That doesn't make any sense. Whether you display the battery state of charge as percentage or miles, it gives you the exact same information. For example if you have 290 miles at 100% charge, when at 50% charge your battery meter will say 145 miles if set to miles, or 50% if set to percentage. The percentage is just the rated miles at that time/rated miles at full charge. Or you can say that rated miles is the rated miles at full charge x percent SOC. Changing the display does not give you different information. It's just math.
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Not getting enough miles
- Thread starter OptimusQPrime
- Start date
The problem is that the fuel gauge range number has nothing to with actual range. The estimated range in the energy energy graph however does, based up on your actual driving over the last 5, 15 or 30 miles. Most people can figure out that 50% indicated is roughly half full, much easier for my simple mind than trying to remember that 145 is about half.
gnuarm
Model X 100 with 72 amp chargers
I find the energy display to not be overly useful for planning charging precisely because it does depend on the last X miles only. I find the predicted range varies widely with terrain and road speed. To be useful it would need to look at the roads ahead rather than the roads behind.
The one time I can get useful info from it is in seeing how much my range changes if I adjust the speed of the car or adjust the climate control... sort of. That display depends so much on the terrain that it is hard to see anything unless the car is traversing fairly flat ground.
The one time I can get useful info from it is in seeing how much my range changes if I adjust the speed of the car or adjust the climate control... sort of. That display depends so much on the terrain that it is hard to see anything unless the car is traversing fairly flat ground.
Yup mostly correct. Except the car cannot predict the future. It has no idea what to "expect" even when navigating a route. The range estimate in the energy display is based upon the last few miles driven. Just like the stock market ("past performance should not be used to predict future performance"). You kinda have to know you are going to climb an upcoming mountain, even if you have been going down hill for the last 30.
The fuel gauge range indicator does not even include recent history.
There have been several threads on this, and it's a holy war, like Android versus iOS. People are in one of two camps, and you can't change anyone's mind. Here's a thread and poll on it:
State of Charge: Percentage or Distance?
@KerryOH is taking this position:
#1 Percentage is what it is and is always telling you a correct number. People suggest that to people who are freaking out and going insane if they can't get over the idea that "rated miles" is not correlating exactly 1-to-1 with real distance miles. You can't use percentage for anything, so you can't get worried about anything, eh?
#2 As you point out, percentage is not informative or useful at all. We, as humans, don't think of driving distances to the store or to grandma's house in percentages. So if you're OK with the rated miles being a shifting value that you can use to compare to things, and are not bothered by it being a bit high and optimistic versus your real driving, it can be useful.
(Can you tell by my biased descriptions which camp I fall into?
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gnuarm
Model X 100 with 72 amp chargers
Estimating based on available knowledge is not unlike forecasting the stock market, but requiring MUCH less data. Turns out there are lots of computers doing exactly that, forecasting the stock market and making an awful lot of money in the process. Estimating the range going forward would take into account the speeds of the roads on your route, congestion, elevation changes and your driving history. Because the data set is not large this would not take a lot of computing power. But it is not a straightforward algorithm to develop. That said, compared to the ginormous efforts put into the self driving modes this would be a snap. Heck, they could use a Bayesian filter that adjusts itself to your driving style and conditions.
I believe that range vs. charging facilities is the single biggest obstacle to widespread adoption of battery electric vehicles (BEVs). The second biggest obstacle is range anxiety. Providing better range estimates is the key to reducing range anxiety.
Kipernicus
Model S Res#P1440
when you set a destination in the Navi, and go to the Trip tab of the energy display, it does predict the usage based on terrain (hills), but not weather (headwinds, cold, etc). It's still useful and as you drive it adjusts the prediction with a second line so you can compare how you are doing versus its original estimate.
gnuarm
Model X 100 with 72 amp chargers
Sounds like I need to dig into the display further. I don't recall the energy display having tabs. It has two "average" lines through the data which are not clearly spelled out. (I've mentioned in a display thread that I feel every control and display should have an info button to learn about it). One seems to be the average of the data displayed. I think the other is the average used in the battery state thermometer display, but I'm not sure.
2012MS85
Member
Where do you live? If it’s a cold climate, that’s the #1 issue because batteries like to be warm...and that consumes a huge amount of juice! I often got 90-100% of the EPA range in the spring and fall (no A/C or heat used). Summer range dropped to 75-85%. Cool winter with heater running dropped further to 65-75%. Extreme sub-zero and I got 50% of EPA range (about 130 miles out of 265 rated on my S85 with 19” wheels). Add high speeds and energy usage keeps rising fast, too...just physics
My wife's X75D lifetime (about 15000 miles) is at 340 wh/mi. I am not sure you are exactly "very light on the gas". I know my wife is not LOL. When I drove the X occasionally, I always get under 300.. I AM very light on the gas (my son always told me mama drove much faster than you). Yesterday I drove the X for 170 miles and it was at 295 wh/mi on the trip meter (since last charge). And I was about at the rated miles. I left the house with 208 miles (90%) and got home with 40 miles left on the screen.
gnuarm
Model X 100 with 72 amp chargers
Interesting. I never get below 300 Wh/m unless the road has a lot of downhill on it. Even on roads that are fairly flat and low speed limits I get 333 Wh/m or more typically. I'm starting to wonder if there is something different about my car. When I leave on the longer trip the first 30 miles is back roads at 50 mph max. I typically lose 10 more miles from my range than I put on the odometer. That might be a systematic error estimating the true capacity of the battery at the top of its range. But the systematic lower mileage than others get is likely something else.
Anyone know why the larger wheel diameter would cause poorer range? I don't think I have the larger wheels, but I'm curious about this.
If you don't like the EPA rating, then you need to address that with the EPA, as they're the ones that specify the testing and certification procedure.
2012MS85
Member
[QUOTE="gnuarm, post: 3230870, member: 83534] Anyone know why the larger wheel diameter would cause poorer range? I don't think I have the larger wheels, but I'm curious about this.[/QUOTE]
Physics. Bigger, wider tires have more surface area making contact with the road. More resistance means more energy consumption. For similar reasons, I need to lose weight post Thanksgiving so I have less resistance, thus would need less energy to finish my workouts
Physics. Bigger, wider tires have more surface area making contact with the road. More resistance means more energy consumption. For similar reasons, I need to lose weight post Thanksgiving so I have less resistance, thus would need less energy to finish my workouts
gnuarm
Model X 100 with 72 amp chargers
How does the EPA factor into the design and operation of Tesla cars? The only thing they dictate is how Tesla arrives at the number on the sticker in the window!
gnuarm
Model X 100 with 72 amp chargers
Physics. Bigger, wider tires have more surface area making contact with the road. More resistance means more energy consumption. For similar reasons, I need to lose weight post Thanksgiving so I have less resistance, thus would need less energy to finish my workouts
[/QUOTE]So you are saying the larger diameter tires are also wider?
I think for the X, the front tires have the same width at 265 for both 20" and 22" wheel, but the rear tires are wider for the 22" at 285 instead of the 275 for 20". Also the weight would make a difference too. The 22" wheel + tire would be much heavier.
He's saying that, but I just got these numbers from shop.tesla.com:
19" Winter Package: 265 all around (265/50R19)
20" Slipstream: 265 front (265/45R20), 275 rear (275/45R20)
20" Sonic Carbon: 265 front (265/45R20), 275 rear (275/45R20)
22" Turbine: 265 front (265/35R22), 285 rear (285/35/R22)
So the 22" rims are roughly 3.6% wider in the rear only (same width in the front).
Using Tire Size Calculator I can see that that leads to roughly the following Diameters & Circumferences:
20" Front 29.4" Dia & 92.3" Circ
22" Front 29.3" Dia & 92.0" Circ
20" Rear 29.7" Dia & 93.4" Circ
22" Rear 29.9" Dia & 93.7" Circ
So that actually makes the front tire smaller on the 22 than the 20 (albeit probably negligibly), and while the rear is larger, it seems likely to also be negligible. I'm not sure on the math to determine the front-to-back contact patch size, but it would vary due to a lot of factors and the difference is probably going to be negligible given all of the above.
Lots of people say it's because they're heavier, too, but I don't buy that, either. Seems to me that the weight would work like a flywheel and only be a negative during acceleration. I suspect that it has more to do with aerodynamics. That is to say that there is likely more air churning around causing constant resistance due to the larger wheel (with holes for air to go through) and smaller tire surface area (where air can only go around and not through).
ETA: For the record, I had already typed all of this before seeing the post below (which came through as I typed):
I was told that the wheel weight would not make a huge difference in constant speed driving, but for city driving, they made a huge difference because of the stop & go. Something about the wheel weight counts twice as much their real weight to start them rolling.
That sounds logical, but "counts twice as much as their real weight" is still a pretty small percentage of the weight you're moving around (100lbs of wheel would count as 200lbs and that would be 3.3% of the weight of a 3 ton vehicle). In the city, regen doesn't occur at the lowest speeds and even at higher speeds, regen wouldn't gain as much as you lose to acceleration even with my theoretical flywheel effect with heavier rims. However, in the city, I would suspect that heat and a/c would bigger culprits since they draw per hour instead of per mile (if heater was drawing 6 kW, it would use 6 kWH in one hour whether you went 1 mile or 60 miles). My impression is that people with 22" wheels get significantly worse range, and I'm again not sure how to do the math, but let's say a MX 20" wheel gets 325kWH/Mi and assume we add those % differences together (3.3% for weight in city + 3.6% for wider rear wheel), while that's probably way overstating what those changes do since one is in city only and the other is rear wheels only, that'd make it 6.9%, and 325 * 1.069 = 347.425. I'm thinking that still leaves a lot of energy getting burnt somewhere else...
Which is the highest number so everyone uses in their advertising and on their web sites. Also having the same test is the only way to objectively compare mileage.
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