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Old 11-27-2007, 06:53 PM   #479 (permalink)
MetroMPG
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Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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10-17-2007, 02:20 Pm

Quote:
Originally Posted by omg
If ya had li-ions you'd be at 231Wh/mile and given that the Tesla's charger is such a hog, they're likely more than 127Wh/mile from the plug. Just sayin...

Here's some more from GCC

Quote:
Henrik,

Click "Where the Rubber Meets the Road" above and scroll down to the section on Range Testing. They show recharge energy of 31 kWh/100 miles for combined cycle. That's at the wall plug, not the battery. As you note, the car only needs a little over 200 Wh/mile from the battery. This means 1/3rd of the wall plug energy is lost in the charging process. Tesla's well-to-wheel white papers claim 90 or 95% charging efficiency instead of the 65-70% implied by this data. That's a huge gap.

Ok I get it. That is an interesting observation. Wonder what went wrong. Lithium batteries should have very high charging efficiency near 100% according to http://www.batteryuniversity.com/partone-12.htm. So the problem must be the charging transformer. As far as I remember they often lose a lot of energy possibly 30% but it is possible to buy some that loose very little energy. Maybe they have chosen a model that is cheaper and perhaps lighter but that waste more energy in the conversion. Most people will never notice such a change anyway but you do. Plus electricity is still very cheap compared to gasoline so the economics is still ok and the people that can afford a Tesla will not care about the economics of driving anyway.

Remember that the EPA tests that tesla ran now include running the air conditioner. The california sun beating down through the windows, and on a dark green roof will require alot of air conditioner power to keep temperate. That could explaine alot of the difference between the 216 WH/mile that they got when actually commuting (probably with the top down), and the 310 WH/mile they got while running the EPA designed tests (top up, air on).

Coalburner, the problem with your theory is they show 245 mile range on the combined test.Even if they used all 53 kWh in the battery pack that only comes out to 216 Wh/mile. The diff between 310 and 216 is apparently charging efficiency. It's a really horrible result, hopefully caused by a really inefficient non-production charger. If not Tesla needs to completely re-do their well-to-wheels white papers.

Update, Tesla deleted my question but in response to another message said the difference between 216 and 310 Wh/mile was due to charging inefficiency, including the need to run a cooling system to keep the batteries cool during charging!

Somehow I doubt they'll update their well-to-wheels paper or stop making their ridiculous "penny per mile" claims. Tesla is doing good work but there's no shortage of snake oil, either.
Good diggin', omg. Thanks for posting that.

On at least the speed/acceleration front, there's little debate which car is superior...

I did an acceleration run (on fresh, happy batteries)...

0-50 km/h (31 mph) took 36 seconds

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