[donald]

Warm is not necessarily abnormal, but of course there is a sliding scale of what is indicative of something going amiss.

Up to 'body temperature' (for typical humans) is OK. If it feels 'feverish' then maybe look more deeply, but doesn't sound like that is the issue.

Feel and stroke the cable to check for any 'knots' and kinks in the cores within the cable. If it feels twisted and gnarly inside then there could be an issue (which will be from unsympathetic twisting and coiling).

 

[donald]

Consider that 6mm^2 has a resistance of around 3mOhm/m, so a 10m cable has 20m of that, so 0.06Ohm.

At 32A, I^2.R = 61W.

Resistance from the contacts in the plugs will be similar. Probably around 100W total is being lost as heat.

Now stick a loosely coiled cable directly under a 100W halogen/"old-fashioned" filament spotlight bulb that is set to shine its entire spot directly on it. How warm do you think it would get?

That is how hot you should expect it to be. Not cold, not super hot.

 

[donald]

The contact resistance of an IEC62196-2 Type 2 plug or socket is way, way lower than the resistance of 10m of 6mm² cable. The IEC62196-2 Type 2 connector is rated to handle up to 70 A single phase, 63 A three phase with a contact resistance of 0.5mΩ maximum per contact, so just 1.66% of the loop resistance of 10m of cable. Consequently, the heat generated by 32 A flowing through the Type 2 connector will be less than 1.3 W, nowhere near enough to make a connector warm up to any noticeable degree.

I have now seen three Rolec cable failures, though. All three showed signs of the cores twisting internally, as the crappy cable Rolec uses seems to have an extremely soft sheath, one that is not well moulded to the internal conductors, so they seem free to move and twist internally. All three failed cables I've seen had broken control pilot conductors near the end of the cables. There were also signs of early failure of the power conductors as well, though, with broken strands visible when I cut the cables open to check. It seems possible that this may be a cause of localised heating, perhaps.

Another cause might be if anyone has tried to use some sort of contact cleaning spray on the connectors. I once spent half a day fixing a Leaf and it's associated charge point connector where a well-meaning, but misguided, chap had thought using contact cleaner was a good idea (it isn't). He was getting failed charges, not sure about overheating as he only charged at night, but bad contacts in the connector turned out to be the cause. What happened was that the area behind the thin leaf contacts in the free socket (at the end of the cable) and the area at the base of the fixed plug in the car, got clogged with dust that had stuck in place hard due to the residue left by the contact cleaner. Devil of a job to get both connectors clean, and needed the connector and loom to be stripped out of the car just to get it hung upside down to wash it out properly. With hindsight, replacing the connectors with new ones would have been a lot less work.

The heat generated in the cables will flow into the connectors, and thus into the plug housing, one can expect all parts of the cable and those things it is attached to to be at the same temperature, more or less. It is a process generally understood as the principle of 'thermal equilibrium'.

 

[donald]

I would diagnose that the thermal impedance of the crimp, or cable, at the back of the receptacle on the plug has degraded, or was never good enough in the first place.

I had something similar on the Renault-supplied lead to my Fluence back in 2012. I had an x-ray microscope at work and the crimp had not caught all the core strands. Electrical resistance looked fine, but it could not conduct heat. I relayed this to Renault and returned the lead, who paid me for a new lead in the meantime and gave me a replacement too when they eventually did a recall for those early leads as a result.

So, it does happen, despite what all the nay-sayers are about to say (I am sure).

This is why I keep banging on about 'thermal impedance' but the level of sophistication on this forum isn't quite up to understanding this subtlety.

It's not possible to do simple electrical tests for thermal impedance. Normally, but not always, electrical and thermal impedance are synonymous, so it is possible that resistance testing alone would not alert you to this.


What to do?....

My feeling is that the car socket has survived, albeit a bit ugly. Replacement cost = extortionate, so try to avoid that outcome.

The lead and plug are dead, never to be used again.

Replace the lead and plug, and try again. I think it will be OK after that so long as there is not further damage to the car socket, but you'll discover this soon enough with the new lead/plug.

HTH and it works out for you.

 

[donald]

Most of the heat from the 10m cable conductors will be lost through the sheath, directly to ambient, not conducted linearly down the conductor and into the connectors.

It is about the heat formed in the pin/receptacle contact. It has no-where to go if there is a thermal resistance behind the receptacle and it cannot get out on to the cable.

The cable IS the heat sink to the receptacle. A thermal impedance barrier between the two will cause the receptacle to overheat.

I'm not concerned about resistive heating in the cable, that gets lost easily, as you say. This is about heating at the plug.

 

[donald]

Yeah, I suspect that what you've said is right. I'm hopeful that the car socket is still fine because the car had charged to 97% and my energy monitor reports that the car was still charging when it reached the end of the charge schedule at 3.30am.

I've ordered a brand new 10m cable from EV Extras and I'll get the electrician back to fit it ASAP. Fingers crossed there is no other damage.

Is there anything I can ask the electricians to check after the new cable is fitted? I'm not exactly sure what tests they carry out.

I don't think so, they are not equipped for the sorts of evaluations needed. Just try it, and be cautious and attentive the first few charges, trying short charges, then progressively longer charges.

One thing you can do in the meantime is clean the burned socket receptacle. You can 'just' use a dry cotton bud, but it's best to have a 'transport medium' on it to carry the muck away. I use WD40; spray a drop onto the cotton bud and work it in around the pin. Back and forth, working your way around the pin.

Don't force it, if 'your' cotton bud doesn't fit don't force it, you do not want to bend the pin. Back and forth. Fortuitously, a standard cotton bud is juuust the right size to work in that gap.

You will see a load of black crap appear on the cotton bud. Keep doing that with more buds until you don't get too much black crap off the pin. Then dry the pin off with a clean dry bud or two, to remove any excess WD40. The pin should be left clean and dry.

All the best with that.

 

[donald]

Really useful info Donald. Thanks. I'm hopeful that the Leaf charging socket is okay, but only time will tell. I did notice in my photo that the black tip of the live pin seems to be missing. I can't say for sure what it used to look like, but presumably it was like the one on the right. What purpose does that serve?

I wonder whether it is worth finding out how much it would cost to replace the socket. I expect ££££.

It'll have melted I think. It's a plastic protection/insertion guide against scoring the inside of the plug's receptacle. It does run the risk of degrading your new plug if you misalign it as you insert it, just be careful.

Of course, you might prefer just to get on and have the socket replaced. I mean, it will degrade the value of the car in the future if you come to sell it, and there is also a small chance that the thermal impedance was actually a fault in the socket. It doesn't 'look' like that, but who can say for sure.

I mean, I'd ask the dealer, and/or HERVA garage, for a quote to swap it out, there's no pretending that it isn't damaged, and it might make sense to do that sooner than later. Depends on whether you are the sort of person who likes everything just so, and of course if you have the cash to do the job.