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Is the "Rated Miles" count really dynamic?

Discussion in 'Model S: Battery & Charging' started by brantse, Dec 8, 2015.

  1. brantse

    brantse Member

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    There is often much discussion regarding the rated miles being affected by influences such as driving style, weather, terrain, etc. Isn't this really just a measure of available energy divided by some fixed wh/mile (ie. ~289). Perhaps that fixed value varies from vehicle to vehicle based on the battery size, "P" models, firmware, and possibly even wheel size, but beyond that does this value ever change. As far as the other part of the equation (the battery's available energy), I suppose this could be slightly affected by temperature or other factors.
     
  2. BertL

    BertL Active Member

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    Yes, IMHO Rated Range is some sort of an algorithm that estimates range, and it can sometimes vary without real explanation other than perhaps Tesla needs to refine the algorithm and how it's presented to reduce owner confusion -- at least on a 90D with 7.0 2.7.56 software level I have. Remaining Rated Range (likely because of rounding and inconsistencies in UI presentation) can also be off by 1 miles between what is shown on the 17" Energy Trip screen and the IC at the same moment in time. As I explained over in the 90D Range Thread a few weeks ago, I caught my Rated Range changing back and forth more than just a rounding difference, and wrote it all down:

    • 253 @ 4:30AM after overnight 90% charging was complete
    • 254 when stopped backing it out (15') for a wash @ 8:00AM
    • 253 again @ 9:10AM when I put it back in the garage
    • 253 @ ~11:30:00AM while parked, not charging, but plugged into my HPWC
    • 252 @ ~11:30:05AM (or sooner)
    • 254 @ ~11:30:10AM (or thereabouts) when it stayed that way for the rest of the day

    Check the 90D Thread for discussion about temperature and Rated Range correlation. There is some data there from 85 owners suggesting seasonal variation in Rated Range, but some of us 90D-owners in more moderate climates are not so sure that is as much of a contributor to our dropping number.
     
  3. AWDtsla

    AWDtsla Active Member

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    Yes but it's doing something stupid. I don't know who can achieve rated miles, but it's not me. 526 Wh/mile.
     
  4. brantse

    brantse Member

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    It certainly depends on lots of factors, but on a dry highway at about 72 MPH, I can definitely match rated miles pretty easily. Unless your quoted 526 wh/mile is just for a very short duration, or while doing repeated launches, you might want to check into some issue.

    - - - Updated - - -

    Couldn't it be possible for this waffling to happen just based on slight variations of cell/string/pack voltage? As every measurement has some inaccuracy and even slight system loads could affect the measured value, I could see this happening. Also, you note that you were plugged in at the time. I believe the car will start to charge at times that the climate control is enabled, so perhaps your car picked up a very brief charge.
     
  5. BertL

    BertL Active Member

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    Yes, it could and likely is -- although no one on these boards knows as an absolute what the algorithms are that Tesla uses. My point is, if the underlying measurements in the battery, temp, etc are changing, Tesla should even out some of the variation before presenting the information to reduce concern. IMHO, simple (almost "dummy proof") data presentation is very important in mass marketed products -- which even our MS is starting to become as it approaches 100,000 on the road. For a number of us with 90kWh batteries, we're seeing perhaps faster initial degradation of Rated Range (see other 90D Thread on all that), so some of us watch these numbers very closely and odd numbers give us even more concern, especially if they change before our eyes for no apparent reason.

    While I agree MS will pull charge sometimes when it's parked and plugged-in, I don't believe that was the situation here... There was a full 90% charge (which started at 12:00AM and completed sometime before I checked it at 4:30AM). From my experience, if I leave my MS sitting for 2-3 days and don't drive it, but leave it plugged into my HPWC, it does not begin it's own charge cycle to replace the vampire loss until it reaches a larger threshold of several miles (8+) under the set charging limit. It also does not come on, go off, in rapid succession within seconds or even minutes if I'm not doing something to the vehicle with climate control. It was also between 60-70 degrees F during all this time so there is no reason MS would have likely tried to keep the battery warm. To me, it's hard to say how or why the number varied up and down by 2 miles in less than 15 seconds -- it may be real, but if it is, I'll go back to the point that Tesla needs to normalize the result in what's displayed to the user -- Remaining "Rated Range" is after all, much like what ICE owners are used to when reading a gas gauge to determine how far they can still travel -- the gas gauge keeps going down but does not present the data to some infinitesimal decimal point in how much is remaining and even when going up/down hills in more modern vehicles, the gauge doesn't generally vary enough to make a driver worry -- it's all been normalized using physical devices and in the way the data is presented to make it more usable. IMHO, Tesla needs to do the same to instill driver confidence.
     

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