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evnow
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 11:50 am

TimeHorse wrote:But enough of my crazy East-coast state. The point is, I drive an average of 51 mph to work. That's by no means my top speed. I hit speeds well in access of that (though never more than 14 over the limit -- did I mention the Class-6 Misdemeanor??) and a number of local roads. That's why US06 is such a good measure for me. It has acceleration, deceleration, reasonable maximum speeds and an average speed of about 48 mph, much closer to my 51.
My question is - why is that avg speed non-negotiable ?
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AndyH
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 12:30 pm

TimeHorse wrote:Preaching to the choir, sir! That's why I want a power curve so we don't have to so much extrapolate as simply run the numbers.
<snip>
In my state of Virgina I'd never drive that fast even if I could since I don't want a permanent Class-6 Misdemeanor charge on my criminal record.
<snip>
But anyway, thanks for the numbers, sir, as those 3 data points are just what I need, in theory, to compute the power curve for the cars listed. Not the Nissan LEAF, alas, but if I can get it to work for the others, I know I'm on the right track!
I'm here to help and am happy that the numbers are useful! I look forward to the rest of the Leaf data as well - curves, 'fuel economy' numbers, etc.

Are radar detectors still illegal in the Commonwealth? ;)

[edit] If you haven't seen them already, the one-page summaries are linked from the first post in the thread. More detailed info on the US Electricar Prizm and Ford Ecostar can be found here. The Prizm and Ecostar results provide much more 'energy used VS. speed' data.[/edit]

Andy
Last edited by AndyH on Thu May 13, 2010 1:28 pm, edited 2 times in total.

AndyH
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 12:33 pm

Charts are updated to include the 2009 MiniE. Test report is here. Constant-speed range is now reported at 55 and 65 VS. the old 45mph and 60mph.

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TimeHorse
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 1:14 pm

evnow wrote:My question is - why is that avg speed non-negotiable ?
Do you mean why I can't just take the calculation at an average speed? Well, for the most part an average speed is good, but technically, from my research, your main drag -- if you'll pardon the pun -- is air resistance which is proportional to the square of the speed of the car. That means that if it takes x watts to go 45 mph, it may take 2x watts to go 60 mph and then 4x watts to go 75 mph, as a rough calculation. Now that's the power you need to go that speed. To get the energy draw, you just multiply the power times the amount of time you're exerting that power to get the energy. Hence kWh: kilowatts times hours. For illustration purposes, if you spend 1 second at 45 mph and the next at 75 mph you've basically used 5x Joules of energy, but if you spent those 2 seconds at a constant speed of 60mph, your energy used is only 4x. That's why average speed isn't the whole story. That's why EPA LA4 is more complicated than just 19.6 mph: it's really the sum of the intervals from second 1 to 1370, over a minute of which is idle and another nearly 2 minutes are at highway speeds.

However, if the Power Curve of the Nissan Leaf is known or reasonably estimated, we could calculate the expected range of the LEAF under HWFET or EPA75 or US06 or under any other custom, well-defined regime. And with 3 points, e.g. 45 mph, LA4 and 60 mph, it should just be possible to tease out that quadratic power curve equation...
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evnow
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 1:16 pm

TimeHorse wrote:
evnow wrote:My question is - why is that avg speed non-negotiable ?
Do you mean why I can't just take the calculation at an average speed?
No. Why do you have to drive at that high avg speed ?
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TimeHorse
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 1:33 pm

evnow wrote:
TimeHorse wrote:
evnow wrote:My question is - why is that avg speed non-negotiable ?
Do you mean why I can't just take the calculation at an average speed?
No. Why do you have to drive at that high avg speed ?
Sorry, I'm still confused. I don't have to drive at an average speed. But if I drive at LA4 on the I495 Capitol Beltway I'm gonna get a ticket. Sure, I could spend nearly 2 hours in traffic to get to work each day just so my average speed remains around 19.6 mph, but who in their right mind would spend 3-4 hours getting to and from work when there's this lovely highway that we taxpayers paid for that will get me there in typically 45 minutes or better. After all, I have to go 33 miles to work, 33 miles home, estimate about a 67 mile round trip. Sure, I could do that at low speeds, but really, does that make sense?

But certainly I don't have to drive at that speed. I also don't have to go to work or pay my mortgage but if I don't do these things there are consequences. I'm just weighing my options and I feel I am better off going 51 mph on average to and from work, the great majority of which I spend on roads with speed limits of 55 mph.
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AndyH
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 1:44 pm

Here's another look at range. This info is from the DOE and Southern California Edison's Pomona Loop city and highway on-road testing. They run the vehicles with different loads and with/without AC and lights. Testing included Nissan Altra and Honda EV+.

Here's the Pomona urban and highway loop maps and elevation data.

Image

Image

The Altra was a somewhat heavy station wagon - but look at how much better the lithium-powered car performs compared with its lead- and nickel-powered stablemates.

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garygid
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 2:42 pm

Note that some do BETTER on the "freeway" test.
Maybe that test had less stopping?
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evnow
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 2:47 pm

AndyH wrote:The Altra was a somewhat heavy station wagon - but look at how much better the lithium-powered car performs compared with its lead- and nickel-powered stablemates.
I thought Altra did worst - in the sense its UR4 dropped considerably compared to UR1.

More surprisingly UR4 is worse than FW4 for almost all cars.
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palmermd
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Re: Reliable EV Data for Comparison

Thu May 13, 2010 2:49 pm

AndyH wrote:Here's another look at range. look at how much better the lithium-powered car performs compared with its lead- and nickel-powered stablemates.
Looks like running AC an such has an equal impact as running with a fully loaded car, and then when you do both...wow. Shows just how much impact weight has on the efficiency of a car. Time to go for a run...I'll be right back.
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