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What am I doing wrong?

Discussion in 'Model S' started by ILLCOMM, Mar 29, 2018.

  1. Derek Kessler

    Derek Kessler Active Member

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    While I agree that truck tires fail at a higher rate than personal automobile tires, it's also still a very low failure rate per mile driven. It's not like they're dropping treads left and right from every passing truck. There's always an increased risk with drafting, even at a reasonable distance, but there's also an increased risk in simply driving.
     
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  2. FlyinLow

    FlyinLow Enjoy the journey

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    When drafting off of a larger vehicle, sometimes you can find a utility van or large vehicle smaller than a semi.

    When drafting at 65 mph and above I set AP1 to follow at TACC setting 5 and see a decent efficiency increase with some margin of safety. I could draft for a longer period of time and use setting 7 for the same benefit, as long as the truck stays on the road.

    I enjoy the challenge of maximizing my range while minimizing the time I spend on a trip, including charging as much as possible at SuCs between 15 and 50%, or only as much as is needed to make it to the next charge stop and repeat. Two hours in a car seat is enough, then a 20 min break feels good. My family appreciates that drive to break ratio, so does the dog if I have her with me.

    As many have commented in other threads, turning off the HVAC, lights and turning off the MCU screen are unnecessary. If those thoughts cross your mind slow down 5 mph and you'll have much more an effect.

    Oh, and, remember to enjoy your amazing all electric car! Sometimes we get so wrapped up in "mileage" we forget to have fun. BMW and Mercedes drivers rarely, if ever, obsess over their MPG. Just sayin'.
     
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  3. Derek Kessler

    Derek Kessler Active Member

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    I agree on all points but HVAC — when it is cold the cabin heater is a massive power draw. For comparison's sake, just two weeks ago when it was 40° F, I drove my S 75D (250 miles range) 100 miles into the country and used 51% of my battery with no opportunity to charge. On the way back, not wanting to cut it that close, I dropped from 5mph over the speed limit to 5mph under (net -10mph), and saw a modest improvement in my forecasted final charge, but not enough for a comfortable margin with no DC chargers nearby. Realizing that the sun was shining and proving enough solar heating, I switched off the AC entirely for the last 80 miles. Range improved by another 10%, giving me enough of a margin to not be white-knuckling it in at 45mph on the highway.

    It's an anecdotal tale, but it speaks to the fact: cabin heating draws a LOT of power.

    In the summer, when you'd be switching off the AC instead of the heat, you won't see a substantial improvement. When it's cold is another story.
     
  4. BigCity

    BigCity Member

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    Yeah, guess I should have clarified, I usually set back from a truck or box truck or the like by 5 car lengths and that still provides enough gain and space to be more than comfortable. In my short 40 years on this earth I've never even witnessed a tire coming apart on a big rig, obviously it happens as you see reminants on the road ways. 5 car lengths isn't out of the norm especially if the road ways are congested as you would be well within that length if the traffic was heavy.

    Honestly, I'm way more worried about a truck or other vehicle cutting me off, a pot hole in the road, or other debris more than a truck tire instantaneously coming apart in front of me not allowing enough time to brake or avoid it lol.
     
  5. ytwytw

    ytwytw Member

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    Put heat on and lose more ranges as well
     
  6. ILLCOMM

    ILLCOMM Member

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    Thanks all for your thoughts so far. Help me understand this....

    Last night I charged my car to 90% which the app reported as 228 miles.

    IMG_1820.jpg

    I then drove a bunch today, with the following stats, achieving 299 Wh/mi which is basically 300 Wh/mi or the consumption at which the car is rated:

    IMG_1818.jpg

    My IC says I have the following remaining range (95mi):

    IMG_1819.jpg

    The math doesn't work out.

    I had 228mi when I started and have 95 left, that should mean I drove 133mi as my range was 299 Wh/mi. Yet, I only covered 116.3mi. Where did the phantom 17 miles go?

    What gives!? This is very frustrating.
     
  7. BerTX

    BerTX Supporting Member

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    That 300 Wh/mi is just something that works out about right most of the time. Don't try to use it to do calculations.
    [​IMG]
     
  8. Derek Kessler

    Derek Kessler Active Member

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    Rated efficiency in a 75D is more like 285 Wh/mile. I can't gauge your driving style, but the 21" wheels you've got on there do hurt efficiency.
     
  9. ILLCOMM

    ILLCOMM Member

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    300 Wh/mi * 259 miles = 77,700 Wh / 1,000 = 77.7kWh, so I guess you're right.

    Math seems to be ~289 Wh/mi (to arrive at 75kWh) and 259mi range. Ugh. The car's UI puts a line at 300 Wh/mi that, if you achieve, will not equate to the range the car is telling you it has.

    I guess we can kill this thread, but given what I am seeing I would be shocked if the distribution of achieved efficiency was centered at 289. The TeslaFi folks probably have the data to show this. And seems like advertised rating should be reflective of fleet norm.
     
  10. whitex

    whitex Well-Known Member

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    I've been driving Model S'es since 2013 and here is what I learned about the energy "math" and range:
    1. Estimated Range is approximate, not exact. It is actually possible to gain range while parked when temperature changes.
    2. The Wh required to reach rated range is not 300Wh/mile - that's just a round number people here use. The actual is (battery capacity - brick buffer)/rated max range. In your case it's about 274Wh/mile. (75KWh - 4KWh) / 259 miles.
    3. You can only get rated range in mild temperatures and keeping it under 55
    4. The used energy doesn't account for everything, some things that it doesn't account for:
    • energy lost while parked (including any cabin preheat, whether manual from app or automatic) - will show up in your Wh/mile but not in energy consumed. When cold and/or windy, that can be a significant amount. Cold wind blowing under the battery cools it off fast, requiring heater to kick in.
    • HVAC and some other energy drains - can be as much as 1,500W according to some calculations I did a long time ago (hooked up a gopro taking pictures of the energy monitor, etc). Here is the graph I ended up with:
    Lost_Energy.png
    5. How you drive matters just as much if not more than temperatures, but you can control that vs. you can't control the temperatures (or weather, heavy rain will use more energy too). Using regen well can help. Speed also matters a lot more than people think. Below is an example of how "estimated" compares to some smooth, fun interstate highway driving (not a lot of braking) - temperature was not too bad (50's, 60's IIRC). I knew from earlier on that trip that my driving preferences burn more than estimated energy, so I supercharged more than suggested, then adjusted the speed somewhat watching the estimated destination % to make sure I don't strand myself. This one was probably the lowest I've ever drained my car (3%). Note that for my everyday driving I get way better energy usage, just showing you this to show you what speed can do to your energy (as it would to you fuel consumption in an ICE car).
    Mitchell2Murdo.png
     
    • Informative x 1
  11. Evoforce

    Evoforce Active Member

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    Just keep in mind... If you were using an ICE vehicle, you would also be having all of these variables. Unless you are racing at the track, and the race depends on pitting, you would not be worried about every last drop of fuel in your car.

    You still would want to know that the gas stations would be within your reasonable range but would generally not worry about gauging your fuel down to zero. I however, have attempted to drive on fumes trying to interpret gas gauges and I have personally failed at that a few times. ;)

    A Tesla does a good job at factoring range and speed while you are traveling and plot through Superchargers. I find comfort in carrying every adapter on the planet for 240 volt while also including chademo for quick charging. In my travels across the States, 98% of the time, Supercharging and Destination Charging made it a piece of cake. Quick chargers and 240 volt outlets filled in the rare gaps.
     
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  12. ucmndd

    ucmndd Well-Known Member

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    Advertised rating is what the EPA says it is. Just like in gasoline cars. I have a 2015 Toyota Highlander that gets “27mpg” on the highway according to the EPA, but I’ve never gotten within spitting distance of that.

    Seriously, do yourself a favor. Set your preferences to percentage instead of miles remaining. Then never look back and enjoy your newfound peace and sanity.
     
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