Granny charger plug burn out

[securespark]

The only time I used a Granny was when we got the MG4 and before our Ohme Home Pro was installed. I have an MK Masterseal outside on the drive that I ran as a 16A radial using a length of 1.5 butyl heat resistant cable that I had left over from installing immersion heaters. I installed it as a GP outdoor socket for garden tools, lawnmower etc, well before we decided to get an EV.

We used it a lot in the early days and I did check the plug and socket every time, but didn't notice any issues.

 

[securespark]

And a big dollop of luck.

I know you're cynical. I'm just answering Coulomb's query about British Standards.

Hager make a 13A EV charging specific socket.

Chop off your potentially dodgy plug and replace it with an MK646 plug. I should have mentioned these earlier. They are very robust and a reliable plug to use at higher currents.

I don't know about these days, but back in the day, organisations like the PO (and then BT), the BBC, Granada and even the MoD, just to name a few, used to swear by them and all had their marks moulded or printed on the tops of the plugs in place of the MK logo.

 

[securespark]

these sockets I have must be quite something.

What brand are they?

 

[EvTek23]

Do check though before you chop off the plug that it hasn't hot a temperature sensor built in.
The lead is normally quite large and will say something like...3G X 2.5 + 2G X1.5 printed or moulded into the cable. This indicates 5 wires, the 2.5 mm sq being the main power conductors and the 1.5mm sq are the two wires for the sensor.

 

[securespark]

Thanks, yes, please check there are only 3 conductors in your flex before you get snippy!

Regarding 2.5mm² conductors in 13A plugs, BS1363 says the following:

View attachment 367091

So you may find 2.5mm² a little tight, but I have managed it To be honest, the trickier bit is not getting the conductors in the terminals, but getting the flex sheath under the cable grip.

 

[Everest]

So you may find 2.5mm² a little tight, but I have managed it To be honest, the trickier bit is not getting the conductors in the terminals, but getting the flex sheath under the cable grip.

and FWIW; I found the plug mention in my posting below suitable for 2.5mm² arctic flex.

Post in thread 'Granny Charging'

Jul 15, 2025

I made up an extension lead with 2.5 mm2 arctic cable with a rubber plug and single socket.
Granny charging with this lead gave a higher rate of charge on the same granny charger, no heating of the cable / plugs / sockets. Many 13 amp plugs have a max cable size of 1.5 mm2, I drilled mine out for the 2.5 mm2 flex, all worked out really well

we did almost the same to extend our 'granny charger' (as in 2.5mm2 arctic cable, albeit with a command socket on the other end). FWIW, this 'heavy-duty' BS1363 plug accepts 2.5mm2 arctic cable without any modification...

• Everest

 

[Porsche944]

I use one of these

EzGoGo EV Charger - Official Website

Welcome to the official site for EzGoGo, your source for reliable and fast EV charging solutions. Discover our Type 2 charging cables, 3-pin plug electric car chargers, and accessories featuring advanced protection and user-friendly controls for all major EV and PHEV models.

ezgogo.org

Seems well made, its installed in a water proof & glanded box outside. I rewired the pug on it after threading it through the gland. Getting 3 x 2.5mm into a Duraplug was a challenge but I managed it.

 

[securespark]

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.

Advice from appliance manufacturers is that if the appliance is under 700W, it should have a 3A fuse fitted, if over 700W, it should have a 13A fuse fitted.

The leaflet mentions older appliances may have 5A fuses and they are still available to buy.

Well actually, you can buy 1A, 2A, 3A, 5A, 7A, 10A and 13A fuses.

If you see higher values, don't buy them.


Safety Advice: Plugs and Fuses | Electrical Safety First Safety Advice: Plugs and Fuses | Electrical Safety First

 

[TimothyN]

and it never even got warm.

I would point out that my plug, which eventually burnt out fairly dramatically, as can be seen in the OP, never even got warm towards the beginning, and I have now replaced both the socket and the plug; neither even get warm at a continuous 13 amp.

It does seem to be a cumulative problem, and therein lies the danger.

Also, a lot of focus seems to be put on the socket, whereas it would seem that the problems mostly, if not exclusively, originate in the plug.

 

[securespark]

TBF, the problem can sometimes lie with a sloppy socket where the plug pins don't fit tightly enough into the socket contacts.

Everyone has it in for the 1363 plug...but sometimes, it's the 1363 socket!

 

[Lovemyev]

Advice from appliance manufacturers is that if the appliance is under 700W, it should have a 3A fuse fitted, if over 700W, it should have a 13A fuse fitted.

The leaflet mentions older appliances may have 5A fuses and they are still available to buy.

Well actually, you can buy 1A, 2A, 3A, 5A, 7A, 10A and 13A fuses.

If you see higher values, don't buy them.


Safety Advice: Plugs and Fuses | Electrical Safety First Safety Advice: Plugs and Fuses | Electrical Safety First

I always have spare 3 / 5 /13Amp fuses ready to hand.
The majority of our electrical items are covered by 3 or 5 amp fuses.
Only the heavier load appliances have 13 Amp fuses installed.

 

[Everest]

Advice from appliance manufacturers is that if the appliance is under 700W, it should have a 3A fuse fitted, if over 700W, it should have a 13A fuse fitted

That advice - whilst better than using a 13A fuse for everything - is IMHO, badly worded, technically inaccurate and does not consider the bigger picture.

The majority of our electrical items are covered by 3 or 5 amp fuses.
Only the heavier load appliances have 13 Amp fuses installed.

Absolutely.

My 2p worth... if anyone is awake...

A fuse is required to protect circuits from overcurrent situations and the subsequent risk of fires from the overheating of wires and components in the circuit.

For any given device, the power it draws should be known or determined Based on that power draw the size of the cable supplying the device should be calculated, allowing some leeway.

The power that a given cable can safely handle will be a result of its material, cross-section, max temperature characteristics of its insulation and the method of installation (e.g. whether it is in conduit, under insulation or in open air).

The fuse used on the circuit supplying that cable should therefore be rated less than the maximum carrying capacity of the cable, to protect the cable from overheating in failure conditions.

My 'rule-of-thumb' is that for a given current draw of a device, then the fuse should be rated at that current + 20% and the wire supplying the device should handle the fuse current + 20%.

So, taking the example of a 900W toaster. The current draw at nominal 230V will be 3.9A. Adding 20% gives a fuse size of 4.7A. Therefore a fuse rating of 5A is appropriate. The wire used to supply the toaster should be (assuming regular domestic 3 core flex in open air) a minimum of 4.7A + 20% which is 5.6A. Therefore flex of size 0.75mm² would be suitable as that will typically handle 6A.

But if, for example, the 900W toaster you buy comes with 1mm² flex, that cable will have a current carrying capacity of around 10A. Which is all good and generously sized for the toaster's power draw. BUT 1mm² cable should not be used with a fuse of 13A. The fuse should blow before the cable melts should the end device fail and draw too much power. Hence a fuse of 5A or 10A should be used, not 13A as that linked advice suggested.

 

[Lovemyev]

Better to have a fuse that is rated too low installed, rather than a fuse that is over size rated for the appliance.
The fuse is correctly intended to be the weakest point in the circuit.