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286 wh/mi @ 65mph, is this reasonable?

Discussion in 'Model X: Battery & Charging' started by tlouden, Jun 25, 2017.

  1. tlouden

    tlouden Member

    Joined:
    Dec 29, 2016
    Messages:
    28
    Location:
    Highlands Ranch, CO
    I just ran a test to see what energy efficiency my Model X achieves at 65mph (to get more accurate estimates from abetterrouteplanner.com). I love the results, but they seem significantly different from what others have reported. Can someone with more experience weigh in on whether these results are reasonable? If not, where did I go wrong in the testing?

    I drove 11 miles at 65mph, 5.5 miles each way to minimize the impact of elevation changes.
    Round trip: 286 wh/mi.
    First leg: 394 wh/mi
    Second leg: 177 wh/mi
    Obviously, there is an elevation difference, thus the roundtrip measurement.

    Test conditions: 20" tires, TACC and Lane Assist on, 60F outside temp, music and AC on, light breeze, light traffic (car never slowed from 65) well paved and mostly straight highway. I measured once I was at 65mph and stopped the measurement before decelerating, this was to minimize the impact of starting and stopping a trip on such a short distance measurement.

    I am interested in the measurement for a cross country trip that will be entirely highway and happen this week, so I think the conditions are applicable.
     
  2. jerry33

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

    Joined:
    Mar 8, 2012
    Messages:
    13,291
    Location:
    Texas
    I suspect the results are low because most folks are closer to 300-350. 11 miles is just too short a distance to get a good number. However, I wouldn't sweat it because factors like wind, rain, and road construction will mess up any average that you happen to get.

    Here's what to do:

    Use the trip graph. When you set a destination, there will be an estimate based on speed limits and hills. I believe that now wind is also taken into consideration (at least it seemed to be on my trip last week). This is something new and not yet confirmed. Anyway, every so often look at the graph and see if you are doing better or worse than the estimate. If worse, just slow down a bit (or stop somewhere to pick up a few miles--slowing down will get you there faster though, unless there is a significant variance). After your first trip, you will likely look at it only once or not at all.

    Start slower, you can always speed up at the end if you have extra energy. Bear in mind that extra speed requires a lot more energy because you are pushing air and as speed increases, the additional energy used is not linear.

    It's not a crime to slow down a bit when going up hills. Racing up a hill is a big energy eater.
     
  3. tlouden

    tlouden Member

    Joined:
    Dec 29, 2016
    Messages:
    28
    Location:
    Highlands Ranch, CO
    Update:

    I drove 72 miles of highway at an average speed of 77.5mph and a max speed of 85mph. The energy usage for the trip was 342wh/mi and again this was a round-trip style with the start and end location being the same.

    For this trip, I used battery state and distance to calculate wh/mi instead of the trip meter, so it includes all energy usage rather than just motors. The temperature difference from outside to inside was 20F and the AC fan was at 3-4 the entire time. The trip meter was significantly lower at about 300wh/mi for the same stretch. Measurement errors could account for up to 20wh/mi.
     
  4. hill

    hill Member

    Joined:
    Apr 21, 2015
    Messages:
    798
    Location:
    Lake Forest, CA
    Consider temps AND speed
    Think it's just kidding?

    2017-03-04-09-45-46.png
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