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For how much charge left does the trip planer aim?

Discussion in 'Model S: User Interface' started by znib, Jul 1, 2016.

  1. znib

    znib Member

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    If I use the navi to go on a long trip, it will route me from super charger to super charger an tell me how long I will have to charge at each super charger to reach the next super charger.
    But what does "reach" mean? If I charge for as long as the navi tells me, will I (theoretically) reach the next super charger with 0% left? Or 10%, 20%?

    I'd like to arrive with at least 20%-30% left, so will I have to charge longer than the trip planer / navi tells me?
     
  2. kort677

    kort677 Active Member

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    I find that it gets "upset" when the plotted SOC would be below 10%. at that point it might try to provide absurd reroutes. The best plan is to plan your trips ahead of schedule so you have an understanding of the distances that you'll need to travel and be able to use your head to override the trip planner.
     
  3. GlmnAlyAirCar

    GlmnAlyAirCar Member

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    20-30% is a pretty huge margin. I usually plan to arrive with around 10%. Nav app seems to shoot for around 20.
     
  4. TaoJones

    TaoJones Beyond Driven

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    Between 7-13% over rated miles.

    Utterly useless for many legs around the country.

    If you are unfamiliar with the terrain/speed limits/wx/headwinds for the next leg, and haven't examined the .csv file for your trip from evtripplanner.com, and you don't want to risk having to drive at up to 30mph below the posted speed limit to reach the next SC, then do yourself a favor and charge to +20% beyond whatever the "ok, you're good to go" number is.

    Once you've traveled the leg in question, ideally in both directions, you'll know for the next time. Until then, keep in mind that it's easier and faster to spend an extra 15 minutes at an SC than to lose 20 minutes or more driving very slowly on an 80mph interstate because you didn't account for all factors along the way.
     
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  5. znib

    znib Member

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    Ok, and how will I see when I have charged enough? Will it tell me to which percentage I have to charge while connected to the super charger?
     
  6. kort677

    kort677 Active Member

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    if trip planner is on yes, if not you need to estimate the time on your own. this is where your own experience using the SpCs comes into play.
     
  7. bob_p

    bob_p Member

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    Drove over 1000 miles over the last two days using Trip Planner. Each time, we always stayed a few extra minutes to add more than was recommended.

    The Trip Planner seems to assume you'll be driving at the posted speed limit - so if you plan to drive above that (and stay on pace with most of the other cars on the highway), you'll need more charge than Trip Planner projects.

    You'll also need more charge if conditions are not ideal - such as higher or lower temperatures, rain, high winds, traffic congestion (requiring more slowdowns), ...

    Before leaving a Supercharger, we would look at two items before deciding it was time to go. We'd look at the projected energy at the next destination (PEND) - the TP usually wanted to stop when the PEND was at or approaching 10% - which really doesn't provide much cushion. We would usually stay long enough to get at least 20% for PEND.

    The other number was the rated range on the dashboard. We'd use a rough estimate which we were calling our "30-20" rule. We'd take the distance to the next charger, add 30% plus 20 additional miles - and we wouldn't leave the charger until the rated range hit that spot.

    And, if it looked like 30-20 was underestimating, we increased it to 40-20 for the next stop (we had a stretch with either high winds or uphill driving, which used more energy than expected).

    While driving, we would monitor both the rated range and the PEND. If PEND dropped to 10%, we would slow down 5MPH. If PEND started increasing again, when it hit 15%, we'd increase speed by 5MPH. By making the adjustments early enough, we were able to ensure we would arrive at the charger with at least 25 miles of range left - keeping the battery from getting too far below 10%.

    The Trip Planner seems to do a reasonable job - especially when driving at the speed limit - in ideal conditions - but probably not good enough to be counted on 100%.

    We did notice some quirks in the TP software while driving. We had several periods when PEND would jump up and down, by as much as a 10% change (i.e., jumping from 11% to 21% and then back). That didn't provide us a lot of confidence in the estimates - though we could do a sanity check on the estimate by doing our own calculations using the remaining rated range and the distance left to destination.
     
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  8. dgpcolorado

    dgpcolorado Member

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    #8 dgpcolorado, Jul 2, 2016
    Last edited: Jul 2, 2016
    On my S60 Trip Planner seems to shoot for about 13% (about 26 RM) left. On short legs of 60-90 miles to the next Supercharger Station that's usually enough unless I hit unfavorable conditions, such as strong headwinds. On longer legs of 120 to 148 miles, it is usually too little when driving at the speed limit or 75 mph, whichever is lower, in mild temperatures. If temperatures are cold (dense air, possible heater use) or hot (AC use for both cabin and battery/inverter/motor) that 13% buffer will be too little.

    One thing I should note is that TP does not seem to assume speeds higher than 75 mph even if the speed limit is 80 (others have reported this and I agree). And speeds higher than 70-75 mph really suck down energy, so it makes a big difference. [Unlike many here, I drive the speed limit or less, depending on conditions; I see no reason to speed on highways (but I will push the limit on mountain twisties just because it is fun). I'm in no particular hurry and I don't have to keep an eye out for the state patrols, which is more relaxing.]

    I keep trip logs so that I will know what worked in the past. But, having driven many legs for the first time, I'm coming around to something like TaoJones's approach: charge to at least a 20% buffer unless the leg is fairly short. When I don't, I often end up lowering my speed to make it, until I get close enough to my destination and can speed up to use my remaining buffer safely. That's driving high speed Intermountain West Interstate Highways. For slower speed routes I expect that TP might get the estimates closer to accurate (but I have little experience with driving long trips on roads with speed limits below 70 mph).

    I will also point out that TP does take elevation changes into consideration and does a pretty good job with them. But overall it does not allow for enough energy to make a trip leg, at least for my car driving the speed limit.
     
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  9. chillaban

    chillaban Member

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    You got a lot of great practical advice big I don't think you got a good answer to your question yet: having completed my first road trip, the car tells you these things.

    Before you get to the charger, you're told how long you can expect to charge. When you plug in, it tells you that as well, and the energy prediction graph will show the projected remaining charge to the next supercharger. For example, when you first plug in it'll say something like -15% or something. And you can wait for that to get to a comfortable number for you, whether it's 15% or whatever. The phone app shows the countdown to when the trip planner thinks you have enough buffer.... And after that, it will simply show an ETA to complete supercharging.


    Overall I found my very first trip quite easy and intuitive to plan with the Trip Planner, and overall it was fairly accurate. It wanted to aim for 10-13% margin, but I went for around 15-20%. Then, even going 5-7mph above the speed limit, I was able to consistently arrive 2-3% above the original estimate through the route from SF to Vegas which includes some terrain.


    Maybe the trip planner doesn't account for certain factors but it seems to do terrain pretty well.
     
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  10. BertL

    BertL Active Member

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    #10 BertL, Jul 3, 2016
    Last edited: Jul 3, 2016
    Agree the estimates are pretty good taking terrain into account, however, it cannot estimate weather. Outside temperature (esp very cold) and one's evolving choice on use of heat inside the cabin, as well as strong winds, rain and snow/sleet can dramatically alter estimates.

    My last trip from SoCal to Vegas ended-up with 40-50MPH winds and rain for several hours, that slowed freeway traffic to a crawl for at least an hour of the outbound leg, and temp drops from 70 to 40ish for part of the time. Trip Planner did a great job considering what it could base its initial estimate on but at time was 25-30% off because of inclement weather; then every few minutes it caught-up it's estimate as the vehicle encountered real conditions -- no different than it does if one changes speed during the trip.
    My suggestion is, if there is a chance of bad weather, one should increase their planned buffer when trip planning before hopping into your MS. (I do the same with EVTripPlanner, which I ALWAYS use before a new long road trip. Being a planner-type, I much prefer sitting in a comfortable chair in my home, doing rough estimates of route and probable charging locations to determine a rough ETA, than going by the seat of my pants relying only on the more real-time Trip Planner once I get into my MS. As I and others have said in other threads, I just wish Tesla would buy and integrate EVTripPlanner with Tesla's Trip Planner. The combination would be awesome especially if integrated with the Tesla App, and a huge boon for people like me that prefer to do pre-planning outside our vehicle, and have to keep Range Anxiety tucked-away. ;))​
     
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  11. grichard

    grichard Member De-Luxe

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    When I am supercharging on long trips, the car and app reliably fire the "you have charged enough to continue on your trip" notification once the projected energy at the next charger reaches 10%. I think that that's your answer.

    Like most people on this thread, I usually let it charge for a few extra minutes. But I *can* keep my energy use in line with the planner's predictions if I drive carefully.
     
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  12. WannabeOwner

    WannabeOwner Member

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    its probably a naive question, but is there a benefit to charging to the point of taper? Charging speed at subsequent stops (assuming all below taper) will take the same amount of time, but the "reserve" will be higher.

    Perhaps all/most trips require charging past the point of taper?
     
  13. David99

    David99 Active Member

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    There isn't a point of taper. The supercharger starts at full speed when the battery is empty and stays like that only for the first 20% or so. From there on it reduces the power and gets slower and slower. From that perspective it's always good to arrive with a low battery and only charge as much as you need. The larger your buffer, the more time you lose.
     
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  14. bob_p

    bob_p Member

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    Because charging is faster when the battery is low on charger and slower as the battery charge increases, to get the minimum charging times, you'd want to charge only enough to get you to the next charger with around 10% left (or slightly lower) - and then charge again only enough to reach the next charger.

    However, since the (beta) Trip Planner makes some optimistic assumptions (driving the posted speed limit, ideal weather conditions, ideal traffic conditions, steady speed, ...), most of us appear to charge more than what Trip Planner recommends. And that may mean we'll have more than 10% when we reach the next charger - but that also means we have more cushion if conditions are not ideal.

    Before leaving the charger, we'll use the Trip Planner's recommendation plus apply our 30-20 rule - distance to next charger plus 30% plus an additional 20 miles of buffer.

    And, we still monitor energy usage while driving - and slow down 5 MPH if we see that the projected energy at destination is going to be below 10%.
     

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