Don't leave unless it shows 6% or more arrival

[David99]

Driving over 5 years and 200k miles in my S I learned a few things that are not documented. One of those things is the range prediction in the trip graph. It calculates what your battery percentage will be at your destination. An incredibly useful tool! It can me tricky to use, though as it automatically assumes a lower driving speed once it gets tight.

As you drive and it gets tight, the car will warn you by suggesting to stay below a certain speed to make it to your destination. It happens when the predicted arrival is 5%. At this point the car switches it's calculation to the suggested lower speed. We are all familiar with that.

What most people don't know is the same behavior is happening when you charge. It will actually start calculating with a slower speed. Once it's at 5% arrival or higher, it switches to normal speed. Not suddenly of course. It does so gradually.

It is a little difficult to explain, but below is a timelapse video that shows it really well. As you charge, the trip graph goes up. Once the arrival percentage hits 5% the calculation transitions from using a lower speed to normal speed. Note how it shows 5% arrival when the battery is at 81%. While it continues to charge it uses a faster and driving speed as a basis. The battery reaches 95% while the arrival is still at 5%. At this point, for the purpose of calculating the prediction, the normal driving speed is reached and now the arrival percentage goes up with the state of charge. If you watch the video it becomes very clear.

What does that mean? If you are charging on a road trip, never leave when arrival percentage is 5% or lower. Always wait for it to be at least 6% or higher to make sure the calculation is assuming normal driving speed. If you leave at 5% (or lower) you are going to have to do the entire trip with a reduced speed to barely make it.

 

[wycolo]

> We are all familiar with that. [op]

Is this about NAV (which I don't have) or some other magic?
--

 

[spottyq]

Nicely found, and thanks for making that timelapse. It really makes it clear.

 

[maximizese]

Thanks for sharing. I've learned to give myself at least 15% overhead when on a road trip. If the highway is clear or if I don't want to get stuck behind a caravan, I will increase both my average or passing speed thereby increasing energy consumption. I try to get to the Supercharger destination with 10-20% remaining to make best use of my time (I've read your other informative posts). I had no idea there was a stall at the 5% calculation to the reached destination and I will make sure my wife is aware. I'd hate for anyone to come up short. Hopefully this is corrected in a software update.

 

[BigTonyTones]

Great Video! Didnt even know that was there

 

[RDoc]

Great job! Personally, I allow at least 10% because of things like hills, head winds etc. If it's below about 40F, allow a lot more!

 

[BigTonyTones]

I personally never trust Tesla's estimate to begin with on long trips. I use evto app for planning those things. I believe his algorithm is more accurate.

 

[BigTonyTones]

Great job! Personally, I allow at least 10% because of things like hills, head winds etc. If it's below about 40F, allow a lot more!

Great tip ontemperature. It has messed me up in the past when I wasn't aware

 

[commasign]

Very interesting. Thank you. What do you think are the slower and faster driving speeds it is using to calculate? For faster driving speed, maybe the speed you were driving before you arrived at the supercharger? For slower driving speed, posted speed limit or rated range speed?

 

[R8M3MS]

With unpredictable temperatures (in winter I am doing long range driving at anywhere from -25F to 40F) and the SOC prediction is often way off. It will sometimes tell me to drive speeds much lower than the posted speed limit (65mph on highway that is 80mph limit) which is not really that practical. Luckily the route I typically drive superchargers are at ideal locations that I never have to worry (and they are never busy) so in low temps I just plan on a stop to supercharge even if I probably could make it. Also one end of my typical long journey is a 7mile uphill and it's hard to predict how much energy it will use. The neat thing is that going back the other way (down the hill) I gain 3% of battery charge if I have full regen available.

 

[R8M3MS]

Very interesting. Thank you. What do you think are the slower and faster driving speeds it is using to calculate? For faster driving speed, maybe the speed you were driving before you arrived at the supercharger? For slower driving speed, posted speed limit or rated range speed?

My guess is it uses the posted speed limit for the faster driving speed. This is my guess based on traveling the same 200-mile route twice a week and seeing how the prediction system works.

 

[commasign]

My guess is it uses the posted speed limit for the faster driving speed. This is my guess based on traveling the same 200-mile route twice a week and seeing how the prediction system works.

Got it. Hopefully the slower speed isn’t something ridiculous like 55mph.

 

[R8M3MS]

It will adjust the recommended slower speed as you drive. It will tell you "DO NOT DRIVE ABOVE xxx MPH TO MAKE IT TO THE DESTINATION". The message will change as you drive, sometimes 75MPH then 70MPH then back up to 75MPH then it goes away. It's actually intelligent in that regard.

 

[kavyboy]

Fantastic, thanks! That is helpful and interesting. There's always something new, just when I think I've seen it all.

 

[David99]

Very interesting. Thank you. What do you think are the slower and faster driving speeds it is using to calculate? For faster driving speed, maybe the speed you were driving before you arrived at the supercharger? For slower driving speed, posted speed limit or rated range speed?

That's a very good question. I don't know for sure. The highest 'reduce your speed' warning I got was 'Stay below 85 mph'. The lowest I remember was 45 mph. My theory is that it does the same as most navigation systems these days. They work with historical crowd data from car that drive on roads. I guess that's what Tesla uses as a normal speed. Obviously, once you drive faster or slower, the graph will update to your actual energy consumption whatever that speed may be. I think once it sees that it gets down to 5% arrival, it will ask you to slow down from whatever speed you are going at right now. If that isn't enough, it will go a step slower and warn you and so on. At least that's what I'm seeing in my car.

I found the trip graph to be very accurate when I drive the same speed as the average person on the road. On open freeways that is usually speed limit + 10. That's why I believe the default speed it assumes is the actual average speed most people drive rather than the speed limit. If I drive the speed limit I always use less energy than the trip graph predicts.

 

[BerTX]

That's a very good question. I don't know for sure. The highest 'reduce your speed' warning I got was 'Stay below 85 mph'. The lowest I remember was 45 mph. My theory is that it does the same as most navigation systems these days. They work with historical crowd data from car that drive on roads. I guess that's what Tesla uses as a normal speed. Obviously, once you drive faster or slower, the graph will update to your actual energy consumption whatever that speed may be. I think once it sees that it gets down to 5% arrival, it will ask you to slow down from whatever speed you are going at right now. If that isn't enough, it will go a step slower and warn you and so on. At least that's what I'm seeing in my car.

I found the trip graph to be very accurate when I drive the same speed as the average person on the road. On open freeways that is usually speed limit + 10. That's why I believe the default speed it assumes is the actual average speed most people drive rather than the speed limit. If I drive the speed limit I always use less energy than the trip graph predicts.

If you have seen it warn to stay below 85 mph to reach your destination, then it MUST be using something other than the speed limit data to do max speeds. The only road with an 85 mph speed limit is SH130 in Texas.

Google supplies crowd-sourced average speed data. I'm sure those are what they are using as the base.

 

[BerTX]

Driving over 5 years and 200k miles in my S I learned a few things that are not documented. One of those things is the range prediction in the trip graph. It calculates what your battery percentage will be at your destination. An incredibly useful tool! It can me tricky to use, though as it automatically assumes a lower driving speed once it gets tight.

As you drive and it gets tight, the car will warn you by suggesting to stay below a certain speed to make it to your destination. It happens when the predicted arrival is 5%. At this point the car switches it's calculation to the suggested lower speed. We are all familiar with that.

What most people don't know is the same behavior is happening when you charge. It will actually start calculating with a slower speed. Once it's at 5% arrival or higher, it switches to normal speed. Not suddenly of course. It does so gradually.

It is a little difficult to explain, but below is a timelapse video that shows it really well. As you charge, the trip graph goes up. Once the arrival percentage hits 5% the calculation transitions from using a lower speed to normal speed. Note how it shows 5% arrival when the battery is at 81%. While it continues to charge it uses a faster and driving speed as a basis. The battery reaches 95% while the arrival is still at 5%. At this point, for the purpose of calculating the prediction, the normal driving speed is reached and now the arrival percentage goes up with the state of charge. If you watch the video it becomes very clear.

What does that mean? If you are charging on a road trip, never leave when arrival percentage is 5% or lower. Always wait for it to be at least 6% or higher to make sure the calculation is assuming normal driving speed. If you leave at 5% (or lower) you are going to have to do the entire trip with a reduced speed to barely make it.

Thanks for this insight. I have sat in the car and watched, but I guess I wasn't pondering why it was doing what it was doing. Now it makes sense. I knew that it plateaued, but I guess I thought that was about the time the tapering was kicking in pretty seriously and the charge rate was slowing, causing the percentage not to increase very fast. It didn't dawn on me that one of the variables was changing in the calculation (speed), rather than the arrival percentage.

I have learned my something for the day. Nap time.

 

[cusman]

For our trip from Fort Worth, TX to Loveland, CO and back, what I learned is for any 2-3 hour drive (140-200 miles) the best tool in your car is the Energy app which shows your current consumption rate plotted for last 5, 15, or 30 miles and the predicted range calculation it provides if you were to maintain that consumption rate.

Check this value against your miles shown and miles needed to reach destination and try to have a 30-50 mile buffer.

Things that affect actual range efficiency

• Increase in wind resistance (greatly increase if you go higher speeds)
  
• Elevation increases which require more energy
  
• Road conditions which decrease traction
  
• Weather conditions (rain / snow / slush)

The biggest of these to watch out for is wind resistance which greatly increases if you go higher speeds as you do when traveling long distances between cities / states.

If you want to go fast and still get close to 1-1 actual range (what you see before you start trip and how much gets used by time you get there) is to get behind something big like an 18-wheeler or large RV vehicle going 75-80 mph. You will be amazed how much less energy you will consume going at such high speed when you get into the slipstream of larger vehicles that are pushing the wind out of the way for you. You will also find your regenerative breaking going downhill to be much better in such a scenario.

It is the single best tip I can give and removes the need to overthink or worry about range. While using this tip, you will see your estimate of how much % of battery will be left when you get to destination / next supercharger actually go up.

 

[RachH]

Driving over 5 years and 200k miles in my S I learned a few things that are not documented. One of those things is the range prediction in the trip graph. It calculates what your battery percentage will be at your destination. An incredibly useful tool! It can me tricky to use, though as it automatically assumes a lower driving speed once it gets tight.

As you drive and it gets tight, the car will warn you by suggesting to stay below a certain speed to make it to your destination. It happens when the predicted arrival is 5%. At this point the car switches it's calculation to the suggested lower speed. We are all familiar with that.

What most people don't know is the same behavior is happening when you charge. It will actually start calculating with a slower speed. Once it's at 5% arrival or higher, it switches to normal speed. Not suddenly of course. It does so gradually.

It is a little difficult to explain, but below is a timelapse video that shows it really well. As you charge, the trip graph goes up. Once the arrival percentage hits 5% the calculation transitions from using a lower speed to normal speed. Note how it shows 5% arrival when the battery is at 81%. While it continues to charge it uses a faster and driving speed as a basis. The battery reaches 95% while the arrival is still at 5%. At this point, for the purpose of calculating the prediction, the normal driving speed is reached and now the arrival percentage goes up with the state of charge. If you watch the video it becomes very clear.

What does that mean? If you are charging on a road trip, never leave when arrival percentage is 5% or lower. Always wait for it to be at least 6% or higher to make sure the calculation is assuming normal driving speed. If you leave at 5% (or lower) you are going to have to do the entire trip with a reduced speed to barely make it.

I've found this to be true too. I never leave the supercharger unless it's at least 10% to my next destination- especially if you drive faster than the speed limit. Much better to pad it as much as you can. Having to drive slower than the speed limit while cars fly past you, flipping you off, while you are driving a super fast Tesla is a bit embarrassing ;-)

 

[RachH]

For our trip from Fort Worth, TX to Loveland, CO and back, what I learned is for any 2-3 hour drive (140-200 miles) the best tool in your car is the Energy app which shows your current consumption rate plotted for last 5, 15, or 30 miles and the predicted range calculation it provides if you were to maintain that consumption rate.

Check this value against your miles shown and miles needed to reach destination and try to have a 30-50 mile buffer.

Things that affect actual range efficiency

• Increase in wind resistance (greatly increase if you go higher speeds)
  
• Elevation increases which require more energy
  
• Road conditions which decrease traction
  
• Weather conditions (rain / snow / slush)

The biggest of these to watch out for is wind resistance which greatly increases if you go higher speeds as you do when traveling long distances between cities / states.

If you want to go fast and still get close to 1-1 actual range (what you see before you start trip and how much gets used by time you get there) is to get behind something big like an 18-wheeler or large RV vehicle going 75-80 mph. You will be amazed how much less energy you will consume going at such high speed when you get into the slipstream of larger vehicles that are pushing the wind out of the way for you. You will also find your regenerative breaking going downhill to be much better in such a scenario.

It is the single best tip I can give and removes the need to overthink or worry about range. While using this tip, you will see your estimate of how much % of battery will be left when you get to destination / next supercharger actually go up.

Yes- drafting off 18-wheeler/RVs is the way to go to save a lot of energy. They even draft off each other to do just that. We use to show horses and pull a gooseneck horsetrailer filled with horses. Drafting helped a LOT. I do the same in my Tesla