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Combining two 120V into a 240V connector

Discussion in 'Charging Standards and Infrastructure' started by splitsec002, Aug 26, 2012.

  1. splitsec002

    splitsec002 Member

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    I was wondering if someone more electrically inclined could figure out some type of device that would combine two 120V outlets and turn it into a 240V so that you could charge faster.

    What I'm imagining is if I went to a friends house or somewhere that didn't have a high power charger. I could use 2 extension cords and plug in two 120V plugs into a small device that would combine it to make a 240V. The extension cords would have to be plugged into different breakers since most house breakers have a 15 amp capacity.

    Is this possible?
     
  2. TEG

    TEG TMC Moderator

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    This has been discussed before. I will dig up some old threads in a few moments.

    Short answer - it is only possible if you find two outlets that are are different halfs of "split phase" service.
    Most North American houses have half the outlets out of phase with the other half. With long enough cords, you can combine the two and get 240V, but you will still be limited by the circuit breakers behind them... For instance, perhaps 16A max current draw.
     
  3. Yggdrasill

    Yggdrasill Active Member

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    It is possible. The issue is to make it cheap, easy to use, reliable and compact.

    Probably the best way is to turn AC into DC, have some voltage regulation to ensure you have the same voltage from both connections, combine the DC, then turn the DC back into AC. You can make this sort of system very non-picky about the input. You could even combine a 240V and a 120V and generator outputs, if designed correctly.

    (I think it would probably be too expensive to make sense.)
     
  4. TEG

    TEG TMC Moderator

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    #4 TEG, Aug 26, 2012
    Last edited by a moderator: Dec 26, 2013
    Related old threads:
    220 charger from 110 voltage
    Fast charging from 120V


    Related product:
    220 240 Volts from 110 120 Volt Outlets - Catalog & Pricing

    - - - Updated - - -

    Not the best way for USA! Just hunt for outlets that are out of phase with each other, then you can take the alternate "hots" from each and you get 240V. It is basically the same power lines that the house 240V outlets use, just they split them apart each to different halves of the house with hot+neutral for 120V. If you don't have access to a 240V outlet, you can make one once you find the two halves.

    Home Electrical Wiring- Diagram and Installation
    (Visualize some more 120V outlets on the left side of this diagram going Line 2 to Neutral...)
     
  5. Yggdrasill

    Yggdrasill Active Member

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    It is better from the ease-of-use angle. Just plug it in. (And maybe adjust how many amps to take from each connection.)
     
  6. TEG

    TEG TMC Moderator

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    But you would still be limited to ~1.5kW because of 15A or 20A breaker on each 120V outlet.
    Besides, modern EVs in USA all let you charge from 120V directly, so stepping up voltage with an AC->DC->AC to 240V really wouldn't get you anything (other than a big piece of equipment and wasted efficiency.)
    Doubling the voltage by getting both parts of the split phase gives you twice the power capability. (Like 3kW instead of 1.5kW)

    USA "split phase":
    Split_phase2.png

    Not to be confused with "2 phase":
    http://en.wikipedia.org/wiki/2_phase_power
     
  7. Yggdrasill

    Yggdrasill Active Member

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    No, you'd still take as much as each breaker can handle. 2 * 15A * 120V = 3600W. Efficiency losses would mean you could probably output 3 kW.

    But of course, you could combine other inputs without worrying about phases and the like. For instance: 2 * 15A * 240V = 7200 W.

    And it would have a dual purpose, as you could use it to clean up generator outputs and the like. Of course - if designed correctly.
     
  8. TEG

    TEG TMC Moderator

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    Outlets nearby tend to be on the same breaker... So I don't know how you plan to get 2x 15A from your 120V->240V converter device.

    If you get 240V from two different sides of the house then you know you have at least 2x 15A because they are from different circuits.

    Anyways, your proposal of AC->DC->AC seems way "overkill" for something like this. You could just use a transformer if all you wanted was higher voltage...

    I think all this 'sidebar' talk of rectifications and transformation distracts from the fact that there is a simple solution available that just selectively connects existing wiring...
     
  9. Yggdrasill

    Yggdrasill Active Member

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    Outlets nearby also tend to be the same split phase. So, by that reasoning you can't produce 240V. :rolleyes:

    I'm proposing the exact same thing as you - plugging into two different outlets in different parts of the house. My solution is just less picky - it doesn't care if the two breakers are on the same split phase or different split phases. It doesn't care if the outlet is wired this way or another way. As long as there is a (for instance) 120-240V sine 5-20A supply - my solution will work with it.

    And you can plug in my solution into the exact same outlets, and get out 240V with nearly the same power.

    But it wouldn't be easy to combine the output from two outlets, so you gain nothing. (It is of course possible to do, if you make sure to use the same split phase. But this isn't something an idiot can do.)

    The box of electronics you need is simpler, but it's harder for a layperson in use, as it requires being able to figure out how to wire it up. My solution can be made by an expert and used by an idiot. Your solution can really only be used by an expert.
     
  10. mitch672

    mitch672 Active Member

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    It doesn't take an "expert" to see when a light is on, that's the indicator on the "Quick220" device that's made commercially to get 240VAC, from seperate 120V outlets on opposite phases. If you plug into 2 outlets on the same phase, the indicator light doesn't light up... Not rocket science. There is a post above from TEG (#4) with a link to the various models of the "Quick220" availble.
     
  11. mnx

    mnx 2013 P85

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    this probably should be in the charging forum and not the Model S forum. :)
     
  12. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    #12 FlasherZ, Aug 28, 2012
    Last edited: Aug 28, 2012
    Would my mother know how to rectify that? Not sure. She'd try every outlet in the garage - half of which are on the same circuit, and perhaps even the other half on the same hot leg. The person using the Quick2x0 needs to know that he/she needs to try circuits that are likely to be on different circuits, and hope those circuits are on different legs. That's lost on many non-engineering types.

    In one emergency case long ago, I had to find outlets on two different legs so that I could feed limited circuits in my house from a portable generator; even having the knowledge of which circuits are on which leg(based on my panel's map), it was still a matter of hunting the best outlets down among my choices. No disrespect to my family members, but that's something my mother would be very nervous with. I'm an engineer at heart, so the talk of legs ("phases" when used incorrectly) and circuits is easy for me to deal with; not so much any random person on the street.

    I agree with the point above - a solution that load shares two different inputs without regard for specific hot leg is going to be more complicated in engineering, but much more simple to use in practice.
     
  13. wycolo

    wycolo Active Member

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    Please retire the word PHASE from these home-oriented discussions. It is confusing to thems that need clarity.
    LEG is clearer, as in "the red leg is 120 volts from white (neutral) and 240 volts from the black leg".
    Leave the word PHASE to commercial 3-phase installations.

    Also, modern home service panels come with separate connector strips for NEUTRAL and GROUND. TEG's diagram
    shows them as a single entity, but that is no longer the case. Code and safety requirements need to be considered
    when deciding on the treatment of NEUTRAL vs GROUND.
    --
     
  14. mitch672

    mitch672 Active Member

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    The issue is, the device you are asking about is impossible to make. If its supposed to take two 120V outlets and generate 240V, how will it even be aware these are on 2 seperate circuits? If they are on the same circuit breaker, you won't even have any more power availble than a single 120V outlet.

    I they are totally non technical, they should hire an electrician and have a proper 240V outlet installed, or just charge at 120V

    For temporary, portable use the Quick220 is fine and works.
     
  15. FlasherZ

    FlasherZ Sig Model S + Sig Model X + Model 3 Resv

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    It is *not* impossible and there are several options available but it does require more electronics than simply going leg-to-leg (e.g., rectification and a 240V inverter).

    It *is* true that if they end up on the same circuit breaker you will have problems and will likely trip the circuit breaker.

    It *is* true that for an engineering type, Quick220 works just fine. But you're ignoring the usability problems that come from it for a non-technical user. This isn't about permanent installation, it's about charging at a faster rate when visiting someone else - hence the "proper 240V outlet" isn't an option, and perhaps the charge time of 120V/12A isn't an option.
     
  16. TEG

    TEG TMC Moderator

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    If you don't like "fishing" to find the alternate legs, there is another way:
    Really no need for an expensive/heavy/big transformer or AC->DC->AC even if you stick to "Parallel" 120V instead of finding the two hot legs to get 240V. If you know you got plugged into two different breakers, then you could just ask the vehicle to pull double amps at 120V. For instance, [email protected] instead of the [email protected] like the QIC220 provides. With this "solution" you would want both outlets to have the same "leg orientation" because you could cause a short if you tried to join outlets that used the other "hot". It would need to detect that both plugs are using the same hot, then parallel them for 120V at double amps.

    Anyways, at this point, nothing I am saying is an endorsement of any of this. There are safety issues to consider with shorting and grounding, and even trip hazards of running long extension cords around the house. Probably best to stick to commercially available products. I linked the QIC220... Are there any other existing "off the shelf" devices available to get 3kW+ from standard household outlets?

    I think the QIC220 type device just makes a lot more sense from a cost/size/weight/complexity standpoint. I don't think the 'ease of use' argument negates that.

    I am surprised that this topic turned into a debate of sorts!





    By the way, over on the LEAF forums, a bunch of people have built their own QIC220 style devices.
    People have various ways to tell when they found both "legs" to get 240V.
    Mine has a voltmeter on it.
    Some people put a neon light.
    Some people even have a buzzer that makes a noise when you get 240V (then you flip a switch to turn it off.)

    You don't need to be that technical to figure out how to use one.
    Just plug in one cord, then start walking around the house trying other outlets until the box tells you that you are ready to go.


    Perhaps a bigger issue with any of these solutions is that the 120V outlets tend to be on shared circuits.
    So you could get your 3kW+ charging going, then someone turns on a microwave, air-condition, vacuum, or some other high current device and pops one of the breakers.
     
  17. Cottonwood

    Cottonwood Roadster#433, Model S#S37

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    I actually bought a box that does this when I got my Roadster 3 years ago. You can find it at 220 240 Volts from 110 120 Volt Outlets - Catalog & Pricing. I got it to work in my home to test and verify. As has been said already, you have to find two 120 V. outlets that are on opposite sides (phases) of each other (red and black behind the wall).

    The second, more-annoying condition you need satisfy is that both outlets cannot be GFI outlets. If a 120V GFI outlet sees a current imbalance between the hot and neutral wires, it trips thinking the rest of the difference current is going to a ground fault. In the combiner box it is just going to the hot from the other outlet, but the GFI sees the imbalance and trips. GFI outlets are now required on all outside, bathroom, kitchen, and garage outlets in new construction. This means that you have to drag extension cords into the house or office. By the time I figured all of this out, and saw how many wires and extension cords that were needed, I decided that it was just too much overhead for the gain in charging speed.

    If anyone wants to buy my Quick220, A220-15D adapter box, I would be happy to sell it. $150, ground shipping included to any 48-state address. It is in like new condition, having only been used for testing, but sold as is.
     
  18. n00b

    n00b Member

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    Combining Two Lines to Double the Amperaage

    From reading the forum it appears combining two 120V into a 240V requires finding two outlets that are out of phase. How about doubling the amperage instead of voltage? Is it possible to combine two 120V @ 12A to provide 120V @ 24A of charging, or two 240V @ 24A into a 240V @ 48A? Could this reduce the charging time by 50%?
     
  19. RDoc

    RDoc S85D

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    I'd suggest pretty strongly that you talk to an electrician. This stuff really can get dangerous.
     
  20. mknox

    mknox Well-Known Member

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    This kind of thing can be very risky. Even if you find two 120v outlets on opposite legs, you don't know how much load may already be on each of the circuits (and I can pretty much guarantee they won't be equal), so trying to pull x amps at 240v from 2-120 volt circuits could overload the one circuit and cause its braker to trip while leaving the other breaker closed. In a proper 240v circuit, the two breakers are "ganged" so that if it trips, the whole circuit is dead. Depending on the orientation of circuits in the house,you also run the risk of induced neutral voltages.

    Paralleling 120v or 240v circuits to double the amperage... don't even think about that.

    Have an electrician do it up properly and sleep at night knowing your house isn't going up in flames or someone isn't getting electrocuted!

    Mike
     

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