TRIP % at destination function of Energy graph

[quickstrike12]

Just got back from road trip and had some time to play with energy graph.
I’m wondering if anyone has any information about how the estimated arrival % at the destination under the TRIP tab works. What information does it use to calculate this number?
Does it use the last Wh/mi average from previous 5,20,30? Or possibly just the “rated” mile number.
And most importantly I’m trying to understand if it looks at terrain elevation. On my trip it changed by 3,000 feet.
Trying to learn to trust it for planning.

 

[sakimano]

Just got back from road trip and had some time to play with energy graph.
I’m wondering if anyone has any information about how the estimated arrival % at the destination under the TRIP tab works. What information does it use to calculate this number?
Does it use the last Wh/mi average from previous 5,20,30? Or possibly just the “rated” mile number.
And most importantly I’m trying to understand if it looks at terrain elevation. On my trip it changed by 3,000 feet.
Trying to learn to trust it for planning.

It doesn't use rated mileage...it is far more realistic.

I am guessing it uses your recent 30 or even longer and factors in how much highway driving you're doing on teh trip etc. It seems pretty smart. I've only had it let me down in EXTREME cold. i.e. where it said I'd get there with 5% and I arrived on virtual zero (happened twice in one day at -29 celsius aka -30 fahrenheit). Usually even on 100 mile trips, it's within a couple of percentage points.

 

[quickstrike12]

Thank you for replying. It has been pretty close on this trip as well. I think what throws me is it changes throughout the trip up 4-5% and then down a few % but when I areivyseems to be back about where it said at the planning stage before I left.

Obviously if I drive to fast it starts going down. Just trying to get gutsy enough with a leg of 210 miles and it says arrival at 5%. I would just do it but the last 60 miles has NO options or backup plan.

 

[quickstrike12]

I've only had it let me down in EXTREME cold. i.e. where it said I'd get there with 5% and I arrived on virtual zero (happened twice in one day at -29 celsius aka -30 fahrenheit).

So do you think it is taking temperature into account. I guess it would have to? 0 deg trip would be differ energy wise than a nice 65 degrees.

 

[animorph]

This calculation has been getting better in the past two years. We were seeing some crazy numbers on our first trip over mountains. It was like elevation was not considered, or did not sync up with where we actually were. EVTripPlanner said we'd arrive at the Supercharger with 20% remaining. The car got as low as -6% for charge remaining at destination, during our uphill runs. Without adjusting my driving, we got there with 20% remaining. The last time we did this the nav did a good job and no longer scares us like that. Although now I would pay more attention to that -6% and slow down.

We did a 5% remaining driving segment when the Quartzite SC went offline. The nav told us to stay below 75 MPH as soon as we started the drive. We kept an eye on the charge remaining at destination and slowed a bit if it went below 5% at any time. I think we arrived with 6%.

The things that are more dangerous are changes in weather, like rain or a headwind. Our worst driving segment was when a pouring rain started just as we left a Supercharger. The past 30 miles had been dry. We charged a little more than usual, but it wasn't enough. The charge remaining at destination dropped like a rock during our first 30 miles or so. We were under the speed limit quite a bit in order to make it to the next Supercharger, though with the rain that was probably a good thing.

The good thing is that you can practically double your range just by slowing down. While I'd still hesitate to head out on a 5% remaining drive, it can be done with just a little care.

 

[quickstrike12]

@animorph
That was really great and very helpful.
Thank you both for the help.
That’s always my backup plan, slowing to a crawl. May not get there fast but you won’t be on the side of the road.

I’ve often tried to calculate which is better.
Stop at a level 2 charge for 30-60 minutes or slow down by maybe 10-15mph.
Seems like slowing would beat the other car to destination.

Thanks folks

 

[AronAZ]

Does the regen setting have any impact on highway mileage? (i.e. allowing more coasting vs aggressive regen)

 

[rsg123]

I hardly ever use the cabin heater on my daily commute, but when my wife is a passenger it is frequently used during cold weather. These trips lead to my car’s most inaccurate % at destination estimates. It’s like the car is caught off guard that I would use the heater.

 

[tstafford]

I do a lot of road trips in my MS. Here’s what I’ve found:
- Weather is a risk to the estimate - temp change, rain, headwind
- The original estimate leaving a SC or starting the NAV is generally conservative (I lock in AP at 82 MPH on highway)
- I used to want a 10% cushion to feel “safe” on a trip, I now routinely use 5% unless I know of some potential issue ahead
- Agree point above - if you monitor it and feel at risk just slow down. The difference b/w 80 and 55 is massive in range. I’ve never had to slow down that much. Sometimes I drop to 70 MPH if things look dicey but I usually regret doing so because the calculation bounces back and by the end of the drive I’m back at 82 MPH

 

[quickstrike12]

It’s good to hear others have feel confident enough to start with a 5% arrival estimate. I did my first yesterday and was a bit nervous. Mostly because after mile 160 there were zero options if it all went bad. No chargers the rest of the way. Not even slow ones(except for begging for a 110 outlet).
But like you said @tstafford i just figured worst case I’ll keep an eye on percent and keep slowing to maintain it no lower than 5%.
I arrived right on the money.

One bothersome thing though was while it was supercharging near 99% it’s showed arrival at 9%.
As soon as I put it in drive and pulled out it changed to 5% and displayed yellow “stay below 65mph to make it to destination” or words to that effect. What if I stopped charging at 5% and started and it dropped to 1 or 0%?
seems like it changed its mind or recalculated a bit when I started.
I ignored it for part of the way and went 75 and it was still maintaining 5% arrival but then started to dip. So last hour I slowed to 65 and it stayed at 5% and that’s what I landed with.
I think your exactly right. It’s a little on the conservative side for planning and I think that’s good.

Wish I knew for planning purposes the details of how it arrives at those calculations ie: temperature, Wh/mi, and the biggie terrain. Obviously winds and rain will be up to us.

 

[quickstrike12]

Well heck this was very timely. Just ran across this old article.
Answers some of my questions.
https://electrek.co/2019/01/24/tesla-range-prediction-algorithm-temperature-data/

 

[Brass Guy]

Does the regen setting have any impact on highway mileage? (i.e. allowing more coasting vs aggressive regen)

Speculation: no most of the time. But if you're driving downhill steep enough, low-regen may not be enough to maintain speed. In this case, if your car has TACC it would probably use the brake to maintain speed; which would obviously be less efficient.
If you do not have TACC (like my 2013), you'd speed up. I've read arguments both for and against coasting downhill, but logic would suggest that if you speed up to a terminal velocity, any gains coasting after leveling out would be negated by the loss of regen on the way down.

 

[dark cloud]

I
One bothersome thing though was while it was supercharging near 99% it’s showed arrival at 9%.
As soon as I put it in drive and pulled out it changed to 5% ....

When I enter a destination with the car being in the garage overnight, the car shows 12 degrees Celsius, and nav estimates a 22% SOC upon arrival. I open the garage, drive down the street where it is -6 degrees, the car reads the new temperature, and in a few hundred feet the estimation adjusts to a 14% SOC at destination.

So I am guessing perhaps after supercharging for half an hour the air around the car warms up, as the heat expelled from the coolant through the condenser fans from supercharging can do, the car thinks it is (translating to your language) 75 degrees F, but then when you leave the car readjusts to the actual ambient air temperature of maybe 50 F, and that is why the estimate changes from 9% to 5%?