JoeS
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Location: Silicon Valley, California

Speed vs. Power Gauge: Request for Data

Wed May 09, 2012 10:08 am

By far, the largest number of questions received regarding the iMiEV deals with RANGE. For the iMiEV, range has NOT been empirically quantified. The simplistic EPA ratings is all we presently have available, and some of us have a problem with their numbers.

Intuitively, we iMiEV drivers recognize that going fast disproportionately decreases our Range Remaining; conversely, slowing down disproportionately slows down the decrease of our Range Remaining. It sure as heck is not linear! Technically, we of course recognize that drag is proportional to the square of the vehicle's velocity.

Trouble is, we don't have these numbers, and thus I am soliciting the help of all the iMiEV drivers out there.

jjlink was kind enough to modify the photo of the iMiEV power gauge to show divisions that should be easy to assess by eyeball: breaking up each division into "thirds" ("Quarters" was felt to be too fine a division).

Image

Now, here's what I would like us all to do: while driving our iMiEVs on a flat level windless surface and holding it steady with the red needle at a particular point, it would be great if you could record the vehicle's SPEED vs. red needle POSITION. If you could each do this for as many points as are realistically feasible for you (without breaking any laws) and I would appreciate it if you could then send the data to me.

Originally, I thought we could each publicly post our data, but in the interest of avoiding being influenced by others' data I would appreciate it if each of you could PM (Private Message) me the data directly, by simply clicking on PM at the bottom of this post.

What I will then do is compile this information into a spreadsheet with datapoints and then perform a nonlinear regression analysis to end up with a curve of SPEED vs. POWER GAUGE LEVEL which of course I'll publish. If you'd like, I could also publish the anonymized raw data y'all sent in.

This will now form the basis for quantifying our RANGE vs. SPEED (with perhaps some discussion about things like voltages and Peukert prior to that).

OK, if there are any questions then let's get them out in the open on this thread, and in the meantime I'd appreciate all your help in getting the data to me. I think you'll find that it is not as simple as it sounds to hold the car at a steady speed in zero wind on a flat level surface... but please try, and I realize this may take some time to accomplish for us to get sufficient data. I found that using a voice recorder works well for capturing this information.

Thank you for your help.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

JrCRXHF
Posts: 63
Joined: Sat Apr 28, 2012 5:37 am

Re: Speed vs. Power Gauge: Request for Data

Thu May 10, 2012 9:49 am

You will also need tire pressure information and road surface can also make a difference but not as much as tire pressure.

JoeS
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Posts: 3843
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

Re: Speed vs. Power Gauge: Request for Data

Thu May 10, 2012 11:12 am

JrCRXHF, you're absolutely right about tire pressure, which I should have been including in all my mileage posts. Might as well include ambient temperature as well. Hmmm, if someone's at a significant altitude, that should also be noted. Thanks.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

Don
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Location: Biloxi MS

Re: Speed vs. Power Gauge: Request for Data

Mon May 14, 2012 9:36 am

It seems to me that there are just too many variables for the collected data to be meaningful

Speed is easy enough measure, but temperature, a few MPH of head or tail wind (or even crosswind) a degree ot two of uphill or downhill when it appears to the driver that the road is absolutely flat, vehicle loading, condition of the pavement, etc, etc

To get something meaningful, all cars would just about have to travel the same stretch of road under the same conditions. Even then, I can sometimes do 70 on a stretch of road I travel regularly while keeping the needle right on the "1" and then other times (no matter how hard I try) I can't

Don
2012 iMiEV SE Premium, White
2012 iMiEV SE Premium, Raspberry Metallic
2012 iMiEV SE, White
2017 Chevy Volt Premier
2014 Ford Transit Connect XLT SWB wagon

fjpod
Posts: 529
Joined: Tue Apr 17, 2012 2:31 am
Location: NYC

Re: Speed vs. Power Gauge: Request for Data

Mon May 14, 2012 9:45 am

I would agree.

JoeS
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Re: Speed vs. Power Gauge: Request for Data

Mon May 14, 2012 2:14 pm

Don wrote:It seems to me that there are just too many variables for the collected data to be meaningful. Speed is easy enough measure, but temperature, a few MPH of head or tail wind (or even crosswind) a degree ot two of uphill or downhill when it appears to the driver that the road is absolutely flat, vehicle loading, condition of the pavement, etc, etc To get something meaningful, all cars would just about have to travel the same stretch of road under the same conditions. Even then, I can sometimes do 70 on a stretch of road I travel regularly while keeping the needle right on the "1" and then other times (no matter how hard I try) I can't
Don

Don - I agree that trying to get a windless perfectly flat stretch of road is difficult, which is why I'm asking everyone to do the best they can and send in the raw data. The more data points we have the better we can subsequently analyze it. Like you, I have found it very difficult to pin down. Whenever I'm driving the car (when my wife reluctantly relinquishes it) I look for flat stretches of road and try to hold steady on one of the points. It's a slow process...

Regarding the other variables: temperature is probably the least important variable, but it is available on our dash display. Altitude (less dense air) only matters if it's significant. Extremes of each of these two variables is what we primarily care about.

Don't lose sight of what we're trying to do: quantify speed vs. power consumption in order to quantitatively assess the range issue. You wouldn't believe how many people "don't think" that driving 65mph vs 55mph makes any significant difference...

If anyone has any better ideas on how to do this, I'm open to suggestions. In the meantime, sure would appreciate some more data...
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

dumemama
Posts: 28
Joined: Sat Mar 03, 2012 9:38 am
Location: Malibu Appalacians

Re: Speed vs. Power Gauge: Request for Data

Mon May 14, 2012 10:19 pm

I had the rare opportunity today to drive constant speeds on flat surfaces. I used D mode. Ambient temp was in the 60s. Tire pressure nominal (36). Road surface reasonably smooth asphalt. Winds less than 5mph. I tested speeds in the range of 35 to 65. In every case, maintaining the current speed, the needle was dead on 1/2 tick. It didn't matter what speed I was going, as long as I was maintaining rather than accelerating or decelerating. There was no perceptible difference in needle position for different speeds for zero dV.

Anything above 1/2 tick was under acceleration or incline surface. Anything below 1/2 tick was during deceleration or decline surface.
-Barb
2012 White ES w/QC, 4/30/12

JoeS
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Re: Speed vs. Power Gauge: Request for Data

Thu May 17, 2012 4:54 pm

dumemama - I'm confused, so let me make sure I didn't misunderstand you: you are saying that you are able to hold a steady 65mph (or any other speed between 35mph and 65mph) with the red needle sitting steady on the letter "c" in the word "Eco" in the middle of the green zone, irrespective of speed?

If that's the case, then I need to re-install the ammeter and take my time re-visiting my previous readings:
http://myimiev.com/forum/viewtopic.php?p=1378#p1378
(assuming I can get the car away from my wife)

If you're right, then that gauge shows us the penalty we incur due to acceleration and it is not simply a pretty ammeter. Dang, and here I thought I was starting to get somewhere with my own data-taking, despite my wife thinking I'm my usual nutcase as I've been asking her to write down numbers as we drive along :geek: ... and then giving her different numbers :roll:

Anyone else want to chime in?
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

jennrod12
Posts: 230
Joined: Sat Feb 11, 2012 8:51 pm
Location: Santa Clara, CA

Re: Speed vs. Power Gauge: Request for Data

Thu May 17, 2012 5:01 pm

Hi Joe,

I agree with dumemama, there is a large penalty for accelerating, but holding a speed, once attained, is pretty low-cost barring changes in elevation or wind resistance. I don't think I could hold the car at a full tick for too long on a flat road with no wind, I'd be constantly accelerating.

Have you seen something different?

Jenn
2012 Diamond White i-MiEV ES
with green racing stripes and hubcaps (thanks to WeeJohn)
Santa Clara, CA

JoeS
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Posts: 3843
Joined: Thu Dec 15, 2011 5:47 am
Location: Silicon Valley, California

Re: Speed vs. Power Gauge: Request for Data

Thu May 17, 2012 5:36 pm

Jenn, interesting, as you are corroborating what dumemama is saying.

I just recently started trying to get serious about data-taking and am finding variations which I attributed to the hilliness of all the roads around here (not to mention the windy afternoons). I do, however, have two different speed vs. needle positions that I believed to be 'solid' and repeatable, but which I will now have to revisit again. :cry:

Anyone else?

Let's not lose sight of the reason for doing all this: I am trying to quantify the iMiEV's energy consumption as a function of vehicle speed in order to empirically identify the speed vs. range penalty.
EVs: 2 Wht/Blu SE Prem., '13 Tesla MS85, 3 156v CorbinSparrows (2 Li-ion), 24v EcoScoot(LiFePO4)
EV Conv: 156v '86 Ram PU, 144v '65 Saab 96
Hybrids: 48v1kW bike
ICE: '88 Isuzu Trooper. Mothballed: '67 Saab (orig.owner), '76 MBZ L206D RHD RV

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