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The Rules of Model S Road Tripping

Discussion in 'Model S' started by Doug_G, Apr 22, 2013.

  1. electronhauler

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    Great post!
    I would add on the subject of drafting that a 3 second following distance should be observed. 1 second is less than most people assess and react (studies show it's closer to 1.5 seconds). Travelling less than 1 second behind another vehicle virtually eliminates any chance of dealing with an unexpected situation. (ADoNA: The Clear Leader in U.S. Driver Safety and Training - a Research Victory)

    On the range expectations, I have found that rain reduces range by about 15 to 20%. On a fossil fuel vehicle it increases fuel consumption by only 3 to 5%. I think this is due to the amount of water that gets moved by the tires as they rotate. Obviously this is more of a problem at highway speeds where each tire is displacing several gallons of water per second.
     
  2. Doug_G

    Doug_G Lead Moderator

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    On the subject of drafting, it is safer to do this on a big heavy truck. They can’t brake hard. Also a good use case for cruise control set to 1. It can react faster than you can.

    Heavy rain can be a lot worse than 20%, if the car is constantly plowing through standing water.
     
  3. sauce

    sauce :P

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    @Doug_G, I'd be careful with stating heavy trucks can't brake hard. Here in Canada they can have 4 and even 5 axles on their trailers and despite higher load tolerances than in the US, this allows for formidable stopping power EVEN if fully loaded. Better stability as well.

    I remember a situation a dozen years ago, having to stand on the brakes side by side with a 4-axle-trailer heavyweight in my '95 Accord and I couldn't outbrake the truck though it was fully loaded with gravel (that was scary as hell), so I would tend to believe a 1-second gap remains unsafe.

    That being said, I can say I wouldn't do it because of rock projections much before being worried about the tight gap. :D
     
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  4. vseno

    vseno Member

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    Wow, great. Owned Model S for 2 years now and learned a few tips here. Thank you.
     
    • Informative x 1
  5. Brea_3

    Brea_3 Member

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    Great tips, thanks!
     
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  6. gpetti

    gpetti Supporting Member

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    Hi Doug,
    I've read this a few times over the years - still very useful and I see you've updated it. Just one minor point I would suggest when driving AWD performance models. The range mode for these vehicles is MUCH more useful than for others. In Range mode, these cars favour the front (more efficient) motor and use something JB called "torque sleep" when at highway speeds. The help for Range mode implies this but I've actually verified it when in ludicrous plus mode which shows motor usage stats. In non range mode it definitely uses the rear motor more, though it may still torque sleep ultimately. I haven't done any scientific analysis on how much difference this makes but it is clearly more important than on cars that don't have AWD and presumably on cars that have the same motor front and rear.
     
    • Informative x 1
  7. Doug_G

    Doug_G Lead Moderator

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    Would be interesting to do an A/B comparison. I've found that even without using Range mode my newer 100D has much more range than my old P85, by a lot more than 100/85! More like double that difference.
     
  8. croman

    croman Active Member

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    I believe AWD cars always torque sleep regardless of Range Mode setting based on certain factors. Range mode only turns off DRL and adjusts HVAC consumption for cabin.

    That's why Range Mode seems mostly useless, I think it is. You might get 1-2% more range (which could be significant, but its still 1-2%). Aero wheels are far more effective though. DRL consumes next to nil energy.
     
  9. richlvt

    richlvt New Member

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    Well I just did my first road trip with my 2018 Model S 75D. Vermont to Richmond, VA then to Blacksburg, VA, back to Richmond and home to Vermont. Left Vermont it was 15 degrees. Realized would not make it to Newburgh Supercharger so stopped in Albany, NY. Cold weather really took energy I learned. Was a great road trip and can relate to a lot said in this blog, plus learned much from your advice. In Blacksburg found two level 2 chargers not working but finally found a Holiday Inn that was "public" with even a Tesla Plug. So again, learned to "charge" so can make it back to the Lexington Supercharger. All in all, was very nervous about the trip to start. As going along, charging, my tension lessened. Trip back on the busiest travel day of the year went very well. Superchargers were available. Stopped probably more then I should have but was as ease. Nice that you can see how many chargers are open at a location. Never had to wait. Tesla autopilot made the trip so much more relaxing, love the ride, the quiet, the sound system. Just a fantastic automobile.
     
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  10. sumitkgarg

    sumitkgarg Member

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    Question: To get the most from the regeneration going downhill, it is better to go at 35 m/hr or 55 m/hr?
     
  11. Doug_G

    Doug_G Lead Moderator

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    That’s not a simple question.

    Generally speaking, going slower is better because the aerodynamic losses are lower. That’s true at all times, not just on hills. Once you’re above about 20 mph, the faster you go the worse the energy consumption. It’s a big effect; slowing down just 5 mph can have a very significant effect on your range.

    Regen is way better than hitting the brakes, but it is worse than coasting. The drive train has a certain efficiency - there are always losses and that includes during regen. If you could go down a hill without using regen at all, while avoiding going excessively fast of course, that would be most efficient. So it’s probably a good idea to crest the hill at a low speed, and let the car speed up down the hill, and then use regen as needed to prevent the car from going too fast.

    To summarize... for best range:

    1. Drive slower
    2. Coast when you can
    3. Use regen when you need to
    4. Brake as little as possible
     
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  12. sumitkgarg

    sumitkgarg Member

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    So if you can avoid breaking, low regeneration setting is better than standard regeneration? That’s a great piece of info that I didn’t know.

    I was running really low leaving Dealth Valley last week trying to make it to Lone Pine SC. I tried going downhill at approx 35 m/hr but the estimated charge at destination kept going down. It was estimated at less than 5% at one point. It was a bit of a stressful situation with kids in the car, in the middle of nowhere at night and 0 cell phone coverage.
     
  13. ThosEM

    ThosEM Space Weatherman

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    How can regen be worse than coasting? The choice is between accelerating to a higher speed down a hill (which as you point out is always uses more energy), and harvesting energy with regen to keep your speed from increasing.

    You might ask, how can I use more energy when I'm coasting and no power is being used? Well, not harvesting available energy into the battery is the same as using that energy. Using it to accelerate the car increases drag and reduces the energy available for regen. The slower you go down a hill, the greater the regeneration power will be during the descent. Try it out: while going down a long steady hill on regen, decrease the setpoint speed a couple of notches. That will increase the regen power and vice versa.

    So I would revise your summary as follows:
    For best range:
    1. Drive at a slower, constant speed up and down grades (using cruise control or your foot does not matter)
    2. Regen will activate automatically whenever it can, and will be stronger at slower speed
    3. Think ahead so you can slow sufficiently with regen instead than using the brakes
     
  14. Doug_G

    Doug_G Lead Moderator

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    Like I said it is complicated.

    If you are going down a steep hill, and the car would speed up excessively, then it's clear you're going to lose a lot of additional energy to aerodynamic drag (not to mention going unsafe speed and/or getting a ticket), and harvesting energy via regen is the best solution.

    If the hill is just going down just enough to keep the car going a constant speed, despite the aerodynamic drag, then obviously you're going to use zero power traveling the length of the hill. The drive train efficiency is not a factor.

    In the real world, my advice would be to not worry about this too much. If you're concerned about range slow down 5 mph and turn on the cruise control. Oh, and if it's cold turn down the cabin heat and crank up the seat heaters.
     
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  15. vickh

    vickh Active Member

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    how about AC effect on range?
     
  16. Tam

    Tam Well-Known Member

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    Heater eats a lot more energy then AC does.

    I tested 2012 Model S AC consumption while parking, set at 72F while the ambient is 93F with all windows down and it used 15 rated miles per hour.

    I did the same with windows up and it used 5 rated miles per hour.
     
  17. Electroman

    Electroman Supporting Member

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    Thank you... in the name of Science.
     
  18. Hugh-SG

    Hugh-SG Member

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    Seven years after you wrote this, this still relevant and it also applies to the Model-X, Model-3 and Model-Y.

    Very nicely put together. Well done.

    Cheers! Hugh-SG
     
  19. Doug_G

    Doug_G Lead Moderator

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    Thanks! Goes to show... the basic physics/engineering hasn’t really changed. Tesla did an amazing job on their first cars, and have only improved on them since.
     
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  20. Pollux

    Pollux Supporting Member

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    These rules were my bible when I got my first S P85+ back in Aug '13. I was grateful for them then and I'm still grateful for them now. I made my first road trip from Boston to DC in November '13, plotting carefully in advance, drove 55 or even 50 mph in the right-hand lane on I-95, turned off the heat in favor of the seat warmers, and with Doug_G's guidance I made it to the Supercharger at Darien, CT and still had 30 miles of buffer left in the battery. (My wife in the passenger seat: why can't we turn on the heat? Why are we driving 50 mph and holding up traffic? How much money did we pay for this car?!)

    My use of these rules has changed, though. Today, if I'm operating within my home city or along the SuperCharger grid, and with my M3P @ 305 mi range or my '16 S P100D @ 315 mi range I rarely focus on these rules. I leave for trips without thinking anything through. I just go. I pick Superchargers based on schedule convenience and amenities. Rarely do I think about range. I can't remember the last time I slowed down to achieve a goal; the last time I deliberately charged to 100%; the last time I turned off the heat and relied on the seat warmers. I don't think I've used Range Mode since... 2015? 2014? I leave home with whatever State of Charge the car happens to have; it has been four years, at least, since I worried about charging the car in advance for a trip. Including in the winter. The only time I check my route in advance is when I know I'm going to an area where I can't be certain of the availability of Superchargers.

    No, the basic engineering and physics haven't changed a bit. The basic rules that @Doug_G has outlined haven't changed either and are as applicable today as they were then. What *has* changed is the continual improvements Tesla has made to the vehicle AND continued build-out of the SC network AND improvements to the SC network (e.g., charging speed). As long as I'm operating in my known travel universe, I am free to forget worrying about @Doug_G's rules. And when I leave that universe, I do a little advance planning keeping @Doug_G's rules in mind.

    Thanks, @Doug_G!

    Alan

    P.S. I do look forward to a Cybertruck with 500+ miles of range, or the next S (already over 400!) I get. I get it that most people only travel 30 miles per day or less, but psychologically most people are unwilling to travel with ⅛ of a tank of gas even if range is adequate. Most people are more relaxed when the tank is full, or nearly full, or at least over half full. I'm in that camp.
     
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