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New Tesla owner, how do you charge low and slow

Discussion in 'Model S: Battery & Charging' started by sknaf, Jun 12, 2018.

  1. sknaf

    sknaf Member

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    I picked up my S 2 weeks ago.
    I had a 100a wall charger installed. I get right around 55mph charging.
    I am getting solar installed this week.

    Just wondering if I should de-rate my Wall Charger, or is there a way I can select to charge slower ?
    The solar can generate about 55a at Max, and I would rather use just solar vs solar + electric co.

    There are times I might want full charge speed, but charging overnight is no rush; so I would rather not change the dip switch on the WC to only charge slow.

    I did not see anywhere in the app to set a charging rate.

    ~Scott
     
  2. miimura

    miimura Active Member

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    You can adjust it on the car's touch screen.
     
    • Informative x 3
  3. scottm

    scottm Active Member

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    it's not in the app, only on the console - for dialing down amps

    Since you're grid tied solar, you'll be back feeding the meter when you're not charging... why don't you just be happy charging whenever at whatever rate you need, knowing all the time you're not charging in the day you'll be earning credit on the powerbill?

    is power cheaper during the day when solar is abundant? do you have time of day billing rate

    or is power during the day more expensive (high demand)... I just don't know how progressive AZ is

    I do know one thing for sure... charging during the night is not going to benefit from solar in-the-moment :p
     
    • Helpful x 1
  4. sknaf

    sknaf Member

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    Look like I need to search a little better next time. Similar discussion: https://teslamotorsclub.com/tmc/threads/adjusting-charging-amps-remotely.105814/

    It does seem like a miss that you cannot change from App.

    So when I change on touch screen, does it only change for this single charge ?

    On the charging - Get paid less in credit's than the electric cost. Not enough of a delta here yet to justify a powerwall, but I suspect that is coming ...
     
  5. jelloslug

    jelloslug Active Member

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    You could change the dip switch in the wall connector to a lower max current output.
     
    • Informative x 1
  6. TexasEV

    TexasEV Well-Known Member

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    No reason to change amps from the app. The only time you would be changing amps is when you plug in and start charging. If you lower the amps on the touch screen, it remembers that setting for that location. Except when it doesn’t— some updates have been known to cause the setting to go back to the default.

    This whole discussion should be moot. There’s no reason to charge your car slower than what your HPWC is wired for. The reason amps can be lowered on the screen is when you plug into poor circuits that can’t support the amps that it’s supposed to, or if you are using a homemade adapter and the UMC adapter sets it for a higher input than the circuit can handle. Neither of these apply to using a HPWC. Plug your car in, let the amps be set automatically, and don’t make this more complicated than it needs to be.

    Let the battery management system manage the battery, and just enjoy your car.
     
    • Helpful x 1
  7. Rocky_H

    Rocky_H Active Member

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    Your statement is technically true, so I am withholding the official "Disagree" rating, but I strongly disagree with the idea. There is no good reason to recommend doing that.
     
  8. gregd

    gregd Active Member

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    Lowering the charge rate when it's not needed reduces the stress on the various electrical components in the circuit, such as breakers, relays (contactors), and electrical connections (plugs/sockets). Lower current is less heat, and heat goes by the square of the current, so half the current is a quarter the heat. Any heat, besides putting stress on components, is a waste, since it's not going into the battery's charge.

    There is also the intangible impact on the local power grid, where the higher peak draw could force your electric company to upgrade things that may not need upgrading, potentially (but unlikely) digging up the street. It's your electric bill in both cases.

    I would not recommend reducing the charge current via the dip switches inside the EVSE, as that prevents you from going higher if you need to. Just set it in the car (which will remember the setting for your location). I have my car on a 14-50 outlet (so, 40 amps capable), but let the car charge at a gentle 24 amps most of the time, since it's got plenty of time to do so.
     
  9. Rocky_H

    Rocky_H Active Member

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    I was starting to get pretty irritated at those first couple of paragraphs because you seemed to be missing the point. Yes, lower heat is good, but the point is that putting the wall connector into a straight jacket by artificially restricting the amount of power available is just the wrong way to do it. You use the settings in the car if you want to run lower. I do as you mentioned as well, using only about 31 amps for my charging with the 1st gen UMC from a 14-50 outlet to keep it a little cooler.
     
  10. TexasEV

    TexasEV Well-Known Member

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    And increases the stress of the components of the car’s charging system, as it has to run for hours longer than it otherwise would if you slow down the charge rate.
     
  11. Rocky_H

    Rocky_H Active Member

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    I think that's where there is a smart balance there. Like with the UMC, running it in the mid 30's reduces the heat quite noticeably, but doesn't change the charging time very much. But turning all the way down to 5 or 6 amps isn't much more difference as far as the heat level, but makes the equipment run for far longer, which is the part you're mentioning.
     
    • Like x 1
  12. gjunky

    gjunky Waiting for the Model ☰

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    As mentioned, set it in the car once and it will remember the charge rate for that location. I never had to reset it yet with two years of updates (not saying it couldn't happen, just hasn't happened to us). I have the HPWC hooked to a 100a breaker. I have it set to charge at 50a just to be nice to the grid and because it easily charges overnight. I love to have the option and on occasion push it all the way up when we want a quick charge if we need to head out again.
     
  13. gavine

    gavine Petrol Head turned EV Enthusiast

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    Elon tweeted once that they were planning on adding the amp selection on the phone app. I can't think of the examples, but I know there have been times when I wanted that capability.

    Edit: he agreed that it was a good idea. Didn't commit to doing it:

    https://twitter.com/elonmusk/status/932649922666438656
     
  14. sknaf

    sknaf Member

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    I also think it would be great to add a charge time feature (esp to the iPhone app); ie
    I need 100 miles charge and I have 5 hours - so charge at the slowest rate to get me the charge I need. Seems like that would be better for the batteries as well: to charge them as slow as possible in the time you have.
     
    • Disagree x 1
  15. miimura

    miimura Active Member

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    Charging at 3kW vs. 9.6kW may be slightly better for the batteries, but it's not significant. Charging slower will have lower efficiency because extending the total charge time will lead to a higher consumption from the wall for the same energy added to the battery. The longer the charge duration, the longer you're running overhead items like cooling pumps.
     
    • Informative x 1
  16. sknaf

    sknaf Member

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    Didn't think about the fans, good point.

    I was more thinking like I need to get 100miles charged in 2 hours, or I can stretch it out over 10 hours.
     
  17. miimura

    miimura Active Member

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    Personally, I don't think there's any point to going less than 16 amps @ 240 VAC, which would be about 7 hours in your example for a Model 3. I charge both my cars at 32 amps so that I can finish both of them within my Off-Peak rate period (11pm-7am) without thinking too much about it and without them overlapping. The first one starts at 11pm and the other starts at 3am.
     
  18. TexasEV

    TexasEV Well-Known Member

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    You’re missing the point of owning a Tesla or other long range EV. There’s no need to make it this complicated, or to think about charging at all, unless you’re planning a long distance trip. Just plug in when you get home, and you always start with a full charge (meaning 90%) in the morning. You just don’t need to focus on how much charge you have or need, or when. Don’t worry about the batteries— if they can charge at >100 kW at superchargers, they’re not going to notice the difference beteeen 3 kW and 6 kW, or whatever. Just enjoy the car and let the battery management system manage the battery.
     
    • Like x 2
    • Helpful x 1

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