Real world range touring 19 inch wheels
- Thread starter ISOI
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With or without aero covers? I have the same car, but it has never had the aero covers on.
Our last trip to visit family I attempted to get better efficiency on the 250 mile drive back home. Kept it in smooth mode and set the cruise at 72mph instead of 77mph. Managed 4.1 miles per kilowatt on that drive. AC was running as it was in the 90's outside.
The data I have seen RE: highway driving (my own road trips and review sites such as OoS) are consistent. @70mph, you should be getting ~4 m/kWh. Going to 75mph will drop that to ~3.4 m/kWh.
Separately, most owners are reporting "lifetime" efficiency ~3.6-3.8 m/kWh with a mixture of city and highway. Needless to say, elevation and temperature changes can modulate the resultant efficiencies.
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How … did it reset itself?!
My lifetime average is 3.7 after almost 4000 miles, so that sounds about right. Mostly highway for those miles.
I normally set the cruise at 77mph and occasionally do bursts of 80+ to quickly pass and that still gets me around 3.6 or 3.7 according to the trip meter. That's with the AC on. I'm in the Midwest and it's fairly flat here though and the weather hasn't been extreme yet so far in my almost four months of ownership.
I played the math on this, using my Pure AWD specs, and assuming I run from an 80% SOC to a 15% SOC. Over a 1,500 mile trip, the time you eliminate charging is just a half hour less than the time you save going faster.
It began showing 0 kw-hrs used with 9000 miles. Posted here seems to be a not uncommon fault. With out energy I reset miles to zero.
That is with Aero covers. Highway speeds are around 75 (indicated). Driven in Swift mode with lowest regen setting selected.
My wife and I just completed a 1,000+ mile road trip, mostly on highways at 75 mph, getting about 3.7-3.9 mi/kWh in 90+degree heat with the air conditioning running pretty much all the time. Air Touring, 19" wheels. The lifetime (20,000+ mi) reading indicated is 3.7 mi/kWh
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Wild. Mine hasn’t done that. Was there any precursor? Battery replaced or anything?
I presume you are saying:
> by driving faster, you cover the distance in less time. But, you have to charge more often, at least 1X more charging @75mph than 70mph.
> thus, assumption the charging stop times are "instantaneous" vis-a-vis, no cue time, chargers immediately available, etc., etc., then driving faster will only be about 30min slower. Did I get you correctly?
No. Driving faster is about 30 minutes faster. At 70 vs. 75 MPH, I assumed that the trip would take 1.43 hours more, but would require 1 less stop (1.1 actually). For the stop, I figured 35 minutes to charge, plus 15 minutes to get to/from the charging station. (On trips, we have found the charging stations to be very conveniently located, and seldom busy, but that certainly can vary.) So, going slower adds 1.43 hours to the drive time, but saves 0.92 hours of charging time, for about .51 hours more total travel time.
Between 70mph vs 75mph on a 1,500 trip, what you said might be true. That said, you know that the decrease in "efficiency" does not scale linearly with the speed, right? Rather, it scales (to a first-order) with the square of the speed. Thus, if you extend this argument beyond this narrow range (70mph vs 75mph), you will find a much bigger differences between the slower speed and the higher speeds.
I drive the Phoenix to Marin County route often, 780 miles, mostly along I-10, I-210, I-5. The posted speed limit is 75mph in AZ and 70mph in CA. I drive 75mph all the way. It is a balance between economy, time, and attention required to safely navigate the trip. Now, if I increase the speed from 75mph to 85mph, I save the travel-time LINEARLY, but my efficiency (hence frequency of charging) will increase by the SQUARE OF THE SPEED (to a first-order). It is a different ballgame!!
Thus, I think 75mph is a good speed for my route.
When I drive the Rivian R1S, I alter my routes slightly. Mostly, I go from Phoenix to Quartzite, charge at the RAN station there, then onto Barstow (again, RAN), and then again at Firebaugh (RAN) before I get to my place in Marin. I prefer the Rivian RAN stations/chargers. They are new, 300 kW, (until recently) only for Rivians, off the beaten path, less crowded, and 36 cents/kWh.
Yes, I understand that. I just used the data you specified, which was that you got 4.0 miles/kWh at 70 MPH and 3.4 miles/kWh at 75 MPH. Here's my math. I imagine that bumping the higher speed to 80 MPH would be enough to tip the scales.
| 100% kWh: | 92 | |||||||
| @ 80% kWh: | 73.6 | |||||||
| @ 15% kWh: | 13.8 | |||||||
| 15% to 80% kWh: | 59.8 | Charging Time | Total Trip | |||||
| Charges | Driving Time | at 50 min/charge | Time | |||||
| Distance | Speed | Miles/kWh | kWh Used | kWh/Charge | Needed | Hours | Hours | Hours |
| 1500 | 75 | 3.4 | 441 | 59.8 | 7.38 | 20.00 | 6.15 | 26.1 |
| 1500 | 70 | 4.0 | 375 | 59.8 | 6.27 | 21.43 | 5.23 | 26.7 |
| 75 vs. 70 | 5 | -0.6 | 66 | 59.8 | 1.11 | -1.43 | 0.92 | -0.5 |
I haven't looked through your every entry, but I trust your math. It looks reasonable. That said, my long road trip methodology is mostly based on I-10/I-210,/I-5. Truth is, this is a cake-walk for EVs as there are many charging stations en route, and even more if you care to go slightly off route. As such, I was never paranoid about charging or getting stranded. I regularly start my first leg with 100% SoC and run to just below 10% SoC before I charge to minimize the number of charges.
If you are on a different route and if you traverse cold weather and large elevation changes, "your mileage might be different"!. I am very comfortable with 2 charges on my 780 miles drive from Phoenix to Marin in my AGT. My Rivian only has the Large Pak (135kW) and the R1S's efficiency is lower so I have to charge 3X. However, the R1S consistently deliver at or above the EPG efficiency even at 75mph whilst the Lucid AGT is about 20% below @75mph. All of that have to be taken into consideration. You just have to know your car and know what you can get away with.
Would you please walk me through the exponential math between 75, 80 and 85... using the 3.4 miles/kWh you referenced at 75 as the starting point?
Here's my 'guess', if I understood you correctly. I ended up using 4.0 @ 70 as the starting point...
| 70 | 4900 | 4.0 |
| 75 | 5625 | 3.5 |
| 80 | 6400 | 3.1 |
| 85 | 7225 | 2.7 |
Well, it has been a long time ago since I studied fluid dynamics. I don't consider myself an expert in the mathematics of drag vs speed.
That said, the generally accepted (highly) simplified "rule-of-thumb" is:
> the Drag Force on the car, which the motors have to overcome to propel the car forward, is proportional to the SQUARE of the speed the car travels.
> hence, the faster you travel, the (drag) force hold you back is proportional to the square of the speed you are attempting to reach. Thus, the additional energy you have to expend to reach a higher speed is proportional to the ratio of the square of the speed you are at and the speed you want to achieve. For example, if you are travelling at 70mph and you want to go to 75mph, the ADDITIONAL ENERGY required is proportional to 75**2/70**2 or ~ 1.148X or ~15% more energy. Now, if you want to go from 70mph to 85mph, it will be 85**2/70**2 or ~1.475X or about 48% more energy. It gets worse and worse as speed increases.
> if you think that's bad, these "rules-of-thumb" are nothing but first-order estimations. It ignores secondary effects of disturbed air flows at higher speed, turbulance, etc. which can further degrade efficiencies.
The numbers I quoted are from my personal driving experience and logs on my 2022 AGT and my 2023 R1S AND from sanity checking against ACTUAL 70mph/75mph tests done on ACTUAL cars (not just the Lucid, but also MB, BMW, Tesla. Rivian, etc.) by Out--f-Spec and Car and Driver (and others).
I DON NOT profess to know all the answers nor have I accounted for all the nuances that affect efficiencies and speed.
As you might have seen from other posts, my main focus and my beef is to get some realistic figures based on realistic driving conditions as opposed to just defaulting to the EPA benchmarks which are done under "ideal" lab conditions and at significantly lower speed and combines city and highway driving PLUS "Adjustment Factors" submitted by the car manufacturers.
If Grouch Marx were here, he would ask, "Do you believe in real data or your lying eyes?"
Given that, the numbers I just sent you look about right.
