MYLR first road trip - 900 miles in California - notes and findings

[LeaveMeAlone]

Having just completed my first long trip in the MYLR (~900 miles roundtrip from LA <--> Bay Area), here are my findings and notes going forward - probably obvious to most but maybe helpful to fellow new Tesla owners shocked by real world range and prospective buyers:

Estimated range is BS unless you're slow and intentional. As others have elegantly pointed out (@DayTrippin, @nadalset), incremental required power increases exponentially at higher speeds, and it's not clear that the estimated range takes into account weather conditions (temp, winds), your driving patterns, your imminent plans to crank the AC, charge two cell phones, bump some Emancipator, hit major traffic, etc. I think it does factor in speed limit and elevation, but if you're in the left lane, climbing and enjoying that electric thrust (!!!), be prepared to see those numbers tank. Others have posted great rules of thumb and have even suggested using percentages instead of mileage estimates to reduce anxiety. Conservatively, I think 40-50% of estimated mileage on the highway makes sense if you're winging it, and psychologically, if you can get in the habit of stopping every 1-2 hours for shorter charges (and are near superchargers) then you'll be ok. But, that said...

Trust the nav system. Yes, this slightly contradicts the first point, but I've learned to trust the nav system (after some initial resistance) with estimated supercharger stops. You just have to be intentional about your speed and how you're driving. Tesla will even implicitly "reward" good driving by decreasing the amount of time required to charge at the next stop and bumping up your ETA - real world evidence that going faster != earlier arrival. Meanwhile...

Study and "gameify" range. On the second leg of the trip, I started using TezLab to track efficiency of each "trip", paying close attention to acceleration, speed limit, temperature, elevation, etc., and trying to stay above 100% on local city trips and above 80% on highway trips. It became a game for me and the friend I was traveling with quickly grew tired of hearing about it. Winning the game meant driving delicately on local roads and within 10 mph of the speed limit with limited passing on the highway - all best practices anyway, but somehow felt ironic after dropping $50k for a sub-5 second 0 to 60. Speaking of best practices...

Don't stop looking in your blind spots. The Tesla saved me from side swiping someone on the 101 by auto changing lanes. It also contributed to the near-accident to begin with. Tesla Vision isn't perfect and sometimes it doesn't pick up shorter, smaller cars, and when cars are actually in your blind spot, it shows them as slightly farther behind you, which is dangerous if you're changing lanes quickly and not actively looking (i.e., turning your head). This near-accident would have been very costly, but thankfully...

You'll save money on gas, even at Superchargers. We stopped a few times on each leg, costing around $15-20 a pop. All in, we averaged approx. $0.10/mile using Superchargers only. With current gas prices in California, that's 30-40% savings over an ICE vehicle. However, don't kid yourself. You're probably closer to breakeven in other parts of the country, and the real economic value of EV vs. ICE is charging at home and longer-term maintenance. We'll see. Overall...

This is an amazing, beautiful piece of technology, but probably not a road trip car. Yes, it's doable and yes, there are plenty of people posting videos of cross-country roadtrips that are making out fine. But unless you have the patience of Joseph and are ok stopping frequently, you're going to have issues with longer trips in this car (though I will say many Superchargers are located in great little shopping centers). If Tesla achieved its EPA rating all the time, this would be a moot point. That said, it is still a fantastic daily driver and perfect for shorter trips. It's also genuinely a pleasure and joy to drive. Hopefully 500mi real-world range isn't too far off. And finally, most importantly...

Avoid the Bakersfield CA Supercharger at night. Some real sketchy stuff going on in that IHOP and in the Jack in the Box parking lot.

 

[whisperingshad]

Avoid the Bakersfield CA Supercharger at night. Some real sketchy stuff going on in that IHOP and in the Jack in the Box parking lot.

I did a trip to Bakersfield and went out of the way to charge there, albeit in the morning and was fine lol
I did Vegas(7+ hours both ways) and really easy and comfortable drive.

 

[DayTrippin]

@LeaveMeAlone - I think you hit a lot of salient points dead on. Sort of like Cliff's notes of Tesla Travel. Very nicely put.

I have totally given up on maximizing range. I am an adrenalin junkie first and foremost and I can't see that changing anytime soon. So my engineering side of the brain says conserve energy and my right foot says 'eff it. So the little devil smashing my right foot down is the one to blame. I spent too many years racing motorcycles and cars and I really try to be good on the street but I really need a 12 step program.

This will sound contradictory to some of my posts in other threads, BUT, I would be less inclined to go fast if the MY wasn't so smooth and quick on a roll. Yes, that is one of the things I love about it and gripe that I wish it was a bit quicker off the line. The nice pull at 60, 70, 80, 90, (all speeds are in km/h as I don't want to get in trouble with any traffic authorities on public roads) just keeps me coming back for me.

The fact that I can charge at home, for cheap, and do it all over again, are playing to the addictive aspects of the car I already can't resist. I've resigned myself that on trips we'll be charging every 150 miles. The only estimated range display I trust is the one on the energy tab. I took eldest child for a ride and showed them the impact of range when you accelerate. Their comment was "dad, I thought it was supposed to go 300 miles on a charge, why is it just showing 80?" So I am good with stopping every 2 hours to do a shorter charge interval and keep moving. After doing all the math, and our real world usage patterns, the MS we have on order is making a lot more sense. Elon is full of BS saying 400 miles range is enough. Maybe if it was 400 miles like I and a lot of other people drive, not 400 miles according the EPA rating.

As for Bakersfield, doesn't surprise me it was sketchy. Generally a pretty dangerous town. My son got a flat on his motorcycle there and was sweating it out until I could get there from LA.

 

[boulder.dude]

Great report. I noticed that the Tesla web site, in-car nav, and A Better Trip Planner provided wildly different estimated SC charging times all for the same trip. Which is the most accurate? (I’ve had my MY for 3 weeks but have only ever charged at home.)

 

[MY-Y]

...

Estimated range is BS unless you're slow and intentional. As others have elegantly pointed out (@DayTrippin, @nadalset), incremental required power increases exponentially at higher speeds...

At highway speeds, the main force to overcome is wind resistance. That goes up with the square of speed. Since you are getting there in less time, the energy per mile goes up roughly linearly with speed - not a square, and not exponential.

In other words, driving 30% faster than 60 MPH (78 MPH) will take 1.3*1.3=1.69 times more power. You'll be using that power for 60/78=77% of the time you'd need to go 60. The end result of this 30% increase in speed is 1.69*77%= 1.301. At highway speeds where wind is the dominant factor, 30% faster equates to 30% more battery used.

It's also worth noting how much a headwind impacts power usage. If you go 60 MPH in an 18 MPH headwind, you'll need roughly the same 69% more power. There is no benefit of getting there faster, so your Wh/mi will go up by 69%.

 

[LeaveMeAlone]

At highway speeds, the main force to overcome is wind resistance. That goes up with the square of speed. Since you are getting there in less time, the energy per mile goes up roughly linearly with speed - not a square, and not exponential.

In other words, driving 30% faster than 60 MPH (78 MPH) will take 1.3*1.3=1.69 times more power. You'll be using that power for 60/78=77% of the time you'd need to go 60. The end result of this 30% increase in speed is 1.69*77%= 1.301. At highway speeds where wind is the dominant factor, 30% faster equates to 30% more battery used.

It's also worth noting how much a headwind impacts power usage. If you go 60 MPH in an 18 MPH headwind, you'll need roughly the same 69% more power. There is no benefit of getting there faster, so your Wh/mi will go up by 69%.

Well said, but I think you need a cube of extra power, not square. The square is incremental drag, so you'd need 1.3^3 (2.2)x power to overcome 1.3^2 (1.7)x drag, resulting in 69% more battery for 30% increase. I think this then scales as a square:

Speed​	Increase​	Incr. Drag​	Incr. Power​	Time Ratio​	Net Power/Time​	Scale vs. Speed​
60​	1.00x​	1.00x​	1.00x​	100%​	1.00x​	1.00x​
70​	1.17x​	1.36x​	1.59x​	86%​	1.36x​	1.17x​
78​	1.30x​	1.69x​	2.20x​	77%​	1.69x​	1.30x​
80​	1.33x​	1.78x​	2.37x​	75%​	1.78x​	1.33x​
90​	1.50x​	2.25x​	3.38x​	67%​	2.25x​	1.50x​
100​	1.67x​	2.78x​	4.63x​	60%​	2.78x​	1.67x​

Someone jump in if I messed any of this up...

 

[LeaveMeAlone]

Great report. I noticed that the Tesla web site, in-car nav, and A Better Trip Planner provided wildly different estimated SC charging times all for the same trip. Which is the most accurate? (I’ve had my MY for 3 weeks but have only ever charged at home.)

I've only used the former two, but have found that if you obey the speed limit, the in-car nav is pretty reliable. It's also the closest to your battery and can make real-time adjustments for weather, driving, etc. I think the route planner on Tesla's website is a sales tool and overly optimistic.

 

[iustin]

Well said, but I think you need a cube of extra power, not square. The square is incremental drag, so you'd need 1.3^3 (2.2)x power to overcome 1.3^2 (1.7)x drag,

Sorry to ask, but why do you need to add another factor (going to cube)? Power is only needed to compensate for increased drag, so it should be still squared, where does the cube come from?

 

[RedWhite19]

I think you mean avoid all of Bakersfield.

 

[LeaveMeAlone]

Sorry to ask, but why do you need to add another factor (going to cube)? Power is only needed to compensate for increased drag, so it should be still squared, where does the cube come from?

I'm departing my lane on this one, so to speak, but as I understand it:

- At incremental velocity v, you hit v times as many particles at v times the speed - hence v^2 incremental drag
- To overcome v^2 incremental drag, you must do v^2 work in 1/v the amount of time for any set distance since you're going v times faster
- So in general, you need v^2 / (1/v) incremental power to overcome incremental drag in a set distance at incremental speed v, or v^3

There's a much more eloquent explanation that goes way over my head here:

Aerodynamic Drag – The Physics Hypertextbook

Drag is the friction from fluids like air and water. A runner feels the force of aerodynamic drag. A swimmer feels the force of hydrodynamic drag.

physics.info

Again, feel free to jump in if I've misspoken.

 

[MY-Y]

Fortunately, my post is correct. If it was a cube, we'd all have to drive a lot slower. Take a look at some test data that shows this for other cars. Tested: Speed vs fuel economy if you take 55/75*(MPG@55), you'll roughly get the MPG@75.

 

[LeaveMeAlone]

Fortunately, my post is correct. If it was a cube, we'd all have to drive a lot slower. Take a look at some test data that shows this for other cars. Tested: Speed vs fuel economy if you take 55/75*(MPG@55), you'll roughly get the MPG@75.

Interesting - counterintuitive given the physics. Thanks for sharing. That said, these are pretty narrow bands - 55mph to 75mph - suspect you'd see a more meaningful decrease at higher speeds. Anecdotally, I am definitely not losing range linearly above 80mph. Once I have some more data hopefully I will be able to plot Wh/mile and est. range at various speeds.

Here's another take on MPG in ICE cars at higher speeds, albeit rooted in theory and not test data, but is exponential:

What Will an 85 mph Speed Limit do to Your Mileage

I already looked at one consequence of increasing the speed limit from 70 mph to 85 mph. There is obviously another question to answer: what will this do to your car’s fuel consumption? Cars are complicated things. You put gasoline in, and the engine essentially converts this to mechanical...

www.wired.com

 

[Johnny Vector]

Fortunately, my post is correct. If it was a cube, we'd all have to drive a lot slower. Take a look at some test data that shows this for other cars. Tested: Speed vs fuel economy if you take 55/75*(MPG@55), you'll roughly get the MPG@75.

LeaveMeAlone is correct about the physics of air drag.

The reason your table doesn't show it is almost certainly because at 55 mph the rolling resistance is still dominant in most of those cars*. Note that the Insight (the highest efficiency car they tested) has a significantly faster than linear reduction in efficiency. Rolling resistance (by which I include friction in the engine and transmission) is very high in ICE vehicles. As you can demonstrate by downshifting to slow down. All that deceleration you feel in a lower gear is due to friction, and that friction doesn't go away when you're pushing the accelerator.

For an EV, rolling resistance is dominated by the tires (that's why EV's generally run with higher tire pressure than ICEs), and is thus much lower than for an ICE. You would need to redo that test with EVs if you want to directly measure how efficiency scales with speed.


*Given the poor understanding of efficiency demonstrated by the text in the Consumer Reports article, it's also possible that they just plain messed up the data. This test would be rejected by reviewers for any actual physics publication.

 

[iustin]

I'm departing my lane on this one, so to speak, but as I understand it:

- At incremental velocity v, you hit v times as many particles at v times the speed - hence v^2 incremental drag
- To overcome v^2 incremental drag, you must do v^2 work in 1/v the amount of time for any set distance since you're going v times faster
- So in general, you need v^2 / (1/v) incremental power to overcome incremental drag in a set distance at incremental speed v, or v^3

Ah, I was completely missing this 1/v factor. I can't say I understand it intuitively (as it seems we account multiple times for v), but I see at least where it comes from.

There's a much more eloquent explanation that goes way over my head here:

Aerodynamic Drag – The Physics Hypertextbook

Drag is the friction from fluids like air and water. A runner feels the force of aerodynamic drag. A swimmer feels the force of hydrodynamic drag.

physics.info

Again, feel free to jump in if I've misspoken.

No, thanks for the time. Also, my google searches were all going nowhere (not native speaker), until you mentioned drag - and Wikipedia has a nice article that agrees with (and expands on) the above link, regarding power.

I always thought it's just speed squared, which made the discussion about energy loses at 50mph-70mph-80mph a bit too high; but if it is cubed, it makes much more sense why the losses grow so fast. Thank you!

 

[whisperingshad]

I did a trip today at 70 instead of 80 on freeway and 50 on the street parts(with chill mode on for streets). Was able to get my #'s under my normal 290 to average about 190-200. Light AC use, about 20 miles 50/50 or so.

 

[LeaveMeAlone]

Ah, I was completely missing this 1/v factor. I can't say I understand it intuitively (as it seems we account multiple times for v), but I see at least where it comes from.



No, thanks for the time. Also, my google searches were all going nowhere (not native speaker), until you mentioned drag - and Wikipedia has a nice article that agrees with (and expands on) the above link, regarding power.

I always thought it's just speed squared, which made the discussion about energy loses at 50mph-70mph-80mph a bit too high; but if it is cubed, it makes much more sense why the losses grow so fast. Thank you!

Sure. That article is good. I think the intuition for 1/v is as follows: if you increase speed 3x, you need to "move through" 3^2 = 9x drag at a speed that's 3x faster than your original speed, or in 1/3rd of the original time it would have taken you. So it would not be enough to simply overcome 9x drag as that would not net you an increase in speed - you'd need an extra factor: 9x / (1/3) = 27x power to overcome incremental drag.

However, part of what @MY-Y was saying is that when you net against a set distance (vs. gross time), you end up losing the extra cube factor, since for a given distance you'll only need to exert extra force for a fraction of the amount of original time it would have taken you. On a net basis for set distances, this squares (i.e., at 3x 60mph = 180mph, you'll only need to go this fast for 1/3rd of the amount of time for any given distance), but for gross amounts of time (i.e., traveling at 180mph vs. 60mph for the same amount of time) I believe it cubes.

In practice it's clear that efficiency degradation may not be perfectly exponential or linear, especially in ICE cars, as @Johnny Vector and @MY-Y have both pointed out. There's a good article on Stack Exchange that dives deeper into some of the other dynamics at play here:

Why doesn't car fuel/energy consumption scale like the cube of the velocity?

The power required to overcome drag is relative to speed cubed. When I'm driving $100 km/h$ my car consumes $~10 $litres/$100km$. At $200 km/h$ the consumption should be $2^3 × 10$ litres/$100km = ...

physics.stackexchange.com

All that said, it's a safe assumption for us in the EV world that we lose a lot of range at high speeds.

 

[MY-Y]

There is much complexity in this topic. I appreciate how polite everyone has been as we noodle through this. Wind drag isn't precisely described easily. There are linear and square components. The efficiency of our motors isn't constant with speed. The road resistance isn't described precisely with a simple equation either.

For highway speeds (55-80 MPH), the Wh/mi tracks fairly linearly. Teslike.com has lots of data points on this as well that should be of interest. I wish they had tables for the newer model years.

 

[kishkaru]

I just drove from LA to Bay Area and back last week. I cruised at 85mph on I-5, the normal speed as any ICE car. My average consumption was 357 Wh/mi, or 2.8 mi/kWh efficiency. If I slowed down to 80mph, I got 333 Wh/mi or 3 mi/kWh. The entire trip was super stress-free. Plenty of supercharging options along I-5 between LA and Bay Area, so never got range anxiety.

For any Tesla, take the EPA range number and remove 1/3. That's the more realistic range figure at higher freeway speeds.
Model Y: 326 miles EPA * 66% = 210 miles.

Now remove 20% from the top (supercharge to 80%) and 10% from the bottom (safety buffer) and you get 210 * 70% = ~150 mi of usable freeway range.
I stop to supercharge every 150 real-world miles, ending at roughly 10% at the supercharger. Works for me every time!

 

[Rocky_H]

I stop to supercharge every 150 real-world miles, ending at roughly 10% at the supercharger. Works for me every time!

Yeah, this sounds totally reasonable and normal to me, and especially with the longer range and faster charging of the Model 3 versus my old Model S. So I am dumfounded at these kinds of dismissive perceptions by people like the OP:

This is an amazing, beautiful piece of technology, but probably not a road trip car.

Why not a road trip car? I do multi-thousand mile trips with mine, and it seems fine.

 

[LeaveMeAlone]

Yeah, this sounds totally reasonable and normal to me, and especially with the longer range and faster charging of the Model 3 versus my old Model S. So I am dumfounded at these kinds of dismissive perceptions by people like the OP:

Why not a road trip car? I do multi-thousand mile trips with mine, and it seems fine.

Right - the 150 miles jives with my original quote of 40-50% of estimated mileage: 326*.45= ~150mi. At 80mph, you're stopping every ~2 hours for 20+ mins to recharge (provided you've stayed on the route you're given). Like I said, amazing piece of technology, but less flexibility and more time/patience required = not an ideal road trip car.