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SuperCharging starts to feel slow

Discussion in 'Model S: Battery & Charging' started by widodh, Mar 24, 2015.

  1. widodh

    widodh Model S R231 EU

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    #1 widodh, Mar 24, 2015
    Last edited: Mar 25, 2015
    I do a lot of roadtrips with my Model S: I just got back from a 2200km roadtrip to Prague (Czech Republic) and I did a 5500km roadtrip through Denmark, Sweden and Norway. So I spend quite some time at the SuperChargers and after all these trips it simply starts to feel slow.

    Nothing wrong with my Model S. It doesn't charge at 60kW max, it charges at ~120kW. The tapering is just the big killer.

    I often have to drive ~240km stretches between SuperChargers and the tapering is what makes it really slow. To add 54kWh to the battery I needed 43 min yesterday. That's an average of 74kW. Going from 18km to 300km SoC it took 47 minutes and added 56kWh.

    Nothing wrong with the SuperCharger itself, but it's the tapering which really slows you down. In real life you have about 60kWh of capacity available between SuperCharger stops to travel a distance of 250km. That's 240Wh/km at highway speeds (~130km/h). But adding 60kWh to a Model S will take about 55 minutes and that's long. Not mentioning trying to do a range charge.

    So Tesla says it is not interested in a 500 mile battery, well, I'm not so much, but I'd rather want a battery which I can charge with an average of 100kW or even more.

    I'm fully aware of the limitations and why tapering happens, but if I would get a 110kWh battery, the tapering kicks in later. I can charge up to 60 or 70kWh quicker and be on the road again. 30 minutes is about the max I'd personally would like to see.

    While Elon says that a 200 mile EV should be sufficient for anyone with the expanding SuperCharger network I kind of disagree due to the long SuperCharger times you will need with a smaller battery, again.

    But let me be clear, I'm fully aware:
    - Lithium-ion requires tapering
    - A SuperCharger is at least twice as fast as CHAdeMO
    - The Model S is a great car
    - Speed kills range

    I love my Tesla and I will never buy a ICE again (promise), but if we want to proceed into the future I think people would really want shorter stops. The 4 hour driving and 30 minutes charging simply doesn't exist.

    You drive for 2 hours, charge ~45 minutes, drive for 2 hours. My 1080km trip yesterday took me 12 hours.

    I know that highways speeds in the US are officially lower, but I think a lot of the US drivers would like to drive 80 mph, right?

    After owning your Model S for some time, how do you experience SuperCharging?
     
  2. jerry33

    jerry33 S85 - VIN:P05130 - 3/2/13

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    Living in an area where there has been a dearth of Superchargers until recently, I can say that even the slowest Supercharger experience is better than the RV park charging I used to do for trips. One of the big advantages of an 800 km battery is that charging will be much faster if all you are doing is charging enough to get to the next available Supercharger. However, even then after some time you'll become jaded :)
     
  3. Alain13

    Alain13 Member

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    Totally agree with you and that was my first tought when Elon said it: "Yeah I don't need the extended range of an 110kWh battery (for example), but I still would like to have it so you can charge it much quicker for the same kilometers then an 85kWh.
     
  4. Johann Koeber

    Johann Koeber Member

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    Fully agree with you, widodh.

    And don't forget, a larger battery also means we can drive longer before we ever have to hit the first SuC.
     
  5. widodh

    widodh Model S R231 EU

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    Oh yes, but as soon as you get SuperChargers to start to use them and the first-world problems start to rise.

    That as well. Leave with a 110kWh battery fully charged, drive for 400km and then hit the first SuC.

    I'm just wondering how Tesla expects Model 3 owners with a smaller battery to undertake roadtrips.
     
  6. Basvdpoel

    Basvdpoel Member

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    I have had the same experience during my 2000 km round trip to Austria.
    I don't mind that I have to wait but almost an hour is a bit too long. Especially my wife can't handle these "long" stops. :)
    This eventually means we are going with an ICE car to Italy this summer.. :crying:
     
  7. sefs

    sefs 2012 Ford Focus Electric

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    I agree with the theory here, but I'll add a larger battery would support even faster low SOC charging rates, meaning you'd spend even less time waiting to charge for the same range recovered.
     
  8. gelden

    gelden Active Member

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    Maybe it is possible for Tesla to provide a solution to keep charging fast till a higher SOC. For instance by adding a capacitor that will absorp part of the charge at higher SOC's, and then transfer this to the battery shortly after charging was stopped? I would expect Elon and his team to be able to come up with a solution for this.
    Would be nice...
     
  9. widodh

    widodh Model S R231 EU

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    True, but at some point we will hit the limit of the connector Tesla uses. It currently maxes out somewhere around ~350A and that is already very high.

    You can overcome this by having a battery with a higher voltage, but the current (Amps) is the real limiter there.

    A hybrid battery :) A part which charges fast and a part which chargers slower. But the main thing, you want to draw as much power from the SuC as possible.

    And I don't like driving down to 5% SoC before hitting the SuC. Some spare range is always great.
     
  10. NigelM

    NigelM Recovering Member

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    There's unlikely to be anyone posting that they wouldn't like faster charge times, but it does seem to me that there's basic math issues unless/until storage density improves:


    1. Larger battery pack weighs more, therefore more energy is required to move the car.
    2. Fully charging a larger battery pack will take even longer than fully charging a smaller battery pack.
    3. Partially charging a larger pack (to avoid the taper) will reduce immediate range (and don't forget point #1) and potentially require more frequent stops.

    There will be changes to energy storage density eventually, and that's the most likely factor to reduce waiting-at-Superchargers time, but in the meantime it is what it is.
     
  11. RiverBrick

    RiverBrick Active Member

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    Most people don't often go on 1,080 km trips. However, when someone does with a Model 3, the money saved on gas will likely be an even more significant to them.

    With typical speed limits, congested roads, and average stops in the USA, 1,080 km is going to take almost 11 hours in an ICE anyway. 10% longer for a rare trip is nothing when you consider the time saved charging at home and not going to the gas station on a regular basis.
     
  12. deonb

    deonb Active Member

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    For it to be worthwhile, you would have to have a capacitor that at least has half the energy density of the battery, otherwise you may as well just add more batteries and charge them up to the 50% limit before tapering takes place.

    Capacitors are nowhere near 50% the energy density of Lithium batteries at the moment. State of the art grapheme capacitors get to about 20%.
     
  13. widodh

    widodh Model S R231 EU

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    Agree, everybody wants more, but for this to happen you will need a chemistry change in the batteries. Simply adding more cells is not wise due to the increased weight.

    Model 3 will consume less (probably), so it will require less charging (gain more range in shorter times), but it will also have a smaller battery.

    Is Lithium-ion really bound to tapering or can chemistry changes resolve the tapering?
     
  14. Mario Kadastik

    Mario Kadastik Active Member

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    Living in a region with no superchargers yet (closest one is an overnight ferry trip or 1000km by land away) and having received the CHAdeMO adapter about a month ago already that is a huge improvement over my single charger charging times and I've done 1500km trips on only 3x13A charging!!! Being able to charge 43% of the battery in 55 minutes was a bliss yesterday when a blizzard with strong winds hit me and driving at 90km/h took 250Wh/km over the whole distance (both directions as the wind was side-wind). I plugged the car in and went indoors to eat a nice pepper steak. From ordering to calmly eating it and allowing for a bit of time to digest I discovered 50 min had passed and the car was at 96% already tapering on CHAdeMO so I continued. If I'd be able to charge 3x as fast on a supercharger I'd be in heaven ;)

    And I know the first P85D owner in Estonia got his car in Tilburg around noonish on Wednesday two weeks ago, around 2PM he set off and on the next day he drove onto the 4PM ferry in Stockholm. That's 1800km in around 25-26h including sleeping. I doubt ICE drivers do much better so it's already fast enough. Sure, driving 2h resting for 30 min is the ~best solution and it's not far off from that. We'll see how I feel after I've done the same trip in the summer when I'm hoping my S85D arrives ;)
     
  15. widodh

    widodh Model S R231 EU

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    Yes, it's all possible. I've done 700km trips on just 18kW charging, no problem.

    BUT, if we want everybody to go from a ICE to a EV (Tesla), progression has to be made. Not everybody will be willing to wait so long.

    We might want to do that, but does everybody want to stop? I was driving with 4 adults on this trip, we rotated with driving. In our case we really didn't need to stop, we could have just swapped drivers and continue.

    "No compromises" is what you are looking for. Charging in 5 minutes is nearly impossible, I know that, but EV's should become better in every aspect then a ICE. It's just the 'refuel' which takes most of the time and thus slows you down.
     
  16. ItsNotAboutTheMoney

    ItsNotAboutTheMoney Active Member

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    Think Tesla! Think modular!

    You can also overcome this by having two sockets. I'm very confident that Tesla would push the connector as far as they can and then just add another one. Got to put _something_ on the next gen Model S/X to sell them, right? :p

    When Elon Musk talked about the optimum range being around 250 miles, he was taking cost and efficiency into account. Should a magical super-cheap, super-dense, super-fast-charging battery technology appear, along with super-cheap, super-small power electronics, then sure, 500 mile range, and 1MW charging for everyone.
     
  17. NOLA_Mike

    NOLA_Mike Active Member

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    I definitely know the feeling you are describing. I went the first year of ownership never having experienced a supercharger at all. The first time I plugged into one I was blown away at the speed of charging. Initially I would willingly sit at the supercharger sites for an hour or more just to watch it charge.

    Now that the novelty has worn off and superchargers have made their way into my area I find I am using them more "as intended". I.e., I will arrive at the supercharger with low miles remaining and charge just until I have the range I need to reach the next one with a small buffer in case I run into any unexpected conditions. This has resulted in 20-30 minute stops which I don't mind as I enjoy getting out of the car and moving around a bit after a couple hours of driving. Having said that, if I need to range charge at a site to reach the next one or my destination I am finding the wait a bit long now...

    Mike
     
  18. jwheinen

    jwheinen Member

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    Just a bit of technical insight here. The charging of a Li-Ion battery takes place using constant-current, constant-voltage curve. Meaning: At constant current phase, a battery may draw as much current as it can, just as long as either cell voltage and cell temperature do not exceed certain thresholds. Whenever sufficiently charged, constant voltage will kick in. Cell voltage will rise to a certain 'switch' voltage and from that point forward, charging current will be reduced at the level needed to keep voltage at a safe level. Tapering of the SuC is when constant voltage starts. What I have seen is that pack voltage when really low is about 299V. When really full, pack voltage is 400V (or a bit higher) which is constant voltage. Point being: there is not much space left for Tesla to play with the battery pack and supercharging. Whenever high voltage is met, the supercharger will have to taper.

    In all, it is quite disappointing to see that whereas a few years ago Tesla took the 'no compromise' approach, there is now a different stance. Going beyond 85kWh or even charging at 22kW is no off-limits. Both are to my opinion very attractive options to improve long distance traveling with Model S and a catalyst for customer acceptance in say, Germany.

    If the customer is willing to pay for it - deliver it I would say!
     
  19. RDoc

    RDoc S85D

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    The obvious solution is battery swapping.
     
  20. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    #20 Cottonwood, Mar 24, 2015
    Last edited: Mar 24, 2015
    A week ago, I drove from St George, UT to Boulder, CO, a distance of about 1,100 km (~700 mi). I did the trip in 12 hours including Supercharger stops and many sections with 130 km/hr (~80 mph) driving. I did not notice your concerns of excessive time at Superchargers. In fact, many times by the time, I used the facilities, got a snack, etc, I had more charge than I needed for the next segment. My method was to enter the next Supercharger into the nav, look at the energy prediction, and depart with 10-15% excess. This meant that the max I ever charged to was 70% SoC and usually about 60% SoC. My average charge rate stayed high with these charge levels.

    Why was my experience so different than yours? I went back and looked at the trip. The reason was simple: the longest segment was about 200 km (~125 miles) and the typical segment was 160 km (~100 miles). Reducing Supercharger spacing to 160 km from 240 km has the same effect, on not needing to charge into the taper, as increasing the battery from 85 to 127 kWh. It does mean more frequent stops with the on and off highway overhead, but it works.

    The far simpler solution for Tesla for now is closer Supercharger spacing. My I-15/I70 experience is empirical evidence that 160-200 km (100-125 mi) spacing and good use of energy prediction is the short term solution to long Supercharger waits into the taper.
     

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