Inefficient trip

[Austindude]

My wife and I often make a trip to McAllen TX from Austin TX in our LR RWD Model 3. I have 5.15 software, 18 inch tires, third party wheels and tire pressure is set to around 42 to 43 psi. Charge to between 95% to 100% at home, go about half way to Three Rivers TX supercharger, charge back to around 90 to 95% and easily make it to McAllen supercharger at the convention center. No sweat or range anxiety ever until this trip. Second half (which is a little more than half way) of the trip we usually drive 80 mph with the AC set to 74 degree. No big deal. But this time we had a strong headwind all the way from Three Rivers to McAllen and the efficiency dropped from what is normally 250 Wh/mile or less to about 365 Wh/mile. Wow, we went from 93% charged to 15% charged when we got to McAllen and in fact that only happened by reducing the speed to 75 mph (which was the speed limit) instead of 80 mph. Climate set to 76 degrees to reduce our energy load. This is the first time that I have had the car (about a year) that I actually was starting to get concerned that we might really need to slow down to make it. Overreacting for sure, but the navigation kept dropping our predicted battery arrival percentage all along the trip. I've never arrived with anything less than 25% previously. The point is that after taking this trip many times and feeling so confident I had to rethink things. Sure glad I wasn't in my old S 70 or in a MR or standard Model 3.

 

[S4WRXTTCS]

My wife and I often make a trip to McAllen TX from Austin TX in our LR RWD Model 3. I have 5.15 software, 18 inch tires, third party wheels and tire pressure is set to around 42 to 43 psi. Charge to between 95% to 100% at home, go about half way to Three Rivers TX supercharger, charge back to around 90 to 95% and easily make it to McAllen supercharger at the convention center. No sweat or range anxiety ever until this trip. Second half (which is a little more than half way) of the trip we usually drive 80 mph with the AC set to 74 degree. No big deal. But this time we had a strong headwind all the way from Three Rivers to McAllen and the efficiency dropped from what is normally 250 Wh/mile or less to about 365 Wh/mile. Wow, we went from 93% charged to 15% charged when we got to McAllen and in fact that only happened by reducing the speed to 75 mph (which was the speed limit) instead of 80 mph. Climate set to 76 degrees to reduce our energy load. This is the first time that I have had the car (about a year) that I actually was starting to get concerned that we might really need to slow down to make it. Overreacting for sure, but the navigation kept dropping our predicted battery arrival percentage all along the trip. I've never arrived with anything less than 25% previously. The point is that after taking this trip many times and feeling so confident I had to rethink things. Sure glad I wasn't in my old S 70 or in a MR or standard Model 3.

Even in my 70D I never had too much issue with wind.

Sure I've certainly encountered headwind, and that anxiety of "Oh, crap my efficiency is dropping like a rock". But, the fact that it tells me up to date info means I could always address it. Where I could slow down or pull behind a big rig. I didn't even need to draft it because even a fairly reasonable following distance worked fine.

The most anxious time was when I missed an exit to a Supercharger, and the next exit was 20+ miles away. So that added 40+ miles to the trip which was my buffer.

 

[Sputnik19]

I had my first road trip in the p3d+ this weekend from OC to Los Olivos past SAnta Barbara. Averaged 270kw/hr over 210 miles each way. 50-70 deg weather the whole way. Drove up and down steep hills, lots of highway driving, and some good old fashion spirited driving on the back roads of Santa Barbra. This beast is quite efficient and we ran the ac at 70 off and on NoA used about 30% of the time - LA traffic. Me and my wife couldn’t be happier. Wind and the noise it caused was our biggest issue. But who cares 270 kw/hr for my performance is just butter.

 

[Takeo]

This past February I took at 3,000 mile road trip in my Model 3; California to Oklahoma using I-40. It made me realize how much adverse driving conditions and a "heavy foot" affects range. The drive included cold weather (had to use the heater), significant elevation changes and I don't drive conservatively (teetered on auto-pilot's upper speed limit).

Based on the above, I had to ensure I had more than enough charge to make it to the my next targeted charging station, and "more than enough" depended on the conditions ahead. If really cold, going uphill and clear roads (i.e. could "keep the pedal floored"), I had to have at least 90 miles of charge over what the navigation indicated I needed.

There are/were several areas in AZ and NM with great distances between Tesla charging stations. I'm so glad I got the long range battery, but a few times I was still "sweating it".

I also realized it was a waste of time to always charge to 100% (I know, just during long road trips) If the next targeted charging station was 200 miles away and conditions were favorable, I only needed to charge up to around 240 miles. Charging anything over that was wasted time (until the next gen chargers are in the field?).

The trip proved to me, family and friends long trips in a Tesla is definitely doable; just have to be a bit more aware.

 

[nvx1977]

aerodynamic drag goes up expontentially as a function of speed. Driving 80mph is already getting pretty steep on the drag curve. Add in strong winds and your net speed is easily over 100mph.

 

[SageBrush]

aerodynamic drag goes up exponentially

Ughh.

b^x is an exponential function
Aero drag is a quadratic function of the form v^2

If we assume a 20 mph headwind, OP's description of driving 75 mph with a headwind instead of 80 mph without implies (95/80)^2 more aero drag, about 41% more drag.

 

[GlmnAlyAirCar]

Ughh.

b^x is an exponential function
Aero drag is a quadratic function of the form v^2

If we assume a 20 mph headwind, OP's description of driving 75 mph with a headwind instead of 80 mph without implies (95/80)^2 more aero drag, about 41% more drag.

Thank you for making that correction.

Seems like everything is exponential these days.

 

[TexasEV]

It’s not “inefficient”, it’s physics. You were driving fast against a strong headwind. An ICE would similarly use more energy.

 

[SageBrush]

It’s not “inefficient”, it’s physics. You were driving fast against a strong headwind. An ICE would similarly use more energy.

Yep.

OP's thread can be re titled to "driving the equivalent of ~ 95 mph uses a lot more energy!"

No kidding

 

[lolder]

The M3 energy use per mile is more like an aircraft and highly dependent on airspeed. There are several apps including a Tesla Waze that show winds. Range loss is 6 miles per thousand feet climbed. You only get about 4 miles back descending.

 

[Jbuntz]

On the March 23rd at 5pm the wind at Alice, TX was 20 gusting to 26. If that was similar then the car thinks it is going 100+mph.

 

[ewoodrick]

My wife and I often make a trip to McAllen TX from Austin TX in our LR RWD Model 3. I have 5.15 software, 18 inch tires, third party wheels and tire pressure is set to around 42 to 43 psi. Charge to between 95% to 100% at home, go about half way to Three Rivers TX supercharger, charge back to around 90 to 95% and easily make it to McAllen supercharger at the convention center. No sweat or range anxiety ever until this trip. Second half (which is a little more than half way) of the trip we usually drive 80 mph with the AC set to 74 degree. No big deal. But this time we had a strong headwind all the way from Three Rivers to McAllen and the efficiency dropped from what is normally 250 Wh/mile or less to about 365 Wh/mile. Wow, we went from 93% charged to 15% charged when we got to McAllen and in fact that only happened by reducing the speed to 75 mph (which was the speed limit) instead of 80 mph. Climate set to 76 degrees to reduce our energy load. This is the first time that I have had the car (about a year) that I actually was starting to get concerned that we might really need to slow down to make it. Overreacting for sure, but the navigation kept dropping our predicted battery arrival percentage all along the trip. I've never arrived with anything less than 25% previously. The point is that after taking this trip many times and feeling so confident I had to rethink things. Sure glad I wasn't in my old S 70 or in a MR or standard Model 3.

A 20 mph headwind is effectively the same as adding 20 mph to the speedometer. And drag increases exponentially, that's a heck of a drain on the battery.

You need to learn to be comfortable letting the battery go to 5%, take a drive and get then numbers low. Even 5% is a lot of miles. It's so much fun to watch it get down to only a few miles remaining. And it's a good thing for people to get used to.

 

[nvx1977]

Ughh.

b^x is an exponential function
Aero drag is a quadratic function of the form v^2

you dinged me once for getting my Wh/mi units wrong once I'm seeing a pattern here. You care about the details.

Ok, quadratic function. Increases as a function of the square is no joke either. For the layman, the point I wanted to make is that the drag curve shoots sky high very quickly, just like the positive side of a parabola does. For the average car, the inefficiency really starts to hit over 55mph. Model 3 can probably get away with something higher given how aero it is, maybe 65mph. OP is well within non-optimal speeds even at 75mph with no wind.

And I pulled the 20mph headwind number out of my a$$ as a reasonable wind speed that someone might characterize as strong. A few weeks ago, we had sustained winds of 35mph for over a day here in NE, and air temps were in the single digits F. An increase in air density in conjunction wind speeds will totally kill efficiency.

 

[SageBrush]

You care about the details.

Sometimes, but in this instance I posted to encourage clarity and accuracy.

E.g., x^2 and 2^x are two very different functions.

 

[SomeJoe7777]

For real-time wind information, along with an estimate of your air speed, you can use Tesla Winds and Elevation on the car's browser.

Follow instructions in the following thread to properly sign up for the API keys:

Tesla Winds and Elevation Web Browser App

Post # 5 in that thread will help you with the Geonames website.

 

[RyanT]

When you encounter a strong headwind try tucking in behind a semi. It makes a huge difference. Something to keep in mind f you find yourself in a situation like this.

 

[SageBrush]

When you encounter a strong headwind try tucking in behind a semi. It makes a huge difference. Something to keep in mind f you find yourself in a situation like this.

I prefer slowing down to the risk of windshield damage, or worse.

 

[woodisgood]

The M3 energy use per mile is more like an aircraft and highly dependent on airspeed...

Or more specifically, spaceship.

 

[Big Todd]

Well I'll add my 2 cents of observation..

I regularly drive 168 miles one way all freeway.. I average 2 hours and ten minutes give or take 5 minutes due to traffic and fast lane slow pokes .. normally during first few months of ownership oct18 awd i arrive with 100-110 miles of stated range after a full battery charge from home ..

Now that's it has 12k miles and or it's colder than when I first owned it .. bay area weather ... I'm lucky to get 60 miles left .. no rain or wind. Still driving fast as I want when I can under a felony.. average 325w per mile .

When the temperature is above 75 I will retest .. but if this is any insight into my future I'll not be happy with the battery degradation with heavy freeway speed.

It like my Dyson v10 after a few months..

 

[woodisgood]

Well I'll add my 2 cents of observation..

I regularly drive 168 miles one way all freeway.. I average 2 hours and ten minutes give or take 5 minutes due to traffic and fast lane slow pokes .. normally during first few months of ownership oct18 awd i arrive with 100-110 miles of stated range after a full battery charge from home ..

Now that's it has 12k miles and or it's colder than when I first owned it .. bay area weather ... I'm lucky to get 60 miles left .. no rain or wind. Still driving fast as I want when I can under a felony.. average 325w per mile .

When the temperature is above 75 I will retest .. but if this is any insight into my future I'll not be happy with the battery degradation with heavy freeway speed.

It like my Dyson v10 after a few months..

Temperature makes a HUGE difference, after speed (which is assumed in your case to be the same between different "same" drives).

There's a graph floating around that shows efficiency at different temps. Even small changes (like in the Bay Area, say a drop of 10 degrees F) make a big difference, let alone in places where you actually have a frigid winter.

EDIT: There's a table/graph at approximately 2:41 in this vid (I'm not sure whose data they're quoting):