg/m^3)(21.5m/s)(21.5m/s)(.41)+1225kg(m/s^2)(.012)=129N, or 129N(21.5m/s)=2.774kw, so it should use 2.774kwhr in an hour, I think. Now with a 50kwhr pack, due to engine efficiency and transmission losses, maybe only ~81% makes it to the road, so 50kwhr(.81)=40.5kwhr. If it uses ~2.8kw in an hour, is going 48.3mph, and has enough energy to go for 40.5/2.8=14.5 hours, then it should go a smidge under 14.5(48.3)=700 miles. Of course anything that's on will bring a power overhead, so that'll drop, but I think 600 miles is doable, no AC/heat/other large draws. Unless I missed something huge, which I have a tendency of doing...

Edit- I think I missed something huge. It's more like ~165miles highway, ~330miles city.
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Old 08-07-2006, 12:09 AM   #46
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Or perhaps it doesn't have a ~.41 CdA. That would be way low! My own educated guess of around .50 stems from its claimed 250 miles range and guessing the car has sticky tires. Given the losses in all the starts and stops, it turns out the EPA highway cycle range would be roughly equivalent to the 60-65 mph range(at least calculated).

I also have a few cars to compare it with. At 60 mph:

Venturi Fetish: 270 Wh/mile (Similar weight, slightly higher Cd*A than Tesla)
AC Propulsion TZero: 150 Wh/mile (700 pounds lighter than Tesla, LRR tires)
GM EV1: 140 Wh/mile (exceptionally aerodynamic)
Toyota RAV4 EV: 280 Wh/mile

Many similarly sized sports car conversions to the Tesla on the EV list such as Porsche 914s and Fiat 126s are seeing between 200-250 Wh/mile at 60 mph. Food for thought.


With LRR tires, range of the Tesla may increase by 30% if it is currently using very sticky tires for traction. Going from a .012-.015 coefficient of rolling resistance to around a .006 Cr is very dramatic for an EV as far as efficiency and range are concerned.

If a coupe version were made with a Cd*A in square feet around 3.0(about on par with an Opel Eco Speedster), with LRR tires, 500 miles range at 60-65 mph and 450 miles range at 70 mph may be doable with that same size pack.
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Old 08-07-2006, 12:44 AM   #47
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Well, I've seen two numbers for wh/km, 110 and 125. 110 yields .49m^2, and 125 .57m^2, both of which are a bit more reasonable. The 110wh/km comes from the tesla white papers, and the 125wh/km is mentioned on wikipedia. If you include Teslas battery/charging efficiency ratio ~.86, then we're pretty close to 125wh/km, so I think it's .49m^2 for the glider, and when factoring in drivetrain the number goes up. I can fill you in on the details if you'd like, it's all pretty straight forward. Even an Elise has much less reference area than an Insight, so I think that's where they're picking up the most in terms of efficiency. The ~125-155wh/km you mentioned seem to sync up pretty well with what Tesla's getting...

I'm still not sure where I came up with those crazy range figures. I guess that's why I should do something like relube my road bike or write a patch instead of screwing around with back of the envelope calcs in the am.

Yup, 50,000wh/(125wh/km)=400km=250mi. The 110wh is what the glider needs.
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Old 08-16-2006, 06:26 PM   #48
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Tesla Roadster Electric Sports Car Sells Out 'Signature Series'

Source: Telsa Motors
[Aug 16, 2006]

SYNOPSIS: The limited-edition 'Signature One Hundred" series Tesla Roadster, the first high-performance electric car manufactured by Tesla Motors, has sold out in three weeks.

http://www.evworld.com/view.cfm?sect...sid=12794&url=
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Old 08-17-2006, 09:04 PM   #49
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But that can't be. EVs are slow, ugly, unreliable, and people don't want them!
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Old 08-18-2006, 03:23 AM   #50
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I wonder if they used any Sony cells in the battery.
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