Model X battery operating at roughly 50%....

[Ethanah]

I charged my model X to 94% in order to make a 120 mile trip. It’s a 2018 model X with 30,000 miles. I have the 75D. It is telling me to stop and charge or else I will arrive home with 3% battery. I am driving in range mode on the interstate going 68 mph. I should be able to make a 120 mile trip with a battery that has a supposed mileage of 238 without charging!!? It’s 50 degrees out. Should I make an appointment at the service center? Will they even do anything?

 

[Harvey Danger]

First, if you're posting about this in the middle of a road trip and your car says to charge, don't wait for a reply, just charge. Figure out why later.

Second, What does your trip meter say you are consuming? 500 Wh/mi? 600? Must be a lot more than 300 if you are getting half the rated range.

 

[Ethanah]

Today it says 400.
I am not dumb enough to strand myself. We stopped to charge.

 

[Bigriver]

@Ethanah, several things to note.

• 238 miles is the original rated range for the 75D. 3 years and 30,000 miles later, it will have degraded - rough guess will be -5%. It could be more.
• The estimated need for charging that the car provides is based on the past 30 miles of driving. If you have had the heater on high or other transient conditions, it will sometimes predict that you will need to charge until it gets a better last 30 mile energy consumption to make a better prediction.
• Wind and other weather conditions can take a real hit. I have a regular trip that I do in which I range from 75% to 100% of actual miles per rated miles. But I don’t drive it from 100% to 0%, so that means I never have trip segments that approach the distance of the rated range.
• Doing the math for your situation, assuming 5% battery degradation, you saying you charged to 94% and it was predicting arrival at 3% (91% to be used) and about 120 miles, that means you were getting about 59% efficiency, which is over 500 Wh/mile. That is high energy usage. Watch to see what your sustained Wh/mile is. I would not expect it to stay anywhere near that high for travel at 68 mph. Also observe the effect of turning the heater down or off.

 

[Bigriver]

Also, what wheels do you have? My only experience is with 20” and the 22” are known to eat up range.

 

[scottf200]

I charged my model X to 94% in order to make a 120 mile trip. It’s a 2018 model X with 30,000 miles. I have the 75D. It is telling me to stop and charge or else I will arrive home with 3% battery. I am driving in range mode on the interstate going 68 mph. I should be able to make a 120 mile trip with a battery that has a supposed mileage of 238 without charging!!? It’s 50 degrees out. Should I make an appointment at the service center? Will they even do anything?

I thought you could expect 5% degradation the first year and then it to be slower after that. I'm at 8-10% on my 2017 X with 60K miles. I would guess you were 6-7%.
Try your route in A Better Routeplanner as they have a lot of real-world data for Tesla cars and the various battery sizes.
You can specify all the parameters. Start+end; 94% start; 50F; 400 WH/MI, (additional weight in car)
Then play with the degradation option. ie. try 5%, 8%, 10%.
I did a guess like this with your numbers (and 75D setting) and a 130 mile trip. With 5% degradation it didn't want to stop at a supercharge but with 10% it did.