Optimum / Max Speed Calculator

[Naonak]

Is there an app that will tell me what my optimum or perhaps my maximum speed should be between superchargers? I realize there are many factors that go in to this, such as wind, temperature, hills, etc... but, for example, with EVTrip Planner, you can enter some of those variables and it will route you through a supercharger or skip one if you can make it to the next one.

I would like to know if it would be better for me to drive say 85 mph between superchargers and arrive at the next SC saving, for example, 10 minutes and costing me an extra 5 minutes of charge netting me a 5 minute gain, vs driving 55 mph and taking 10 minutes longer but saving me 15 minutes at the SC, also giving me a net gain of 5 minutes. The X/Y graph crossing at different speeds vs Supercharger distance/time to charge is what I'm looking for ... and if an app or website exists that already does this, I haven't found it... so i'm reaching out to see if anyone knows of something like this?

If not, is there a chart as to what the % drain on the battery is at a given speed? I will embark on creating the site to do this type of planning if I have a good place to start and nothing similar already exists.

 

[commasign]

Even if such a calculator or program existed, the main confounding factor is that superchargers often provide less than the advertised charge rate depending on age/model of supercharger (90kw vs 120kw vs 135kw), how many stalls are occupied (A/B pairing) and various other factors (time of day, grid factors, throttling). Plus, if you arrive at a fully occupied supercharger station, the 5-60 minute delay could easily eliminate any theoretical time savings that may have been possible for a drive faster/charge more frequently approach.

 

[David99]

The #1 thing to optimize overall speed is to run the battery on the lower end. When driving you have two speeds to consider: driving speed and charging speed. The faster you drive the more energy you need for the same distance. Weather, elevation, wind can all contribute in one way or another.

Charging speed depends very much on the state of charge of your battery. The lower it is, the faster it will charge. So, to optimize charging speed, you want to plan your charging and driving so you always arrive at close to zero on your battery. For the first 100 miles your charge speed is way faster than you can drive. About 200 miles per hour. Since you can charge that fast, you could theoretically also drive that fast and thus save time.

I did the math with different kind of driving and charging speeds. The best speed overall is always a little higher than your charge speed. At least in theory. In reality, you have different distances between Superchargers. The farther apart they are, the more energy you will need. If you go extremely fast, your energy usage gets way up and you end up having to charge into the higher levels of your battery. And that's where the Superchargers get slow. What it means is if you go very fast and have a long distance between Superchargers, you might end up having to spend more time charging than you saved driving that fast. So while you are driving very fast, overall you are losing time as charging takes so much longer. If you do the math, it only becomes a problem if the distance between Superchargers is more than 100 miles and you are driving 90 mhp or faster.

Long story short, I don't know of any app that will do all the calculations combined. EVTripplaner.com calculats charge time now, but I'm not sure it does it based on state of charge you arrive at. I have done the math myself many times for all kinds of speed and charging combinations. Bottom line: The best way to keep your overall drive time short is to arrive at a Supercharger at near zero. That will greatly increase charging speed. Do not charge any more than you need. Charging longer to skip a Supercharger will take longer overall, than charging less and using every Supercharger. I know this seems counter intuitive, but again, I did the math (included time to get off the freeway and back on for the extra stop) and it works in favor of using every Supercharger instead of trying to skip one.

 

[Camera-Cruiser]

The #1 thing to optimize overall speed is to run the battery on the lower end. When driving you have two speeds to consider: driving speed and charging speed. The faster you drive the more energy you need for the same distance. Weather, elevation, wind can all contribute in one way or another.

Charging speed depends very much on the state of charge of your battery. The lower it is, the faster it will charge. So, to optimize charging speed, you want to plan your charging and driving so you always arrive at close to zero on your battery. For the first 100 miles your charge speed is way faster than you can drive. About 200 miles per hour. Since you can charge that fast, you could theoretically also drive that fast and thus save time.

I did the math with different kind of driving and charging speeds. The best speed overall is always a little higher than your charge speed. At least in theory. In reality, you have different distances between Superchargers. The farther apart they are, the more energy you will need. If you go extremely fast, your energy usage gets way up and you end up having to charge into the higher levels of your battery. And that's where the Superchargers get slow. What it means is if you go very fast and have a long distance between Superchargers, you might end up having to spend more time charging than you saved driving that fast. So while you are driving very fast, overall you are losing time as charging takes so much longer. If you do the math, it only becomes a problem if the distance between Superchargers is more than 100 miles and you are driving 90 mhp or faster.

Long story short, I don't know of any app that will do all the calculations combined. EVTripplaner.com calculats charge time now, but I'm not sure it does it based on state of charge you arrive at. I have done the math myself many times for all kinds of speed and charging combinations. Bottom line: The best way to keep your overall drive time short is to arrive at a Supercharger at near zero. That will greatly increase charging speed. Do not charge any more than you need. Charging longer to skip a Supercharger will take longer overall, than charging less and using every Supercharger. I know this seems counter intuitive, but again, I did the math (included time to get off the freeway and back on for the extra stop) and it works in favor of using every Supercharger instead of trying to skip one.

Wow! Great info, that I wasn't even looking for, but am happy for readying the post. I always thought being able to skip a Supercharger would make more sense, but I get it. If you want fastest door to door, your way is better.

On the other hand if skipping a charger gets you to a better charging location with more to do, or better food options, it's always worth considering.

 

[chriSharek]

Charging speed depends very much on the state of charge of your battery. The lower it is, the faster it will charge. So, to optimize charging speed, you want to plan your charging and driving so you always arrive at close to zero on your battery.

This is all fine and good (and accurate) however, when will Tesla be able to communicate with the cars to let them know the current occupancy of the Superchargers? Are all the stalls being used? Won't do you any good to get there close to 0 miles if there isn't a SC to be had!

This has been done with Chargepoint and other EV charging systems for the past 5 years. I see this as the ONLY advantage these public stations have over the SCs, and I'm sure Tesla has a plan to reach this bar, but when?

 

[Naonak]

The #1 thing to optimize overall speed is to run the battery on the lower end. When driving you have two speeds to consider: driving speed and charging speed. The faster you drive the more energy you need for the same distance. Weather, elevation, wind can all contribute in one way or another.

Charging speed depends very much on the state of charge of your battery. The lower it is, the faster it will charge. So, to optimize charging speed, you want to plan your charging and driving so you always arrive at close to zero on your battery. For the first 100 miles your charge speed is way faster than you can drive. About 200 miles per hour. Since you can charge that fast, you could theoretically also drive that fast and thus save time.

I did the math with different kind of driving and charging speeds. The best speed overall is always a little higher than your charge speed. At least in theory. In reality, you have different distances between Superchargers. The farther apart they are, the more energy you will need. If you go extremely fast, your energy usage gets way up and you end up having to charge into the higher levels of your battery. And that's where the Superchargers get slow. What it means is if you go very fast and have a long distance between Superchargers, you might end up having to spend more time charging than you saved driving that fast. So while you are driving very fast, overall you are losing time as charging takes so much longer. If you do the math, it only becomes a problem if the distance between Superchargers is more than 100 miles and you are driving 90 mhp or faster.

Long story short, I don't know of any app that will do all the calculations combined. EVTripplaner.com calculats charge time now, but I'm not sure it does it based on state of charge you arrive at. I have done the math myself many times for all kinds of speed and charging combinations. Bottom line: The best way to keep your overall drive time short is to arrive at a Supercharger at near zero. That will greatly increase charging speed. Do not charge any more than you need. Charging longer to skip a Supercharger will take longer overall, than charging less and using every Supercharger. I know this seems counter intuitive, but again, I did the math (included time to get off the freeway and back on for the extra stop) and it works in favor of using every Supercharger instead of trying to skip one.

Thanks for the comprehensive response, David (and others) ... I am aware of all the variables that factor into this. As you state, you've done the math several times yourself, so it would seem to indicate that an app or website would be a welcome addition in the toolbox of driving cross country in a Tesla. As with anything that has so many variables, you are going to have to make assumptions and/or assume ideal values when making the calculations. Perhaps providing input fields to fine-tune those to known conditions, as EVTrip planner does with Temperature, cargo load weight, speed, etc...

Since it would seem that no app currently exists to do this, I'll be glad to make one... but the one piece of critical information I would like to find, simply because it's critical and seems like someone would have already done it, is a chart showing the energy usage of a MS at any given speed (and disregarding any mitigating factors like wind, temp, elevation, etc...). What is the energy drain at a given speed given ideal conditions? As long as there is a starting point like that, it shouldn't be too terribly difficult. If no one has actually done the work to get that data, then it becomes much more difficult to make such an app... I have to think someone has already done this, probably Tesla themselves? At least I hope so!

 

[David99]

Since it would seem that no app currently exists to do this, I'll be glad to make one...

EVTripplanner considers all these factors so at this point it's your best bet.
Tesla's own trip calculator does an awesome job on calculating charge speed based on the battery level you arrive at because it knows ahead of time. It doesn't let you enter different speeds and weather conditions. You have to start driving, then the car will account for it by looking at the energy usage over the past miles and adjust it's prediction very good. Between these two you get a pretty good idea what is best.

In the end you are pretty much restricted by traffic and distance between Superchargers. It's not like you can go an average of 100 mph during the day on public roads (even though it might be the optimal speed). For the most part you are kind of limited to the flow of traffic and if you want to keep your license you won't be going too much over the speed limit. Same with Superchargers. They are spaced out in a way that you have to hit each one which dictates your driving pattern. So there is very little room to do things differently and the difference in total time is within a few minutes.

Really the one thing that makes the biggest difference in time traveled is arriving at a Supercharger with a very low battery level. The difference between arriving at 0% or 30% battery level is double! It takes twice the time to add 100 miles when you arrive with 30% in the battery.

With all the speed optimization in mind, don't forget that saving 10 min isn't going to make your trip more comfortable when your mind is constantly occupied with all the trip data and stressing out about arriving at 0% but not running out and having the car dictate how long you are staying where. There are Superchargers where I just want to get out of there. And then there are some with great restaurants and stores around or just a pretty site. Enjoy the good things, don't let technology rule your life

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On the other hand if skipping a charger gets you to a better charging location with more to do, or better food options, it's always worth considering.

Totally agree! On our many road trips we pick our favorite places to eat or do something and stay (charge) longer. Making a long road trip enjoyable isn't always about being the fastest.

 

[Naonak]

EVTripplanner considers all these factors so at this point it's your best bet.
Tesla's own trip calculator does an awesome job on calculating charge speed based on the battery level you arrive at because it knows ahead of time. It doesn't let you enter different speeds and weather conditions. You have to start driving, then the car will account for it by looking at the energy usage over the past miles and adjust it's prediction very good. Between these two you get a pretty good idea what is best.

In the end you are pretty much restricted by traffic and distance between Superchargers. It's not like you can go an average of 100 mph during the day on public roads (even though it might be the optimal speed). For the most part you are kind of limited to the flow of traffic and if you want to keep your license you won't be going too much over the speed limit. Same with Superchargers. They are spaced out in a way that you have to hit each one which dictates your driving pattern. So there is very little room to do things differently and the difference in total time is within a few minutes.

Really the one thing that makes the biggest difference in time traveled is arriving at a Supercharger with a very low battery level. The difference between arriving at 0% or 30% battery level is double! It takes twice the time to add 100 miles when you arrive with 30% in the battery.

With all the speed optimization in mind, don't forget that saving 10 min isn't going to make your trip more comfortable when your mind is constantly occupied with all the trip data and stressing out about arriving at 0% but not running out and having the car dictate how long you are staying where. There are Superchargers where I just want to get out of there. And then there are some with great restaurants and stores around or just a pretty site. Enjoy the good things, don't let technology rule your life

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Totally agree! On our many road trips we pick our favorite places to eat or do something and stay (charge) longer. Making a long road trip enjoyable isn't always about being the fastest.

Well, I plan on having a "buffer" setting, so instead of arriving with 0% arrive with say 10% buffer, or whatever you feel comfortable with to take into account unexpected or unknown variables. As far as speeds go, I would disagree that you can't go an average of 100 mph - it's very easy to do that between KC and Denver for example. 450 miles of straight road with virtually no one on during a large portion of the day. Not that I'm advocating 100 mph by any means... I'm more thinking in line of, should I drive 65 MPH or should I drive 85 MPH and arrive a few minutes sooner. Maybe there is very little room to do things differently, that's one of the things I aim to find out and if that's the case, then so be it! It saves me the mental gymnastics of trying to factor in everything and whether or not I can drive 85 to the next Supercharger or should I be autopiloting a truck at 60?

However, I do find the mental gymnastics a good way to stay awake, on the other hand.

I hope someone can point me to a chart showing energy drain at varying speeds for each type of battery pack.

 

[ggr]

You all seem to be overthinking this. If the rate of charge (in mph) is higher than the rate of discharge while driving, you are better off driving faster. Since the rate of charge is highest when the car is empty, you should drive as fast as you can to still get to the next supercharger. As soon as the charging rate tapers to below the expected consumption rate, unplug and head out.

Of course the Highway Patrol may well disagree with this analysis, since optimum speed is usually well in excess of 100mph if the superchargers are close together enough.

 

[Naonak]

You all seem to be overthinking this. If the rate of charge (in mph) is higher than the rate of discharge while driving, you are better off driving faster. Since the rate of charge is highest when the car is empty, you should drive as fast as you can to still get to the next supercharger. As soon as the charging rate tapers to below the expected consumption rate, unplug and head out.

Of course the Highway Patrol may well disagree with this analysis, since optimum speed is usually well in excess of 100mph if the superchargers are close together enough.

I tend to agree, that's why I'm wondering where I can find the rate of discharge at any given speed for the MS?

 

[mspohr]

Is there an app that will tell me what my optimum or perhaps my maximum speed should be between superchargers? I realize there are many factors that go in to this, such as wind, temperature, hills, etc... but, for example, with EVTrip Planner, you can enter some of those variables and it will route you through a supercharger or skip one if you can make it to the next one.

I would like to know if it would be better for me to drive say 85 mph between superchargers and arrive at the next SC saving, for example, 10 minutes and costing me an extra 5 minutes of charge netting me a 5 minute gain, vs driving 55 mph and taking 10 minutes longer but saving me 15 minutes at the SC, also giving me a net gain of 5 minutes. The X/Y graph crossing at different speeds vs Supercharger distance/time to charge is what I'm looking for ... and if an app or website exists that already does this, I haven't found it... so i'm reaching out to see if anyone knows of something like this?

If not, is there a chart as to what the % drain on the battery is at a given speed? I will embark on creating the site to do this type of planning if I have a good place to start and nothing similar already exists.

As others have stated, it's best to arrive at the SC with a low battery charge.
One way to do this is to set the trip planner for the next supercharge stop and charge to give yourself a cushion of 25 to 50 "rated miles" (depending on weather). Then when driving, use the trip energy graph to monitor your progress and the estimated battery remaining at the destination. You'll be able to see that as you drive faster, the graph will shift down and when you drive slower, it will shift up. I aim to have 10% battery remaining when I arrive at the SC. You'll find that you can drive faster to use more battery (and have a lower state of charge at your destination which gives you faster charging). As you get closer to the SC, drive faster to use up more battery. Ideally, you should be able to arrive at the SC at a high rate of speed (Dukes of Hazard style)...

 

[David99]

I tend to agree, that's why I'm wondering where I can find the rate of discharge at any given speed for the MS?

EV Trip Planner does that. Set start and end point to two Superchargers that are on your route and start putting in different speeds and different cars. It will tell you exactly how much energy is used for that leg. The only thing that is a little odd (but makes sense for real world route planning) is it doesn't allow you to set the speed as a number directly. It uses real world data from Google maps. It assumes you go as fast as the average person driving on this route. You can then put in a speed multiplier to make the calculation assume a higher or lower speed. This is what I have used to do all my calculations about what the ideal speed is.

But again, to keep it simple: a higher speed is always better because the Supercharger speed is always higher. The optimal driving speed is theoretically the same as the charging speed. But since the Supercharger is faster than you can drive, just drive as fast as you can. Only exception is when you have legs more than 100 miles between Superchargers. Then the amount of energy needed to go these long legs becomes so large that you have to charge deep into the levels where the tapering slows down the Supercharger significantly.

 

[Nosken]

This guy some testing and concluded 75 mph. Great chart.
https://teslaowner.wordpress.com/2014/12/09/driving-charging-time/

 

[WSE51]

There is a lengthy discussion with additional graphs here:

Chewing up time savings at the Supercharger

Elevation changes are an important factor in optimal speed.

 

[supratachophobia]

Thanks for the comprehensive response, David (and others) ... I am aware of all the variables that factor into this. As you state, you've done the math several times yourself, so it would seem to indicate that an app or website would be a welcome addition in the toolbox of driving cross country in a Tesla. As with anything that has so many variables, you are going to have to make assumptions and/or assume ideal values when making the calculations. Perhaps providing input fields to fine-tune those to known conditions, as EVTrip planner does with Temperature, cargo load weight, speed, etc...

Since it would seem that no app currently exists to do this, I'll be glad to make one... but the one piece of critical information I would like to find, simply because it's critical and seems like someone would have already done it, is a chart showing the energy usage of a MS at any given speed (and disregarding any mitigating factors like wind, temp, elevation, etc...). What is the energy drain at a given speed given ideal conditions? As long as there is a starting point like that, it shouldn't be too terribly difficult. If no one has actually done the work to get that data, then it becomes much more difficult to make such an app... I have to think someone has already done this, probably Tesla themselves? At least I hope so!

How does 40k miles of VisibleTesla data sound as a starting point?

 

[Brass Guy]

I thought about this subject (as I'm sure many have), but don't really have the skillset to come up with an app. I crunched a bunch of numbers to try to find a theoretical optimum speed at different distances, and put them in a spreadsheet.
When I did it, EVTripPlanner didn't estimate charge times.

The results indicated it won't really make a huge difference, but optimum speeds I found were between 75mph for a long trip to 105mph for a very short trip. Typically, the optimum speed is around 80-85.

Here's a link to the results I posted:
Optimum Supercharger driving speed

 

[Naonak]

Thanks guys, those are all good starting points. I need to go over them in detail and understand what they are presenting though!

 

[AWDtsla]

I think people overcomplicate this. I think the answer is relatively simple. You will make gains in trip time until the average speed of charging meets your average consumption. It is clearly well above 75 mph. At 75 mph you could be just about getting EPA rated miles. How hard is it to average 75mph on the supercharger? Not hard at all. You're still going like what, 100mph at 90% SoC? While your average rate is much higher.

edit - forget mph, look at your average draw in kW while cruising and compare the supercharging speed. Not one outside of the autobahn is going to be able to cruise fast and long enough to go past optimal.

 

[David99]

I think people overcomplicate this. I think the answer is relatively simple. You will make gains in trip time until the average speed of charging meets your average consumption. It is clearly well above 75 mph. At 75 mph you could be just about getting EPA rated miles. How hard is it to average 75mph on the supercharger? Not hard at all. You're still going like what, 100mph at 90% SoC? While your average rate is much higher.

edit - forget mph, look at your average draw in kW while cruising and compare the supercharging speed. Not one outside of the autobahn is going to be able to cruise fast and long enough to go past optimal.

What rate you get at 90% isn't really important. What makes a huge difference is that you can get a much much higher rate at a lower level! If you arrive at a close to zero your charge rate is significantly higher than arriving at 30%. Charge time actually doubles! Why charge at an OK speed when you can charge at a blazing speed. It's really not complicated at all, you just use the car's trip planner and aim to arrive just a little over 0%. The effect on time is significant.

I say, don't worry about what would be a theoretical ideal speed. Just drive as you like and conditions allow and what you feel comfortable with. It's not a race, don't stress. Just aim to arrive at a low level and get the fastest charging speed possible.

 

[Haskell99]

I just did a 900 mile road trip last weekend, Denver to Albuquerque.

I used evtripplanner.com (which was very close to real-world) and I would just change the speed from 1.0 to 1.05, etc. and look at total trip time. Since it takes into account charging time it worked out that 1.15 was about 6 minutes quicker than 1.0. That equated to 84 mph. That would have me arrive at each charging stop with about 25-30 range miles remaining.

BTW- the most boring Supercharger on the trip... Las Vegas, NM! Nothing there!