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Disappointed with range estimate in first long term drive

Discussion in 'Model S' started by Vigile, Jan 1, 2016.

  1. Vigile

    Vigile Member

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    Hey everyone, took my new 85D (just crossed 1200 miles) on its first trip from Cincinnati to Columbus and back today and wanted to share an experience I had. Essentially, I noticed a pretty big discrepancy between the estimated mileage the car showed and how the progress went as I was driving.

    First, some necessary information.

    I was driving from Columbus to to Cincinnati.
    I was going from Exit 100 on I-71 through Ohio and the 18 miles into KY. 118 miles total.
    It was about 32F outside during the drive this evening.
    I never drove over 70 MPH. When the speed limit was 70, I went 70. When it was 65, I went 70. When it was 55, I went 60.
    Using Autopilot the majority of the time.
    Temp was set to 70F in the cabin.

    I came from the east side of Columbus and went to the Supercharger at exit 100, knowing I need some juice.
    I waited for the car to charge to 200 miles estimated range. (Note this is WELL after the notification showed up about the car having enough power to make the rest of my trip, using the in-car nav.)
    I looked at the trip meter with the destination set and it indicated I would have 22% battery remaining when I got home. Great!

    As I was driving home I just keep noticing that the miles I was actually driving were less than the range coming off the car. I started to pay attention. I noticed the battery level estimate (at the end of trip) drop to 20%, 18%, 16% and then 14%. I started to get worried. The line on the trip screen was trending well under the grey line that represents the original estimate at the start of the trip.

    Here is picture I took when the car said it had 100 miles left on the range. Remembering that I charged at the SC to a 200 mile range, that gave me a good way to measure the accuracy of Tesla's info.
    2016-01-01 23.09.12.jpg
    I had been driving just 69.1 miles at that point, giving me an error of 30.9 miles or 30.9% (!!!) on estimated to actual mileage.

    I still had 49 miles to go on the trip so I started to get really worried. How would I possibly run out of juice on a 118 mile trip with a 200 mile estimated range? I turned down the heat a couple degrees, turned the seat heaters off (they were on 1)...

    As I got closer to Cincinnati the speed limit dropped a bit to 55, so I went to 60 MPH, and that seemed to help quite a bit. (Maybe the last 15 miles.) I ended up getting home with 35 miles on the estimation. Doing the math again, with a 200 mile initial projection, and a 118 mile actual trip, gives us a 46 mile range error. Definitely closer than I was after the first 100 miles, but still a dramatic discrepancy.

    I get that it was cold outside...but the car knew that and I would have though Tesla would have taken that into consideration.
    The drive from Columbus to Cincinnati is pretty damn flat, as anyone that has done it can tell you.
    I was the only passenger and I had only a backpack as cargo.
    I know it will get better when it warms up again, but I live in KY and we have winter.

    Anyone have thoughts on this? Or similar / difference experiences? I thought I had charged at the SC to a point where I would have zero range anxiety on the way home, but clearly that wasn't the case. What if I had left the SC when the software told me I had enough juice to get home? It's very possible I would have been stranded.

    For a car that I am otherwise in love with, consider me somewhat concerned.
     
  2. stsanford

    stsanford Member

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    I think you've just discovered one of the issues with batteries in the cold. I have had a 60 and now a P85, and cold weather (and it seems anything below 60 or 70 degrees is considered cold) really has an adverse effect on range. I have seen as much as a 6:1 range loss when doing around-town, short hop type driving in the bitter cold. More normal is a 25-30% reduction in range when the temps drop below 65 or 60 degrees...

    My rule of thumb once the winter hits is to make sure you have DOUBLE the range needed to go anywhere. This is with a combined 65k miles of driving experience in the Tri-State NY area year-round.
     
  3. Cosmacelf

    Cosmacelf Active Member

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    Your experience is pretty typical. I always use evtripplanner.com to gauge how many rated miles a freeway long distance trip will actually use. In general, I try to add 50% rated range to a trip calculation. So a 118 mile trip, I would try to charge to about 180 miles, at a minimum. Then cold weather, speed and and headwinds come into play.

    The Tesla range estimator is crap. Starting a journey, it may say 12% estimated level at end of journey, but then five minutes into the trip, it'll have fallen to 8% and dropping. Then as the trip is nearing the finish, the estimation will start to go up again.

    Bear in mind that the "rated range" is for level ground, at 70 degrees, no heating or AC, no headwinds, and at 55 mph with just a driver and no cargo. Yeah, sometimes you can hit rated range on a trip, but certainly not in cold weather, and I would never plan on it.
     
  4. Jool

    Jool Member

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    Yes, cold weather really does make a huge dent in the car's range. The combination of the car having to keep the battery warm plus running the cabin heater is killer.
     
  5. stevezzzz

    stevezzzz R;SigS;P85D;SigX

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    First, let me say that I'm sorry you experienced range anxiety after taking sensible steps to avoid it.

    Next, welcome to the wonderful world of winter. When the OAT drops below about 40° F., consumption per mile goes up dramatically and range takes a big hit.

    Third, remember that your first line of defense when range becomes an issue is to slow down. The difference in consumption between 60 mph and 70 mph is dramatic, for instance.

    Let's examine the information you presented and see if your anxiety was warranted. It looks like you used an extra 30 miles of Rated range in the first half of your trip, and only an extra 15 miles of range in the second half. Why? Because your average speed was lower in the second half. You said that the predicted SOC remaining dropped from 22% at the outset to 14% somewhere along the way; that's not necessarily a cause for concern, because the algorithm is projecting the remainder of the trip based on your actual performance in the early stages, so an initial drop is not an indication that the predicted SOC remaining will continue to drop as you go along. And 14% SOC is roughly 40-45 miles of Rated range, which is a comfortable buffer in most circumstances and reasonably close to what you ended up with at the end.

    I hope I'm making sense; my larger point is that while you should by all means pay attention to changing conditions and adjust your speed downward if things really are going badly, you were never in any real danger of running out of charge before reaching your destination. Look at it this way: you started the trip with about 60% more Rated miles than actual driving miles, and though that buffer diminished somewhat, there came a time in the second half of the trip where you actually surpassed that initial percentage and were 'home free'.
     
  6. musicious

    musicious Member

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    This why on my 85D I have it display the energy level (% battery remaining) rather than rated range. In the winter I get about double the % battery so at 90% its 180 mile range rather than the 240 rated range. In the summer its a little more than double, around 200-210 but still easier to multiply the % times 2 and add a little than to trust rated range.
     
  7. Al604

    Al604 Member

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    I picked up a 70D on Dec 19th, i've quickly realized the "rated range" is probably in ideal weather and temperatures. My rated 385KM on 100% charge is actually about 210-220 KM of real driving in the city where the temp is at 32-40F outside with the cabin at 71F.

    I'm not looking at my wh/mile or wh/km to figure out how far I could actually make it on what energy I have left in the battery.
     
  8. Troy

    Troy Member

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    The range you see in your car is EPA rated range. Their score is high because they test cars at low speeds. They do a 5 cycle test. 3 of those simulate city driving at 21.2 mph average speed. That's why 85D scored 270 miles rated range. Tesla is required to display this number. The same 270 mi number is also shown on the window sticker of your car. It would be better if their test method included only highway because that's where range matters. I think they should update their test method again. In the past their scores were even more optimistic when they did a 2 cycle test. I think they changed it in 2012. This is their more accurate version. In Europe the scores are even more messed up. If you go to Tesla UK website HERE you can see that 85D displays 330 miles NEDC rated range. This is very unrealistic but Tesla is required to use this number in their advertisement.

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  9. thegruf

    thegruf Member

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    Nothing unrealistic at all in Europe ;)
    just we are all used to VW figures over here. ie we treat all figures from car manufacturers as a load of complete bllx.
     
  10. Jbailey

    Jbailey Member

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    We have the same 85D car. To get it to follow the range estimate you basically have to use about 285 kw/mile or less. You were using over 400. When I need to get range estimated miles (avg 285kw/h or less), I set cruise to 64 and don't use heat (preheating the car while plugged in and using seat heating helps). I then watch the average kw/mile to make sure this is enough. If there are a lot of hills or rain(wet roads are rough on kw/mile), I may need to slow down more. Once I am close enough to a charger or my destination and know range will not be an issue I revert back to pre-electric mentality and crank up the heat and or speed.

    I live near Gainesville Florida and recently drove to Vicksburg MS. I left my house at 90%, drove fast with heater/ac on, supercharged in Tallahassee, Defuniac Springs for around 30-35 min each...No prob. However at Mobile I knew I had 222 miles to my final destination and no superchargers (and did not want to take the time to stop at a level 2). I charged to 264 miles, turned off the heat/AC, set cruise on 64, covered the 222 miles with 50-60 miles to spare and driving normal the last 50 miles. Until they get the software refined, I pretty much ignore the software advice.

    I used similar strategy to drive to myrtle beach. I now have 22,000 miles on my 85D and have taken many long trips. I have never once had any range anxiety or close calls. Driving an electric car on long trips requires a little knowledge, planning, monitoring and a little more time, but well worth it. As the superchargers and other chargers increase in number it will become a non-issue.

    If you remember and use the 285 kw/h number and the impact of speed, rain, heater use you will have all you need to eliminate range anxiety
     
  11. David_Cary

    David_Cary Member

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    There have been some incorrect posts here. Rated range is based on EPA and is not ideal conditions.

    I have a 70D and ideal conditions gets me close to 300 miles and my rated is 240. But it bears repeating, you will not get rated range at 32 degrees. You will not get rated range at 70 mph. If you are doing both, you will be 30% off rated range - which sounds about what you were.

    Cold air is more dense and adds to aerodynamic losses significantly. The effect on the battery after supercharging (which heated the battery fully) is actually pretty small. The dense air makes the speed penalty much worse. The difference between 60 and 70 mph is much greater at 32 degrees vs 70 degrees.

    You still have new tires - that hurts range. Most people don't check tire pressures often enough in the winter so they are low and that hurts range. So bump up your tires a bit.

    Seat heater uses next to nothing (typically 50-100 w vs up to 6 kw for air heating). So next time, bump the seats to 3 and turn the air down more.

    Rated range is EPA and does not change with ambient temperature or driving style. If you hear all the complaints from the Leaf's GOM (guess o meter), you will realize that there is no easy solution to range estimating. Choice is good and we have that on the energy meter. An EV tripplanner algorithm combined with nav destination and ambient temp would be great. This combined with actual measurements as you drive could be great. I suspect we will get it someday. But for now - experience limits anxiety greatly. Slowing down works miracles. And getting to back roads at 45 mph even better than slowing to 60. So once you have experience, you can drive at 70 with only 5 buffer miles knowing that you could jump to a back road and have 50 buffer miles.
     
  12. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    The energy trip graph is one of the best tools in the car because it takes speed limits and hills into account. It doesn't take cold weather or wind into account though. For an 85 170-180 miles is about right when it's below freezing. this can be mitigated somewhat by preheating the car, ending the charge just before driving, keeping the tire pressures up, and driving slower. In general, the best strategy is to start a trip using slower speeds and then speed up towards the end if there is a lot of energy left.
     
  13. Jim MacInnes

    Jim MacInnes Member

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    #13 Jim MacInnes, Jan 2, 2016
    Last edited: Jan 2, 2016
    As others have recommended and based on my own experience, a successful strategy is to start out at slower speeds at the beginning of your trip and until your Tesla trip planner graph settles in. After that you can adjust your speed upward or downward to along the way to maintain the desired battery SOC at the end of your trip. Speed makes a huge difference on battery consumption. Even a few miles per hour one way or another can make a difference and it is easy to follow on the graph when you are using up your charge faster than planned. For example, I once had 35 miles of SOC showing yet 33 miles to my destination. I dropped my speed down to 45 mph, and ended up with 10 miles of charge remaining upon reaching my destination. It was pretty amazing to watch the predicted range amount increase as I approached my destination at 45 mph. Here are some range vs speed curves from Tesla https://www.teslamotors.com/blog/driving-range-model-s-family
     
  14. ROCDOC

    ROCDOC Member

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    Agree that this is real world range for an 85. My experience is very similar. There are many threads on here and elsewhere that advise you on how to drive in cold weather. Count on 30 - 35% less range, maybe more in very cold weather. It's really a very different car in the winter.
     
  15. Adm

    Adm Active Member

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    Another factor to consider is wind speed and direction. Head wind at 20MPH or 20 MPH tail wind makes for a serious difference in range. At 70 MPH that adds up to 50% more air resistance between the extremes. Add this to the temperature effect and it explains a significant part of your problems.
     
  16. RedSoxFan18

    RedSoxFan18 Member

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    Took possession of my 85D on Wednesday - I live 150 miles form the service center. It was my first read drive in the car and I'll admit to driving in a spirited manner on the way home, just could not help myself I was grinning the entire time. I had planned on stopping at the Seabrook NH SuperCharger just try it out. Boy was I grateful for the SC as I went through quite a bit of charge. Forecast is for -2 F on Monday AM commute, it will be interesting to see how much charge I use.
     
  17. ToddRLockwood

    ToddRLockwood Active Member

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    You did not indicate whether you started your trip with a cold battery. If the battery is cold when you start off, the battery heater will use roughly the same amount of energy as the drive motors do for the first half-hour of your trip. If you add the cabin heater load, you can understand why the range is greatly affected on shorter trips like this one.

    If you preheat the battery while the car is still plugged in, it will use energy from the mains to power the battery heater. I believe the only way to activate preheating is from the Tesla smartphone app. While outside the car, open the phone app and select the Climate tab. Then touch the TURN ON button. Set the temperature well above your normal setting—I suggest 80+ degrees. Depending on how cold your battery is, this will take 20 to 30 minutes. Once the battery is warm, it tends to stay warm due to its high mass. Getting the interior good and warm also helps too, by causing the HVAC fan to run at a slower speed. Make sure to keep that fan speed in Auto mode.

    I also recommend using the Trip Chart within the Energy app. When using the navigation system, the Trip Chart will give you realtime information about your energy use. If the percentage predicted at your destination is consistently shrinking, simply slow down a bit. Slowing from 70 to 65 will even make a difference.

    Last winter I drove my P85 from Burlington, VT to Boston, MA at -10F, driving at 74 mph without any problem. I made one 30-minute Supercharger stop along the way.
     
  18. dsm363

    dsm363 Roadster + Sig Model S

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    Glad you made it. Agree with everyone to slow down when range becomes an issue especially at start of trip. It also sounds like you took off from the supercharger early at 200miles rated range with what would have been a good buffer under normal weather conditions. If not in a rush and at a Supercharger makes sense to get a much bigger buffer when cold out.
     
  19. ecarfan

    ecarfan Well-Known Member

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    Good post Jerry, I agree with all of it (including parts I'm not quoting above) but want to add that the energy graph also does not take headwinds, rain, and snow (basically, "weather") into account, and they can dramatically effect range.
    To the OP: I think you have seen from all the good posts on this page how to use the energy graph more realistically. I just want to add one comment, you said "the car knows the temperature" and wondered why that was not taken into account. Yes the outside temp is displayed but that does not mean it is factored into the energy graph predictions.
    The energy graph is a great tool once you understand its current limitations. I find it very accurate in moderate temperatures with no headwinds, rain, or snow if you go the speed limit or a bit below that. If you go much slower or faster than the speed limit it will adjust its energy prediction during the trip. When you saw your predicted range dropping that is because it was not taking the cold temperature into account, and possibly other factors. So then you just slow down for awhile and watch the graph to see if you have slowed enough.
    I prefer to charge to the point where the energy graph shows I will arrive with 20% left, that gives me a buffer, though in more severe weather conditions one should leave more of a buffer.
    In the future Tesla will surely make the software smarter and include weather factors into the energy graph prediction algorithm.
     
  20. Vigile

    Vigile Member

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    Thanks for all the feedback and comments on this. I understand the general consensus is that cold weather and speed dramatically lower range estimates, which makes sense.

    Couple of things though.

    1. Someone said that "Tesla has to use the EPA/etc rated range estimate in the car" and I disagree there. It has to display that on the car sticker and advertising, but once you own the car I'm sure that's not the case. Tesla can and should strive to make it as accurate as possible based on surrounding information once you are actually driving and depending on the MS.

    2. As ecarfan mentioned above, clearly the car is not taking temp into consideration, but I have to wonder...WHY??!? The car has is starting its 5th year of production and many many people have been driving these cars in low temperatures. I see no way that Tesla is not stock full of statistics on how the car and batteries perform at a WIDE range of conditions... Is it time we start demanding more of them in this regard?

    3. Also, in regards to speed - slower is better, totally understand why. But 70 MPH in this part of the country is SLOOOOWWWWW. I guess in San Jose where Tesla is based traffic is so bad that no one ever drives over 40 MPH (heh) but some highways near me have limits of 80 MPH and getting accurate range estimates while at least following hte flow of traffic would be nice.

    4. The battery was very warm at the start of the trip - had been diving 40+ miles already and the heat was on and was only at the SC for about 25 minutes.

    In the end, I'm not asking Tesla and the MS to magically get more battery capacity or to overcome headwinds and temperatures by black magic, I simply think that my first experience here shows that the company doesn't put enough effort into providing accurate information the driver in all conditions. If I had run out of juice somewhere before home, it could be a danger. I travel with my 6-mo old daughter, etc.

    I'm still a fan here, just trying to put together some constructive criticism. :)
     

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