daniel
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Re: 0 - 60

Sun Apr 25, 2010 12:51 pm

efusco wrote:Assuming that the available power and capability of the motor can give you a 0-60 of 8 sec., Nissan's testing might show that "normal" drivers tend to accelerate hard enough that it has a negative impact on real world range. Negative press about range could kill this car before it gets started. If reports start surfacing of people running out of juice at 60 miles Nissan will have a serious problem after "promising" 100 mile range.

So, if they govern the acceleration rate to 'encourage' drivers to drive more conservatively and thus are better able to stretch the range close to the 100 mile mark that's one issue they don't have to worry about.

I think it'll be a balancing act...and others here may be right that 15 seconds is too long, but 12 seconds or so may be where the compromise comes. It really depends upon what Nissan decides to do I think.
This is the best argument I've seen yet for waiting a year before buying the car! I don't want the manufacturer deciding for me that I mustn't accelerate hard! As a long-time EV driver, I KNOW that hard acceleration shortens range, and gentle acceleration extends range. I want to have the CHOICE whether to spend some of my range on acceleration. Driving the car constantly hard is a bad idea. But having the capacity enables safer merging.

Instead of limiting acceleration, they should teach drivers what kind of driving will enable them to achieve 100 miles.

Actually, I don't expect that they will limit acceleration merely to extend range. They've made it clear that the 100 mile range is based specifically and uniquely on the LA<whatever-it-is> test protocol.
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KarenRei
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Re: 0 - 60

Sun Apr 25, 2010 3:04 pm

KarenRei wrote:Re, energy used for hard accel:

1) Motor efficiency varies, and it's hard to make any generalizations. Depending on the situation, a high torque accel may actually be *more* efficient than a slow one. Or less. You need the brake-specific energy consumption data for the powertrain.
2) Battery pack efficiency does drop with increased currents, but for li-ion, that drop is very small.
3) In terms of energy used, the laws of physics don't care whether you go from 0-60 in 2 seconds or 20 -- excepting that in 2 seconds, you'll have 18 more seconds of the sort of aerodynamic drag you get at high speeds ;)
daniel wrote:This runs counter to my experience with my Zap Xebra and also counter to my experience with my electric Porsche (during the short time I was driving it -- long story).
I'll repeat, with bold:
KarenRei wrote:2) Battery pack efficiency does drop with increased currents, but for li-ion, that drop is very small.
I don't know what your electric Porsche was like, but the Xebra is lead-acid. Lead-acid batteries suffer from something called Peukert's Law -- the faster you draw them down, the less you can get from them. This isn't nearly as significant with li-ion.

Also as mentioned, if you accel faster in city driving, you may expose yourself to braking more or driving more at higher speeds. Both of these will reduce range, but are not a requisite element of fast accel. There's an additional illusory aspect: if you're watching your current, you'll see it spike up much higher on hard accels. However, this is largely just an illusion, as you're using more current for a correspondingly shorter period of time.

E=1/2 * m * v^2, no matter how fast you get to v.

daniel
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Re: 0 - 60

Sun Apr 25, 2010 4:18 pm

KarenRei wrote:
KarenRei wrote:Re, energy used for hard accel:

[...]
2) Battery pack efficiency does drop with increased currents, but for li-ion, that drop is very small.
daniel wrote:This runs counter to my experience with my Zap Xebra and also counter to my experience with my electric Porsche (during the short time I was driving it -- long story).
I'll repeat, with bold:
KarenRei wrote:2) Battery pack efficiency does drop with increased currents, but for li-ion, that drop is very small.
I don't know what your electric Porsche was like, but the Xebra is lead-acid. [...]

Also as mentioned, if you accel faster in city driving, you may expose yourself to braking more or driving more at higher speeds. [...]
My Xebra has an aftermarket LiFePO4 battery pack, and the Porsche has the same (just more of them). And while I stomp on the go pedal if I am not concerned about range (i.e. my trip is well within my range) I almost never stomp on the brake unless a light turns yellow when I am very near the intersection.

You obviously know what you are talking about and are very educated. Electrical engineer maybe? I appreciate your insights. Your posts are very knowledgeable and useful. I'm just reporting my experience with my two EVs. I've been driving the Xebra for 4 years, most of that with the lithium batteries. I only drove the electric Porsche for a couple of months before I realized that the conversion was done so incompetently that it was dangerous to drive. It's now being done over by someone more trustworthy.
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"You can order" email late September, but was out of the country so...
Ordered very early October.
Dashboard says: more of the usual worthless Nissan b.s.
(Not on spreadsheet cuz I can't figure it out.)

KarenRei
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Re: 0 - 60

Sun Apr 25, 2010 8:32 pm

I work in the EV industry. Ouch, sorry to hear about your Porsche :(

I think part of what we're seeing here could be different ways of looking at acceleration. If one measures acceleration to a fixed speed, you get different results than acceleration for a fixed length of time (heavy accel in the first case is for a shorter duration, while heavy accel in the latter case leads to a higher max speed). Of course, there's also the potential of the drivetrain efficiency profiles, particularly heavy losses in the connectors from the pack to the inverter, and so forth. Most of my experience is with the Roadster, mind you, which is designed for some pretty intense accel. ;)

scottsim
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Re: 0 - 60

Wed Apr 28, 2010 8:51 am

All I can add here, after driving a PHEV-Prius (10KWh LiPO4) for several months is that it has made me a slower driver. I think that most Prius drivers see how much their mileage improves with more "hypermiling" techniques.

Granted, the Prius electric motor is on the wussy side and was not meant to be the sole propulsion of the hybrid.

I also think that Leaf drivers will see the obvious improvements to their range, or possibly begin to notice the lower KWh numbers to recharge when they drive less aggressively.

Scott

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garygid
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Re: 0 - 60

Wed Apr 28, 2010 9:05 am

After the "Great Gas Tax Bill" of 2032 (5x on ICE vehicles, 2x on hybrid, 20x on gas itself, or some such), perhaps highway driving will become less of a sport or competition, and more just another transportation mode.

We must also be building alternative transportation systems and "city architectures", that will require much less personalized transport.

I believe that even the currently-popular concept of "owning" a single place to live will come to be re-evaluated.
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evnow
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Re: 0 - 60

Wed Apr 28, 2010 9:29 am

garygid wrote:After the "Great Gas Tax Bill" of 2032 (5x on ICE vehicles, 2x on hybrid, 20x on gas itself, or some such), perhaps highway driving will become less of a sport or competition, and more just another transportation mode.
In 2032 - there won't be much gas to go around. There will definitely be rationing of gas by then.

Even the US military is warning of major shartage by 2015.

http://www.guardian.co.uk/business/2010 ... ion-supply
"By 2012, surplus oil production capacity could entirely disappear, and as early as 2015, the shortfall in output could reach nearly 10 million barrels per day,"
We actually hit Peak Oil in 2005, and the production has been flat even though the price has increased substantially.

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Last edited by evnow on Wed Apr 28, 2010 11:04 am, edited 1 time in total.
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garygid
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Re: 0 - 60

Wed Apr 28, 2010 10:55 am

Well, maybe 2022, or 2017?
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evnow
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Re: 0 - 60

Wed Apr 28, 2010 11:04 am

garygid wrote:Well, maybe 2022, or 2017?
I don't think you got it. If there is a shortage of gas the prices will sky rocket (as it happened in 2008). No need for any taxes.

BTW, everytime we spend more than 6% of gdp on oil, US goes into a recession - which in turn leads to demand destruction and thus price down. So in the future we will see rapid cycles of boom & bust. Prosperity and continuous growth we have seen in the past decades is essentially over.
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garygid
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Re: 0 - 60

Wed Apr 28, 2010 11:49 am

Assuming you are correct, then the free-market for oil is "broken", and other methods of regulation will be tried (like paying a tax credit to buy an EV).

Before too-highly priced oil is allowed to "paralyse" the nation or world, I hope some bright people will provide other solutions.

Perhaps only commercial uses, huge taxes on private use, large taxes on all oil-based uses, and building trains, etc. to move things around.

Or, grow and make things locally. When it costs $200 to make something and $800 to ship it ... ?

Sounds like an expansion-based (growth-based) economy might be ready for a replacement?
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