Model X Roadtrip Woes

[glenhurst]

By the way, you may get significantly better range on the trip home: At least across Minnesota, the wind tends to blow west-to-east. So, you may have been fighting it on the way out; hopefully you'll get a boost from it on the way home.

 

[ModelX]

EV trip planner had told me I wouldn't make it with my normal model X adjustments, but car said I could do it. Like I said, heading up was stressful with lots of slowing. On the way back I was heading through a storm and programmed the trip to add the West Yellowstone charger. No range anxiety; but slower speed limits also.

 

[X Fan]

Good conversation here: How to save a lot of time on long trips

I've done 8 760+ mile trips with my X & I have also used EV planner. I select S85D 19" tires and have found that selection to be about right. Plug in your temps and expected weight and speed and it's darn close. My trips are now much easier since I've tracked through excel spreadsheets and then TeslaFi & know within 5-7miles what my usage will be in various weather conditions between12 SC's now.

FWIW: when I know there will be rain/wind, I've taken vehicle's recommendation and made sure I had at least 25% more than projected range miles required when charging. As an aside, counsel you have received is good. No need to charge to 100% unless it's convenient to your schedule.

 

[vandacca]

Yeah. It sounds like the combination of a headwind (~10MPH)...
No, but they're hella cute nonetheless!

Wow, that has to be the longest posting ever on TMC! No wonder you're almost always running out of charge! That posting would make @AnxietyRanger envious.

 

[aesculus]

EVTripping is suggesting I should expect more like ~290-310 Wh/km on the route back.

My estimate for your return trip first day (Bozeman to Rapid City would be 383 Wh/mi (~240 wh/km). But that is driving the speed limit or just a bit above. If you drive 10 above then the ~300 Wh/km is probably correct.

Keep in mind you can either sit in the car driving or sit in the car charging (or sit being towed, if you don't estimate right).

 

[VerityZooms]

Wow, that has to be the longest posting ever on TMC! No wonder you're almost always running out of charge! That posting would make @AnxietyRanger envious.

Hah! I'll take that as a compliment. (Though you must not have seen the post linked in my signature — that's substantially longer … although most of that is photos.)

 

[bak_phy]

A 10 MPH headwind is actually much worse than going 10 MPH faster. The reason is that when you are driving faster you are getting to your destination faster and thus you are exposed to the extra wind resistance for less time. With a headwind you don't get to your destination any faster. Another way to think of it is that you are exposed to the same wind resistance in both cases but for longer with the headwind.
EV Trip Planner accounts for that

Using a MS 90D (just picked randomly) going from Mitchell SC to Murdo SC at 72 MPH uses 176 RM, Going 77MPH uses 191 RM (+8%), but going 72MPH with a 5MPH headwind uses 203 RM (+15%). So twice as bad!!

Going to 86 MPH with 5 mph head wind uses 253 in which case you are in trouble!

None of this is specific to EVs. ICE cars have the exact same issues but you just go and fill the tank an extra time.

 

[wdolson]

You don't notice it with ICEs because a) most ICEs don't give you as much feedback on your mileage as Tesla does and b) it gets buried in with all the other inefficiencies.

When you have a car capable of 90% energy efficiency, everything that hurts efficiency is going to hurt more than a car that is only capable of 20% efficiency. A loss of 20% on top of 90% drops you to 72%. A loss of 20% when you're starting at 20% drops you to 16%.

 

[chillaban]

You don't notice it with ICEs because a) most ICEs don't give you as much feedback on your mileage as Tesla does and b) it gets buried in with all the other inefficiencies.

When you have a car capable of 90% energy efficiency, everything that hurts efficiency is going to hurt more than a car that is only capable of 20% efficiency. A loss of 20% on top of 90% drops you to 72%. A loss of 20% when you're starting at 20% drops you to 16%.

I think (b) is a huge part here. Most gas engines are relatively inefficient at the sub-50HP output levels (that aren't true zero-torque coasting, for which ZF has done a ton of work optimizing), so the difference between 20HP and 30HP (say, 70 and 80mph cruising) is virtually insignificant. Meanwhile on an EV the motors are so efficient at low torque output ranges that the difference between 20HP and 30HP is practically 50%, and most of the cruising range estimates are based on this metric.


For folks who want to speed in a Tesla (or account for headwind), one deficiency in the current Trip Planner is that it's not adaptive. It seems pretty bad at projecting your arrival charge percentage based on your current driving habits. As a result, if you cruise at 85mph for example, you'll tend to see an estimate that gets more and more pessimistic every time it recalculates, despite your driving habits not changing.

It'd be great if it recognized driving habits more, or allowed you to configure your habits. Right now we have to blindly eyeball an additional buffer percentage and constantly re-evaluate our driving habits based off the latest projection.

 

[PGeer]

We've taken two road trips so far. Olympic Peninsula-Phoenix-San Diego-home, and a loop around Washington State.

On both (which included mountains and some head winds) we averaged <350 wh/mile. Routed through superchargers 100%, charged enough to give it a 20% buffer, and never had less than 15% by the time we arrived at each supercharger. My strategy is to do 1-4 mph over speed limit as long as the trip graph remains on its initial slope. If it starts to go below, I drop speed incrementally by a few mph until its back on track.

Only explanation of your low mileage is speed and headwinds.