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Discussion Starter #1
Does anyone know this: What sort of display does the Tesla offer the driver regarding the energy consumption in the last 50 miles, or since a full charge, or since a reset. I have been working hard trying to get GM to fix the error in the Bolt screen, so it is interesting to see how other makes handle this.

Bolt: Show bars for mi/kwh over distance.
Prius: Shows bars for mi/gallon over time. (the use of time in denominator here is horrible).
Tesla: ???
Others? Leaf?

Also, the Bolt refuses to show negative numbers.
Prius also.

Does Tesla show negatives? Leaf?

And for those new to my mission here, I am working hard to get GM to admit and fix the horrible error re. the red average line in their Efficiency History Bar Chart. It is almost always overestimating mileage by 1000% - 2000% for drivers, like me, in hilly terrain.

Details of that are at: http://www.chevybolt.org/forum/9-2017-chevy-bolt-ev-general-discussion-forum/20513-measuring-energy-use-euro-vs-usa.html
 

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The LEAF just gives an average mi/kWh since reset numerically, and an instantaneous bar chart.
During regen that goes to a very high value, but not negative (it's a positive range bar chart).

If they do the right thing in Canada (e.g. kWh/100km)...perhaps that is tack you can take.
 

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Tesla shows a line chart for the past 5, 15, or 30 miles…

it also shows "trip planning" where it will show you an "ideal" line chart of your trip form the GPS nav - and your actual performance vs. the "ideal" performance - the line chart takes terrain and road speed limit into consideration as part of it's planning…

if you have a destination entered into the navigation system the car will show you your estimated battery (SOC) at your destination and the estimated battery for a round-trip back to where you started:

Example: when I get in the car in the morning I plug in "work" into the navigation system and after "thinking" about it it typically will show 81% as the estimated battery percentage for when I arrive (down from the 90% I charge to over night).
 

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Discussion Starter #4 (Edited)
David: I saw on a Tesla forum that they give it in watt hours / mile, so essentially same as kwH / mile. This is very different than Bolt, that does mile/kWH (except if one switches to metric). There are advantages to have energy in the denominator. Can you confirm that Tesla units are only this way: energy/distance.

Of course, people prefer different things. On that Tesla forum one commenter said how he much preferred distance/ fuel, as in mpg. That American way is very ingrained in Americans (and perhaps has some advantages too). All very interesting in my opinion.

But does Tesla allow only energy/mile?

JustFrank: Sounds like bar chart on Leaf is like Bolt. Distance on the x-axis? Correct? (as opposed to time, say). And mile/kwH as the height of the bars? It is not so important, but I imagine the LEAF allows a switch to metric units, and possibly things would change then to energy/km.

David: Another matter. Suppose you are in Tesla. And you start on a hill with less than a full charge. And you have reset the chart to 0, or perhaps asked for the last 5 miles. Suppose you descend 5 miles. Will the line chart show negative fuel consumption? I realize you might have to guess at this, but it would be very interesting if so. GM (and Leaf) have decided that negative numbers would confuse the public, and so they view a negative number as a very big pos. number. It would be interesting to know if Tesla deems its owners ready to handle neg. numbers, which would be the truth for such a drive (which is atypical, but it does happen: Eisenhower Tunnel to my town: 2500 feet down in 8 miles with no up, and hence purely negative consumption over 5 miles).
 

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David: I saw on a Tesla forum that they give it in watt hours / mile, so essentially same as kwH / mile. This is very different than Bolt, that does mile/kWH (except if one switches to metric). There are advantages to have energy in the denominator. Can you confirm that Tesla units are only this way: energy/distance.

Of course, people prefer different things. On that Tesla forum one commenter said how he much preferred distance/ fuel, as in mpg. That American way is very ingrained in Americans (and perhaps has some advantages too). All very interesting in my opinion.

But does Tesla allow only energy/mile?

JustFrank: Sounds like bar chart on Leaf is like Bolt. Distance on the x-axis? Correct? (as opposed to time, say). And mile/kwH as the height of the bars? It is not so important, but I imagine the LEAF allows a switch to metric units, and possibly things would change then to energy/km.

David: Another matter. Suppose you are in Tesla. And you start on a hill with less than a full charge. And you have reset the chart to 0, or perhaps asked for the last 5 miles. Suppose you descend 5 miles. Will the line chart show negative fuel consumption? I realize you might have to guess at this, but it would be very interesting if so. GM (and Leaf) have decided that negative numbers would confuse the public, and so they view a negative number as a very big pos. number. It would be interesting to know if Tesla deems its owners ready to handle neg. numbers, which would be the truth for such a drive (which is atypical, but it does happen: Eisenhower Tunnel to my town: 2500 feet down in 8 miles with no up, and hence purely negative consumption over 5 miles).
Tesla's units are:

wh/mile - no adjustment allowed

the line graph shows "negative" energy gained for going down hill

you can show distance in in one of 3 ways

wh/mile
rated range (EPA rated range consumed or "left"
battery percentage

there is no way to "reset" the 5/15/30 mile consumption charts

in the line chart showing consumption (wh/mile) Orange is "consumed" and Green is "regen" - the Line chart clearly shows "regen"

I hope these answers help ;-)
 

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here are some screen shots from the Tesla showing:

1. the energy consumption chart
2. the "trip" estimate for power used
3. the navigation display showing estimated battery at destination
 

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Discussion Starter #9
XJ12: Absolute values don't help. If the consumption was -1 mile / kWh for the Bolt, the chart will show it not as the absolute value of -1, which would be very wrong, but as +252, which at least is in the spirit of getting a lot of miles.

David: Thx for details. Will examine. But a first glance makes it clear: Tesla assumes its owners can handle the truth. Negative numbers. A little frustrating that GM does not so assume.

And, yes, that first chart you posted is very helpful to me... I can live -- more or less -- with Bolt charts. But it is worthwhile understanding the alternatives.
 

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XJ12: Absolute values don't help. If the consumption was -1 mile / kWh for the Bolt, the chart will show it not as the absolute value of -1, which would be very wrong, but as +252, which at least is in the spirit of getting a lot of miles.
I think part of the confusion here is the placement of the negative. It will never be possible to drive negative miles. Just like in an ICE car, where you can’t have -mi/gal. The lowest possible consumption will be 0 mpg, and the highest will be infinite, if coasting with no fuel usage.

What we’re seeing with EV regen is mi/-kWh, which is a difficult thing to show on a graph. Personally, I would rather have the gauge show wH/mi. I can understand that most Americans have mpg ingrained in their heads, and it can be hard to unlearn, but it just doesn’t work as well, for EVs. Since we can already set it to kWh/100km, it should be simple for Chevy to give us an option for wH/mi.
 

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Discussion Starter #11
Yes, it is becoming clear to me that energy/distance (the Euro style) is more useful and natural than distance/energy. And yes, I agree that the placement/interpretation of the minus sign (numerator vs denominator) is a possible point of confusion. But it should be easy to have several choices available. Really, all I want is one number: The overall average for a trip. I like the simplicity of aiming for 4 mi/kwH, so I like to know which trips of mine will help that and which will be below that. I don't want to reset the trip odometer on each trip because there is only one of those, and I like seeing lifetime consumption. Of course, on the Tesla screen a big plus is their display of a specific number for an average (as opposed to an unlabeled line).
 

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Tesla line graph – what is it saying / what am I missing ?

David M or anyone: I don’t understand the Tesla line chart that David posted (copied in below). The horizontal ‘X’ axis denominated 30, 20, 10,0 from left to right is throwing me off. What does that show, is it merely the range of wH’s used or recaptured sometime over the past 30 miles ? And why is that a particularly useful set of information.

That thing as well as Bolt’s bar chart both strike me as: not useful. Other than to impress your neighbour. Showing off another golly-gee screen of info that sets my advanced EV apart from other cars on the street.

If the line chart would show the usage by mile marker passed, or say by quarter of a mile or tenth of a mile passed, during the current trip over the last 5, 15 or 30 (or more) miles ? Now that would be useful.

In terms of units of energy, I prefer kWh/mi to one decimal place. Rather than Wh/mi.
The latter number seems just too big. Example: 4.1 kWh/mi lets me quickly calc 4.1*60 (60 kWh being Bolt’s battery capacity) = 246 miles at that rate; not bad, above the EPA test of 238 mile range.

Anyway perhaps I need to be corrected about the below Tesla line graph.
 

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LEAF is just one bar, that changes dynamically, as an 'instantaneous' measure, and a separate numerical average since reset. No idea if they do the average correct or not.
 

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Discussion Starter #14 (Edited)
Leaf: Having a numerical value of the average is a good thing. Bolt could easily have done that on their DETAIL screen where they have the very large numbers: kWh used, and miles driven. Of course, multiplying the first by four is so easy that it is not a big problem.

Cehjun: Yes, the 4 seems like a very natural unit. The problem is that any graph that shows how one is doing -- how the 4 is changing over previous X miles from 3.8 to 4.2 has to deal with the "singularity". When fuel consumption is 0 the "4" is nowhere near 4, but could be near 334,123 (same as my waiting list number for the Tesla!). The graph can't realistically show such large numbers at the same time as small ones. Hence the Tesla approach: Show not "4" but "0.25". The decided against decimal points and show 250 in such a case. That is not a bad solution.

As for the Tesla chart: Like Bolt it shows the most recent 30 miles (50 on Bolt, or 30 in metric). Now, each bar on the Bolt shows mi/kWh in a 5-mile segment. Tesla is showing the full graph. So instead of 5-mile segment they are perhaps using 100-yard segments and putting a dot at the usage for that 100-yd. segment. They are coloring it green or orange according as positive or negative. So it is essentially the same as the Bolt's metric version of the bar chart, with these differences:

Bolt: Average is a red line. One must guess its value. Tesla: Shows actual number. Much better.

Bolt: A value for each 5000 m interval. Tesla: A value for each 100 yard interval (I say yard not meter b/c they use miles). Latter is better.

Bolt: Would show 15.5 kWh per mile. Tesla: 366 Wh/mile. Both are ok. I can easily adjust to the 15.5 value, and have taken to switching to metric in order to: A. see a readable value such as 15 or 14 or 16. B. Eliminate the ridiculously incorrect red line in non-metric Bolt chart.

But at least Bolt is in the ballpark here.

As to why the chart of recent consumption is useful: Certainly it is not useful if one is on a 200-mile trip and needs the whole picture. But most trips are shorter and one wants to know whether one is above or below 4. The chart, with its accompanying average shows the places where one was above 4, and below, and what average was. If average was 3.9 but one is now heading into a flat 5 miles to one's house, one can see that one can probably get above 4, etc.
 

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I find the Tesla graph useful because it’s more real time - updated every 1/10th of a mile - and they have the rated range line the EPA range - comparing current usage to that rated range line let’s me as a driver know if I’m doing better or worse than I should be for the trip I’m currently on...

The graph posted was for driving Hwy 17 north in California fro Santa Cruz to San Jose area - as you can see it’s quite hilly so there is a good mix of uphill and down hill segments showing both high usage and high regen.
 

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Discussion Starter #17
And thanks again for that graph David. Is it certain that it is 1/10th of a mile as opposed to 100 or 200 yards?
I have located a Bolt executive re my mission on the error in the Bolt bar chart and wrote him.

And yes, the 15.5 number is kwH per 100 km. While 15 is a reasonable number, when you get home and see you have have 8 kwH for 64 km, the quick mental conversion one can do in the realm of "4" and miles is not there.
 

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Discussion Starter #18
So a big focus here is MPG vs. GPM (the latter being gals per 100 miles; same as L/100 km). I just found this

http://www.mpgillusion.com/p/what-is-mpg-illusion.html

which explains the MPG illusion (which I was aware of, but did not know it had a name). The US EPA now puts GPM on car stickers!

But I like this quote

"Does using GPM imply that MPG should be scrapped? No. MPG is useful. Specifically, MPG tells you the range of your car's gas tank. For example, MPG can help you decide whether you can wait two more exits to refill your tank.

Both MPG and GPM have a useful role at different points in owning a car. MPG is useful when you're driving a car. GPM is useful when you're purchasing a car -- it better captures the fuel consumption, and fuel savings, when comparing a current car to a new car, or when comparing two new cars to each other.

Note that both measures serve equally well to tell you what is more efficient: 50 MPG is better than 20 MPG; 200 gallons per 10,000 miles is better than 500 gallons per 10,000 miles. They are not equal, however, in accurately conveying the gas savings from efficiency gains."


also

"Our main research finding is that the majority of people assume that equal increases in MPG are equal in gas savings; a minority thinks that gas savings are equivalent to percentage improvement. Both lines of reasoning lead to erroneous conclusions."

Of course, the use of EVs put a completely different spin. The web site cited is about liquid fuel.
 

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Discussion Starter #20
David: That image you sent me has two horiz. lines near the average. I expected one. One is dashed, one not. As a guess, maybe one (dashed?) is an estimate of the expected average at some future time? Do you know why there are two lines there? (Of course, neither is one of the normal grid lines at 300, 600, 900).

The coloring is nice. No coloring between 0 and about 350. Orange above 350, green below 0.
 
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