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How to save a lot of time on long trips

Discussion in 'Model S: Battery & Charging' started by David99, Nov 19, 2015.

  1. David99

    David99 Active Member

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    The Model S and X are the only EVs that can do long distance traveling in a reasonable amount of time. Compared to an ICE car it takes about 20-25% longer for charging on the way. The shorter the trip, the less charging makes a difference. For example on a 300-400 mile trip, you start with a full charge, stop once at a Supercharger and then you can run the battery down to your destination where you (hopefully) have a charger. For 5-6 hours driving you would only have to spend maybe 40 min at a Supercharger.

    The longer the trip, thought, the more charging stops you will need and the ratio between drive time and charge time is about 1:4 to 1:5. That's a significant amount of time on long trips. One mistake a lot of new owners make is to charge to a pretty high level mostly out of uncertainty how much they will need to make it to the next Supercharger. While this is safe it slows you down overall significantly.

    Superchargers are fast, but the charge speed depends very much on the state of charge. IOW, how much is left in your battery when you arrive has a big impact on how fast it'll charge.

    Here are some number that show how big the difference is. Let's say you arrive with 0%.
    In the first 10 minutes you will gain 70 miles
    in the next 10 minutes you will gain 46 miles
    in the next 10 minutes you will gain 36 miles
    in the next 10 minutes you will gain 29 miles

    In 40 minutes you got 180 miles. The average is 4.5 miles per minute

    Now lets see how the numbers look when you arrive at 30% battery left.
    In the first 10 minutes you will gain 29 miles
    in the next 10 minutes you will gain 27 miles
    in the next 10 minutes you will gain 20 miles
    in the next 10 minutes you will gain 18 miles

    In 40 minutes you got 94 miles. The average is 2.35 miles per minute

    The difference is huge! Almost twice the speed when you arrive at 0% vs 30%!

    Now of course it's not very good for the battery to run it down to zero. It is also very stressful on you and if anything goes wrong, you have absolutely no buffer. You should always allow yourself a buffer. But just from a time point of view, you should aim to arrive at the next Supercharger at a low state of charge to significantly cut down charge time.

    I remember a trip where I met another Model S owner going the same route. I arrived 15 min later than she did at the first Supercharger with almost zero on my battery. I charged just enough to make it to the next Supercharger. It was 100 miles away, but I charged to 150 knowing I was going fast and had head wind. I left the Supercharger before the other driver. I arrived at the next Supercharger with 10 miles left. Again I charged just enough to make it to the next one. As I was done charging and pulled out, I saw the other driver pull in. Not only did she charge much more than she needed at the previous Supercharger, she also arrived at a high state of charge slowing her down again. Over a 200 mile distance I gained aprox one hour over the other driver. Same cars, same driving speed, same conditions. Just by optimizing the charge speed.

    Again, I don't advocate to run your battery down too low. My message is: don't add in a big buffer just to be safe and then drive slow on top of it. It'll slow you down a lot. As I said in the beginning, it won't matter much on trips where you only have one or maybe two Supercharger stops. But the longer the trip, the more it makes a difference.

    Use the trip energy app. It will predicts (based on your driving and the conditions) how much you will have in your battery when you arrive. Keep an eye on it and use it to aim for a low state of charge without risking anything. It's very useful to optimize your trip.
     
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  2. green1

    green1 Active Member

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    One thing to keep in mind though, if you're at the charger anyway (not yet finished your meal, or whatever) there's no downside to keeping charging more.

    I found on my last trip that often I wasn't ready to go when the car was, so I let it keep charging, it's just that much less you need at the next station.

    What I've found is that if you're the type of person who stops for gas, runs in, grabs a sandwich, and eats it while you're driving, then driving in a Tesla is slower. If however you actually stop and sit down to eat, the car will likely be ready before you are, so there's no speed downside. Now there's still the issue of charger placement dictating stops, but that's a different issue.
     
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  3. brianman

    brianman Burrito Founder

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    If at all possible, align your schedule such that "eating time" is at a supercharger where (A) there are food choices you like and (B) when you have a long "next leg" to the next supercharger.

    When finishing the "supercharger portion" of your journey (i.e. the last supercharger before you go into "the badlands"), plan for that to be your top off point. All other charging events after that will simply suck by comparison.
     
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  4. mmccord

    mmccord Member

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    I find a lot of other factors go into this.

    1) Skipping superchargers. Sometimes it's faster to charge higher into the taper, and skip a SC, if the SC you are skipping is inconveniently located. Some are a minute or two off the freeway, or stuck in a rest area right on the freeway, but some others require a 15-20+ minute detour off the freeway, into city traffic, mall parking lots, etc.
    2) Travelling with kids. Seriously, a 15-20 minute stop just isn't possible with 3 kids in tow. It literally takes more time to get them out of the car, walk them into the restroom, take care of the baby, drag them back to the car, get them all buckled back in, etc. Add in getting something to eat and I'm there for an hour, whether I want to or not.

    I posted this blip on a non-Tesla forum in a discussion about the Model S. It is my typical 'maximum drive' day and how it ends up laid out:

     
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  5. brianman

    brianman Burrito Founder

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    #5 brianman, Nov 19, 2015
    Last edited: Nov 19, 2015
    Thanks for sharing the example. I like to run the numbers sometimes to see if my modelling matches up. This data was interesting; like a word problem from school days.

    TMCPost57673_mmccord.png

    For the curious, the yellow boxes were my guesses. The rest was calculated, assumed (like consumption rate), or provided by the anecdote.

    Another note:
    The peak charging rate shown is 353.75 mi/hr. If we assume 80 kWh spanning the [0%,100%] range, then the charging rate maps to 353.75/(266.6../80) or 106kW. Why is this interesting? This shows that (for this napkin calculation) an A battery pack can't even reach (<= 90 kW) what mmccord's car is averaging for that first charge. That's pretty significant IMO -- especially since it doesn't even take into account the impact of "equivalent tapering" much less the measured "non-equivalent" tapering we've seen for A vs. non-A packs.
     

    Attached Files:

  6. mmccord

    mmccord Member

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    Any chance you can label your columns?. Trying to make sense of it and failing.

    Edit: oh, i guess it's minutes, mph and range in miles
     
  7. brianman

    brianman Burrito Founder

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    duration (minutes) [negative for driving]
    rate/speed (mph)
    range delta (miles)
    .
    .
    range in battery (miles)
    .
    leaving time

    - - - Updated - - -

    If you can get the XLSX attachment to open, you'll can look over (especially the green notation boxes) the calculations.
     
  8. mmccord

    mmccord Member

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    Thanks. Obviously the superchargers don't always line up perfectly for this, but they did on our last long trip down the East coast. The nice thing about a relatively complete SC rollout in the area is there were 8 SCs on our route and we only needed 3 of them, giving us a lot of options as to when we stopped.
     
  9. brianman

    brianman Burrito Founder

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    Yup. When/if superchargers are <= 100 miles apart on all routes that I travel, things simplify dramatically.
     
  10. Oba

    Oba Member

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    I concur with the OPs methods. It's just silly to overcharge for that next Supercharger, if the goal is to minimize time (the kids issues notwithstanding).

    If your % remaining is falling into the uncomfortable area, SLOW DOWN!!! Turn off the heater (and use only seat heaters). Otherwise, as you get closer to the next Supercharger, you can speed up to burn down even closer to 0%.

    My personal goal is 10-20% remaining at destination at the start of the trip (I don't even want a fully charged car to start). At 50 miles or closer, I allow the % to drop under 10% and within 25 miles, below 5%.
     
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  11. Cyclone

    Cyclone Active Member

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    That's how I did Charotte <-> Miami a couple weeks ago. Right around 750 miles, but I had 4 SpC stops along the way (Santee, Savannah, St. Augustine, and WPB).
     
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  12. Max*

    Max* Autopilot != Autonomous

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    Agreed with the OP, I do the same. My goal is 7%-10% buffer at each SpC.
     
  13. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    Another nice trick is to enter your next Supercharger or destination in the Nav after charging has started. Then bring up the Energy:Trip screen and it will update the predicted battery energy at your next stop. I usually aim for 15% or so. This static prediction while charging is based on average conditions. If you know there is bad weather or wind ahead, or you like to drive aggressively, give yourself some more margin. When you start driving, this graph is projected from the usage over the last 5-10 miles vs the internal model. If you see the prediction for the destination going below your comfort level, slow down, drive 10 mile and reevaluate; if you are still below your comfort level, consider alternative charging opportunities.

    By aiming for a 15% or so buffer at the next Supercharger, charging goes very quickly. As others have said, I often don't have time to go use the facilities, get a coffee, etc before the car has enough charge.

    The exception to this rule is when you need some charge at an L2 charger between the Supercharger and your day's destination to make it to the destination. Some will say do a 100% charge, but that takes forever. A good rule of thumb is to move on when the Supercharger charging current is half of the AC charging current at the L2 ahead. For example if the L2 ahead is a 14-50 that will give you 40 Amps AC, then leave the Supercharger when the charging current is down to 20 Amps; at that point it will be faster to charge at the L2 down the road than the final taper on the Supercharger. As another example, if you have an 80 Amp HPWC or HAL2 for the top up on the way to your destination, leave the Supercharger when the charging current drops to 40 Amps.
     
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  14. Cyclone

    Cyclone Active Member

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    More ballsy than me! I shoot for 15%.
     
  15. Max*

    Max* Autopilot != Autonomous

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    Heh, yeah, when I just got the car I started with a 20% buffer, then learned how accurate the trip computer is to my speeding (75mph typically) and now feel comfortable with 7%-10% (just out of the red and into the yellow on the trip planner tab). If the trip graph dips into red, I slow down to 70mph, if it starts giving me more than 10%, I speed up to 80mph.

    Works perfectly for warm weather. I may need to adjust this for cold weather, we'll see how I do in the winter.
     
  16. tomas

    tomas Traded in 9 rep bars for M3, used to be somebody!

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    This useful thread is a heartening, I guess I've been subscribed to too many complaint-ridden threads!

    Just completed 2,000 mile trip, and totally agree that quickest charge approach is to stop at every available charger (subject to tradeoff of those that require detour from direct route or involve heavy traffic) with zero, and only charge as much as you need to get to next charger with 0. Most of us are not crazy enough to do that with NO leeway around zero. So, it becomes a matter of how a) close you are willing to cut it, b) your confidence in the trip projections, and c) your confidence in your ability to hypermile if it is getting too close for comfort.

    B is perhaps most important. I was amazed at how well the trip projections in the energy graph take into account elevation. Having never driven into Albuquerque from the east, I approached with 40 miles left to go, and 28 miles of rated range, though trip projection said I was still OK. Naturally, I started to stress. Arrived with 18 miles of range, because the last 15 miles were all downhill. That taught me to trust the trip projections, and from that point I cut my "buffer" from 20% to about 12%.

    Nonetheless, I'll add one other personal observation: I've never felt less fatigued after long drives. I really put that down to ~4 supercharging stops per day. Making it from point A to point B fast is sometimes essential. But, when it isn't, there's nothing wrong with an additional 15 minutes spent at charger... it makes the trip much less tiring. For me.
     
  17. Zextraterrestrial

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    #17 Zextraterrestrial, Nov 20, 2015
    Last edited: Nov 20, 2015
    This is all some pretty good advice and estimates. The only thing that (everyone knows) that will mess up all of this is severe wind (or flat tires)
    otherwise the trip prediction estimates are really quite good now.
    here are 3 shorter trips - Fresno/Vegas - Vegas/Fresno and Los Altos/Vegas.
    drive to charge ratios on the right. I didn't quite get down to as low of a charge as I usually would try for at most stops because I was very unsure of the wind conditions down south & across to Nevada + driving fast on I5 and getting excellent range with all of the fast trucks and cars is not what I am used to! no traffic here :wink:
    anyway I just want to add that the faster you can drive legally &(or?) safely the better your ratio of charge to drive will be
    you can see that the ratio is worse on the trips with higher rated range when I start charges (also the final high state of charge messes it up a bit for proper analysis assuming you have charging at your destination)
    trips.jpg

    adding drive time and distance assuming I went to 0 at the end of each trip pushes the top two trips to 4.4 drive / charge (530mi trips)
    and the last 3.6 (630 mi) but I was close to 20% when I hit all the SC's - makes quite a difference
     
  18. Max*

    Max* Autopilot != Autonomous

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    Someone did the math a while back, IIRC the ideal spot was 75mph. Going 65mph increases your overall trip by about 5-10mins, and going 85mph increases your overall trip by about 5-10mins. Going 90mph increases it be 10mins.
     
  19. Zextraterrestrial

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    #19 Zextraterrestrial, Nov 20, 2015
    Last edited: Nov 20, 2015
    I do remember the graph. I thought it was pretty flat between 75 and 85. If there is traffic at all like on I5 then 90+ is just as good or even better than 80

    thanks Brassguy
    http://www.teslamotorsclub.com/showthread.php/43957-Optimum-Supercharger-driving-speed

    very dependent on distance to the next SC

    and it seems the 140 mi SC spacing is ideal for optimum drive speeds
     
  20. Max*

    Max* Autopilot != Autonomous

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    That's the one! You're right, my memory was close, but not quiet there. So for long distances 75mph is the sweet spot, and it's about 5-10mins more total time for every 5mph. But for short trips, you're absolutely right, the faster you go, the quicker the overall trip.
     

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