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

Thanks to this additional paper http://www.empa.ch/plugin/template/empa/*/135716/---/l=1 I was able to draw a much more interesting chart:



These are ranges in World Lightduty Test Cycle, both at standard temperature (23°C), winter temperature (-7°C) and summer temperature (35°C). It results that A/C requires around 1 kW, while heating arrives up to 4 kW!

Here we can also see how much inertia accounts in real range, as if you go at low speed, it means you're in town, and this mean continuous starts&stops; in this situation, up to 40% of the energy from the battery is used to accelerate car, and not all of this energy can be recovered by the Brake Recovery System: some of these systems have just 70% efficiency (=28% energy recovered), although I read about some reaching 90% (=36%).

At higher speeds (highway driving) actual range comes closer to max theoretical range.

Comparison between BRS present / not present:



We can see here how BRS is "useless" in winter, as the percentage of energy recovered by the system is negligible w.r.t. energy "wasted" by heater.

So the black curve must be considered just as a major theoretical limit: by sure you'll be never able to go ABOVE that limit, but it is also sure you'll ussually be way below it.

From these charts I think we can conclude that minimum "guaranteed" range for iMiev is 45 km in heavy-traffic cities, where average speed is around 20 km/h, and 60km in "better" cities.

Although it could appear as a low range, actually it is ABOVE the 30 km which some studies state being the average daily-trip length for a typical driver (sorry, can't find a source).

jumpjack, thank you for this interesting update.

One of the many studies discussing typical daily driving distances is:
http://www.solarjourneyusa.com/EVdistanceAnalysis.php

Our i-MiEV satisfies most people's 'average' needs, and the modern first-generation EVs (Tesla excepted) were designed with this in mind. The problem we're seeing is in larger sprawling urban areas (e.g., Los Angeles, San Francisco Bay Area, etc. where round-trips of 100 miles (160km) are common) is that unavailability of guaranteed charging at a destination is resulting in the need to travel the longer distances round-trip on one charge. If the Leaf comes out with the rumored optional larger battery size, it will be interesting to see how many people will opt for it.

One of the problems I have with including A/C, heating, and BRS (regen) in any mileage range discussions is that those are uncontrolled variables; nevertheless, these graphs are good indications of their possible effect.

Jumpjack, those charts are excellent! This is exactly what I wanted to see for a long time - they show what are the most efficient speeds (giving the longest range) depending on various conditions and loads.
It looks like with all accessories off, about 20km/h (13mph) is the most efficient, with A/C on about 32km/h (20mph) and with heating on 55km/h (35mph) are the most efficient speeds. This is especially useful to know in the wintertime for us northerners, that slowing down below 35mph with the heat on is not getting you any more range, actually less.

I think the previous graph which basically shows all EV's as most efficient at 22.5km/h is very inaccurate. I would speculate that a Model S most efficient speed would be about double what the most efficient speed would be for an i-MiEV, considering all the Tesla's electronic gadgetry and its slippery shape. Most other production EV's would probably fall in between.

Thanks for the research!

Great chart! Thank you. Any chance you could make another copy in mph?

Thanks, Dave

HParkEV said:

Jumpjack, those charts are excellent! This is exactly what I wanted to see for a long time - they show what are the most efficient speeds (giving the longest range) depending on various conditions and loads.
It looks like with all accessories off, about 20km/h (13mph) is the most efficient, with A/C on about 32km/h (20mph) and with heating on 55km/h (35mph) are the most efficient speeds. This is especially useful to know in the wintertime for us northerners, that slowing down below 35mph with the heat on is not getting you any more range, actually less.

I think the previous graph which basically shows all EV's as most efficient at 22.5km/h is very inaccurate. I would speculate that a Model S most efficient speed would be about double what the most efficient speed would be for an i-MiEV, considering all the Tesla's electronic gadgetry and its slippery shape. Most other production EV's would probably fall in between.

Thanks for the research!

Click to expand...

Of course it's not my research,it's just my chart.
About the maximum range, it depends on the standby power consumption, which is not knwon unless somebody measures it, but I think it's very tricky to disconnect the traction battery of an EV...
So I consider 300W for all vehicles, which by sure is not true. But with the interactive chart you can change this value as you like.
I know A/C and heating consumption only for iMiev, but maybe this datum can be found also for other vehicles? I think I read it for the Smart ED in its manual months ago.

Later I'll publish both MPH version of the chart and raw data.

I didn't read the source data behind the graphs - Do you know if the Peukert Effect was taken into consideration?

Don

Don said:

I didn't read the source data behind the graphs - Do you know if the Peukert Effect was taken into consideration?

Don

Click to expand...

Peukert effect is negligible in lithium batteries: discharge them at C20 or C2, and you'll get same capacity.

Lead:



Lithium:


But maybe you were thinking to coulombic efficiency, i.e. ratio betweeen energy you actually store in the battery and energy you get from grid; this is a good point.
My charts do not take into account coulombic efficiency, but some data are available in the paper: it's between 75% and 80%, which means you need 1 kWh from grid to put 800 Wh in the battery.
I'll study this.
In the meantime, here it is mph chart:

Thank you for the mph version, but I think the velocity scale is incorrect. My I-Miev will not go 200 mph.
Dave

DaveMiller said:

Thank you for the mph version, but I think the velocity scale is incorrect. My I-Miev will not go 200 mph.
Dave

Click to expand...

Yes, I put a * rather than a /...

And these are the sad charts taking into account coulombic efficiency...



edit:
damn imperial units... X axis was wrong too. Now it should be ok in all images.

jumpjack said:

Don said:

I didn't read the source data behind the graphs - Do you know if the Peukert Effect was taken into consideration?

Don

Click to expand...

Peukert effect is negligible in lithium batteries: discharge them at C20 or C2, and you'll get same capacity.

Click to expand...

I agree it's 'negligible' (at least when compared to other chemistries) because lithiums have such low internal resistance, but it's still there and will most certainly have an effect on EV range

Your second graph shows about 4.8 Ah for 1/2C compared to about 4.6 for 4C which is a loss of about 5% over that range. In addition to the wind resistance loss at higher speeds, you can probably tack on another 2 or 3% because of diminishing battery capacity due to Peukert losses

Don

Here is the wetransfer ...imiev.xlsx file link: https://www.wetransfer.com/download...f029c43df84e38e7bcb76dba20140813041419/f93a2a

GdB, I took the liberty of moving your post over to this thread. Wow, that wetransfer link is one of the longest I've seen! Thank you for posting. As you noted, the quiescent power draw of the i-MiEV is not included and is actually quite significant with all the car's electronics drawing on the order of a 1/2-kW IIRC, with the car just sitting there turned on and not moving. Your graphs show the dramatic effect that aerodynamic drag has on the vehicle's range, and correlate quite well to the other graphs as well as our practical experience.

Prior to purchasing the i-MiEV, all of us were wondering about its suitability for our daily driving needs in terms of range. After a while, we all come to the realization that Range is whatever we want it to be, and adjust our driving accordingly and, if necessary, pre-plan our en route charging to meet our needs. It really is a non-issue, with the recognition that most of us have an ICE/hybrid available for longer trips, with the i-MiEV satisfying the vast majority of our daily driving needs.

How was 1/2kW quiescent power measured? Something is not adding up. I put that into my xlsx file and now the 220km record does not match at all.

1/2kW sounds like a lot to me. Where is all that heat going, to do what? The ecu and cooling fans should be much less than 1/2kW.

I assumed a combined motor and battery efficiency of 80% based on this US DOE test report http://avt.inel.gov/pdf/fsev/fact2012mitsubishii-miev.pdf I found. But that may have been the wrong interpretation. Assuming 1/2kW quiescent power, the motor efficiency has to be 92% to match the 220km record. Seems reasonable for these high efficiency rare earth motors, but I am still skeptical of 1/2kW with no lights, A/C, radio...

There are several contactors engaged to provide high voltage power to the car, the DC-DC converter is on, all of the vehicle systems are on, the 12 volt battery is absorbing a charge, and the coolant pump runs every few minutes. CaniOn shows .3 kW being used, and a member left their car on overnight and measured what the car drew to top off the lithium battery. That returned a power load of 146 watts.

.5 kW is a tad on the high side, but not if lights are on. Holding all four power window switches up with all windows up (window motors stalled) will surge draw to 1.2 kW!! 900 watts going to the windows, I don't recommend holding the switch after the window stops for any length of time.

I just checked and CaniOn says 0.4kW with the vehicle in READY and Park, but no radio or fan, with climate control OFF, and only the driving lights ON (not headlights). Hmm, wonder if that varies with SOC?

GdB, CaniOn is an Android App that allows viewing a fair number of battery and driving performance-related parameters - since you're a numbers person, I think you would find it very useful. Here's its very lengthy thread on this forum:
http://myimiev.com/forum/viewtopic.php?p=12558#p12558

I think the .4 vs. .3 kW is the driving lights. My measurements are with lights off, radio, and fan off.