i'er iChart: The iMiev Range Chart. ANY VOLUNTEERS?

[DonDakin]

This chart makes a little more sense if the range line is in KM not miles.

Don......

 

[Don]

Yes, but if the range was in km's, why wouldn't the speed also be in kmh?

Don

 

[Barbagris]

The graph is made (bad made?) with the SCx of the Euro iMiev (Cx:0,33; front area, 2,13 m2; SCx 0,70), I don't know the US iMiev's SCx data (anybody?). I think there isn't a great difference, but...

Anyway, if there is a big difference between the graph and the real world experience, the graph is poorly made. I need to re-check the numbers!

Perhaps with converter&motor efficiency no ideal (global 90%?), and bigger surface (SCx) the results were closer.

Thinking...

 

[Don]

Anyway, if there is a big difference between the graph and the real world experience, the graph is poorly made. I need to re-check the numbers!

Perhaps with converter&motor efficiency no ideal (global 90%?), and bigger surface (SCx) the results were closer.

Translating the numbers to metric ones, if you can go 160 Km's at 80 Kmh, or 80 Km's at 125 Kmh, in your smaller, more aero European version, then your graph is correct but a North American car can't and I doubt the Euro car could either

Don

 

[PV1]

iChart:iMiev Range in MILES v5 – John Annen
MPH        35  40  45  50  55  60  65  70  75
BARS   %                                     
16   100  100  90  83  73  67  62  56  52  47
15    94   94  84  76  67  61  56  50  46  41
14    87   87  72  71  62  57  52  57  43  39
13    81   81  72  66  59  53  49  44  41  36
12    72   72  64  58  51  57  43  39  36  33
11    66   66  58  53  47  43  40  36  34  31
10    60   60  52  47  41  38  34  30  28  27
 9     56   56  49  44  39  36  33  29  26  24
 8     50   50  47  41  37  35  31  27  24  21
 7     44   44  37  33  29  26  24  21  20  18
 6     37   37  31  27  23  21  19  17  15  14
 5     31   31  26  22  18  16  14  12  11  10
 4     25   25  21  18  15  14  13  14  12   9
 3     19   18  18  15  14  13  12  10   9   7
 2     12   12  12  10   9   9   8   7   6   5
 1      6    6   6   5   5   4   4   4   3   3

Reformatted the chart so it's readable here on the forum.

How accurate is this chart in people's real-life experience?

I'm seeing range on a full charge is closer to the 15 bar level. I haven't yet done a capacity test or a calibration. I run my tires at 45 psi and mostly drive 45 mph on a fairly level road. Marker lights only in the morning. No HVAC or heated seat.

Think maybe my battery is weaker from sitting on the lot for so long (at least 6 months)?

 

[JoeS]

PV1, if you're going to look closely at the chart you will find a number of errors. For example, 15 bars at 65mph should probably be 47 not 57, there should be a differnece in mileage at 40mph between 13 and 14 bars, etc. Like I said, not worth our time picking nits.

PV1, depending on your perspective (conservative vs. optimistic) the range shown at the 15-bar level may be more representative and I would not worry about it at all as I don't think we could tell the difference at this early stage of battery life. If I were to set off on a 60-mile trip I probably wouldn't be driving 65mph for a while.

Too many variables enter into the equation, as it is so easy to extend one's range while driving if needed.
http://myimiev.com/forum/viewtopic.php?f=9&t=287

For myself, since I NEVER drive the car down to 'empty', I'll never know (although one of these days I'm sure I'll have to eat those words). I simply adjust my pre-trip charging and then speed and driving style to meet the trip distance needed to arrive at my destination with at least three or four bars remaining.
(Yawn) :|

 

[kps70]

Does this feel a little more realistic?

I can adjust my spreadsheet to get a best fit assuming no heater, tailgating etc

 

[FiddlerJohn]

kps70,

Good job. Thanks.

 

[Don]

Does this feel a little more realistic?

That looks much more realistic to me - It also correctly points out that you can go about twice as far at 40 mph as you can at 75 mph (and nearly 3 times as far at 30) so if you're pressed for range, slow down!!

Don

 

[JoeS]

kps70, thank you for tackling this topic again. FiddlerJohn had given us the original impetus for this theoretical exercise and now you've provided more fodder.

At speeds less than 30mph the curve should peak at some point and then drop down as the vehicle's fixed power consumers take over. This peak for our iMiEV I believe occurs somewhere around 20mph and if we can ever calculate it out properly then I think it could be huge (>200miles). A nice exercise now that we have CaniON to actually measure things.

At the other end of the scale, with the aerodynamic load increasing as the square of velocity, I'm surprised to see only a three-mile drop in range between 70mph and 75mph. Another area where CaniON could help us. Now to find a windless completely flat road to try it out...

I'm only looking at the 16-bar range as all the other numbers would be proportional if we assume a linear relationship in terms of energy consumption per bar at a given speed.

 

[kps70]

I suspect you're right about range being much higher at 20mph but I don't have the patience to check this out! I've cautiously put 130 miles.
I'm trying to model the curve with a fairly simple equation based upon my experience of driving my i-miev in temperate conditions.
I too thought that adjustments might need to be made at the top end of speed due to aero drag getting really painful. I've not driven it for long enough at this speed to see how quickly the bars drop. However, I have adjusted it down.
My next thought is to do a graph showing best case and worst case lines.
I've not driven much with the heater on, but it will obviously affect the range more at lower speeds as it is drawing more of the current as a proportion.
Here's my first 'guess'. Can I have some feedback so I can adjust to what you're experiencing?
Interestingly, I predict that the range goes up with heater on between 20mph and 30mph. The reason for this is because at really slow speeds, you're just drawing current for the heater without getting anywhere. The extreme of this would be when you are stuck in a traffic jam with the heater on and the range drops to zero!
Here it is:

 

[gatedad11]

KPS70:
I concur on the range chart. Assuming, as always, a temperate climate(say 70 degrees F or higher), no wind, level roadway, no temperature controls on in the car. The numbers you have presented are pretty much right in line with what I was seeing in Spring/early Summer. Actually, saw really no differences between a hot summer day and a nice Spring day, other than one would need to us the a/c on the very hot, muggy days.

Lou

 

[jumpjack]

For those interested, I found this interesting equation ( http://www.amt.nl/PageFiles/20661/003_EEVC-23010946.pdf ):
y= x*Batt/(Paux+(1/N)*(m* 9.81 * Frr + 0.5 * 1.225 * CdA * pow(x/3.6,2) )* x/3.6)

• y=km
  x = speed
  Batt = battery kWh
  Paux = standby power kW
  m = mass
  Frr = tyres rolling friction
  CdA = Cd * A
  Cd = air drag coefficient
  A = frontal area

Then I plotted it for various vehicles using this interesting site:
https://www.desmos.com/calculator/8bfswqy3rm

Which are data for i-Miev? I need Cd and Frontal Area (or CdA which combines them), mass, available battery kWh and possibly tyres rolling friction. "Standby" power would be useful but I guess it's an impossible datum to find.

Please note how, on all cycles, real range is around 50% of maximum range calculated at constant speed.

Official data & study on i-Miev heater:
http://www.sae.org/events/aars/presentations/2010/W2.pdf

 

[fjpod]

All well and good, but............life doesn't follow charts.

Have you ever been stuck in traffic in the middle of an ice storm, when it should only take you 15 minutes to get home, but it takes 2 hours? Hard to not use your heater, but even though you are creeping at 5 mph, you are spending an hour and 45 minutes more time in the car.

Bye bye battery.

Don't get me wrong. I love my iMiev.

 

[jumpjack]

All well and good, but............life doesn't follow charts.

Have you ever been stuck in traffic in the middle of an ice storm, when it should only take you 15 minutes to get home, but it takes 2 hours? Hard to not use your heater, but even though you are creeping at 5 mph, you are spending an hour and 45 minutes more time in the car.

Bye bye battery.

Don't get me wrong. I love my iMiev.

"My" graph is not intended to give real life range ("half the max" is just a guess), but to make different vehicles comparable.

I also found the numerical data for WLTP cycle: I think I could use it to take into account also inertia... but I have yet to figure out how!

 

[JoeS]

jumpjack, thank you very much for posting these graphs. Now that you have the i-MiEV CdA, will you be updating this graph to just show the i-MiEV alone?

 

[jumpjack]

jumpjack, thank you very much for posting these graphs. Now that you have the i-MiEV CdA, will you be updating this graph to just show the i-MiEV alone?

You can do it by yourself, in the chart there is a "free curve" which changes according to user specified parameters.

 

[jumpjack]

From this thread:
http://myimiev.com/forum/viewtopic.php?f=22&t=264&start=50


Frontal Area: 24.052 sq.ft (2.2345 sq.mt)
Cd: 0.35 (0.33 European, post Sat Apr 13, 2013 9:33 pm )
CdA= 8.4182 (7.9372 European) (0.782 sq.mt, 0.737 sq.mt)

mass = 1080 kg

http://autoguida.wordpress.com/2014/06/30/458/

 

[JoeS]

jumpjack: wonderful! Thank you so much for producing this chart!

 

[JoeS]

Eyeballing a few select datapoints off the i-MiEV graph:

Maximum range is 149mi (240km) at 14mph (22.5km/h)

At 65mph (105km/h) the range is 50 miles (80km)

At 50mph (80km/h) the range is 71 miles (115km)

At 35mph (56km/h) the range is 106 miles (170km)

Subjectively, the numbers 'feel' pretty good to me.

Another variant on what we've been saying: if in doubt, slow down (it doesn't take much to dramatically increase the range).