ICE Breaker J1772 extension cable technical discussion

[TonyWilliams]

In an effort to put some positive light on this, I'll offer a challenge.

Let's pay to have an independent laboratory do a series of standard load / heating tests, comparing our JLong and Brad's extension cable.

If I'm wrong, I'll be really embarrassed by the results that show Brad's stuff is better / safer / than our product. Heck, let's invite a few of the other "extensions" out there for the test.

Again, Brad isn't the first person I've called out, and it won't be the last.

For the folks who have an issue with me advertising, I'll just offer that I'm a PAID advertiser operating a licensed, tax paying, business. Our company's banner is likely at the top of this page now.

We also have engineers (with professional degrees) that design our products. I will happily put our products against any out there.

 

[dhanson865]

In short I think your tone in this thread has overstepped what is socially acceptable and I could see why Brad would see your posts in a negative light.

Oh and even if you think you have to advertise the heck out of your products you don't have to post a screen full, a simple statement or two with a URL to the full text gets the point across to anyone that wants to read it. I mean why have a multi-line signature with URL below a post that has the entire text of what I'd read at the URL?

Really, this is about me? My signature line isn't good enough?

I have no problem with your signature. My post was about the length and content of http://www.mynissanleaf.com/viewtopic.php?f=41&t=19888#p425735" onclick="window.open(this.href);return false; which I can't even fit on one 1920x1080 screen in my browser to take a screenshot of the entirety of and the tone that set for the remainder of the thread.

For some reason even my neutral voice has angered you. If you have me on ignore so be it. I don't plan to put you on ignore and I don't plan to harass you on the boards so you don't need to put me on ignore.

 

[VegasBrad]

My bad I see where some confusion came from, I didn't have the derating language in my listing as I do in my EVSE listings. fixed it.

 

[TonyWilliams]

My bad I see where some confusion came from, I didn't have the derating language in my listing as I do in my EVSE listings. fixed it.

Thanks for fixing that.

As REMA found out (a German company), and Tesla in my previous examples, when you do this enough times, even with very meticulous planning, design, etc, the **** is going to hit the fan eventually.

If you're doing this uninsured and without the benefit of a corporate structure, you are really hanging "it" out there, particularly when you post details in public.

Last of my speech. Good luck with your product.

 

[eHelmholtz]

Wait. Have I not been using the J1772 cables correctly?

Brad's set up includes 4x16AWG conductors. Each 16AWG conductor would handle 13A times 4 is 52A. Do I understand that this should be derated by 20% and used at 42A?

Tony's 8 conductor cable uses 2x12AWG for each phase. Each 12AWG conductor would handle 20A times 2 is 40A total. I have been using this cable at 40A to charge a Rav4. Should I have derated by 20% and use it only at 32A?

 

[TonyWilliams]

Wait. Have I not been using the J1772 cables correctly?

Brad's set up includes 4x16AWG conductors. Each 16AWG conductor would handle 13A times 4 is 52A. Do I understand that this should be derated by 20% and used at 42A?

Tony's 8 conductor cable uses 2x12AWG for each phase. Each 12AWG conductor would handle 20A times 2 is 40A total. I have been using this cable at 40A to charge a Rav4. Should I have derated by 20% and use it only at 32A?

Our cables are "continous duty". No derate required.

Our 40 amp JLong is safe at 40 amps.

Our 80 amp JLong is safe at 80 amps.

 

[eHelmholtz]

OK, great. That's what I thought. So I should be able to use Brad's 3x16AWG conductor/per phase J1772 cable at 40A and his 4X16AWG conductor/per phase at 50A without problems. I'll test and get back.

 

[evfan310]

I'm a little surprise that either one of you is relying on multiple parallel conductors to provide the necessary capacity. This is generally not good practice since

1. It is difficult to assure that the current is equally shared, resulting on some conductors being stressed, and
2. If one conductor fails, the current is shared among the remaining ones, leading to higher stress and progressive failure.

While the NEC doesn't apply to extension cords, they provide some guidance in using multiple parallel conductors (section 310.4). It's worth keeping them in mind since the same underlying principles apply...

1. Except in special cases, NEC permits paralleling only with very large wires....in other words, don't do it if you could simply have used a single, larger wire.

2. When paralleling wires, NEC requires you to add the circular mils of the paralleled wires when computing the combined capacity. They don't allow simply adding together the capacities. For example, 12 ga wire is rated for 20 A and has an area of 6.53. To get a rating of 40 A, you need to use 8 ga wire which has an area of 16.5...MORE than twice. So two 12 ga wires would not have 40 A capacity.

Similarly, 16 ga wire has an area of 2.58. Four of them would have an area of 10.32, which is about the same as a single 10 ga wire which is rated at 30 A

It seems to me a better way to handle this is to use single conductors of adequate size. At least one other maker of J1772 extension cords does it this way. He uses purpose-made EV cable

http://www.generalcable.com/NR/rdonlyres/6EA49F02-6A77-46E6-B65B-471F31CC9506/0/CAR_0137_R0711CarolGreneEVCableSS.pdf

to do this job. General cable make EV cable rated at 30 A (10 ga conductors) and 40 A (8 ga conductors).

 

[ishiyakazuo]

I'm a little surprise that either one of you is relying on multiple parallel conductors to provide the necessary capacity. This is generally not good practice since

1. It is difficult to assure that the current is equally shared, resulting on some conductors being stressed, and
2. If one conductor fails, the current is shared among the remaining ones, leading to higher stress and progressive failure.

It seems that #1 only matters if you're getting reasonably close to the current carrying capacity of the wire. If you're on that hairy edge, then yes, that's an issue, but if you've got the wires braided together and then crimped, for example, they should be reasonably well-balanced.
As far as #2 goes, I'd say there are some pros and cons with each approach. For example, I've got a 2012 LEAF. It's going to draw at most, maybe 18A. Would I rather have a cable that supplies 40A in one conductor or two? Well, if one fails, I'm still safe if it's being carried over two conductors. Can it run at 40A anymore? Obviously not, and I'd have little way of telling this, as you say. However, the longevity of the product for my use is increased by the redundancy.

 

[evfan310]

Right, if you are not pushing the capability it doesn't matter. But most of the discussion seemed to relate to how hard can one push it? Is it safe at so many Amps. I'm simply saying 4 fifteen-Ampere wires in parallel don't equal a 60-Ampere wire. And it's better to use a single 60-Ampere wire if that's what you want to carry.

 

[wwhitney]

2. When paralleling wires, NEC requires you to add the circular mils of the paralleled wires when computing the combined capacity. They don't allow simply adding together the capacities. For example, 12 ga wire is rated for 20 A and has an area of 6.53. To get a rating of 40 A, you need to use 8 ga wire which has an area of 16.5...MORE than twice. So two 12 ga wires would not have 40 A capacity.

To my knowledge, that is not how the NEC calculates the combined ampacity of parallel wires. Do you have a reference?

I believe that in paralleling wires, you do add the underlying ampacities. That is one of the reasons for paralleling wires, to get a greater ampacity for a reduced cross sectional area. This makes sense because parallel wires have a greater surface area for a given cross-sectional area, so the parallel wires can reject heat more efficiently than a single circular cross section. In NEC applications that typically means putting the parallel wires in separate conduits, so that you don't have to take a reduction for more than 3 current carrying conductors in a single conduit or cable.

Cheers, Wayne

 

[ishiyakazuo]

2. When paralleling wires, NEC requires you to add the circular mils of the paralleled wires when computing the combined capacity. They don't allow simply adding together the capacities. For example, 12 ga wire is rated for 20 A and has an area of 6.53. To get a rating of 40 A, you need to use 8 ga wire which has an area of 16.5...MORE than twice. So two 12 ga wires would not have 40 A capacity.

To my knowledge, that is not how the NEC calculates the combined ampacity of parallel wires. Do you have a reference?

I believe that in paralleling wires, you do add the underlying ampacities. That is one of the reasons for paralleling wires, to get a greater ampacity for a reduced cross sectional area. This makes sense because parallel wires have a greater surface area for a given cross-sectional area, so the parallel wires can reject heat more efficiently than a single circular cross section. In NEC applications that typically means putting the parallel wires in separate conduits, so that you don't have to take a reduction for more than 3 current carrying conductors in a single conduit or cable.

Cheers, Wayne

This is my understanding as well. Surface area is key for dissipating the heat. Now, there is something to what evfan310 is saying here, and I think it's been said before here: Certainly you can't enclose three 15A wires in an enclosed space and expect it to operate as well as a single 45A wire, because some of the surface area of one will be "aimed" at one or more of the others. I'd think that there's some overhead that's needed if you're enclosing them in some sort of sheathing. There are probably complex calculations needed to determine the various theta-Js of the wiring in these cases. Yes, the three wires can carry 45A if they aren't jammed up against each other, but will it be as cool as if each one was carrying 15A separately? Unlikely.
If you took each set of lives, (neutrals as needed,) and grounds and split them up and sheathed them separately such that each one is a 15A cable, and kept them separated from each other for the majority of the cable's length, then it should be totally fine. Ganging them all together would lead to extra heat build up in the cable and require some derating. I think Tony's comment earlier of "test the resultant cable while under stress" is probably the wisest thing.

 

[evfan310]

Here's an article that discusses exactly that question

http://www.ecmag.com/section/systems/conductors-connected-parallel

Note below that in the special cases where wires smaller than 1/0 are permitted, they require that each individual conductor be able to carry the entire load. They are worrying about "inadvertant disconnection"

As noted in the article, maintaining balance between the paralleled conductors is harder in short runs. If you have two 20 feet of 12 ga wire in parallel, the resistance s only 0.016 Ohms. So just a few milliOhms of difference in the resistance of the end connections will cause imbalance.

As I mentioned, NEC doesn't regulate extension cords, but it's worth bearing in mind the principles that they are considering. Why not use single conductors, big enough to do the job?


Here's the section:

310.4 Conductors in Parallel.
(A) General. Aluminum, copper-clad aluminum, or copper
conductors of size 1/0 AWG and larger, comprising each
phase, polarity, neutral, or grounded circuit conductor shall
be permitted to be connected in parallel (electrically joined
at both ends).
Exception No. 1: Conductors in sizes smaller than 1/0
AWG shall be permitted to be run in parallel to supply
control power to indicating instruments, contactors, relays,
solenoids, and similar control devices, or for frequencies of
360 Hz and higher, provided all of the following apply:
(a) They are contained within the same raceway or
cable.
(b) The ampacity of each individual conductor is sufficient
to carry the entire load current shared by the parallel
conductors.
(c) The overcurrent protection is such that the ampacity
of each individual conductor will not be exceeded if one
or more of the parallel conductors become inadvertently
disconnected.
Exception No. 2: Under engineering supervision,
grounded neutral conductors in sizes 2 AWG and larger
shall be permitted to be run in parallel for existing
installations.
FPN to Exception No. 2: Exception No. 2 can be used to
alleviate overheating of neutral conductors in existing installations
due to high content of triplen harmonic currents.

(B) Conductor Characteristics. The paralleled conductors
in each phase, polarity, neutral, grounded circuit conductor,
or equipment grounding conductor shall comply
with all of the following:
(1) Be the same length
(2) Have the same conductor material
(3) Be the same size in circular mil area
(4) Have the same insulation type
(5) Be terminated in the same manner

(C) Separate Cables or Raceways. Where run in separate
cables or raceways, the cables or raceways with conductors
shall have the same number of conductors and shall have
the same electrical characteristics. Conductors of one
phase, polarity, neutral, grounded circuit conductor, or
equipment grounding conductor shall not be required to
have the same physical characteristics as those of another
phase, polarity, neutral, grounded circuit conductor, or
equipment grounding conductor to achieve balance.

(D) Ampacity Adjustment. Conductors installed in parallel
shall comply with the provisions of 310.15(B)(2)(a).

(E) Equipment Grounding Conductors. Where parallel
equipment grounding conductors are used, they shall be
sized in accordance with 250.122. Sectioned equipment
grounding conductors smaller than 1/0 AWG shall be permitted
in multiconductor cables in accordance with 310.13,
provided the combined circular mil area in each cable complies
with 250.122

 

[TonyWilliams]

I'm a little surprise that either one of you is relying on multiple parallel conductors to provide the necessary capacity. This is generally not good practice since

1. It is difficult to assure that the current is equally shared, resulting on some conductors being stressed, and
2. If one conductor fails, the current is shared among the remaining ones, leading to higher stress and progressive failure.

While the NEC doesn't apply to extension cords, they provide some guidance in using multiple parallel conductors (section 310.4). It's worth keeping them in mind since the same underlying principles apply...

It seems to me a better way to handle this is to use single conductors of adequate size. At least one other maker of J1772 extension cords does it this way. He uses purpose-made EV cable

http://www.generalcable.com/NR/rdonlyres/6EA49F02-6A77-46E6-B65B-471F31CC9506/0/CAR_0137_R0711CarolGreneEVCableSS.pdf

to do this job. General cable make EV cable rated at 30 A (10 ga conductors) and 40 A (8 ga conductors).

Well, you answered your own question. NEC does not apply. For folks who may want to follow NEC for whatever reason, they could simply buy our 80 amp rated cable http://shop.quickchargepower.com/Cable-80-Amp-C8-80A.htm with 8 gauge conductors and only operate it at 30 amps or less.

It's almost an inch in diameter, and somewhat heavy.

Obviously, these cables are not in walls or conduit, as NEC typically pertains to. You can actually see if the cable has been abused (or driven over) and may be compromised.

As to other "purpose built EV" cables, first know that our cables are purpose built for EVs and General is one of our competitors in the J1772 cable market. The design wasn't an accident!!! The cables were not designed for any other purpose. The link you provided is not a cable that is adequate for a proper J1772 extension cable, as every one uses a singular 18 gauge pilot conductor without any proximity conductor. That shortcoming is industry standard, and exactly why we started building our own cables when we started doing this two years ago.

Our 40 amp cable was designed specifically to be light weight, extremely flexible and able to safely handle up to 40 amps continuously for EV charging. Because we are the manufacturer, we could make them with single conductors, but then that would compromise flexibility and the overall diameter of the cables, without any safety benefit.

We have no immediate plans for a single conductor cable, unless we decide to compete in the low end of the market with heavier, less flexible, usually made in China cables. We will continue to proudly build in the USA, even if it costs more (it does).

It's why our products are premium quality.

 

[wwhitney]

Our 40 amp cable was designed specifically to be light weight, extremely flexible and able to safely handle up to 40 amps continuously for EV charging.

Did you look at using very finely stranded conductors (as in welding cable or locomotive cable) to achieve flexibility without paralleling conductors? Just curious.

Cheers, Wayne

 

[evfan310]

Yes, that's my question. If someone wanted to follow NEC (and I agree, this is not required) one could use something like General makes, much smaller and lighter. That's my very question...why not use one conductor?

With regard to the proximity question, I'm not entirely clear how you handle this. In most cases, the proximity function is handled entirely within the J1772 plug.....when it is in normal operation, 150 Ohms to ground, when the release button is pushed, 450 Ohms to ground. So the vehicle end of the extension cord will have the normal proximity function, with or without a dedicated wire in the extension cord. I agree in this case, it's not desirable to disconnect the EVSE from the extension while hot. Manufacturers claim to address this by disconnecting the pilot signal before the main power, but I agree, this is iffy. One should be careful to not disconnect the EVSE from the extension cord while hot in this case and it would be good if pressing either button stopped the charging.

I'm curious how you were able to do this. I presume you are trying to protect against a hot disconnect if the EVSE plug is disconnected from the extension cord, rather than first disconnecting the extension from the cord. If you simply parallel the two proximity circuits, then the effective resistances would be:

Operating 150 in parallel with 150 = 75 Ohms
Either button pressed 450 in parallel with 150 = 90 Ohms. Since this is still below 150 Ohms, I would expect the car to not recognize the button push.

How do you make this work? Or what am I missing? Do you perhaps use the release button to interrupt the pilot signal? I think this would be OK.

 

[ElectricEddy]

In an effort to put some positive light on this, I'll offer a challenge.

Let's pay to have an independent laboratory do a series of standard load / heating tests, comparing our JLong and Brad's extension cable.

If I'm wrong, I'll be really embarrassed by the results that show Brad's stuff is better / safer / than our product. Heck, let's invite a few of the other "extensions" out there for the test.

Again, Brad isn't the first person I've called out, and it won't be the last.

For the folks who have an issue with me advertising, I'll just offer that I'm a PAID advertiser operating a licensed, tax paying, business. Our company's banner is likely at the top of this page now.

We also have engineers (with professional degrees) that design our products. I will happily put our products against any out there.

In British Columbia , from the Electrical Safety Regulation (21) 1 " Subject to subsections (3) and (4), a person must not use electrical equipment ,or offer for sale, sell, display or otherwise dispose of electrical equipment for use in British Columbia, unless the electrical equipment displays a label or mark as follows; (a) a certification mark; (b) a label or mark of a certification agency that is acceptable to the appropriate provincial safety manager to certify electrical equipment for a specific installation; (c) an approval mark issued under section 10 of the Act". The Act being the Safety Standards Act and under section 10 allows for a provincial manager to issue approval without a certification label on the regulated equipment. Additionally , Information Bulletin No; B-E3 071019 3 specifies the certification/approval marks and labels that are acceptable i British Columbia. ( ie: CSA, ULc, enteela etc.). The one thing to watch for is some equipment shipped from shall we say "overseas' bears marks that counterfeit approved marks or labels by a small difference or change in their appearance. I like Tony's idea of in a previous post of third party evaluation. The certifiction agencies generally test equipment to higher than standard ambient temperatures during their tests ( higher than 30*C) which will de-rate ampacity parallel or not. I say leave it to the engineers and certification agencies to do their jobs, and yes, cables are derated in Canadian Electrical code in Tables 5A- Ampacity for temperatures over 30*c, Table 5B-spacing proximity and 5C - cable tray, BUT NOTE these are for building cables on a permanent install , NOT for temporary appliance or equipment cables, for those it is covered by the regulations stated above. Long story short... Make sure any cable you use is approved by the certification process.

 

[TonyWilliams]

We don't compromise on safety, and we don't do "hot" disconnects.

The proximity arrangement we use for JLong was pioneered by our company. The way we handle this is to not have any 150 ohm resistor.

So, the 150 ohm resistor on the proximity pin of the "host" charge plug is passed through JLong to the car, uninterrupted. When the button is pressed on the host plug, 330 ohms are added in series (480 total) to signal the car to disconnect. Simple, right?

Then, we use our own 330 ohm resistor in the JLong plug, so that pressing the disconnect button at either plug (host or JLong) will trigger the 480 ohms required to indicate to the car to stop charging.

 

[evfan310]

Sounds like a good approach. Cleverly done.

 

[VegasBrad]

We don't compromise on safety, and we don't do "hot" disconnects.

The proximity arrangement we use for JLong was pioneered by our company. The way we handle this is to not have any 150 ohm resistor.

So, the 150 ohm resistor on the proximity pin of the "host" charge plug is passed through JLong to the car, uninterrupted. When the button is pressed on the host plug, 330 ohms are added in series (480 total) to signal the car to disconnect. Simple, right?

Then, we use our own 330 ohm resistor in the JLong plug, so that pressing the disconnect button at either plug (host or JLong) will trigger the 480 ohms required to indicate to the car to stop charging.

This is a good design and exactly what I did in mine. Simple electronics. Thanks Tony for describing it so simply.