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I'm Doing Something Wrong

Discussion in 'Model S' started by tstafford, Jan 10, 2016.

  1. tstafford

    tstafford Member

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    A few weeks ago I posted this thread and got some helpful replies (Road Trip Advice - Inexperienced Driver) so some folks may recognize my questions as clarifications from that thread.

    Anyway - the situation is simple - I live in Nashville and my wife wants to drive the Tesla to South Carolina. Most of this is fairly straightforward but there is a long stretch between Nashville and the Knoxville SpC. My title of the post is because the car is essentially telling me that it can't make it. (I'm sure people drive between Nashville and Knoxville all the time so I must be screwing something up.)

    I figured since I am worried about my wife having issues that I would try to do a bit of the drive myself and see what the Nav and Energy App trip tab told me. So here are the conditions and results:
    • Ambient temp = 31 degrees. Weather = snowing lightly (so probably reasonable approximations for her drive in late January)
    • Car charged to 100%
    • Preheated for about 30 mins using Visible Tesla
    • I FORGOT TO SET RANGE MODE (maybe this is huge, I have no experience so I don't know)
    • Distance from my garage to the Knoxville SpC (all highway) is 171 miles per Google Maps/EVTrip Planner
    • I set out driving what I consider normally - if not conservatively - HVAC off until things fogged up then set to 68, AP engaged/TACC set at 75 mph (5 mph over the posted limit)

    Results:
    • Nav would not route me to Knoxville SpC rather it tried to find (endless spinning circle) SpC's in-between and there are none. I guess this means the car thought it couldn't make it. Note: this was before I left my garage
    • I started driving to see if it would get comfortable routing me to Knoxville but it never did
    • I set the Nav to a city (Crossville) that is on the highway on the way to the SpC. It is 117 miles from my house. The trip tab showed that I would arrive with 37% battery capacity
    • I drove on this route for 34.9 miles in 33 minutes, used 13.5 kWh and averaged 388 Wh/mi and then gave up and went home to post this
    • The Projected Range at the end of my test (on the 30-mile avg per the Energy App) was 167 miles at 81% battery capacity
    • At the end of my test I was 122 miles from the Knoxville SpC per the Nav (this is odd because 35+122 doesn't equal 171)
    • I believe the Nav is wrong and I was actually 136 miles from the SpC - this lines up to the mile markers and also totals out to 171 as it should

    So I'm confused!

    A) Assuming the car is right and going 117 miles to Crossville would use 63% of the battery that calculates out to a range of around 186 miles at full charge - so I can get to Knoxville but only damn near empty
    B) If the 30-mile average Projected Range is correct I would have about 31 miles to spare - so I can get to Knoxville with a little room to spare

    Net/net: I have never done a road trip in the car so I don't know how to process all this information. Neither my wife nor I is going to drive 60 mph in a 70 zone just to drive the Tesla so maybe we are this issue.

    Questions:
    • Would Range Mode have solved my problem?
    • If the ambient temp was say 50-55 degrees would that have solved my problem?
    • Did I misinterpret the data and not have a problem at all?

    Another concern is that if this trip is on the razor edge (if even possible) starting out at 100%, preheated, etc. the drive BACK is going to be double extra super dicey and/or require a very long SpC stop in Knoxville.

    Help!
     

    Attached Files:

  2. brec

    brec Member

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    With evtripplanner.com, specifying...

    P85D with 19" wheels;
    origin of 1748 21st Ave N Nashville TN (a J1772 charging station 169 miles from destination);
    destination of the Knoxville SpC;
    1.1 speed (77 mph on the I40 portion);
    70F cabin temp.;
    32F external temp.;
    200 lb. payload

    yields...

    75.3 kWh -- which is about the total usable capacity of an 85kWh battery.

    With speed at 1.0, which is 70mph on the I40 portion, the result is 68.3 kWh. For me, that's not a sufficient safety buffer.

    I would not attempt that trip without a charge stop on the way.

    DISCLAIMER: I've never made a winter road trip using range mode; evtripplanner.com doesn't have a range mode calculation.

    P.S. Had I done your test drive, I would have looked at (reported) the end-of-trip SoC (percent of battery capacity) shown by the Trip tab of the Energy app.
     
  3. jerry33

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

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    1. Range mode isn't all that important on a long trip. Before leaving, have the charge end about the time you are going to leave. Charge with range mode OFF (that's important).

    2. Only route to the next charging point, not the whole trip.

    3. 75 mph at 31 F is a range killer. 65 mph would make a large difference in energy used. At 75 mph you're mostly pushing air.

    4. Make sure the tires are inflated. On a trip, put a bit extra in as there will typically be more weight in the car than usual.

    5. Don't use the projected range except as a comparison to rated range. For trips use the trip graph. It will tell you how you're doing compared to the estimate, and you can adjust accordingly.

    6. Start the trip slower, and speed up towards the end if you have enough energy.

    7. The difference in time between traveling at 65 mph and 75 mph is minimal compared to the additional energy used.
     
  4. Daniel Meola

    Daniel Meola Member

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    Check out plugshare. Superchargers aren't the only way to get a charge on your trip :)
     
  5. ZBB

    ZBB Emperor

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    How many rated miles did EV Trip Planner say the trip would take?

    You need to learn to trust EV Trip Planner. I've done over 8k miles in road trips in our Tesla (which is an S60) -- and all but ~1500 miles were before Tesla added the range estimate features. One of those trips was 4500 miles from AZ to BC and back.

    I recommend setting EV TP at a speed setting of 1.1 (which means 10% above the average speed of traffic on the route -- and is effectively forces it to be a bit more conservative), with approx payload for humans and luggage, and setting the temp to close to what you expect the average temp to be during the drive. I then drive the speed limit to 5 over -- and have found EV TP estimates to be very good -- usually arriving at my destination within a couple miles remaining range of the estimate (almost always on the conservative side).

    The built-in trip planner in the car is not as accurate (which is surprising...). But I've been learning to trust it also -- but with buffer. I've found that if I target a 20% range buffer (i.e. The planner graph shows you'd reach your duration with 20% battery), I generally arrive arrive with anywhere from 10-14% (and I generally drive 5 over the posted limit).

    But I find that the built in trip planner can be nerve racking at times. Driving from El Centro to San Diego Superchargers last July (when it was 114 degrees in El Centro...), the destination % estimate kept dropping from 20% and bottomed out at about 8% while driving the speed limit. But that was on an uphill section -- and once we hit the downgrade, it started going back up a bit. We arrived with about 11% remaining. And that section took a couple less miles that EV Trip Planner estimated.
     
  6. kort677

    kort677 Active Member

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    the time needed for l2 charging far outweighs the "inconvenience" of sticking to SC. chademo charging is too hit or miss to be depending on using those chargers. I've done many long distance trips relying on the SC network and overnight l2 charging. I only had an issue when I parked overnight without being plugged in when it was below 15f, I lost almost 30 miles of range and had to "limp" to a 30 mile away supercharger. I think that the OP is afflicted with newbie range anxiety syndrome that can only be cured by some real world experience.
     
  7. Discoducky

    Discoducky Active Member

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    brec and jerry have provided great info and I'd 2nd it. If your nav just spins, hold down the scroll wheels on the steering wheel until the 17" resets, then try again.

    Also, there are several Level 2 chargers on the way if you are not trending comfortably https://na.chargepoint.com/

    They appear to be all at Cracker Barrel restaurants and are on Blink with an access fee of $3.60. Cookeville, Crossvile and Harriman

    I'd plug in the supercharger, start out slow and watch the trip graph. If you need to stop at CB then so be it.

    I've done several winter trips in the 60kWh where some stretches I didn't think I'd make and I did. And some that I thought would be easy and didn't have enough and had to stop. YMMV
     
  8. ZBB

    ZBB Emperor

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    I also recommend using Plugshare to find backup charging. If this leg really was tight on range, ~30-45 min at an L2 along the way isn't a bad backup plan.

    My first Supercharger visit was the Flagstaff Supercharger, which is only 129 miles from my house. But it's uphill the entire way -- about a 5000 foot net elevation gain. EV Trip Planner estimated that I needed 186 miles of range -- and the actual trip used 190 -- I drove the speed limit for all but the last 20 miles, where I drove 5-10 over since it was clear we had the range, and that last burst drove the variance to the estimate). I ran estimates from a couple RV Parks along. I-17 (there are no J1772 chargers on that stretch, and the Cordes Junction Supercharger was not even on a Tesla's "coming soon" map...), and used those estimates as decision points along the way. I had more RM remaining at each of those points than the estimates -- so kept going. We made it without having to backup charge...
     
  9. ggr

    ggr Roadster R80 537, SigS P85 29

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    What is this "trip graph" people keep referring to? I think I missed something.
     
  10. Discoducky

    Discoducky Active Member

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  11. brec

    brec Member

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    It's 25 minutes for a 200 mile leg. Time taken and energy used are not directly comparable, so their relative values are subjective. However, if the difference is getting there as opposed to being stranded, the time expenditure would definitely be worth it!
     
  12. tstafford

    tstafford Member

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    So it sounds like my insistence on trying to do this at 75 MPH was the culprit. I'll try the experiment again and do it at 65 MPH and see what results that yields.

    Also - thanks to everyone who took the time to respond. I know my post was long but I wasn't sure how else to provide all the info.
     
  13. mmccord

    mmccord Member

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    You said the nav kept trying to route to other (non-existant) scs and wouldn't give you a route. It sounds like 'trip planner' is enabled. Try disabling that and see if it gives you a proper route to the SC. The setting is in Settings > Apps > Nav.
     
  14. tstafford

    tstafford Member

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    Will do. I had no idea that was an option.
     
  15. jerry33

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

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    That's only 13% less than driving at 75--not significant, sales tax is higher than that in many places.
     
  16. S4WRXTTCS

    S4WRXTTCS Active Member

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    The only way I've ever gotten the nav to stop spinning is to turn off the range assurance/trip-planner.

    What happened to the OP is why the range assurance is so messed up. Had he used the trip part of the energy graph he would have seen exactly how much energy the trip would take, and would be able to use it to keep within a given buffer. Or know before hand whether he should bail on even attempting.
     
  17. theslimshadyist

    theslimshadyist NashVegas!

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    #17 theslimshadyist, Jan 10, 2016
    Last edited: Jan 10, 2016
    I'm curious as to why it would matter that range extender would need to be off when charging?
     
  18. SomeJoe7777

    SomeJoe7777 Marginally-Known Member

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    Both Cookville and Crossville have Chademo chargers available (2 in Cookville at Cracker Barrel, 1 in Crossville at Cracker Barrel). I think you could make it without charging at 68 MPH with range mode on, but the buffer would be pretty low when you got there (5-6 %). If the trip graph shows you're using more than expected, then I'd stop at one of the Chademos and pick up 20 minutes of charge (~ 40 miles).
     
  19. tstafford

    tstafford Member

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    This is probably the exact right call. I think the peace of mind is worth just popping for the adapter. I hadn't thought about that option - so thank you.
     
  20. David99

    David99 Active Member

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    No need to disable trip planner. Put in your destination, let the navigation do it's thing. If it adds charging stops, you can tap on trip and then tap on 'Remove all charging stops' and then tap resume. I found the trip planner to be very annoying. It will randomly reroute to chargers, or even tell you to go back to a Supercharger. It's not working that well. By manually removing all charging stops from the trip, you are good to go. Now look at the energy app and use the trip tab.
    I have done done a 200 mile trip in 4 degree cold and windy weather. I had to go slow (60-65) but I made it easily. The energy graph prediction works really well and you can adjust your speed to adjust your energy consumption and this way always be on the safe side. The cabin heater also uses some power of course. Just keep it at a low temp setting and you'll be fine.

    Edit: if there is a CHADeMO on the way, definitely plan a stop and charge there for 20 min or so. I would always plan an extra stop rather than going extra slow and barely making it. Both Superchargers and CHADeMO charge faster than you can drive. In other words, driving faster (thus using more energy) and adding a charging stop is still overall faster than going slow to make it.
     

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