Heiefocken Posted January 6, 2019 Share Posted January 6, 2019 When towing my caravan with my Model X I approx. use about 420 Wh/km when running at a speed of 80 km/h. I never get a speed of 110, so I'm wondering, what Data I should put into the boxes Reference Consumption and Reference speed. My caravan is weighing about 1.800 kg. Thanks for any suggestions. Heie form Berlin Link to comment Share on other sites More sharing options...
BarryH Posted January 6, 2019 Share Posted January 6, 2019 (edited) Hi Heie, You can translate the curve in the following blogpost: from 80km/hr -> 110 km/hr: +38% 80km/hr = 22,22 m/s -> 15-16 kW, while 110km/hr = 30m/s -> 25 kW => 16kWh/80 = 200Wh/km versus 25kWh/110 = 230Wh/km IF you assume weight and drag (~air resistance) change equally by addingthe caravan, you can add 15% (230/200) to the 420 Wh/km Only: 420/200 = + 110% while weight is + 1800 / 2600(?) = +70%. So Drag must be a lot more than +110%, 150%? so: 420Wh/km at 80km/hr -> +15-50%?? -> 480-630 Wh/km at 110km/hr ? Maybe you can plan a trip you already made? I Edited January 6, 2019 by BarryH Link to comment Share on other sites More sharing options...
Heiefocken Posted January 7, 2019 Author Share Posted January 7, 2019 Thanks for your answer BarryH, that are goot hints. Wha I learned from Physics ist, that drag s more important at higher speeds. And my 110 - consumption would much mire be drag nfluenced than the measured 80 is. Therefore it would not be be ideal to measure a trip with 110, because this would lead to over-estimation. I just did one trip yet for about 40 km, where my estimations are from, so I just have this one weak reference. The next reallife date will be my holidaytrips, that I´m just trying to plan. I think I need, maybe a bit more Information about how abrp works, would be helpful. How can I tell him the caravan weight ? is this in additional weight ? or des this not matter, if i have a correct estimation for a 110-speed (mabe drag corrected, as mentioned beforre ?) I hoped, that it would be the case, that I could type in an proven consupton rate at a proven velocity (80 km/h = 72 % of 110 km/h) and would enter these two numbers in Reference Consumption and Reference speed, but I think this is not the concept of Reference speed yet. It looks more like a "are you an aggressive rider or not "- feature as giving an offset or addition in reference to the allowed maximum speed on the track ? Any suggestions welcome. Heie Link to comment Share on other sites More sharing options...
Jason-ABRP Posted January 8, 2019 Share Posted January 8, 2019 You are absolutely correct that drag is the largest part of the equation. Consumption due to drag scales by the square of velocity, so a very rough approximation would be to use a square scale to convert your consumption to the reference consumption speed. This works out to: Cons ~= k*v2 Where k is a constant (depending on your car). In your case, Cons = 420 Wh/km, and v = 80km/h. We can treat this like the ideal gas law, since k will not change: ConsA/vA2 = ConsB/vB2 ConsB = ConsA*vB2/vA2 ConsB= 420Wh/km*(110km/h)2 /(80km/h)2= 794 Wh/km Now, granted, that's not likely to be a perfect result, as the actual curve isn't quite a square, but it should be pretty close in that region. Close enough to give a good result I bet, would be very interested to find out how close it is to reality! Link to comment Share on other sites More sharing options...
Heiefocken Posted January 8, 2019 Author Share Posted January 8, 2019 Hi Jason, mmh, its in pribciple that simple, but the Formula would be more complex because we also have to take care of the mass part. And the formula works with m/s, what lets the square ratio differ a bit. What I wanted to know, was, how abrp takes it ? I don't think it does not care about the mass part, because it calculates hills ups and downs very carefully... Best wishes Heie Link to comment Share on other sites More sharing options...
Jason-ABRP Posted January 9, 2019 Share Posted January 9, 2019 Actually, ABRP does care about the mass part, but in a different input field. Expand "Show More Settings" and input the trailer mass in "Extra Weight". This will include the mass in the elevation calculations separately. I still need to include the extra weight in the rolling resistance in the planner, but it is on my to-do list. In the end, the mass parameter in the Power equation scales linearly with speed, when working out the math it will be a much smaller portion of the consumption at high speeds than low, especially given how unaerodynamic the trailer is likely to be. The best way to do it, though, taking into account all the parameters in the equation is to run ABRP in the car's browser (or in a browser on your phone), log in with your Tesla credentials and follow a plan in the car. The data from tesla will calibrate our plan, and after a few miles of driving at constant speed you'll get an "estimated ref consumption" item on the driving display. Assuming you've been driving pretty consistently, the calibration should be very accurate, and will give you a properly converted reference consumption at 110km/h (based on all aspects of the power curve, not just drag). Link to comment Share on other sites More sharing options...
Heiefocken Posted January 9, 2019 Author Share Posted January 9, 2019 Hi jason, thanks a lot for this detailed answer. I very much appreciate your help. I'll check ist out and hope that I don't get lost on my trip to oskarshamn next summer. But If I put the extra weight into the separate field, shouldn't I better reduce my measured consumoption by the extramass-portion of the formula and then do the squaring extrapolation at this point where I don' t have measurement yet ? Best wishes. Heie Link to comment Share on other sites More sharing options...
Jason-ABRP Posted January 9, 2019 Share Posted January 9, 2019 I would definitely do both, include extra mass in the planning, and use the squared extrapolation from your 80km/h consumption data point. Link to comment Share on other sites More sharing options...
