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 Post subject: Re: 30 amp J1772 extension cord, 20 feet long
PostPosted: Fri Dec 06, 2013 1:48 am 
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TonyWilliams wrote:
It will not pass through the proximity signal, so I won't use those either
Of what use is passing through the proximity signal? Many J1772 cordsets only carry 4 wires, and even if you're using a cordset with 5 I don't think you should connect the proximity wire for an extension cable. Connecting the proximity circuits from two handles together could screw things up by adding in the additional resistors from the upstream handle. If I did the math right, adding in the additional 150 ohm resistor from the 2nd handle in parallel will cause the proximity pin voltage to be .9v in the connected state instead of the desired 1.5v, and will also change the voltage for the button pressed state to 1.25v from the desired 3.0v.

A car with robust J1772 logic will probably handle the lower voltage for the connected state, but the lower voltage in the 'button pressed' state is very close to what it should be in the connected state, and so it could lead to the EV not shutting off charging when the button's pressed and possibly arcing when you remove the handle.

You could get around this by removing the proximity circuitry in the extension cord handle - perhaps that's what you're already doing. Of course then you'd have to make sure to always disconnect from the upstream (EVSE) end while charging, and make sure not to ever repurpose the cable for an EVSE.

*Disclaimer: I'm just an "amateur" EE. :lol: Here are Chris Howell's (of open-EVSE fame) excellent charts on how J1772 works.

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 Post subject: Re: 30 amp J1772 extension cord, 20 feet long
PostPosted: Fri Dec 06, 2013 4:42 am 
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Location: San Diego
fooljoe wrote:
TonyWilliams wrote:
It will not pass through the proximity signal, so I won't use those either
Of what use is passing through the proximity signal? Many J1772 cordsets only carry 4 wires...
*Disclaimer: I'm just an "amateur" EE. :lol: Here are Chris Howell's (of open-EVSE fame) excellent charts on how J1772 works.


I appreciate your concerns. Many J1772 cables only carry four conductors because that is all that is required for an EVSE. The JLongtm J1772 extension cord is not an EVSE. If you are confusing the need for a proximity wire from the J1772 plug to the EVSE logic circuits, that's obviously not required as you referenced. That's different than what I am doing by sending the proximity signal to the place that it must go... the car.

I pass through the proximity signal, which requires all 5 conductors for the extension cord task. This isn't a theory; it's the way I build and deliver the JLongtm J1772 extension cord so that all the safety protocols are passed through.

If there is not a proximity wire, then when you press the J1772 disconnect button on the host J1772, nothing will happen. How could it? The signal has no conductor to carry the 330 ohm disconnect signal to the car. That means you could press the button and REMOVE THE HOST J1772 PLUG UNDER LOAD !!!

Hopefully, you can see the shortcomings in that. No thanks for me, or for the folks who buy my product.

There is no need to disconnect either the "upstream" EVSE or the JLong first, as you suggest. Either one first is fine, since either sends EXACTLY the same signal to the car.

There is no "arcing" (quite the opposite, actually). There is no need to mark this product in some way that it shouldn't be used for an EVSE, as you suggest. There is no change to the resistance of the proximity signal (none whatsoever) with my product. Whether you plug in an EVSE, or an EVSE with the JLongtm, the value of resistance at the proximity pin on the car will be 150 ohms. Again, either way, it will show 150 ohms, per J1772.

When you press either J1772 button, either the EVSE plug disconnect, or the JLongtm plug disconnect, an additional 330 ohms is added in series, per J1772 protocol, to signal a disconnect to the car.

Using a J1772 extension with only a four conductor cable is not safe, in my not very humble opinion.


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 Post subject: Re: 30 amp J1772 extension cord, 20 feet long
PostPosted: Fri Dec 06, 2013 8:32 am 
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First off let me say that I'm not really "concerned", however you make it - and by the same token I don't think you should be concerned about someone using a 4-wire cordset either. The worst that could happen either way is probably just seeing a fleeting EV system error message in the car after an improper disconnect under load, or a tiny amount of damage to a plug/inlet from arcing that probably wouldn't affect anything unless it were repeated a lot. The discussion here is mostly academic, but that said:
TonyWilliams wrote:
There is no need to disconnect either the "upstream" EVSE or the JLong first, as you suggest. Either one first is fine, since either sends EXACTLY the same signal to the car.

There is no "arcing" (quite the opposite, actually). There is no need to mark this product in some way that it shouldn't be used for an EVSE, as you suggest. There is no change to the resistance of the proximity signal (none whatsoever) with my product. Whether you plug in an EVSE, or an EVSE with the JLongtm, the value of resistance at the proximity pin on the car will be 150 ohms. Again, either way, it will show 150 ohms, per J1772.
This is the part where I have to disagree. From my understanding of Chris's charts (slides 14-17 specifically, and see image attached), the J1772 handle(s) don't "send a signal" - they add resistance to ground in parallel to the resistance already present in the car to form a voltage divider circuit.

When no handle is connected, the 5v originating in the car is lowered to 4.5v between the 330 and 2700 ohm resistors present in the car - this is the "not connected" state. When one handle is connected, its 150 ohm resistor, in parallel with the 2700 ohm resistor in the car, brings the voltage down to 1.5v, and when the latch-release button is pressed there's an additional 330 ohm resistor added in the handle that brings the voltage to 3.0v.

If two handles are both connected, then that changes the equations by adding additional resistors in parallel to the other handle's and car's, and you end up with the 0.9v and 1.25v that I calculated before, which could mess things up, depending on how the car's logic handles things. If there are any real EEs out there who can show that I'm doing the math wrong, please speak up, but this is how I understand Chris's charts.

So, you have two options for making a J1772 extension cord so that only one handle is on the proximity circuit at a time:

1. You use a 4-wire cordset or just don't connect the proximity wire, and you leave the proximity circuit in place in the handle. To properly disconnect under load, you just make sure you disconnect the handle from the car before you disconnect the EVSE handle from the extension.

2. You use a 5-wire cordset and attach the proximity wire, AND you remove or bypass the 150 ohm resistor in the handle. In this case you can properly disconnect either handle first.

#2 is preferable as you don't need to worry about the order of disconnect, but #1 is fine if used properly and of course simpler to construct.

EDIT: corrected #2 to show that you would just remove the 150 ohm resistor in the extension's handle, not all of its proximity circuitry.

But if my math is right, what you should NOT do, for the reasons described above, is:

3. Use a 5-wire cordset and attach the proximity wire and leave the handle's proximity circuit intact.

But again, I'd be happy to be proven wrong, and I don't mean to cause a fuss or intimate that your JLong is somehow unsafe, but I think it's worth figuring out what the right answer here is.

Also, I'll reiterate that the option I'd prefer is none of the above - just carry a J1772 to NEMA adapter and a portable EVSE and you get the same functionality and only need one cordset. That way the adapter "acts like a car" as far as all this proximity stuff is concerned and it's just like plugging your portable EVSE into any other outlet (but do be mindful to set your portable EVSE's pilot to something <= the host EVSE's.) And if you ever want to plug your welder or whatever into a charging station you can do that too! :lol:

Image

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Last edited by fooljoe on Sat Dec 07, 2013 1:32 am, edited 1 time in total.

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 Post subject: Re: JLong(tm) 30 amp J1772 extension cord, 20 feet long
PostPosted: Fri Dec 06, 2013 2:37 pm 
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Location: San Diego
When you suggest that disconnecting under load with the associated issues is ok, then you really don't need an EVSE at all. Just do away with J1772, and use regular extension cords. Having said that, I carry two of the NEMA 14-50 to J1772 adaptors just for those situations were I need an extension cord.

Maybe I'll do a video.

https://www.dropbox.com/s/9hj65yckhhraiho/IMG_2248.JPG


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 Post subject: Re: JLong(tm) 30 amp J1772 extension cord, 20 feet long
PostPosted: Fri Dec 06, 2013 4:57 pm 
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Joined: Mon Apr 01, 2013 8:19 pm
Posts: 34
Tony can I get this through you (drop $400 at your house) or do I go through Bob? Do I add a PayPal fee to the $399 or just the $35 S&H? Thanks


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 Post subject: Re: JLong(tm) 30 amp J1772 extension cord, 20 feet long
PostPosted: Fri Dec 06, 2013 7:52 pm 
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Location: Seal Beach, CA
TonyWilliams wrote:
When you suggest that disconnecting under load with the associated issues is ok, then you really don't need an EVSE at all.
Don't be silly. Another thing to note is that the proximity and pilot pins are shorter and so disconnect first during a "hot disconnect." And a properly functioning EVSE will immediately close its relay when the pilot signal is interrupted, so the danger of any arcing or exposed hot prongs on the handle really is minimal.

But back to my original point, I did a little test this morning that will hopefully illustrate what I'm saying more concretely than showing a bunch of math and esoteric diagrams:

Here's the proximity resistance on a regular old J1772 handle:
Image
Here it is with the button pressed:
Image
Now here's what happens when you connect the proximity circuits from 2 handles together:
Image
And when you press one of their buttons (same result with either button):
Image

Now I don't know exactly what the results will be, but it seems to me showing the car 79 ohms instead of 150 for the connected state and 122 ohms instead of 478 for the button pressed state isn't the best idea.

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 Post subject: Re: JLong(tm) 30 amp J1772 extension cord, 20 feet long
PostPosted: Fri Dec 06, 2013 8:58 pm 
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fooljoe wrote:
Now I don't know exactly what the results will be, but it seems to me showing the car 79 ohms instead of 150 for the connected state and 122 ohms instead of 478 for the button pressed state isn't the best idea.



I'm not sure why you are stuck on continuing to imply that WHAT I AM USING is other than 150 ohms connected / 480 ohms disconnected for the proximity signal from the plug to the car. I do fully understand J1772 signals.

I think you're assuming that we use the cables "as-is", without modification? Of course that doesn't work well, and will get the results you've shown above. I've never once suggested anything other than fully compliant J1772 signals.

So,


1. I do not recommend using "79 ohms instead of 150 for the connected state and 122 ohms instead of 480 ohms for the disconnected state". Actually, I'm not even sure it would work.

2. I do not recommend using 4 conductor J1772 cables for extension cords. There is not a way to pass through the necessary proximity and pilot signals without 5 conductors. Folks who are doing otherwise are defeating the basic safety features of J1772. but it will physically work.

3. I do not recommend relying on "first out" disconnect of the proximity and/or pilot pin for EVSE disconnect. Yes, this will stop the flow of power, however, you're not using the proximity to signal it, but instead are disconnecting the pilot signal.

4. I do not recommend disconnecting J1772 plugs while potentially under load. This is just bad practice for any plugged in circuit.

5. If you are going to "dummy load" an existing existing stationary EVSE to a NEMA 14-50 or other regular plug outlet, YOU DON'T NEED ANY J1772 EXTENSION CORD. Just use any appropriately rated three conductor extension cord (8 gauge is fine for 40 amps) with a portable EVSE. Again, this bypasses all the safety of the J1772 protocol.


If you want a fully compliant J1772 extension cord that offers a fully compliant proximity disconnect at both the host EVSE and the extension cord(s) (yes, even if you had two or more of our J1772 extension cords all plugged in together!!!!), that's what our JLongtm will do.

So, let's be clear, while you propose a ton of ways to "do it wrong", that's not how we're doing it. If you had ten JLongstm plugged in, end to end, with a J1772 EVSE on the inlet end of the first JLongtm, the proximity signal would show 150 ohms at ANY of them, including the last one that plugs into your Rav4 EV.

Then, when you hit the disconnect button on the host EVSE, or on any of the JLongstm, you will get 480 ohms at the proximity signal at your plugged in car. I sincerely hope this clears things up. Oh, I better add that, of course, the pilot signal is also fully passed through without interruption. If the EVSE sends a pilot signal, it will go to your car without fail.

One unrelated caveat, however, for Tesla or other EV's with more than 40 amp chargers onboard; DO NOT EXCEED 40 AMPS through the JLongtm. While I probably will test it at 41 to 80 amps soon to measure how hot it will get, 40 amps has been tested without excessive heat.


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 Post subject: Re: JLong(tm) 30 amp J1772 extension cord, 20 feet long
PostPosted: Sat Dec 07, 2013 1:24 am 
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TonyWilliams wrote:
I'm not sure why you are stuck on continuing to imply that WHAT I AM USING is other than 150 ohms connected / 480 ohms disconnected for the proximity signal from the plug to the car. I do fully understand J1772 signals.
I never meant to imply that - to be clear, I've never seen or tested a Jlong so of course I don't know how exactly it works.

Recall that the discussion here began around the question of how to get or simply make a 40 amp+ version of a J1772 extension cord, since you don't make that. I suggested a readily-available 4-wire cordset, and you said 5-wire should be used instead to "pass through" the proximity circuitry. I just want to make sure that nobody goes off and builds their own 5-wire extension with the proximity connected and without making any other mods to rectify the situation, as apparently you have.

Speaking of which, I found your post in the Leaf forum with the plans for a J1772 extension cord, upon which I might presume the Jlong is based. (Why didn't you just link to this in the first place?) Seems like you remove the 150 ohm resistor in the handle, which I hinted at before when I said the handle shouldn't be repurposed for standalone EVSE use - but you then said that wasn't true...

Anyway, my apologies for thread crapping - perhaps it would be best to move this stuff into its own "40amp+ J1772 extension cord" thread to remove any possible implication that anything's wrong with your product.

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 Post subject: Re: JLong(tm) 30 amp J1772 extension cord, 20 feet long
PostPosted: Sat Dec 07, 2013 4:48 am 
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I ordered the Jlong. Thanks Tony.


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 Post subject: Re: JLong(tm) 30 amp J1772 extension cord, 20 feet long
PostPosted: Sat Dec 07, 2013 7:13 am 
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Location: San Diego
fooljoe wrote:
Speaking of which, I found your post in the Leaf forum with the plans for a J1772 extension cord, upon which I might presume the Jlong is based. (Why didn't you just link to this in the first place?) Seems like you remove the 150 ohm resistor in the handle, which I hinted at before when I said the handle shouldn't be repurposed for standalone EVSE use - but you then said that wasn't true...


I have posted those drawings for this very forum, plus the Tesla and LEAF forums. This is the only forum that didn't have any technical comments, until now. There's no secrets. Yes, of course, the only changes from an EVSE plug are removing the 150 ohm resistor, and using the fifth conductor to pass through the proximity. My plans and design are free to copy and use for non-commercial use.

This in no way negates it's future use as a EVSE cable. Just spend the 30 seconds to return the 150 ohm resistor and you're in business.

I've had folks (in other forums) quite aggressively suggest that I needed an attorney, or this would cause a fire, or it doesn't meet some code somewhere, et al. It's a completely different situation to ask how I did it (which has been openly and freely shared throughout the EV interested internet) compared to documenting why it can't / doesn't work, none of which applies to my design.

I personally have no plans to offer anything more than 30 amps capable units, even though it can safely handle 40 amps.


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