Rated vs Ideal vs Projected and how to use them

[PatP]

It's a damned-if-you-do, damned-if-you-don't situation.

I consume ~425-450 Wh/mile on 10 mile trips to the local town (store, bowling alley, post office, etc.) because of my 2 mile multi-hill, multi-turn route to the highway. I consume ~325 Wh/mile on 100 mile shopping trips to the "local" shopping metroplexes. Projected was just as meaningless to me.

I use "rated" as a relative fuel gauge. I'd be happy to solve this argument by changing the "rated miles" to % of battery left.

Yes, a % would be better as it would not create a false sense of available range.

However, on my Roadster, I had the choice to use "rated" or "projected" and I was using projected all the time because it was much more realistic. Also kept the ideal range on the computer screen. This way I never had bad surprises.

 

[wycolo]

@sockpuppet #1: Don't you have a base of operations that consists of repeated trips, i.e. commuting? Or do you begin each day like Bill Gates: "where oh where will I go today?". If the former, then you should have a good sense of where your remaining range is at, at any point on the map/ in time regardless of whatever new guageing scheme is presented on your dash. If the latter, then I'm jealous since I'm restricted to, at most, a handful of possible paved routes to choose from. Yeah, same old same old, but still fun to record the MILES at each waypoint looking for differences in the new algorithms. Or driving mode - today: NO HEAT!!
--

 

[tomas]

I'd be happy if it had an option to just display the kWh remaining in the battery (not taking into account any charge set aside for when you get to 0 miles of range).

That would be a consistently computed value, regardless of driving habits, it just declines with use, whether from driving or accessory use or battery warming or whatever else consumes watts.

Easy.... if you put the trip odometer display on left on your dash, it will always show statistics since last charge on top. Including kWh used since last charge. Rather than all that long division, all you have to do is subtract that from 85 to know what's left.

 

[buzzbuzz]

I use "rated" as a relative fuel gauge. I'd be happy to solve this argument by changing the "rated miles" to % of battery left.

I'm in the same boat (although I use "ideal" as my gauge). I simply have my "since last charge" trip meter which has told me how far I've driven coupled with a visual representation of the charge left in the battery. For example, if I've driven 50 miles and have used 1/4 of the battery bar, I know that I roughly have 150 miles left (200 miles total), if I keep driving the way I have been. It's no different than a fuel gauge in an ICE (I've gone 50 miles on a tank, have 3/4 of a tank left, so I'll get about 200 miles on the tank). The gas gauge never told us how many miles we had until empty. I take all the range numbers with a large grain of salt. Even the projected value is only an average over your last 30 miles so, personally, I have no issue with the projected being displayed on the 17-inch screen only. I find the average Wh/mi and overall energy use far more enlightening as to how much further I can drive on a tank of electrons ...and I could see how a "% SOC left" would be useful in addition to range miles...I, for one, would like that in a future software release.

Just my 2 cents.

 

[Trnsl8r]

Easy.... if you put the trip odometer display on left on your dash, it will always show statistics since last charge on top. Including kWh used since last charge. Rather than all that long division, all you have to do is subtract that from 85 to know what's left.

Doesn't work exactly. First, on a standard charge the battery holds about 90% of 85kwh. Second, I have found that the battery will lose mileage even when plugged in. Sometimes my battery is charged full in the evening (242 miles shown), but the next morning it can be down to about 235 and my garage will usually keep about 55 degrees. I think the car lets the SOC drop quite a bit before it tops it off again.
And once you get going, the trip meter only shows the energy consumed from the point you unplug.

 

[Mayhemm]

I find the projected range to be most useful of the three because I almost always drive faster than 55mph (on the highway) and don't really do much to reduce energy usage. For example, I set my climate control to "comfortable", not to "efficient".

I'll very rarely ever achieve ideal or rated ranges, so I find them bordering on useless. Projected at least gives a closer approximation of real-world range for lead-foots like me. They could maybe add a 50-mile or 100-mile option to the average calculation though (in addition to the 5/15/30 already in place). This would cover most people's day-to-day errands and give them a good approximate energy requirement figure.

Needless to say, I'm in favor of Tesla putting the Projected Range back on the instrument cluster somewhere.

 

[smorgasbord]

I keep thinking there's a huge opportunity for crowd-sourcing actual kWh consumed on a given stretch of road at a given speed at a given temperature. That could then be tied into the Nav system, which could then tell you what speed will get you to your destination given your current SOC.

 

[PatP]

My friend who bought a Model S just sent me an email he sent to Tesla. He thought is battery was defective as he arrived with 1km left at his destination (240 km). I explained to him to never trust the range displayed especially in winter time. He doesn't understand why the car is not showing the true range.

He's a perfect example of a normal user. This confirms my theory that showing a BIG ideal/rated range is not appropriate for non early adopters.

This is not a minor issue. Also delivery specialist should spend more time explaining this to customers (especially in cold climate)

 

[tomas]

Judging from both forums and from other communications I've had with Tesla owners, the "normal" Tesla user has reasonably high degree of technical aptitude, understanding that they are early adopter, sensitivity to range issue, and curiosity about influences on range (temperature, driving habits, vampire load, etc.), frustration that "projected" is not on dash, but knowledgeable enough to display it on center screen. I think that so far, Tesla Motors has designed their offer to this crowd, not to the mass market.

The person who would drive 240km, arrive with 1km rated, and wonder why is probably more indicative of the mass market that Tesla will need to understand better and cater to if they are to broaden their customer base.

I believe the right answer to this is better documentation and - as patp says above - better-trained delivery specialists. Tesla has GOT to know that range anxiety is the biggest obstacle to success - and most of it is psychological.

Example: My last car was Jaguar XF-S. There was a normal gas gauge, and one could optionally display remaining range (as one can on Tesla as well, if instructed how) but with absolutely no transparency as to formula. Had the Jag 5 years and 50k miles. Throughout, projected range was very optimistic on full tank (usually overstating by 50%), and became more accurate as tank emptied. I'd guess that with 1k left, it would be extremely accurate: +/- 1k. Never got there though, and never worried about it, because there's a petrol station on every corner.

With Tesla, I find the projected range much more useful than on the jag - as long as I display energy app on center screen so I can see projected, and use "average" vs. "instant". I almost always have it up, because there isn't a level 3 charger on every corner, and I don't want to be caught short on electrons.

So, Tesla has given us better tools than we ever had with ICE cars regarding range, but shown little sensitivity at delivery and in documentation regarding instruction about using it. So, the curious figure out how, and the less curious get to the destination with 1k rated left and freak out.

Yes, tweak the displays. I'd like projected on dash and default to "average" vs. "instant. But first priority is better handover and documentation, please!

 

[PatP]

Unfortunately the New York Times article is a perfect example of why using rated range is a really bad idea. Tesla will pay the price for this mistake for a long time.

I repeat myself, but its crucial Tesla stops being so California centric. They need to haven a team on the east coast that LIVES in the cold weather.

 

[dadaleus]

I was logging on to make a post about this only to discover my exact thoughts are already covered.

Others may not be aware that an early version of the S software ALREADY HAD projected range as an option on the above steering wheel display, and it used what is now called average. I too think it was a mistake for Tesla to move this to only being available in a complex app for the 17" display. Personally, that was my preferred view of range. If projected had been a default for the center display, maybe the New York Times issue could have been avoided (but maybe not--there was more at play here, mainly the overnight after a minimum charge to theoretically achieve his needed range).

 

[PatP]

The Consumer Reports article conclude with:

"One additional takeaway: Perhaps it's the "projected range" that needs to display more prominently than the "rated range."

Winter chills limit range of the Tesla Model S electric car

 

[Mayhemm]

Others may not be aware that an early version of the S software ALREADY HAD projected range as an option on the above steering wheel display, and it used what is now called average. I too think it was a mistake for Tesla to move this to only being available in a complex app for the 17" display.

Yeah, I would definitely prefer Tesla put the projected range back on the instrument cluster. I don't want to use up half of the touchscreen with the energy app. I'd prefer to use it to display media sources, maps, or the rear camera.

 

[brianman]

Others may not be aware that an early version of the S software ALREADY HAD projected range as an option on the above steering wheel display, and it used what is now called average. I too think it was a mistake for Tesla to move this to only being available in a complex app for the 17" display. Personally, that was my preferred view of range.

+1

If projected had been a default for the center display, maybe the New York Times issue could have been avoided (but maybe not--there was more at play here, mainly the overnight after a minimum charge to theoretically achieve his needed range).

I disagree. I'm convinced Mr. Broder would remain "confused" after "accidentally" changing the units to kilometers because "a voice in his head told him to".

 

[neroden]

I'd prefer a version which displayed "kWh" and let me estimate what my mileage was going to be...

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Easy.... if you put the trip odometer display on left on your dash, it will always show statistics since last charge on top. Including kWh used since last charge. Rather than all that long division, all you have to do is subtract that from 85 to know what's left.

Aha, good workaround.

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Doesn't work exactly. First, on a standard charge the battery holds about 90% of 85kwh. Second, I have found that the battery will lose mileage even when plugged in.

Or not a good workaround, I guess.

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Imagine how useless rated is for me: I'm at an average of 540 wh/miles since I got the car. Try explaining to your wife you have to cut your rated miles in half.

At least that's a simple computation! For planning purposes, I've just decided "half of rated" is a good rule of thumb up here in the Frozen North.

I think we're not helping Tesla when we say this not important and that you just have to do the math in your head... For normal people (non early adopter) it is. My wife Volt's auto adjust the range so you can trust the big projected range display - this is what people expect. In an electric only car you need to be ultra conservative on range - quite the opposite of what Tesla is doing right now.

I agree. I think it would be more helpful to everyone to put up kWh and a *conservative* projection of kWh/mile.

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Yep, I've got climate control on, but Tesla's webpage says such things have about a 10% impact. I'm seeing closer to 40% (430/300 ~= 143%).

Tesla needs to correct that, since it's plainly wrong. Heating can easily have a 50% impact or more.

California engineers, sheesh! They don't know what cold is. :biggrin:

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\The Model S HVAC, at full blast takes about 7.5kW.

Thank you for this data. This is a key piece of information which was previously lacking....

 

[tomas]

I live in Chicago. My early experience after December delivery and mainly city driving was putting car to bed most nights significantly underachieving rated. I found that, still winter, when I started taking longer drives with high proportion highway, I was extremely close to rated. On one unseasonably warm 50 degree day, I beat the crap out of rated over about 90 miles. About 280 wh per mile! So, this is all about learning for each of us but I'm guessing over course of a year, given reasonable city/hwy split, I should be at rated, even in Chicago. Just have to be realistic in cold and know the temperature standard deviation is high. That can be helped by staying plugged in in a heated garage.

 

[jerry33]

Just have to be realistic in cold and know the temperature standard deviation is high. That can be helped by staying plugged in in a heated garage.

In Florida

 

[LazMan]

I live in Chicago. My early experience after December delivery and mainly city driving was putting car to bed most nights significantly underachieving rated. I found that, still winter, when I started taking longer drives with high proportion highway, I was extremely close to rated. On one unseasonably warm 50 degree day, I beat the crap out of rated over about 90 miles. About 280 wh per mile! So, this is all about learning for each of us but I'm guessing over course of a year, given reasonable city/hwy split, I should be at rated, even in Chicago. Just have to be realistic in cold and know the temperature standard deviation is high. That can be helped by staying plugged in in a heated garage.

I think the car uses a lot of energy initially to warms itself and then much less to maintain the heat. For multiple short trips where the car cools down in between, energy use can be twice rated. But I also found that as soon as the car has heated up, energy use drops dramatically.

 

[ThosEM]

Any other comparable car, ICE, hybrid, or EV, is set up to provide a remaining range estimate based on recent history. Unless one knows the mind of the driver and the future of the route topography and weather, there is no better estimate available. What were Tesla thinking when they consigned this to only appear in the energy app?

The Consumer Reports article conclude with:

"One additional takeaway: Perhaps it's the "projected range" that needs to display more prominently than the "rated range."

Winter chills limit range of the Tesla Model S electric car

 

[jerry33]

Any other comparable car, ICE, hybrid, or EV, is set up to provide a remaining range estimate based on recent history. Unless one knows the mind of the driver and the future of the route topography and weather, there is no better estimate available. What were Tesla thinking when they consigned this to only appear in the energy app?

I don't quite understand. The rated range on the speedometer is generally pretty accurate--if a bit conservative. Using the trip meter you can easily tell if you are gaining or losing miles compared to the rated range. The energy app is 99% for entertainment because it covers too short a distance to be useful.