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Thought for a New, Improved UMC?

Discussion in 'Model S: Battery & Charging' started by cpa, Nov 20, 2016.

  1. cpa

    cpa Active Member

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    Remember, I am an accountant. Perhaps my brain is wired differently from most normal folks. :eek:

    Right now, I think there are a number of you who own two Teslas. My wife and I have a deposit down on the Model III. I know a lot more of you have reservations on the III as well. A year or so from now there will be a lot more two-Tesla households.

    Many of these households will only have one 240-volt, 50-ampere plug available for charging at home, and will not or cannot add another to accommodate the second car. Reasons will vary--perhaps not enough space in the panel for another 50A plug--cost--remodeling of garage--space--there could be others.

    Overnight charging is always best. Why not split the UMC into two plugs so that both Teslas could be plugged in from the same receptacle simultaneously? I am sure there could be a way to adjust the current between the plugs in coordination with the automatic start time that we dial into the car on the touchscreen.

    Here is my thinking: Set Tesla A to start charging at midnight at 40A; set Tesla B to start charging at 4:00 AM. A receives the full amperage until 4:00 AM when the software will adjust the amperage based upon estimated time to finish charging. If A is completely charged by 4:00 AM, B receives the full 40A. If A needs another 10kWh and B needs 35kWh, then the software calculates the proper split between A and B. Once A is complete, then B gets the full rate.

    Of course there may be times when this is problematic, but then the owners would just have to start the charge time earlier.

    Our driving habits are such that I rarely need more than 25 kWh overnight. My wife probably would not use 25kWh in a week. This sort of set up would work nicely for us. But I do realize that our situation may not be a common one.

    Oh, did I mention that I am an accountant? :D
     
  2. msnow

    msnow Active Member

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    We are in the same boat and I only charge once or twice a week. If I decide not to purchased a new HPWC, which I believe can be piggybacked to accommodate two cars concurrently, I would just plug in the car that needs it most on my single 50A outlet.
     
  3. ecarfan

    ecarfan Well-Known Member

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    It seems to me that Tesla has already addressed the issue you refer to, where someone has a single 50A circuit in their garage and for whatever reason cannot install another one.

    See Tesla — Wall Connector with 24' Cable or Tesla — Wall Connector with 8.5' Cable
    • Power sharing: Install up to four (4) Wall Connectors on a single circuit breaker
     
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  4. msnow

    msnow Active Member

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    Perfect, will save me from having to buy the HPWC and the larger amperage.
     
  5. Jason S

    Jason S Model S Sig Perf (P85)

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    My solution to the above problem also takes into account the cord running across the garage floor -- whoever needs a charge parks in the spot next to the charger.

    Could be formalized into M/W/F/Su = Model 3, Tu/Th/Sa = Model S. But mostly doesn't matter because of how much range each car has.
     
  6. wesley888

    wesley888 Member

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    Just get 2 HPWC (and configure correctly) and they will talk to each other to make sure they will not use more than what your power can provide.
     
  7. Canuck

    Canuck Active Member

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    #7 Canuck, Nov 20, 2016
    Last edited: Nov 20, 2016
    Unless you have two people with really long commutes each day, I don't see the problem. Owning a long range EV is not like owing a Leaf or other EV's where if you forget to plug in at night, you might be in trouble regarding range the next day. I usually plug in every night but it's rare that I actually need to. All you need to do is alternate the nights you charge.
     
  8. AEdennis

    AEdennis Active Member

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    Or just install a second outlet.

    We have three NEMA 14-50 (used to be 2 and 1 6-50 I had swapped to 14-50)... A J1772 and Model S HPWC...

    It's really not that big a deal. You can always lower the amperage on each car manually, if you're worried about drawing too much.
     
  9. GSP

    GSP Member

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    The existing UMC is already far ahead of the charge cords (mobile EVSEs) that come with other PEVs. I just wish the rest of the industry would at least include 120/240 V dual voltage capability. It looks like it will be decades before they decide to Increase ampacity beyond the usual 12 Amps to the UMC capability of 40 Amps.

    As already pointed out, Tesla has provided this "circuit sharing" solution with the new HPWC design. They also lowered the price of the HPWC to about the same as the UMC. Both of these advancements make installing two HPWCs more affordable, and the most convenient solution for multi Tesla households.

    @cpa's UMC suggestion would take affordability to the next level. If the UMCs could talk to each other like the HPWCs do, then the same convenient solution would be available with just the equipment that comes included with every Tesla sold in North America. Perhaps Bluetooth or other wireless protocol would be the best way for the UMCs to communicate with each other.

    GSP
     
  10. FlatSix911

    FlatSix911 918 Hybrid

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    You still need two separate HPWCs to share the same circuit ... :cool:

    upload_2016-11-20_19-37-44.png
     
  11. msnow

    msnow Active Member

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    Sounds like the most cost effective solution would be to just add another 50A circuit on my panel and use the provided UMC. Agree?
     
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  12. FlatSix911

    FlatSix911 918 Hybrid

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    This is what I installed ... a dedicated HPWC and another NEMA 14-50 :cool:

    IMG_3843.JPG
     
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  13. msnow

    msnow Active Member

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    Cool. Is the second one for a future addition, friends or....?
     
  14. FlatSix911

    FlatSix911 918 Hybrid

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    #14 FlatSix911, Nov 20, 2016
    Last edited: Nov 20, 2016
    A few friends with EVs and perhaps a Model 3 or two ... :cool:

    tesla reservations.JPG
     
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  15. cpa

    cpa Active Member

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    Thanks for your replies. I mentioned in the original post that there will be some people who will not or cannot install another receptacle. I just thought it would be handy for many folks in those situations. If there were such an item, Tesla could substitute this device for the conventional UMC for a few more bucks.

    I looked at the HPWC that was referenced above. For the life of me I do not understand what it accomplishes. I still only see one plug in the illustration. I would expect something more like the Hydra.
     
  16. MorrisonHiker

    MorrisonHiker S 90D 2017.28 c528869

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    Yeah, I don't think they understood/noticed the part of your original message that indicated you just wanted to use one device. The HPWC solution would require multiple devices to be installed but those devices could share the same circuit (or have separate circuits). Those networked HPWCs would communicate with each to manage the amps available to each device. It's not the solution you were wishing for but it can be a solution for some.
     
  17. cpa

    cpa Active Member

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    And I said I was an accountant, twice, even! That should have been the giveaway.:eek:
     
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  18. Akikiki

    Akikiki A'-Lo-HA ! y'all

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    Ooohhh, you're an accountant... what difference does that make, please?

    What's some of the reasons that this sample family can't/will not add a second 14-50 outlet? Because its going to be more simple and quicker to add a second and can be mounted right next to the existing 14-50? You simply plug each UMC in and setup your schedule just as you explained.

    I don't think you are taking into account the volume of owners that this very unique solution would appeal to. And how long it would take for Tesla to develop, test and bring to market a device that right now - one person has commented on.

    Besides the a UMC comes with the S or X maybe the 3. But you are predicting that people will buy another -dual-UMC even though they got one with each car? I doubt the dual-UMC would cost less than just adding another 14-50 outlet next to the existing one - even if the dual-UMC was available today.
     
  19. davewill

    davewill Member

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    Too complicated. The load-sharing that HPWCs already know how to do is easier and cheaper to implement than this. You can already buy two-headed EVSEs, but they aren't cheaper than two HPWCs. That's because the expensive parts (the cables, plugs, and the contactors) all have to be duplicated anyway. Worse, in few cases would the single plug location be convenient to both cars, requiring LONGER cables.

    In most cases, a second 14-50 would be cheaper than either...and certainly much simpler.
     
  20. Canuck

    Canuck Active Member

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    I heard you and I told you one plug is fine for two Model 3's provided you are not the rare exception of a family with two exceptionally long commutes.

    You obviously don't deal with very many accountants. These numbercrunchers are a very odd subset of the human species who require everything to be placed in nice little boxes with no exceptions. He said:

    Yet it went over most people's heads who gave him all sorts of two outlet options. Not good to do an accountant. Their head could explode.
     
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