Granny Charging

[salty]

Definitely looks like overheating of the fuse connection within the BS1363 plug - you can clearly see the melted plastic at that position.

It certainly looks like there is a heat source on the fuse cover in the back of the plug as the plastic has bubbled, so may well indicate a poor connection.

That certainly looks like, why happened.

 

[Everest]

I find if you discard the fitted fuse and fit a live ammo round instead its a good tight fit (please DONT do this!)

The thing is, charging from a BS1363 plug and socket was just about OK when people were driving early EV (thinking Leaf, Zoe, original Ioniq, i3 etc.) which had 20-30kWh of battery and hence charging times were much shorter than they are now.

The BS1363 design of plug is mostly OK for long-term low current applications or say boiling a kettle for 2 to 3 minutes. They are not really up to long duration, high-load, usage, especially after 2 to 3 years usage, weakening of internal metal connections, tarnishing of contacts with damp etc.

As I mentioned on a previous thread, the contact at the fuse is a particular weak spot. IMHO, it would be better not to have a fuse in the plug at all, but to have your dedicated 13A socket (it is dedicated, isn't it ) on a 10A MCB instead, thus protecting the wire from overcurrent problems - but of course, that is not BS7671 compliant.

 

[Lovemyev]

100% agree with @Everest .
When a high current is being drawn over a long period of time, heat is obviously generated here.
Then the live contacts on fuse carrier start to become weaker and weaker over time.
As soon as this starts, the deterioration is fast and very easy to over look.
This is when it becomes dangerous.
It can go from being fine for months, then in a very short time, fail dramatically !.
I used a granny for only 6 months, while waiting for our wall box to be installed, along with a 100Amp upgrade in our main cutout fuse by the DNO.
This was on our 2015 Golf PHEV with a small traction battery.
But every single week I would go to the plug and pull it out.
Checking if is was tight removing the plug, then any brown staining on the socket outlet and condition of the three pin plug on the OEM granny.
The charging socket was on a dedicated circuit and protected by a trip.
A bit “over the top” I accept that, but it pays to be over cautious I think.
This type of problem is not just limited to granny chargers of course.
Even wall boxes can suffer from heat / burning due to poor terminations / connects or component failure.
I have had two Rolec OEM RCBO units fail in our wall box, due to over heating.
Not connections issues, but poor quality RCBO’s that only lasted about 18 months each.

 

[salty]

For sale. Used, one owner. (16 months)
Slightly charred, Granny Charger. Offers?

 

[Everest]

But every single week I would go to the plug and pull it out.
Checking if is was tight removing the plug, then any brown staining on the socket outlet and condition of the three pin plug on the OEM granny.

I suspect @salty discovered some brown staining too, when he saw what happened

Seriously though - that RCBO overheating looks bad (and would have been hidden in the CU). Latest regs. are for metal-clad CU or EV distribution boxes, so damage will be hopefully be limited for that situation, but still dangerous. If you're OCD like me, then having a thermal imaging camera is a god-send for periodic checking of electrics - especially connections to EV charge points when they've been delivering 32A for many hours. Not cheap, but wouldn't be without mine now.

 

[Everest]

For sale. Used, one owner. (16 months)
Slightly charred, Granny Charger. Offers?

Pair of wire-cutters, new plug, wire-strippers and a screwdriver... no problem

 

[EvTek23]

Many of the Granny Charger 13A plugs will have 5 wires in them, 3 will be the power and have a CSA of 1.5 to 2.5mm sq, and two smaller ones that come from a temperature sensor built into the plug for just this reason. It would simply error and stop charging with such heat present.
This type of cable is normally quite thick for 10A and probably states something like 3 X 2.5 + 2 X 1.0 stamped or printed on it.
I guess the one that @salty was using did not have a temperature sensor