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Best Mid-Day Charging strategy?

Discussion in 'Model S: Battery & Charging' started by efusco, Feb 28, 2013.

?

Given the Scenario in the 1st post, what's the best approach?

  1. Charge to 240mi charge w/80A HPWC, even if higher amps might have a negative impact

    9 vote(s)
    37.5%
  2. Just get what amount of charge you can at 40A to minimize battery impact

    6 vote(s)
    25.0%
  3. Don't charge at all--there's no concern about a drain to 100 miles and frequent charging is worse

    7 vote(s)
    29.2%
  4. Other-specify below

    2 vote(s)
    8.3%
  1. efusco

    efusco Moderator - Model S & X forums

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    Just trying to get a grasp of what people think the best way to handle opportunity/mid-day intermittent charging would be.

    Here's the Scenario for the Poll:
    I drove about 15 miles in the morning to a meeting, about 4 miles to my office, then about 13-14 miles on errands on my way home. I had started with a morning Rated charge of ~136 miles (after overnight vampire drain) and just got home with ~189 rated. I pick up child #1 in about an hour and bring him home (20 miles RT), child #2 an hour after than (20 miles RT), then have to run both kids to music lessons and back (about 30 miles RT)--so I have another 70 miles to drive and it's cold, so I'm not getting rated range...I figure I'll be down to 100 miles of rated range if I do not charge while I'm parked here at home. (this is also why a Leaf won't work for me!)

    So what's the best approach?
     
  2. Zextraterrestrial

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    #2 Zextraterrestrial, Feb 28, 2013
    Last edited: Feb 28, 2013
    Is there a negative to charging at 80A?

    if not then go for that
     
  3. efusco

    efusco Moderator - Model S & X forums

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    From some previous threads I've gotten the impression that there might be, but perhaps I'm mistaken.
     
  4. Zextraterrestrial

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    I doubt the superchargers would be able to push that much power ever in that case. I think the S will limit power on the 80A if it needs to, just like doing a range charge, the top 5% or the bottom 5 or so of the battery gets filled slower.



    (in you OP you said 136 mi instead of 236 )
     
  5. Rodolfo Paiz

    Rodolfo Paiz P85 "Plug and Play"

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    I think you should ask Tesla... I have no idea what a knowledgeable, scientifically-valid answer to this question might be.

    However, my personal and uninformed handling of this situation is that, if I knew I was going to end the day with 100 RM or thereabouts, I wouldn't bother charging at midday. But that's partly based on the fact that I have very little need to leave the house unexpectedly in the afternoon or evening, so YMMV definitely applies... in my case, I can always plug in the car for an hour or so (the time it takes us to shower and change) and add 60 RM to my battery if a dinner invitation comes up. I feel no pressure. If, however, my lifestyle involved more -- and more frequent -- driving, I might charge at mid-day.

    My other uninformed and unscientific thought is that a lithium-ion battery should not be charged too quickly. But 80A is still small enough relative to overall battery capacity for a full charge to require 4.5 hours... and that doesn't seem so fast. So, unless someone authoritatively explained to me why I should think differently, I'd just plug in the car and let it charge as its designers programmed it to do. But again, this is based on my personality: I'm forgetful, so I try not to do things like set charging to 40A "this one time" because it often becomes a permanent setting. Other, more organized personalities might set 40A to be gentle because they won't forget.

    You pick. :-D
     
  6. efusco

    efusco Moderator - Model S & X forums

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    Thanks Rodolfo. I guess if I could speak to an actual engineer at Tesla I would believe their opinion, but experience tells me that the usual high school grad at the other end of a phone call knows no more, and often less, than I do so I tend to not trust the information I get that way.

    I usually charge at 40 amps b/c I rarely need to charge faster and it seems more gentle and more energy efficient from some prior threads I've read. At 80 amps you can feel the heat in the charging cable so you know there's at least some waste, but I can't say if that amount of charge is really any harder on the battery itself--which would be my primary concern. A partial charge would probably be fine here...or, as you suggest, none at all, though I am trying to discharge the battery any more than necessary in order to maximize the life and capacity for the next 8-10 years. I don't think this one time would matter, but would doing that 3 times a month or 5 or 10 over the course of a few years result in measurable impact? I just don't know and that's why I'm enquiring.
     
  7. Kevin Sharpe

    Kevin Sharpe Active Member

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    Given it's Mid-Day you might want to factor in the CO2 content of the electricity... if it's Solar then make the most while the sun shines, if coal you might want to minimise the demands you place on the grid.
     
  8. efusco

    efusco Moderator - Model S & X forums

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    Mostly coal, some wind...I hadn't even considered that angle...not a huge demand on the grid here, but still worth putting into the equation.
     
  9. Zextraterrestrial

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    +1

    charging at 80A is only ~ 1 C and the batteries should be able to handle that w/ no problems. As mentioned, some loss will be in the wires getting hot but is that going to be more than what you'd get from 2 X40A wires? maybe not. Higher amps typically runs is cooler.

    I know that the longer(slower) you charge the more power is used so quicker may be better in that case.
     
  10. dsm363

    dsm363 Roadster + Sig Model S

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    Why did you not start with a full standard charge in the morning? If all your driving fits well within that and have over 100 miles rated range before you plug in for the night, can probably skip charging during the day.
     
  11. efusco

    efusco Moderator - Model S & X forums

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    I plugged in when I got home last night, the parasitic / vampire losses cost me a few miles range & I left @ 6am so didn't take time to top up.
     
  12. strider

    strider Active Member

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    I agree w/ Dave. Though I think Evan meant to say 236 in the morning and just typo'd 136. Drive it all day and charge @40A at night. I know you're having a lot of fun geeking out w/ your new car and worrying about how to do things the absolute best way but just drive it. That's why you got the big battery right?

    Also, based on Roadster experience, frequent charges to something less than full makes it harder for the car to keep the pack balanced. Maybe they improved this w/ Model S but if I do very many "charge for a bit while at work" sessions my charge to full range will drop. Then over several days of only charging to full at night the range will return, indicating the pack had wandered out of balance and then was fixed.

    - - - Updated - - -

    You're first post says you started w/ a morning range of "136".
     
  13. efusco

    efusco Moderator - Model S & X forums

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    Sorry, I did mean 236
     
  14. Todd Burch

    Todd Burch Electron Pilot

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    #14 Todd Burch, Feb 28, 2013
    Last edited: Feb 28, 2013
    Unless you're concerned about a sudden unplanned long drive of about 100 miles round trip, charge to a full standard charge overnight. Drive all day. Don't plug in until you get home at night.

    -80 A @ 240V is a relatively small load for an 85 kWh pack...(20 kW, or around 0.25C)...this charge rate isn't too concerning. Tesla has said that Frequent Supercharging to standard charge does not negatively impact the battery in a significant way.

    -One long charge is pretty much the same as several shorter charges of the same amount as far as cycle life is concerned.

    -This leaves your car around 50% SOC the longest, which probably has the best impact on battery health. It also minimizes wear on your cables/charger port from frequent plugging/unplugging, and also (as Kevin said) allows you to shift demand toward the nighttime hours.
     
  15. Doug_G

    Doug_G Lead Moderator

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    Tesla says a Supercharger won't affect battery life, so there's no way 80A is going to come close to having any effect.

    Personally I'd just charge full up overnight and drive the car.
     
  16. EarlyAdopter

    EarlyAdopter Active Member

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    This is one of the joys of the Model S - just standard charge at 40A overnight and drive the car during the day. No need to hassle with plugging in during the day.
     
  17. Puyallup Bill

    Puyallup Bill Member

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    Me, also. I'm retired, so no set schedule. When I park for the day, plug in and stay plugged in until the next time I use the car.
     
  18. hcsharp

    hcsharp Active Member

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    The answer depends... The battery will last longer with shallower discharge per cycle. However, the difference in longevity in your case will be minimal. This would support plugging it in during the day. Another reason to plug it in is to keep the pack warm on cold days.

    The only real reason not to plug it in during the day is convenience. It sounds like you're pretty busy. I would probably plug it in on cold days and not bother when it was above 35 or 40 deg F.
     
  19. Robert.Boston

    Robert.Boston Model S VIN P01536

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    Typo in the scenario -- he starts with 238 miles, not 138​. O/w, he can't have 189 when he gets back from the office.
     

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