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Why does the car not reduce it's harge rate after 3 hours to 80% ?

Discussion in 'Model S: Battery & Charging' started by GJ79, Jul 21, 2016.

  1. GJ79

    GJ79 Member

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    Just a question regarding the 80% load on continous draw.

    Why wouldn't the car charge at full load 3 hours and then ramp down to 80%, especially on low charging cirquits Like the Nema 5-15 or Nema 5-20 that are often only used to get a little charge in to reach a supercharger or such it would be beneficial if the first 3 hours would charge at a full 16 amps on a Nema 5-20.
     
  2. mikeash

    mikeash Active Member

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    I'd guess that's not legal. It also seems unwise, as the car has no idea if the circuit was previously sitting idle or was, say, charging another car at 100% for three hours right before you plugged in.
     
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  3. GJ79

    GJ79 Member

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    True, but if you take that any further you don't know if not a second car is charging at 80% on a Nema 5-15 either which would also overload the cirquit. The Cirquit breaker should protect from such thing.
     
  4. brantse

    brantse Member

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    I'm pretty certain that would contradict the intent of the reason the code was written this way. 3 hours just happened to be the number they referenced to define a continuous or intermittent use circuit.
     
  5. GJ79

    GJ79 Member

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    I would hope there was some scientific testing behind that number and not just the number they picked.
     
  6. Rocky_H

    Rocky_H Member

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    I think the cutoff was actually 4 hours, rather than 3 hours, but that entirely doesn't matter anymore. Intent has nothing to do with it in the revised (2014 I think) version of the national electric code. Electric vehicle charging is now DEFINED as a permanent load. Period. So none of us get a choice in that.
     
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  7. brantse

    brantse Member

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    I'm glad to hear that's the case, as it makes sense (regarding permanent load). I've read that some Teslas have damaged CHAdeMO equipment, as it was never anticipated or designed to be used for longer charging sessions than a fraction of an hour.

    For reference (regarding 3 hour definition), it appears this quotes NEC 2005 - 210.20 Protecting Branch Circuit Continuous Loads.
     
  8. MP3Mike

    MP3Mike Active Member

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    So they never anticipated that there might be a line of Leafs that needed charged? I'm not buying it.

    Some of what I have seen is poor maintenance given the design. (Air cooled and it gets clogged up with dust/dirt so that it can't properly cool the equipment. Either it needed to be designed different to not clog up or they need to have someone service them on a schedule to keep it clean and the air flowing.)
     
  9. Rocky_H

    Rocky_H Member

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    Oh, yep, 3 hours. Thanks for finding that.

    Yeah, regarding the CHAdeMOs, the one at the Nissan dealership here in my town has a sign posted on it: "NO ADAPTERS ALLOWED", because apparently an adapter "broke" it before. I am pretty sure it was not built well to stand running for longer periods of time, and a Tesla with an adapter had it running for an hour or two and it overheated and/or blew something.
     
  10. GJ79

    GJ79 Member

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    I get that and I know the code. However if the charge rate on the Tesla would be full throtle for the first three hours and then reduced by 20% by definition you could still see it as "NOT" violationg the code as the first 3 hours don't count (A continuous load is any load which is on for 3 hours or more). The load becomes continues after 3 hrs. The heat would be reduced after the 3hrs by reducing the current. I am not a lawyer by any means but I see nothing in the code that would disapprove of this.
     
  11. MP3Mike

    MP3Mike Active Member

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    Did you read what Rocky_H posted: that electric car charging is now considered a permanent load by the code, so it doesn't matter if it is charging for one second code only allows 80%. (Even less in Canada.)
     
  12. GJ79

    GJ79 Member

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    I did and I was trying to find references to that other than a forum post. I am sure he is right and it must be written out somewhere otherwise Tesla would have surely done it differently.
     
  13. Rocky_H

    Rocky_H Member

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    Fine—good to get the reference for it anyway. I first saw it from FlasherZ, who is the electric code expert around here, and he quoted the section of the code for it. I just did a quick few seconds of Googling and found it.

    It’s section 625.14, which can be found on this link.
    http://www.calstart.org/Libraries/E-Truck_Task_Force_Documents/Article_625_Natl_Electric_Code.sflb.ashx

    It says:

    “Electric vehicle supply equipment shall have sufficient rating to supply the load served. For the purposes of this article, electric vehicle charging loads shall be considered to be continuous loads.”
     
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