MikeD
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Re: Nissan EVSE J1772 cable wire gauge?

Sun Jul 15, 2018 6:03 am

GlennD: Fine -- at least acknowledge the value towards safety of an upstream GFCI protecting that receptacle! And also acknowledge known safety deficiencies (if any) of the "Open" EVSE versus, say, the EVSE of this post.

BTW I make posts on MNL to try to provide Leaf owners with information that I hope they will find useful, especially about charging issues that involve safety -- but I am hardly perfect in that regard. I do not have a personal financial stake (or have friends who do) in selling EVSEs that ends up affecting what I write. I feel strongly that "good" information helps people make better choices, but it is a struggle (and expense) to find that information -- and it can be difficult to communicate it effectively.

GlennD
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Re: Nissan EVSE J1772 cable wire gauge?

Sun Jul 15, 2018 10:46 am

MikeD wrote:I'm not a EE, but it seems to me that one of the important safety considerations for wire choice is flexibility (or whatever the precise term for resistance to damage due to flexing). Since a charging cable needs to be able to withstand what may be considerable flexing over time, a thinner multi-strand wire should maintain its integrity longer than a thicker one subjected to the same usage abuse. In any case, I recommend everyone treat (any) cable subject to flexing during normal use with appropriate due care.


Quick Charge power like Tesla uses doubled up wires for their 40A cable. This makes it very flexible and it is smaller than most 30pA cables. I use one for its 40A capability but since it is smaller than the old 30A cable that they used to sell they dropped it and now only sell the 40A J1772 cable.
2012 Cayenne Red SL traded for:
2013 Pearl White SL Premium
Traded for a Cirrus White 2014 Mercedes B (totaled)
2016 Urano Gray eGolf SEL w/ drive assist
Loved the VW but it sat too low for my old body
Back to a Cirrus White 2017 B250e

MikeD
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Re: Nissan EVSE J1772 cable wire gauge?

Sun Jul 15, 2018 4:13 pm

GlennD: Isn't there a danger in using "double wiring" (if I am correctly understanding you mean two separate wires are used for part of a circuit instead of just one) that the current can rather easily become unbalanced between the two wires? As an example, if a total of 30a is passing thru the two wires, assuming the wires have initially exactly the same total resistance, then 15a passes thru each wire. But if one (wire A) degrades differently over time such that it eventually has, say, twice the total resistance of the other (wire B) then the current flowing thru wire B will be twice that of wire A, i.e. approximately 20a versus 10a -- i.e. isn't there the very real possibility of eventual heat damage to wire B's insulation? Or am I misunderstanding something?

jjeff
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Re: Nissan EVSE J1772 cable wire gauge?

Sun Jul 15, 2018 4:43 pm

MikeD wrote:GlennD: Isn't there a danger in using "double wiring" (if I am correctly understanding you mean two separate wires are used for part of a circuit instead of just one) that the current can rather easily become unbalanced between the two wires? As an example, if a total of 30a is passing thru the two wires, assuming the wires have initially exactly the same total resistance, then 15a passes thru each wire. But if one (wire A) degrades differently over time such that it eventually has, say, twice the total resistance of the other (wire B) then the current flowing thru wire B will be twice that of wire A, i.e. approximately 20a versus 10a -- i.e. isn't there the very real possibility of eventual heat damage to wire B's insulation? Or am I misunderstanding something?

You might think that, but it's done all the time in high current situations :)
It one of the commercial buildings I work at for the main feed wire they had like 6 wires for each of the phases, 24 very heavy wires in total :shock:
I believe how it works is as long as the wires are similar in size the current will balance between the wires, if say one wire gets a bad connection and starts heating up, it's resistance goes up and current is routed through the other wires(a good thing) as without the other wire/wires, the wire would keep getting hotter and hotter, possibly resulting in a fire or melting of the bad wire.
Whitney probably knows the code but I believe for smaller gauge house wiring, your not allowed by code to double up the wire, things that are plugged in like a EVSE probably go off a different code.
2012 SL purchased used 2/'16
2013 S w/QC purchased new
Juicebox Premium 60a L1/L2 EVSE, Ebusbar 16a L1/L2 EVSE
'12 EVSEupgrade'd 20a L1/L2 EVSE, '13 EVSEupgrade'd adjustable 6-20a L2, 6-13a L1 EVSE
Zencar 13, 20, 30a L1/L2 portable EVSE
GE Durastation 30a

GlennD
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Re: Nissan EVSE J1772 cable wire gauge?

Mon Jul 16, 2018 10:45 am

MikeD wrote:GlennD: Isn't there a danger in using "double wiring" (if I am correctly understanding you mean two separate wires are used for part of a circuit instead of just one) that the current can rather easily become unbalanced between the two wires? As an example, if a total of 30a is passing thru the two wires, assuming the wires have initially exactly the same total resistance, then 15a passes thru each wire. But if one (wire A) degrades differently over time such that it eventually has, say, twice the total resistance of the other (wire B) then the current flowing thru wire B will be twice that of wire A, i.e. approximately 20a versus 10a -- i.e. isn't there the very real possibility of eventual heat damage to wire B's insulation? Or am I misunderstanding something?


The quick charge cable has 2 #12 wires on each side. Each wire is good for 20A thus the total assuming the wires are terminated properly is 40A. I charge my "B" at 40A with no problem from a 63A contactor.

I earlier tinned the wires It needs the contact area of non soldered wires, WRONG! It is the only contactror that I have blown up. It was a 50A unit running 30A. Properly terminated it had a lot of reserve.
2012 Cayenne Red SL traded for:
2013 Pearl White SL Premium
Traded for a Cirrus White 2014 Mercedes B (totaled)
2016 Urano Gray eGolf SEL w/ drive assist
Loved the VW but it sat too low for my old body
Back to a Cirrus White 2017 B250e

MikeD
Posts: 655
Joined: Thu Jun 24, 2010 6:14 am
Delivery Date: 12 May 2011
Leaf Number: 592

Re: Nissan EVSE J1772 cable wire gauge?

Mon Jul 16, 2018 2:13 pm

jjeff: Your comment about the NEC disallowing double wiring is correct, I think (but I haven't tried to research it).

However, I believe your comment "if say one wire gets a bad connection and starts heating up, it's resistance goes up" is not consistent. When wire A gets "a bad connection" its effective resistance goes up right then, causing less current to flow thru it and more to flow thru wire B, with the net effect being wire A immediately starts cooling off (assuming no arcing is also occurring) and wire B starts heating up -- and the concern is eventually maybe to insulation damaging levels.

In your industry example, it's not just two wires but six, so a high resistance defect with one wire causes its current to be shared among the remaining five rather than just one. Plus there may be other safeguards?

GlennD
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Re: Nissan EVSE J1772 cable wire gauge?

Mon Jul 16, 2018 3:27 pm

Neither Tesla EVSE's or Quick Charge Power cables are approved. Never the less they work fine.

Current Tesla EVSE's are reduced current from the earlier ones. In my opinion pushing the P& B relay to 40A was bad. It is rated for non switching current of 4oA but it leaves no reserve.
2012 Cayenne Red SL traded for:
2013 Pearl White SL Premium
Traded for a Cirrus White 2014 Mercedes B (totaled)
2016 Urano Gray eGolf SEL w/ drive assist
Loved the VW but it sat too low for my old body
Back to a Cirrus White 2017 B250e

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