Granny charger plug burn out

[WoNkY]

There are granny chargers available that have temperature sensors in the plug, these are far safer and will error and shutdown when excessive inlet (13 A) plug temperatures are observed.
In a quick search I found the Third Rock EV charger has this facility and is stated in both the features and specifications.
Looking at the cable between the plug and the electronics unit it will state something similar to: 3 X 2.5 + 2 X 1.5. 5 conductors in total. The 2.5 being the main conductors for L, N, E (2.5 mm sq) and the 2 X 1.5 the two sense wires for the embedded sensor in the plug.
The specifications for the unit I have included. There will be others too with this facility, I've shown the Third Rock unit as a guide.

View attachment 44271

That’s a great safety feature to have.

 

[RCK49]

The one I bought to cover the period before my wall charger was installed has a smart plug fitted.

 

[Lovemyev]

Just to be clear, both these granny units and higher powered wall boxes, are merely a large switching / communication device.
They are not charging units.
Have do have the ability to communicate with the modules of the car, but the actual charging unit that provides energy to the traction battery, is integrated into the car when first built.

 

[Kenp1]

Just to be clear, both these granny units and higher powered wall boxes, are merely a large switching / communication device.
They are not charging units.
Have do have the ability to communicate with the modules of the car, but the actual charging unit that provides energy to the traction battery, is integrated into the car when first built.

That is true, but everyone calls them chargers.

 

[Kenp1]

I had the socket getting hot when I used the Granny charger, I did solve this but I was still checking when I plugged it in. I was glad to get a proper wall box

 

[Ian Key]

I think you need to get one from a reputable UK supplier who you know will meet UK safety regs and not a cheapo that someone has just stamped some numbers into the plug.

EVCables.com build and test theirs in the UK and they come with a 2 year warranty. They will supply them from 2m to 30m in length and the power plug has a temperature sensor.

 

[Lovemyev]

That is true, but everyone calls them chargers.

The same applies to vacuum cleaners, because we insist on calling them hoovers .

 

[Kenp1]

The same applies to vacuum cleaners, because we insist on calling them hoovers .

I think that is going away, even I tend to call it the vacuum now.

 

[WoNkY]

I think that is going away, even I tend to call it the vacuum now.

Or robovacs..

 

[Everest]

Oh no.. here we go again... is that the 4th or 5th one reported on here

I did all the right things, got that installed, and imagine my surprise when it was actually the plug on the granny charger which melted.

No, I can't imagine you being surprised tbh.... I and others have highlighted the issue with BS1363 plugs on here several times already and made the recommendation to only charge at 8A max. See some of my postings here.. EDIT to add - more importantly see my posting below.

MG4 - charging from a 13A socket | MG4 EV (2022 to 2025) Forum
&
MG4 powering other stuff (Vehicle to Load aka ‘V2L’) | MG4 EV (2022 to 2025) Forum

I'd advocate charging at 8A max continuous when using a BS1363 plug or, preferably, use a 16A or 32A commando socket type portable/granny charger if you don't want the cost and complexity of a fixed charge point.

 

[Everest]

O... M... G...

We have had a lot of discussion on here on the importance of having a BS 1363/A socket installed if you are going to use a granny charger at a continuous 13 amps.

I did all the right things, got that installed, and imagine my surprise when it was actually the plug on the granny charger which melted. You would really think that they would have thought of that.

I don't want to come across as "I told you so", but a) I did and b) I think this is important to highlight here to avoid others having potentially lethal situations.

You did not do all the right things. It is NOT safe to use a BS1363 based granny charger at a continuous 13A - end of.

You had been warned. On 14th Sept 2025 you said..

Salty, what was the logic of going for one limited to 10A when 13A is available?

I have charged many nights at 13A/2.7kW and had no problems whatsoever, no heating of components, no cut-outs, and going 30% slower would be a pain.

I replied in the next posting...

Basically for compliance with IET Wiring Regulations (722.55.101.0.201.1i), mandates a BS1362-2 EV compliant socket to supply max continuous of 10A for EV charging.

FYI; 'so-called' 13A sockets are only suitable for 13A for a short duration - e.g. 3 mins. kettle boiling.

Max should be 10A with BS1362-2 EV socket and dedicated final circuit.

Otherwise max 8A continuous use.

Otherwise, this may happen...

Post in thread 'Don't charge from a 3 pin plug when it's 27 degrees outside kids'

Jun 19, 2025

Have you got a picture of the 'granny's' plug?

It wasn't granny's plug thank god. It was an industrial extension cable approx. 25m long to a weather proof socket.

• Yorkshire Hillbilly

• 

See details on this page.. 13A EV Sockets Compliant with BS 1363-2 EV
or here https://electrical.theiet.org/media/2422/bs-7671-2018_a1_2020-inc-corrigendum-may-2020_read-only.pdf

you defiantly replied...

I have now charged maybe 50 times, sometimes from 20% to 80% and it doesn't even get warm.

and my response was...

We seem to be going around in circles

You asked "what is the logic" - I have given you the answer with the technical & IET / BS7671 regulatory reasons behind it.

With all due respect I don't give a **** if you set your house on fire or electrocute your loved ones with your V2L 13A suicide cord or your lack of respect of earthing and RCD from your V2L thread.

Good luck and goodbye

I give up

 

[decrep]

There is a faulty logic, that says, "if it worked perfectly once, it will continue to do so"
Be warned everybody, this sort of logic could burn your house down!!!!!

However there must be a flaw in British plug design, if the fuse is getting hot enough to melt and burn plastic, surely it should blow before that happens.
Or is it bad fuse contact, so the outside of the fuse gets hot but the fuse wire doesn't?

 

[EvTek23]

@decrep, I think you're right. The fuse contact in the moulded plug gets hot due to the current which ultimately makes the contact become more resistive and hence more heat. In the specification for the fuse, under test conditions it quotes up to 1 watt of power dissipation in the fuse.
Our UK 13A plug looks great, and as though it will handle lots of current, but when you look at it compared to the European Schuko plug which is non fused and has large round pins, you can see that we've been short changed over the years of redesigns for safety reasons.

 

[Lovemyev]

13 Amp plugs are mass produced and are available from almost anywhere.
The place of origin and quality of these cheap items can vary massively.
They all may look the same and by and large, all can do the same job.
They all come fitted with 13 Amp protection fuses as standard normally.
Should they ? - No I don’t think they should to be perfectly honest, but that’s another debate for another time.
They are purchased and it’s left to the individual, then to fit them to what ever appliance to what they want basically.
If you purchased the cheapest plug you could find and installed it onto a table lamp with a 40Watt lamp installed, it would relatively okay to use.
The fact it has a 13 Amp fuse that is WAY to overrated is another story.
You take this cheap plug ( remember they all look the same here ) and you install it onto you kettle or microwave, because you damaged the original plug somehow, then you're in trouble.
The cheaply made plug is going to be okay to start, but after the while it’s cheap components are going to let you down.
My point here is this, they may all look the same and do a similar job, but the quality of these items vary massively !.
I do have to question the validity of the testing carried out on even the so called “higher end” plugs tbh.
How long ago was the BS standard set for these items ?.
Has it kept in touch with high loads, put on these plugs over longer time scales ?.
Maybe its time they were reviewed ?.
The rating of a microwave / kettle maybe similar here, but I doubt when testing these things, they never. expected this high demand to be placed on the plug, for hours and hours of continuous use, like a Granny unit does !.
I mean, who runs a microwave / kettle for 8 hours plus continuous in a domestic setting ! .
Time for a rethink of the standards folks.
Oh ……. While you're at it, consider placing a MAX upper limit of 8 Amps on the Granny units produced as well .

 

[Ian Key]

It used to be the case that you bought the plug separately but since 1996 new appliances have to have a moulded plug attached.

 

[decrep]

We don't have that particular problem here, our plugs are unfused

 

[EvTek23]

Another home item with high power draw is a slot in oven unit. These typically have a moulded 13A plug, and behind where the oven sits there is normally a double 13A socket. One for the oven and a second to drive the ignition and cut off valves for a gas hob.

 

[Lovemyev]

It used to be the case that you bought the plug separately but since 1996 new appliances have to have a moulded plug attached.

This is very true Ian, but you can still buy replacement plugs over the counter still.
If you purchased an item that was first intended for Europe or even the States, then yes you could install a plug converter from two pin to three pin
But it’s very likely you would chop off the two pin plug and install a three pin plug yourself.
Of course the plug will still be supplied with a 13 Amp fuse of course, which in nearly all cases will be over rated and deemed unsafe.

 

[Micropop]

I would never use that kind of charger for an EV. Neither the socket nor the plug is designed to be maxed out with that amount of current for hours and hours.
For a hybrid it's OK, as the charging time is only a few hours, but even then I have set mine to only charge at 50% on the BMW.
I'd only use it at 6-8 amps max.

 

[Kurisu112]

As others have mentioned NEVER charge using a 13amp granny cable via a 13amp plug.

A 10amp granny cable will spike and occasionally pull upto 13amp. This is why all official cables are capped at 10amps. If you want to use a 13amp granny cable then you need a 16amp fused socket with all the appropriate gauge cabling and plug socket so they don't overheat and burn out like many people are doing.