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How to make a 30 amp J1772 extension cord for public charging

Discussion in 'Technical' started by TonyWilliams, Sep 19, 2013.

  1. TonyWilliams

    TonyWilliams Member

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    #1 TonyWilliams, Sep 19, 2013
    Last edited: Sep 27, 2013
    Link to Nissan LEAF forum thread on the same topic:
    My Nissan Leaf Forum View topic - Need a circuit designed to limit charge to XX amps max


    I'm sure there are folks who would like a J1772 extension cord without all the expense of another EVSE. This will work great in public charge station spots that are blocked by another car, but you could use that charge station if you could just add 25 feet more to the plug!! 30 amps maximum on this one, which is what virtually all public J1772 charge stations are:


    J1772extensionCord.jpg



    DRAFT 2:

    J1772extensionCordDraft2.jpg
     
  2. FlasherZ

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

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    The only thing to note is that you violate NEC 625 when you use a J1772 extension cord. Should your car burn up while it is being used, you may not be able to recover based on an insurance claim. There is a gray-area argument that you could use here - that EVSE equipment is an appliance and isn't subject to NEC oversight, but the insurance company has the money and you'd be out while trying to prove your case.

    - - - Updated - - -

    Full disclosure: I do use the occasional extension cord which violates 625.22 (mostly my 14-50 extension cord). I accept the risks occasionally, just be sure you are knowingly accepting the risk as well.

     
  3. hcsharp

    hcsharp Active Member

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    FlasherZ, do you see any obvious risks from using an extension cord like Tony has designed? I've thought about it but can't think of any. Not that you would necessarily be aware of an increased risk, but wondering if anything pops out at you.

    Also, I didn't know that using a NEMA 14-50 extension cord created a violation. Lots of companies make these extension cords for RVs and some are UL approved. I always assumed the NEC and J1772 prohibition against extension cords only applied to extensions to the J1772 cable like Tony proposed above, and that the EVSE started at the receptacle on the end of the extension cord. NEC 625.22 only states that the cord needs to have a listed system of protection against electric shock. Would your extension cord be in compliance if it had an interrupting protection device within 12 in of the attachment plug? Thanks for your insight.

    @Tony, one other thing you might want to mention is that most J1772 inlets come with a 2.7k resistor installed between the proximity pin and ground. Many vehicles will not charge unless you remove that resistor from the extension cord inlet.
     
  4. FlasherZ

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

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    Not for reasonable lengths as long as obvious precautions are observed. Don't throw the extension coupling in a lake along a dock.

    This is a gray area, one could argue EVSE equipment is an appliance and doesn't get covered by NEC anyway. That would be played out in court but while that is happening you'd likely be on the losing end (i.e., insurance company wouldn't pay until the court forced them to after you fought it). The intention of 6.22 is to provide GFCI within 12" of the receptacle to prevent shocks, and to keep the constantly-energized portion as short as possible, and to keep the greatest amount subject to the car's secure coupling. If you had a GFCI function on the head of the extension cord, that would work as well.
     
  5. hcsharp

    hcsharp Active Member

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    They must have felt like the appliance was the car, and the EVSE was part of the electrical system that supplies the car. So are you suggesting that most of the several pages that constitute NEC 625 are based on an assumption by the NFPA that an EVSE is not an appliance and therefore they can write codes about it?
     
  6. markb1

    markb1 Active Member

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    #6 markb1, Sep 20, 2013
    Last edited: Sep 20, 2013
    What happens if you plug this into a 70A EVSE? Does the pilot signal get passed through unaltered, allowing the car to pull more than 30A? That would be bad.
     
  7. hcsharp

    hcsharp Active Member

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    The pilot signal is unaltered in Tony's design. He specified a 30A cable however. If you use it at 70A then you will need a 70A cable, J1772 inlet and connector. Not sure if Leviton is still selling their 70A cable set but other vendors have them.
     
  8. markb1

    markb1 Active Member

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    So, that's potentially dangerous to build this for anything less that the maximum J1772 current, which I think is at least 80A. Building it for less current means you always have to remember to make sure the car doesn't draw more than the extension is designed for. A better design would be to alter the pilot signal to prevent any user error.
     
  9. TonyWilliams

    TonyWilliams Member

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    #9 TonyWilliams, Sep 21, 2013
    Last edited: Sep 21, 2013
    I appreciate everybody's critiques. First, let me offer that no extension cord that I'm aware of passes a "max amperage command", which means that the guys who are using a NEMA 14-50 extension cord can obviously overload it on EVSEs and chargers that can pull more than the rated amount.

    I find that this J1772 extension, as opposed to a generic extension cord, offers increased safety. The GCFI still operates, and all the other safety protocols of J1772. Extension cords do not. The issues with maximum current over 30 amps is easily rectified with an 80 amp rated cable and J1772 inlet and plug (none of which exist anywhere on the planet that I'm aware of). Alternately, the 30 amp cable could continue to be used safely on public 30 amp charge stations only (which was the impetus).

    The 14-50 extension cord offers no protections for a disconnect under load, possibly causing a spark / fire; this J1772 extension does integrate the 100ms disconnect at both ends. A NEMA 14-50 extension cord "dropped in water" could suffer the same fate as this J1772 extension. But, the J1772 extension would use the GCFI of the EVSE to protect it; the extension cord, once again, does not protection.

    Good point on the 2.7k resistor on the J1772 inlet. The ones I have do not include this, but it's reasonable to expect that some/many would. Yes, it would also need to be removed in addition to the 150 ohm resistor in the plug.

    As to NEC, UL, laws, rules, regulations, insurance, et al, they are different all over the world, and I make no attempt to address them. Safety is paramount. Caveat emptor. No warranty for merchantability. Offered as-is, with all faults.

    Could a circuit be added to limit this extension to only the max rating of the cable? Of course. The simple logic would need:

    1) pilot signal duty cycle at 30 amps or less, no change.

    2) pilot signal duty cycle over 30 amps, change output duty cycle to 30 amps
     
  10. hcsharp

    hcsharp Active Member

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    I agree but public and fixed charging stations don't really give you the option of using a generic extension cord. The safety issue boils down to the same arguments against using other extension cords - it's too easy to undersize the cord/plug/receptacle. I think yours is safer for the reasons you mentioned and because very few public stations are more than 30A. And you specified a thermal protection switch, although marked optional. The only exception is in Europe where most charging stations don't have cords. You have to bring your own. There is a standardized system using passive components in the cord that allows the charging station to determine the capacity of your cable.

    It's also possible to buy 80A EVSE cable here, made in USA, although it probably won't be for sale much longer. ITT-Cannon has a 75A J1772 coupler with 75A cable, and a couple of other sources have couplers rated at 70A to use with a cable like that linked above.

    I have to confess if I was doing this I would be very tempted to build a 30A cable like you did. I can't imagine using it anywhere that has more than 30A.
     
  11. markb1

    markb1 Active Member

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    Assuming the 14-50 extension cord is rated for 50A max and 40A continuous current, it shouldn't be a problem. For instance, a Tesla UMC with 14-50 adapter will never pull more than 40A. It's true that 120V extension cords are commonly rated for less than than the outlets they are plugged into, but the 240V extension cords I've seen are designed to carry the same current as the outlet. (Now that I've said that, someone will surely find one that's not!)
     
  12. FlasherZ

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

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    Yes. They will claim that EVSE is supply equipment, with a J1772 receptacle (or Tesla receptacle), just as a normal 5-15 receptacle is supply equipment.

    - - - Updated - - -

    Unfortunately, in today's world, that sometimes doesn't cut it. If I can demonstrate that you knew the NEC disallowed J1772 extension cords (25' limitation), that I *didn't* know that, there may be a chance I can convince a jury you have shared an obligation to tell me that it was illegal for me to use your product across the 99%+ of the country that incorporates NEC article 625. The key is what you know. You could get out of a claim against you because Bechtenshire, UK passed a law saying that J1772 extension cords must use yellow wiring only - who would expect you to know that? You assume some risk when you know that your cord is technically illegal for consumers to use in 99%+ of the US and you don't disclose that fact.

    Unlike a device that combines multiple circuits, which has very serious safety grounding issues, an extension cord is relatively safe especially when protected by EVSE electronics. The problem is that many extension cords (as I mentioned above) can be used safely for temporary purposes, the problem is that some people use them unsafely for permanent purposes. It's safe but illegal, and when insurance companies are in the business of protecting against claims, they'll use that illegal part every time to deny coverage. Not a shot against anyone's technical expertise.
     
  13. TonyWilliams

    TonyWilliams Member

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    The IEC 61851 standard for the Mennekes socket used in Europe:

    1.5k = 13a
    680k = 20a
    220k = 32a
    100k = 63a



    ITT has discontinued that 75 amp J1772 assembly (I have one of them on my Clipper Creek CS-100 series EVSE). That eBay cable is PERFECT, since it has the needed proximity conductor that few cables have.

    As to the "other sources", I presume you mean the Dostar J1772 plug that I put on the Tesla UMC's. That was recently downgraded to 50 amps after being presented for UL approval.

    So, to date, there has not been a single 80 amps J1772 plug ever offered to the public that I'm aware of. The 70 and 75 amp versions have disappeared.



    The same basic due diligence that we would each use with any extension cord would apply.

    - - - Updated - - -

    Except a Tesla UMC isn't the only EVSE in the world. I can put a 14-50 on any J1772 with a simple, commonly available adaptor.

    If I do that on one of the 70 amp, J1772 equipped Tesla/Roadster Clipper Creek EVSEs, there could be a problem!!!

    We're getting a long way from the issues with the J1772 extension, however.

    - - - Updated - - -


    I'm actually not going to play lawyer on the internet, or pontificate publically how somebody can manipulate the legal system to their advantage. You'll note that I don't criticize somebody who might produce an adaptor for electric vehicle charging, even though that is specifically "illegal" in most of Europe.

    So, again, what I know has nothing to do with what I'm offering, and that offer is specifically "as-as" and "with all faults" and "no warranty for merchantability". Heck, somebody may use if for a noose and commit suicide with it, yet I offer no warranty that it might do that job without injury, death, etc.

    This will be the final rebuke of the legal ramifications.


    This is a common, and often quoted quip, but you'll find that it's actually not the case many times. It's dangerous in a debate to use EVERY TIME, because invariably, somebody will find the exception(s) that make your statement wrong.

    What don't we put some positive energy into developing a safety circuit?

    I need a circuit designed that will limit the maximum EVSE pilot signal "duty cycle / pulse wave modulation" to the following:

    1) EVSE pilot signal > than XX duty cycle, output XX pulse wave modulation (PWM) only
    2) EVSE pilot signal <= to XX duty cycle, let the EVSE's PWM pass through unchanged

    This device would be placed between the EVSE plug pilot signal pin and the car's pilot signal pin. That signal is a 1kHz 12/-12 volt square wave with the following duty cycle:

    10% - 96% = 6 amps - 80 amps
    >96% = Error

    One simple option might be:

    XX% duty cycle = 96%, but then is wouldn't work with duty cycles greater than XX%

    I want to be able to limit to XX%, not stop above XX%.
     
  14. markb1

    markb1 Active Member

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    Source? I would hope nobody is selling such an EVSE, as it is an accident waiting to happen. I would have the same concern about a J1772 to 14-50 adapter, if it doesn't have it's own over-current protection.

    I robust J1772 extension would have the pilot logic you described earlier.
     
  15. hcsharp

    hcsharp Active Member

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    Actually there are several models of EVSE being sold that come with a NEMA 14-50 plug to supply power. The NEC only requires that the cord be no more than a foot long in addition to a max of 40A.
     
  16. hcsharp

    hcsharp Active Member

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    That's discouraging! Are you sure ITT actually discontinued the 75A coupler? I was told they just ran out, and recently began shipping the 75A units again. The Dostar connector looked like good quality but their cable was really cheap and I wonder if that's what caused it to be downgraded by UL.

    Not sure if that comment was directed at me or not since I sell a charging adapter in Europe. I would hope that if you saw something unsafe (even slightly) with one of my products that you would not hesitate to be critical or at least say something. While the directive discourages adapters, they are not always illegal. All the components in my adapter are rated for more than the maximum allowed J1772 charging rate in Europe, so there is no risk of using it where it might be undersized.
     
  17. FlasherZ

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

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    #17 FlasherZ, Sep 22, 2013
    Last edited: Sep 22, 2013
    I made an attempt to explain what I have seen from my own observations and experiences. If that's "pontificating", well, I'd rather stand behind a pulpit and inform people of the risk, rather than knowing it technically violates the law in the greater majority of the US and attempting to hide behind a disclaimer. In Massachusetts, it is not permissible to expressly disclaim warranty of merchantability for consumer products, which would doom you right there anyway.

    I am not an attorney and if you would like legal advice you should seek out your own attorney. My experiences and observations are purely that - experiences and observations, not legal opinion.

    For what it's worth, I'll just reiterate that in this particular case (unlike the use of circuit-combiners), the use of a properly-built J1772 extension cord is going to be safe and you should have nothing to worry about in its use, you will get the protections provided by the EVSE. There is some risk, though, in that use technically violates the law in well over 95% of the United States and that can cause insurance companies to refuse to pay a claim -- I've seen it happen.
     
  18. TonyWilliams

    TonyWilliams Member

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    #18 TonyWilliams, Sep 22, 2013
    Last edited: Sep 23, 2013
    I'm well aware of that issue in Massachusetts. No, I don't want or need additional legal advice beyond what I already have, nor did I ask for any. Thanks for your efforts, however. I'm sure that may aid somebody.

    Can we talk about EV stuff now?

    - - - Updated - - -

    Well, as discussed, it doesn't need any pilot signal logic if the hardware is all rated for 80 amps. The only issue is hardware below that, like my 30 amp specification. I don't really want to lug around heavy 80 amp 3 gauge cables for a public 30 amp charge station with a Plug-In Prius in the way.

    There are several J1772 to 14-50 adaptors out there, and they are as safe as just about any other extension cord or adaptor. None that I'm aware of have over-current protection, but surely that's easy to add if you think it's important. I suspect that before I'm dead, there will be a requirement for GCFI and over current protection on all extension cords.

    - - - Updated - - -

    A2056-PEV (no longer availble), J1772, Leviton, L1/L2, 75A, 25', $218.69

    The old link for the 75 amp plug

    What Leviton has today

    The Dostar part I'm talking about excludes the wiring. Just the pins and J1772 handle/plug. Now, it is 50 amp rated which leaves no J1772 plug available on the consumer market about 50 amps.
     
  19. FlasherZ

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

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    Awww, I <3 you too TonyWilliams. You can talk about whatever you'd like. Just making sure people know the risks of what they're doing. I would really hate to see someone lose a car, a home, or their life. I don't just write them off in a disclaimer.
     
  20. TonyWilliams

    TonyWilliams Member

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    I've actually already had one J1772 plug (that was UL listed) try and burn my house down. Like my decades in aviation, I prefer ultimate safety over what a rule book might approve.

    I really don't like the accusations that I'm a law breaker, however. My "tone" isn't going to change much in that regard.





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    Rav4j1772burntPinA.jpg
     

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