Pre-conditioning and arrival SOC on long drives

[boulder.dude]

I gained some insight on how preconditioning (for Supercharging) while driving plays into estimated Arrival SOC and the Energy > Trip graph.

We were crossing one of America’s “Level 3 Charging Deserts,” the Navajo Nation in northern Arizona. Driving from Tuba City, AZ to Blanding, UT Supercharger (173 miles of rolling hills) under clear skies and about 30F.

Starting SOC was 95% and the car estimates 17% arrival SOC. After driving for less than a mile, it dropped to 13%. With 172 miles to go with no viable chargers inbetween this was less buffer than I was comfortable with, so I limited speed to the 55-65mph limit. The updated Energy > Trip showed no changes for the first half but consistently raised consumption for the second half.

When we got to the halfway point, the preconditioning message came on. Since we were still >1hr away, to stop it I canceled the nav to the Supercharger and used a nearby landmark. Voila! The arrival SOC went back up to 17%. When we were 30min away, I changed the nav back to the Supercharger to start preconditioning.

It’s cool that the estimated Arrival SOC and Energy > Trip graph factor in preconditioning, although I wish it was more explicit. Had I known that 4% was earmarked for preconditioning (which could be canceled if needed), I wouldn’t have stressed or slowed down! Ideally the Energy > Trip graph would be annotated to break out driving vs. preconditioning estimated consumption for us EV enthusiasts doing long trips.

 

[xyeahtony]

Don’t stress about 13% arrival SOC. I’ve driven it down to 1% before. 13% is still basically ~40 miles of range if something goes wrong, potentially 50 miles if you stretch it with extreme slow driving and no HVAC.

 

[boulder.dude]

Don’t stress about 13% arrival SOC. I’ve driven it down to 1% before. 13% is still basically ~40 miles of range if something goes wrong, potentially 50 miles if you stretch it with extreme slow driving and no HVAC.

I was mostly concerned about (1) weather (rain or headwind) or (2) detours having an impact during the 170 mile drive, given the remoteness of the area we were crossing. 🏜

Plus the unexplained drop from 17% to 13% after one mile of driving gave me pause!

 

[xyeahtony]

Plus the unexplained drop from 17% to 13% after one mile of driving gave me pause!

That always happens to me, the car is constantly recalculating the expected arrival charge based on current consumption which can vary wildly. I just drive normally and not worry until the gap between the miles to destination and range left is less than 20mi then I’m like ok maybe i should slow down

 

[Casss]

So is it the case that Tesla have never officially "announced" or confirmed that preconditioning is factored into the predicted SOC when navigating to a SC?

Maybe it's just naivety on my part but I had just always assumed this was the case on the basis that it would be a huge flaw if untrue

 

[Rocky_H]

So is it the case that Tesla have never officially "announced" or confirmed that preconditioning is factored into the predicted SOC when navigating to a SC?

Maybe it's just naivety on my part but I had just always assumed this was the case on the basis that it would be a huge flaw if untrue

It doesn't have to be officially listed as its own separate category, but it's included in real time. The car is detecting and measuring all energy consumption from all sources while it drives to continually update that estimate. So if you turn on the heater, more energy draw, and the estimate changes. Preconditioning starts drawing excess energy through the motors, more energy draw, and the estimate changes. Uphill or headwind, so the motors have to work harder, more energy draw, and the estimate changes. It's all in there, regardless of what's from.

But I guess there is the point that it is not pre-loading that future usage into the beginning estimate. It is only adjusting once it kicks on.

 

[boulder.dude]

But I guess there is the point that it is not pre-loading that future usage into the beginning estimate. It is only adjusting once it kicks on.

What I observed was 1 mile into the 170 mile drive, the car decided it would start preconditioning about 90 min in the future, and adjusted the Arrival SOC % and second half of the Energy > Trip graph based on its plan.

 

[Rocky_H]

What I observed was 1 mile into the 170 mile drive, the car decided it would start preconditioning about 90 min in the future, and adjusted the Arrival SOC % and second half of the Energy > Trip graph based on its plan.

Oh, that is interesting. I had not heard yet that they started putting that aspect into their look-ahead calculation.

 

[Gaige]

I have observed similar behavior.

I started doing the same work around of pick a landmark nearby the supercharger and 10-15 minutes before you get there switch back to the supercharger location to get some preconditioning in.

 

[UKCarl]

I experienced this over the weekend, clear day but maybe 10 deg C.

The s/c was 1hr30 away and with preconditioning at the start of the journey the arrival charge dropped from 26% to 16%. Using a nearby landmark and only selecting the s/c 30mins away meant only dropping 4%. Speed of charging was still 130kw.

 

[TomServo]

I have observed similar behavior.

I started doing the same work around of pick a landmark nearby the supercharger and 10-15 minutes before you get there switch back to the supercharger location to get some preconditioning in.

I know 3rd party tools like ScanMyTesla would display battery pack and stator temps, which would allow you to tailor pre-conditioning a little more accurately given distance and SOC but it would be nice if Tesla would show us the Battery Temp at least.