Trip Projection Works Great Going Up Elevation But Way Off Going Down

[Dugdale]

I live in Colorado, my 2023 Model Y has about 13k miles and I have made several trips up into the mountains. I am noticing a trend, the Trip Projection is extremely accurate going up the Rocky Mountains, and not accurate going down.

I live near Boulder Colorado at elevation 5860' and Breckenridge CO is at 9600'. On my last summer trip to Breckenridge I left at 100% SOC and arrived at 65% exactly like what the Trip Projection predicted. The trip started in the 70's near Boulder and finished at 67 degrees F in Breckenridge. If I am reading the Trip Projection correctly (see image) it was projecting 9.5% consumption for elevation on the trip up, and it ended up using 10.2%. I averaged 286Wh/mi on the way up which is think it is amazing considering I gained 3,740 elevation and traveling at 70mph of most of the trip.

Going down from Breckenridge the Trip Projection was off by a total of 10.5% (see image). I started the down trip in the 60's and ended at 72F. I average 132Wh/mi.

I am totally amazed that I was able to get 209Wh/mi for the round trip covering 182 miles of extreme elevation changes, I am not mad about the car's efficiency, I am just a little concerned that I can't trust the Trip Projection when descending from a high elevation.

Any ideas why it is off so much?

 

[Zoomit]

Yes, this is normal. The trip projections are generally pretty good, except when estimating steep descents. The calculation appears to be overly optimistic for energy regeneration when going downhill.

My commute climbs/descents ~1500 ft and it's been like this as long as I remember (5-yr Model 3 owner).

Don't expect an immediate fix.

 

[Dugdale]

Zoomit, thanks for letting me know this is normal.

 

[Occhis]

So the trip projection said you would arrive with 55 ish%, but you actually arrived with 44%? If so, that’s more than 10% of what was projected. The projection said you would only use 6% to go 91 miles (totally unreasonable) but really used 16.6%. Your usage was 10 full percentage points of the total battery capacity than projected. Huge difference on a 90 mile trip.

 

[fhteagle]

Also Colorado resident, and no stranger to 4000+' elevation swings in each direction. My not so scientific observation is that vehicle speed makes a massive difference to the accuracy of the prediction calculation. Let your speed creep up over the limit by pretty much any amount and you won't get the expected regen. At the limit it's pretty close, I don't do much driving well below the limit unless I'm stuck behind a truck, which also adds a confounding variable.

 

[Occhis]

I was surprised that the trip projection was more accurate on the uphill trip than the downhill one. I would have guessed the opposite.

 

[BillRadio]

My weekly commute is Vail to Denver and back. I'm amazed how close the projection is for my Model 3. It can run + or - 3% depending on traffic.

I get noticeably better regen going downhill westbound from the tunnel at 60 mph than going downhill eastbound at 70 mph, which indeed is opposite of what you'd expect.

Your next trip could be quite different.