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perferred charging power for a given situation

Discussion in 'Charging Standards and Infrastructure' started by doug, May 8, 2011.

  1. doug

    doug Administrator / Head Moderator

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    This topic has come up in a few threads. I tend to agree with this slide (from page 4 here):

    attachment.php?attachmentid=1782&d=1304897003.jpg

    The vertical axis isn't particularly useful (should be a simple list rather than a graph), but I like this grouping charging "events" for different power ranges. The main point being that you'd like better than 8kW to get a meaningful charge while your out and about.



    charging power.JPG
     
  2. TEG

    TEG TMC Moderator

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    #2 TEG, May 8, 2011
    Last edited: May 8, 2011
    I was just thinking of something like that. Nice to see someone did one already.

    At a more granular level:

    Slow: Home, hotel, at work, airport long term parking (basically places where the vehicle will be left overnight.)
    Medium: Movie theater, shopping mall. (Meaningful charge in 2 hours.)
    Fast: Roadside rest stop, fast-restaurant, airport pick-up. (On a road trip hoping to keep moving all day.)


    Or another way -
    Slow in residential neighborhoods.
    Fast next to freeway off-ramps.

    I have seen some recent commentary saying that the public rollout of J1772 next to highway off-ramps isn't going to help.
    How many Leafs want to wait 7 hours to recharge while on a road trip?
     
  3. Nik

    Nik Dreaming no more :-(

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    I disagree. I think that the vertical axis is vital, and I also think that it's incorrect, certainly for me.

    It shows that only 40% of charges will happen overnight. When you consider that most away-from-home charges only need to top up enough to get home plus a safety margin, I just can't see that 10% of charges (more than once a fortnight per car) will need to refill an EV battery in the time it takes to watch a film.

    That said. it's a useful piece of work, and studies of this sort are needed to help determine the required charging infrastructure.
     
  4. doug

    doug Administrator / Head Moderator

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    I think you just showed that the vertical axis is meaningless. Honestly, I think it's just there to look nice, but unfortunately distracts from the main point. All the events would have to add to 100%, which they don't. I had intended to post this slide a while ago but hesitated for this very reason. (Perhaps it's using that error function like curve to illustrate qualitatively the charging rate?? Who knows?)

    At any rate, it shows that public level 2 charging really should be better than 32A, and it's not that useful for the current generation of the Leaf.
     
  5. TEG

    TEG TMC Moderator

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    The J1772s all over the place are going to end up being more useful for plug-in hybrids.
    Some demographic of Volt, Fisker and (next years) plug-in Prius owners are going to find it tempting to run on gasoline unless they have lots of opportunities to add little bits of charge to their small(ish) battery packs as they move from place to place.
    Even if they did a "full charge" at home at night it is going to run out sooner, and force them back to gas mode unless they find lots of opportunities for short recharges.
     
  6. mpt

    mpt Electrics are back

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    There needs to be a third axis; range. This would bring the y-axis a scale appropriate to the car. As a roadster owner, charge at home is, for me 100%, for the 100-mile range MINI it's less, 99.89%. I had to, well, maybe had to, well, decided to because I could charge at a friends one time.

    But, I generally agree with the idea. It's just a shame that fast chargers aren't cheap as this debate would be moot.
     
  7. Nik

    Nik Dreaming no more :-(

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    Ahh, meaningless as displayed. Yes, I'd agree with that.
     
  8. Doug_G

    Doug_G Lead Moderator

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    I don't see how the entire applies to a Roadster, period. I have yet to charge mine anywhere except in my garage. It has enough range to do 100% of my daily driving without recharging during the day.

    The only thing I need charging infrastructure for is a road trip (which I hope to do soon). For that I want the highest power chargers possible at convenient locations along major highways. Preferably in locations with access to restaurants and coffee shops.
     

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