Estimating electricity use based on a route

[jmueller065]

Inspired by a page detailed in the Introductions Thread
(this post: http://www.myfocuselectric.com/forum/viewtopic.php?f=2&t=42&start=190#p8841)

I created a really simple calculator using Google maps: enter in two addresses and it will calculate an estimate of power consumption:
http://jamiegeek.myevblog.com/2014/01/13/estimating-power-consumption/

You can tweak the Wh/mile value to watch how the consumption changes for a given route...

 

[WattsUp]

(Hahaha... put out software and then be prepared for feature requests and bug reports.)

Feature Request #1: The page is neat as it automates the simple calculations I would have done by hand for a trip, but you should consider making the page do something a bit more spiffy. Instead of just letting me change "techy" like numbers Wh/mi, why not have the page tell me the techy numbers. For example, for a given route, compute the maximum Wh/mi that could be used, and still make the trip. Or, better yet, translate that result into the maximum speed one could expect to drive, and still make the trip. You could even allow the user to enter a "surplus" (e.g., I want to drive this trip, and still have +10 miles at the end... how fast can I drive then?)

Feature Request #2: Add a "round trip" mode for a given route (e.g., can I make this trip on a single charge?). This mode should also incorporate the same features as above.

Bug Report #1: Can you make it not reset customized routes just because a number was changed? Currently, if I drag various parts of my route to customize it, and then change a number to recalculate, the entire route is reset is set back to the Google default... it would be nice if the customized route was kept.

 

[jmueller065]

LOL! Funny...sure

Ok bug #1 fixed

Added Round trip fields.

To estimate Wh/mile required for a trip I think I'd need a chart of Wh/mile for various speeds (probably 3 or 4 data points would be sufficient). I know such a thing exists for the Leaf but has anyone attempted measuring such a thing around here? (Going to be just under freezing here so if I did attempt to measure such a chart my values would be a bit high--also something to add to the page: ambient temp to make adjustments for that as well and heater usage--which was why I started simple with the Wh/mile value to begin with.)

 

[WattsUp]

Very nice... thanks! Now that's service.

Btw, apparently there are none of the normal right-click menus on the map? Because of this, it is impossible to remove custom routing points once they've been created. I don't know how easy this is to address with the Google Maps API.

Yeah, I don't know of any "speed-to-energy" table for the FFE. Perhaps we can attempt to create one? A bunch of folks could try to drive on level ground at a steady speed and take measurements of their average Wh/mi. We could all report what we measure, and then we could average all the results to create the table.

 

[v_traveller]

Cool!!! I put my 241 wH/mi average in for my commute, seems to be pretty accurate.

Here's a "feature request" challenge: Since you're using google maps, can you also display elevation loss/gain between the start and stop? If you want to get fancy, try factoring the consumption based on elevation loss/gain.

Here's a data point: I seem to average less than 200 wH/mi on the way down, and 279 wH/mi on the way home. It's an 1100 ft loss/gain between home and work. It's about 39 miles one-way.

Thanks!

 

[jmueller065]

I've now updated it to attempt to calculate the consumption based on a generic formula:

Wh/mile = 2.5*speed + 90
(Yeah I know: it isn't linear but this is the first approximation.)

This yields the following:

Speed   Wh/mile
10        115
20        140
30        165
40        190
50        215
60        240
70        265

In addition it uses Google Maps elevation data to attempt to account for elevation changes (by adding in an additional 250*grade Wh/mile).

Also added a "use heat" checkbox (when checked it only alters the estimated values..not the one calculated from the Wh/mile value you enter).

You will see this new calculation in the Electricity used and % used boxes as well as the original calculations (the new values are preceded by "est:") for example:
Battery Consumption: 3.59 est: 3.58
% Used: 18.39 est: 18.36
The new estimated values are 3.58 and 18.36 respectively.

Note that everything is done in javascript in the html page so you can view all the code by simply using "View->Source" in your browser. You can even save the file locally so you can edit and play with some of the values--if you come up with something more representative than here let me know I'll update it.

Btw, apparently there are none of the normal right-click menus on the map? Because of this, it is impossible to remove custom routing points once they've been created. I don't know how easy this is to address with the Google Maps API.

From what I can see I'd have to construct a right click menu. You can always reset it back to the original route by clicking on "calc route" again.

 

[paw160]

Yeah, I don't know of any "speed-to-energy" table for the FFE. Perhaps we can attempt to create one? A bunch of folks could try to drive on level ground at a steady speed and take measurements of their average Wh/mi. We could all report what we measure, and then we could average all the results to create the table.

I started doing some math when I was looking at ECO-Cruise efficiency. I have a spreadsheet where you can input speed/distance/grade and it spits out Wh.

I have not compared this to actual vehicle stats yet (I'm still waiting for my FFE...) but if anyone wants it they are welcome to it as a starting point.

It accounts for drag, rolling resistance, and road grade. What is not accounted for are vehicle load losses (heater, lights, stereo/nav) and other thermal/mechanical losses. I have a feeling that if someone were to check this out we might find a constant term to add that would make this pretty accurate.

If anyone is interested in the spreadsheet let me know. They don't seem to allow attachments here.

 

[Marc Lee]

Hey nice calculator...thanks for putting it together!

 

[unplugged]

I really appreciate the idea on this. Thanks for putting the time into this map. I agree that the speed of the FFE is an important component of the calculation. I haven't really kept track of the watt hours per mile (I will now), so I'm not sure what the default at 230 equals in terms of average mph. Does anyone have an average watt hours per mile for 65 mph? This would really help put the default into perspective.

One suggestion is that you tweak the altitude calculation. I will give you a great example I am familiar with in real world terms and both at 65 mph. If I go from my house on Whispering Wind, Irvine, CA to Getty Center, Santa Monica, CA, I get 54.3 miles and arrive with 80.6% charge expended. This is a pretty much flat route along the coast. I would usually have around 10 miles remaining on this trip, so it is pretty accurate. Now, from my house on Whispering Wind, Irvine, CA to my folks on Albelia St., Murrieta, CA, I get 58.5 miles, with a usage of 111.65% expended. The overall altitude gain is about 1600 feet. (With a lot of up and down.)

As you see, I shouldn't be able to make the trip to my folks house. But I do, with about 5 miles remaining cruising at 65 mph. So I would suggest the altitude formula is about 10% off. Has anyone else had similar experiences?

 

[GladeStorm]

I agree with unplugged on altitude. Multiple runs on an 1100 ft elevation change is showing me that +=grade*100 to +=grade*125 might be more accurate.

 

[jmueller065]

The grade factor is now 125 (from 250).

 

[jeffand]

I estimate that between 70 and 90 % of the battery energy is converted into vehicle movement.
Does any one know what the frontal area is for the FFE?

 

[paw160]

I used the following numbers:

Frontal Area: 2.23 m^2
Coefficient of Drag: 0.295
Coefficient of Rolling Resistance: 0.01 (depends heavily on the tire...)
Air fluid density: 1.2
Mass: 1674 kg

I gathered these numbers from various websites and making a few assumptions about the car.

In my calculations I also factored in a 0.5kW static load. I am estimating this from the "other" bar on the dash. When all is said and done the numbers seem very consistent with what I see when driving.