Charging cable has died!!!

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Charging cable has died!!!

Post by antiscab » Mon, 23 Feb 2015, 06:48

And another one bites the dust

Image


this time round it was plugged into this 15A powerpoint
Image

I pulled the plug apart to see how bad it was - it was bad
Image

I also pulled apart the power point to see how bad that was - good so far

Image

Hmm...some damage to the plastic here..
Image

contacts look brand new - no problems here
Image

I put the powerpoint back together and replaced the plug with a new 10A one

I think what went wrong is I forgot to tin one of the wires and it corroded, got hot and melted plastic.
the copper wire was actually fused to the pin

This time around I made sure I tinned all the wires before assembly
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Charging cable has died!!!

Post by neilg » Mon, 23 Feb 2015, 07:14

I do believe that you are NOT supposed to solder the wires before making the connection because the solder can deform over time, resulting in a loose connection and overheating.
Strange though that the unsoldered lead was the one that failed!

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Post by antiscab » Mon, 23 Feb 2015, 07:38

neilg wrote: I do believe that you are NOT supposed to solder the wires before making the connection because the solder can deform over time, resulting in a loose connection and overheating.
Strange though that the unsoldered lead was the one that failed!


It's only a cheap (industrial) plug

I'm now on the look out for plugs that have crimped connections instead of a little screw down friction connection

that way neither corrosion nor loosening of the connection are possible

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Post by Johny » Mon, 23 Feb 2015, 12:36

It is also my understanding that you should not tin tin the bundle of conductors prior to using a pressure connection - that includes crimps. Unless you are going to solder the crimp as well.
Let us know when you find a better style of plug as I've burnt one out as well. Kind of disheartening to have a connection fail that you've done your self.

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Post by Johny » Mon, 23 Feb 2015, 13:53

BTW Do you have active and neutral round the wrong way (on the plug) or is that a trick of the picture?

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Post by Gabz » Mon, 23 Feb 2015, 16:26

wouldn't boot laces ferrules be better than soldering it stops stray copper cores from breaking etc. or grounding out etc.

link if you don't know what i'm on about.
http://www.carroll.com.au/terminals-lug ... rules.html
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Post by T1 Terry » Mon, 23 Feb 2015, 18:43

I have been using bootlace crimps for around 12 mths now, all the over heated connection problems are now a thing of the past thank goodness. Mine were all 12vdc and 24vdc stuff so the amps were much higher. The 2 8AWG wire joints that I tinned the cable first got so hot it melted its way out of the brass neutral block while we were away on holidays. Scary stuff the fuse that protected the circuit at the battery end showed no signs of heat distress so it had to be a result of the resistance creating heat and ending in a melt down.
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Post by weber » Mon, 23 Feb 2015, 19:39

In AS/NZS 3000:2007 Section 3.7.2.5
Retention of stranded conductors
The ends of stranded conductors shall be secured by suitable means, so as to prevent the spreading or escape of individual strands. They shall not be soft-soldered before clamping under a screw or between metal surfaces.
There are at least 3 things we need to take care of simultaneously with these connections.
1. Prevent creep due to plasticity.
2. Prevent strand-spreading.
3. Prevent corrosion.

There are a number of ways of doing this. But first lets consider the plug in question.

Both 1 & 2 increase the resistance of the joint purely by loss of pressure, while 3 also increases the resistance by converting metals to compounds which are inherently less conductive. But corrosion requires, at a minimum, that humid air could enter the plug-back to allow water to condense on the joint. But this appears to be a weather-proof plug. I expect the corrosion occurred due to the heating, not the other way 'round.

So I'm guessing the failure was due partly to strand spreading but mostly due to another kind of creep I will eventually describe as requirement #4 below.

The fact that the unsoldered connection failed first, doesn't mean soldering before clamping is a good idea. Soldering before clamping certainly prevents strand-spreading and corrosion, but not creep. By the adjective "plastic" here we mean "slowly flowing under pressure", not "made from an organic polymer".

1. How to prevent plastic creep

Simple. Don't include anything within the joint pressure system that will creep over the expected life of the joint. You want elastic, not plastic. Copper, brass, bronze and steel are fine. Solder is not.

I was taken to task for this myself recently (and rightly so). Not for including solder in a joint, but for including fibreglass-reinforced epoxy (printed circuit board material) within a battery terminal pressure system. See
viewtopic.php?title=weber-coulombs-lyte ... 302#p55462

If there is good reason to include slightly plastic material in a joint, it _must_ be compensated by a spring (e.g. belleville washer) that is capable of maintaining sufficient pressure in the joint over sufficient travel.

2. How to prevent strand spreading

With wire containing only 7 thick strands this can be done by
(a) tightly twisting the strands together (the outer strands need to make at least one full turn within the joint so they are gripped on both sides of the joint and thereby prevented from spreading), or
(b) when the wire is clamped between parallel plates, and sufficient width is available, fully spreading the strands so they cannot spread any further (in this case there must be no strands crossing within the joint.

But neither of these methods work with flexible cable, i.e. cable whose wires have many fine strands.

You certainly can't clamp fine strands directly under a screw-end as the screw-end will cut or break the strands (but that's not relevant to these plugs). And there is no chance of spreading them into a layer one-strand thick. But when clamped between parallel plates, you can get away with tightly twisting them, provided it still makes at least one full twist within the region of pressure _after_ the inevitable partial-untwisting that will occur as you clamp it. Really, the only way to be sure of this is to take it apart again and look at the squashed wire under a magnifier. This can be very educational. Image

As Gabz and T1 Terry mentioned, the best way to prevent strand-spreading (and screw-cutting) is to contain the strands inside a ferrule. I don't know why people call them "bootlace" ferrules since they are not used on bootlaces -- bootlaces have their own kind of ferrules -- and there is no other kind of ferrule that is used on electrical wires (that I know of). They are a thin-walled copper tube that you slip over the wire. You must use a ferrule designed for the actual cross-sectional-area of your wire, typically 1.5 mm^2 for a 15 A flexible cable.

There is no need for a special tool to crimp the ferrules, unless you pre-build wiring assemblies where they might get pulled off before they get clamped in a terminal. They are not really a crimp device, their copper is too thin. It's the terminal that provides the clamping force. Just give them a gentle squeeze with your pliers so they don't fall off while you're working, but allow the pressure in the joint to determine their final shape.

However, there is a reason why even a ferrule won't save you, with this type of plug, without further attention to detail.

One important word above is "parallel" -- clamping should be between parallel faces. The terminals in the back of these plugs simply cannot do that. This leads to the other kind of creep that I alluded to above. I've never seen it described anywhere else, but I call it "wedge creep".

Wedge creep can occur when
(a) the wire itself forms a wedge shape (this can occur with 7-strand wire where an incomplete attempt has been made to fully spread the strands), or
(b) the space (in which the wire or ferrule is clamped) is wedge shaped.

Either way, this leads to the wire or ferrule slowly moving at right-angles to the clamping pressure and thereby reducing the clamping pressure.

I'm almost certain this plug failed due to wedge-creep, with maybe some strand-spreading thrown in for good (bad?) measure. So we'll skip 3 for now and go to:

4. How to prevent wedge creep

Ideally, don't use anything wedge-shaped in the joint, and don't have a wedge-shaped gap between clamping plates.

But with these plugs, you should use a ferrule but ensure it is positioned as far from the screw as possible, hard against the part of the moving clamp-plate that is bent over to prevent escape. If there's a gap here such that the ferrule can slowly ooze around the corner, then don't use these plugs at all.

3. How to prevent corrosion

Keeping moisture out is one way. But in harsh environments, tinned-copper wire should be used. How is this different from "tinning" (i.e. soldering) the wire? Tinned wire has every strand individually plated with a very thin layer of tin before being made into a wire.

Another way is to use a jointing compound. This is a mineral oil which has been thickened with fumed silica so it has a grease-like consistency for ease of application, but is easily squeezed out from between the contacting metals (because it is non-conducting), while preventing moisture from getting to the joint.

So I put jointing compound on un-tinned copper wire before pushing it into the ferrule, in critical applications like this.

Here's another way it could be done, in these plugs, to meet all four requirements. Tightly twist the wire, clamp it far from the screw as described for the ferrule above, and _only_then_ solder it.

There are several problems with this however.

1. The chrome plating on the terminals will not readily take solder because of its passivating oxide layer. You will have to either file it or use a chemical-etch type of soldering flux such as Baker's fluid (zinc chloride solution) which you must wash off after soldering, e.g. with metho. This can be applied as a drop on the end of a toothpick after you have clamped the wire.

2. You will need a high powered soldering iron and do the job very quickly as the pins make good heat-sinks and you don't want them to soften the plastic around them. If it does soften, make sure the pin is in the right position as it cools. You also don't want to have the wire's insulation melt and shrink back up the wire.

3. Make sure you have formed the wires into their final strain-relief position in the back of the plug before soldering, as solder will wick back up the wires and make them impossible to bend.

Phew!

There are even more considerations when you need to terminate more than one wire in the same screw terminal.

And people wonder why it's illegal for anyone but a licenced electrician to do this work. But sadly even many of these have only learned formulas that work in the commonly encountered cases, without really understanding why, and therefore without being able to apply it in unusual cases.

Thanks for posting those photos.
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Post by E-STATION » Mon, 23 Feb 2015, 21:58

Have you checked your household insurance policy? Will it cover fires caused by an electric car? Some policies don't.

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Post by offgridQLD » Mon, 23 Feb 2015, 23:10

Yes worth checking what is covered and what isn't I don't think that plastic enclosure mounted to a brick wall will burn much. I would say the sockets construction material would be reasonably flame retardant.(melt and smolder rather than bursting into flames)


Putting all the great info above around why connections can end up with high resistance aside for a moment. Given the Imiev charger is only 10A (2200w) My thinking is it would take a very sub par terminal connection to get that red hot to start melting plastic with just a 10A load.

I just pulled my Imiev charger out of the wall after 5hrs on charge and you can touch the plug on the side of your cheek and it's hard to tell if its warm or not.

Regarding the melted terminal block mounted to timber picture. Are you sure that wasn't the results of arcing? Edit: is see now they were soldered wires , solder melted and wire could flop around and arc on the terminal.

Kurt
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Post by antiscab » Tue, 24 Feb 2015, 04:00

Thank you for the feedback guys

looks like I'm going to be adding ferrules to my tool box from now on

I never was a fan of the screw down method of termination, but finding something better is turning out to be a real pain

I note that store bought 15A extenion leads has the wire soldered to the pins - a far better solution as the solder is making both a good mechanical and electrical connection - or so goes the theory

hard to find a replacement plug that you can do the same with.
even harder to find a 10A extension lead with 2.5mm2 wire (though you can buy plenty with 1.5mm2 wire)
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Post by weber » Tue, 24 Feb 2015, 04:43

antiscab wrote:I note that store bought 15A extenion leads has the wire soldered to the pins - a far better solution as the solder is making both a good mechanical and electrical connection - or so goes the theory.
A soldered joint certainly gives a reliable electrical connection. But it isn't considered good enough mechanically for earth connections.

In AS/NZS 3000:2007
3.7.2.11 Earthing Conductors
(a) Soldered connections Where soldering is used for the jointing or connection of earthing conductors, the earthing conductor shall be retained in position by acceptable means independently of the solder.
Hence my (and Johny's) suggestion that all wires be clamped (or crimped) _before_ soldering.
antiscab wrote:even harder to find a 10A extension lead with 2.5mm2 wire (though you can buy plenty with 1.5mm2 wire)

Why would you want 2.5 mm^2 wire for a 10 A extension lead, unless it is more than 20 metres long. 1.5 mm^2 will barely get warm carrying 10 A, and it will only drop 0.33 V per metre. That's 6.6 V (~3% of 240 V) for a 20 m lead.
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Post by weber » Tue, 24 Feb 2015, 04:56

The sad thing is that RobM reported on EVWorks' research on failed charging leads and made most of these recommendations over two years ago, here:
viewtopic.php?title=holden-volt-chargin ... 238#p39892
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Post by offgridQLD » Tue, 24 Feb 2015, 14:31

How many amps is the charger your using pulling from the wall?


Kurt

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Post by offgridQLD » Tue, 24 Feb 2015, 14:52

"The sad thing is that RobM reported on EVWorks' research on failed charging leads and made most of these recommendations over two years ago, here:
viewtopic.php?title=holden-volt-chargin ... 238#p39892
"


warning a bit of a rant!!!!

After reading over the above. All I can say is the Australian standard 10A socket along with the plug and pin terminal design is perhaps not a very good one.

Its always driven home about how safe everything need to be and a failure can be life threatening or result in loss of property due to a fire.

Yet I have always questioned the quality and design of domestic electrical hardware.

Who had the smart idea that plastic enclosures only need two screws to secure the lid....Oh it's less screwdriver work for the limp wristed installer and a 0.00001 cent cost saving for the manufacturer.

The hardware is designed for cost first. Ease of installation second and safety and quality last.


Kurt



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Post by offgridQLD » Tue, 24 Feb 2015, 16:45

Should it be regulation that all domestic 10A sockets have thermal overload protection at the GPO?

For example if you used this style of Clipsal 10A outlet. Anything more than 75 deg c at the outlet and it shuts off http://www.clipsal.com/Trade/Products/P ... catno=695T

more details (it even starts flashing to warn you that its about to trip or nearing its limits.
http://updates.clipsal.com/clipsalonlin ... 000875.pdf


It would make them more expensive but given they are usually only ever fitted once to a home and not often replaced why not?

Given a brand name standard double GPO (clipsal) cost about $50 - $70 a box of ten or $5 - $7 each depending on your trade price. How much are they manufacturing them for $2.00? Are we relying on a $2 GPO to function correctly for decades and potentially 1000's of insertion and switch cycles?

That $5 - $7 is most likely not even 10% of the labor cost to install the outlet. I would be happy to pay $50 pr outlet if they were built/ designed better and perhaps had thermal overload protection built in that way if the outlets terminal connection was ever comprised or the plug- appliance plugged into it was compromised the outlet wont get so hot it starts a fire.

Kurt

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Post by offgridQLD » Tue, 24 Feb 2015, 17:07

Here is one (clipsal 695T) for sale for $15 + postage

http://stereophonic.quicksales.com.au/a ... po/4243841

Kurt
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Post by Rusdy » Tue, 24 Feb 2015, 17:11

weber wrote:
And people wonder why it's illegal for anyone but a licenced electrician to do this work. But sadly even many of these have only learned formulas that work in the commonly encountered cases, without really understanding why, and therefore without being able to apply it in unusual cases.


Thanks guys, I never know humble cable connection can bring so much grief. Very informative indeed. I won't approach my cable crimping / connection to "She'll be alright mate" anymore after reading all of the above :)

I guess moral of the story is always have 'bootlace' handy. I got into this habit early enough (thankfully) when I was working in the minesites along with the site's sparkies. Those thing never got taught in unis. Let alone AS3000 Image
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Post by weber » Tue, 24 Feb 2015, 20:39

offgridQLD wrote:Given the Imiev charger is only 10A (2200w) My thinking is it would take a very sub par terminal connection to get that red hot to start melting plastic with just a 10A load.

It's a positive feedback (with negative consequences). Vicious cycle. Thermal runaway. Exponential process.

i.e. It only has to be a little bit sub-par (high resistance) to start with (e.g. due to strand spreading or plastic creep or wedge creep). The little bit of heating from this causes the bare copper strands to begin corroding just with air (not needing moisture as they would at normal temperatures). A little bit of corrosion raises the resistance even more which causes more heating which causes more corrosion which causes more heating etc etc.

Note that RobM mentioned that molded plugs with no air inside were good.

The average extension-lead doesn't run at 10 amps for 8 hours so it never gets a chance to do this thermal runaway, so you can get away with sub-par connections. But with EV Charging, you can't.

Kurt, with your recent posts you seem to be heading off in entirely the wrong direction. I guess neither RobM nor I made it clear enough that the problem is not with the GPOs, and nor is it with the Australian Standard parts of the plug (the pins). It is purely in the joint between the fine-stranded wire and the pins in the back of the plug (and presumably in the back of the extension lead socket), which manufacturers do in various ways.

The HPM extension leads I got from Bunnings are brilliant. They are clear (so I can see if anything bad is happening inside), molded (so no air or water can get in) and I can see that they have been first crimped, and then soldered. Beautiful.

If you're putting your own plugs on, just use ferrules (and either jointing paste or wire with tinned strands) and don't give the ferrule a wedgie. Image

Or twist then clamp then solder the wire, to the pin.
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Post by offgridQLD » Tue, 24 Feb 2015, 21:01

Yes I agree all the hardware if it meets the Australian standards should be able to handle the rated load (10a in this example) continuously. If it has been installed and terminated to standard as well.

I mentioned the thermally protected GPO as (I assume you could get a 15A version to ) In detect response to the melted GPO. I understand the the high resistance on the clamped wire to - pin connection on the plug was creating the heat that intern melted the GPO it was inserted into but if the socket had thermal protection then this meltdown would have never happened as the plug would have tripped the GPO.

A good Automated backup from a dodgy plug at some stage down the track.

My rant around the design of the Australian standard electrical hardware to me it seems to be walking a fine line between functional and inadequate. Defiantly not over engineered in any way.

Sorry for another analogy ..perhaps not a god one but....

If two wheel nuts where to fall off my car the well would stay on just fine.

I just think the hardware is flaky and could be built better to insure a more consistent result with a better outcome and headroom.

Kurt



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Post by Richo » Tue, 24 Feb 2015, 21:03

weber wrote: And people wonder why it's illegal for anyone but a licensed electrician to do this work.


I have never seen a leccy use ferrules on house wiring.

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Post by weber » Tue, 24 Feb 2015, 21:18

Richo wrote:
weber wrote: And people wonder why it's illegal for anyone but a licensed electrician to do this work.

I have never seen a leccy use ferrules on house wiring.

And why would you? Ferrules give no benefit for 1-strand or 7-strand wire. But they do give a benefit for wire with many fine strands, as used in flexible cables, when that wire will be clamped in a screw or spring terminal.

1.5 mm^2 ferrules are available from Jaycar.
http://www.jaycar.com.au/productView.asp?ID=PT4533
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Post by T1 Terry » Tue, 24 Feb 2015, 21:20

There wouldn't be too many that even knew what a bootlace ferrule was. I'd certainly spend the extra $$ and few seconds to crimp the ferrules properly, it does make a much better connection. There are two types, one creates a round ferrule on smaller cable and a square ferrule on larger cable, but with a bit of extra effort you can get them round so the fit better into the retaining screw type connection, the outer type is like terminal crimping pliers and creates a flat ferrule better suited to the clamp plate type connection used in RCD/RVD units and extension cord plugs (see, I did get it back on topic :lol:) Cheap enough on EvilBay and you can either buy the ferrules without the plastic insulator for the jobs where room is a problem, or just cut the plastic bit off with the Stanley type knife. The electrical crimper pliers type even come with interchangeable jaws so you can maximise the uses out of one tool if you don't have that many jobs to use it on. I have one of each type as I use all of them a fair bit.

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Post by weber » Wed, 25 Feb 2015, 08:35

Where to buy Electrical Jointing Compound or Dielectric Grease / Silicone grease

I've been recommending the use of an electrical jointing compound to prevent corrosion -- by putting it on the wire before it goes in the ferrule, and putting it on the ferrule before it gets screw-clamped to the plug pin.

Anyone who is using Lithium cells with aluminium terminals _must_ use such a compound, immediately after steel-wire-brushing to remove the transparent oxide layer from the aluminium.

But it's not much use me recommending it if you can't buy it. I don't know what's happened, but you used to be able to get various different brands and types at Ideal Electrical, Bunnings and SuperCheap Auto. But now I can't find anywhere you can just walk in and buy it in Australia, unless you happen to be near one of the few remaining RS Components Trade Counters.

Don't be fooled by Jaycar's "Jointing Compound". It is not for preventing corrosion in electrical joints. It is only for mechanical joints.

I mentioned that electrical jointing compound consists of a mineral oil thickened with fumed silica. The fumed silica makes it thixotropic. i.e. It prevents it from running with gravity or heat, but allows it to flow easily under pressure. This is so it gets squeezed out from between contacting metal surfaces, but fills any voids that would otherwise let air in. Some use a petroleum oil and some use a silicone oil. And some have fine metal powders added (such as copper or zinc).

Those with silicone oil and no metal powder are called Dielectric Grease (or Silicone Grease, although not all silicone greases are suitable for electrical joints).

I believe this guy when he says there is no significant difference in performance between the different types, in this application.
http://www.w8ji.com/dielectric_grease_v ... grease.htm

The stuff I've been using is Cabac EJCG125, which can be ordered here.
http://energyelec.com.au/45-jointing-compounds
Any of the other Cabac jointing compounds would do as well, for this job.

Here are some types you would think would be sold by SuperCheap Auto or Repco. But not any more.
Permatex Dielectric Grease
http://www.permatex.com/products-2/prod ... ase-detail
Loctite Dielectric Grease
http://www.henkel.com.au/3320_AUE_HTML. ... 3869360129

You can order these suitable Silicone Greases from RS Components
http://au.rs-online.com/web/p/greases/0494124/
and Element14
http://au.element14.com/dow-corning/279 ... /dp/537019

Searching on eBay will turn up several. This one is interesting for being marketed as "Anderson Connector Dielectric Grease".
http://www.ebay.com.au/itm/like/3910603 ... 107&chn=ps
Last edited by weber on Tue, 24 Feb 2015, 21:37, edited 1 time in total.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

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Gabz
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Real Name: Gabriel Noronha
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Charging cable has died!!!

Post by Gabz » Wed, 25 Feb 2015, 13:40

offgridQLD wrote:
My rant around the design of the Australian standard electrical hardware to me it seems to be walking a fine line between functional and inadequate. Defiantly not over engineered in any way.


I think your being too harsh on the plug i would blame the flex wires.

Image

circontrol EVSE with a 15amp extension cable attached for "portability" burn marks on the extension cable. I would say it had a similar problem to above. If it was install with TPS cable with less cores probably wouldn't have been an issue.
Corporate Member Recharging NSW Pty Ltd. http://rechargingnsw.com.au/

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