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Roof/Ski Rack Range Impact

Discussion in 'Model S: Battery & Charging' started by golfski, Nov 12, 2014.

  1. golfski

    golfski Member

    Joined:
    Apr 17, 2014
    Messages:
    178
    Location:
    Seattle, WA
    I recently installed the Whispbar rack on my car and did some range impact testing in various configurations. I have not seen many actual numbers shared on this topic and the range impact when hauling skis, bikes, kayaks, cargo haulers, etc., so figured I would share what I have observed so far.

    I ran the same 12.4 mile loop in 34 degree weather in a few different situations back-to-back to get as close of a comparison as possible. I was surprised that carrying skis on the rack didn't impact the Wh/mi as much as I thought it would, but it certainly had an impact. I plan on taking my Model S on day trips for skiing as well as transporting to longer vacations and think my S60 will do just fine hauling myself and my skis in the cold weather.

    Evtripper.com says the 12.4 mile trip uses about 349 Wh/mi and it was extremely windy last night when I tested this, so I know there was impact there, even on the unloaded numbers.

    Distance: 12.4 miles
    34 Degrees F.
    No Whispbar / No Rack: 375 Wh/mi
    Whispbar Rack Only: 395 Wh/mi
    Whispbar Rack + Yakima FatCat 6 Ski Rack + 1 pair of powder skis: 412 Wh/mi.


    I'm curious what others have observed in terms of impact on range when hauling various things on the roof.
     
  2. Jeroen1961

    Jeroen1961 Member

    Joined:
    Jun 25, 2014
    Messages:
    61
    Location:
    Aalsmeer, Nederland
    Thanks for your post and the interesting Wh/mi figures. It's good to see that the Whispbar Rack + ski rack + skis only add around 10% to the total power consumption.

    What was the speed of the car during your test? Highway speed (55 or 65 mph) or slower local roads only?
     
  3. rsanchez

    rsanchez Member

    Joined:
    Dec 29, 2013
    Messages:
    59
    Location:
    Arizona
    I have the Whispbar with the clamp snowboard/ski mount (can't recall the actual name), very little impact if any at all. I usually carry 4 snowboards and drive 75 on the interstate. Does yours generate a lot of wind noise?
     
  4. dflye

    dflye S Sig Perf 414, VIN 814

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    Oct 7, 2011
    Messages:
    569
    Location:
    Raleigh, NC
    #4 dflye, Dec 4, 2014
    Last edited: Dec 5, 2014
    We loaded two mountain bikes on the Whispbar rack and took a very long road trip from Raleigh NC to St Louis and back via the indirect route of superchargers that connects from the SE to MidWest via Great Lakes states (about 1300 miles each way), so pretty much all freeway driving.

    Based upon the notes from the charging log we kept, looks like we averaged about 450 Wh/mi outbound (with many legs at around 500), and about 415 Wh/mi on the return (with only a few legs hitting the 500 mark)

    Part of the difference may have been that we had a tighter schedule on the outbound trip, so were cruising at a higher speed most of that time, usually at or above the posted limit by around 10.

    After about 55K miles over 2 years, averaging 350 Wh/mi; so the jump to 450 is definitely significant enough to require more route planning and charge monitoring. Having just the roof rack without any load adds a bunch of wind noise, but didn't seem to add more than a few percent to the power consumption rate.
     
  5. golfski

    golfski Member

    Joined:
    Apr 17, 2014
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    178
    Location:
    Seattle, WA
    I was driving highway speeds, but at the speed limit. I would normally drive at about 1.1x the speed limit which equates to about the same impact of having the whispbar rack and driving at speed limit. With two pairs of skis I have found it to be about the same impact of driving 1.25x the speed limit when estimating in EvTripper.

    I have definitely noticed an impact on range, but not as much as I would have thought. Certainly the cold weather impacts the range much more with limited regen and battery warming. When carrying a loaded rack in the cold weather (skiing) I will be sure to time the charging so everything is nice and warmed up. I do get wind noise with just the rack, but I have gotten used to it now. Much more noise with skis on there as well. I am looking forward to taking the rack off and perceiving a near silent driving experience after getting used to the wind noise.
     

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