MG4 - charging from a 13A socket

[Gordon]

In 18 months ownership I have only ever used the granny charger. Plugged into a hard-wired extension from the garden shed which itself is a plug-in extension from the house. All in 13A rated cable. never knowingly had an issue. It takes 2.2 kW according to my mains monitor. The granny charger plug gets slightly warmer than ambient but not as bad a an electric kettle can.

 

[Fogey]

It's not the cabling or the granny charger - it's the plugs and sockets (excluding the granny charger's own 13A plug, which has thermal protection). They're not protected against thermal runaway, which can occur at any time when there are contacting metal surfaces. As I've said.

You have also to be confident about your house wiring too.

 

[tsedge]

Wallboxes offer a number of advantages:

• Engineered to last and take high loads.
• PEN fault (and other) protections, that reduce the risk of electrocution.
• Installed by an electrician, typically on a dedicated circuit which is provided and checked to make sure it is rated correctly.
• Load monitoring for the house so can reduce the draw if you have a high domestic load for your supply.
• Wifi connections and apps for remote control and scheduling and integration with other equipment such as solar / battery and special tariffs.

"Granny" chargers are more suitable for occasional / temporary / emergency use, although many people seem to rely on them.

Main risk with these are:

• Poor quality mains wiring (old / unchecked).
• Shared circuits with other high-load appliances causing occasional overload.
• Use of extension leads not rated for the continuous load, not uncoiled and/or not waterproofed.

The risks are generally cumulative:

• Poor connections cause high resistance.
• High resistance causes temperature spikes.
• Temperature spikes cause expansion / contraction.
• Expansion / contraction worsens connections, increasing resistance.
• The loop continues and gets worse over time.

It is easy to try a granny charger and because it worked fine, assume it will always be fine and forget about it - but regular monitoring is needed to check the temperatures and look for any evidence of charring / scorching / burning on connections.

Unfortunately, this is exactly the opposite behaviour to human psychology: once we've done something a few times we tend to switch to automatic pilot and stop checking.

All of that said, fires and electrocution do seem to be rare.

 

[Everest]

re comments from @tsedge and @Fogey.

The main concern with using a regular (rather than EV-rated) 13A plug+socket is that they are not designed for or tested against continual high loads or disconnection of inductive circuits under load.

The weak points are:-

a) the contact of the live and neutral pins which, being square, rely on a small surface area of contact. The resistance of which will increase due to tarnishing on the brass pins and weakness over time of the spring of the socket's connection and

b) the limited contact area and quality of the connection of where the fuse is held within the plug.

The latter was particularly evident from the heat generated from the fuse connection in the plug as @Yorkshire Hillbilly experienced, shown in these postings...

Noting that all had been working fine for 2 years, before this happened...

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

Jun 18, 2025

Good job tapo KP115s havs thermal protection, lucky escape there. We set to 8 amps too. Never had a problem for 2 years even at max speed during the winter.

• Yorkshire Hillbilly
• charging electricity pin plug safety temperature
• Replies: 28
• Forum: General Chat Forum

• 

and

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

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[GaryMG4]

Oddly enough for the 22 months I used the 3 pin I would check the socket, Tapo (OMG he used a Tapo!) and plug each time I plugged in. Most of the time I just used the (then) 4 hour Go slot without any issues with just the occasional longer slot to use solar excess and one 28 hour charge! Now I only use it when one car is on the Zappi and it is an Octopus free slot, but all I do is make sure the plug is slightly warm.

 

[Everest]

Some fag-packet maths says that limiting it to 6A and only charging at times when we're at home and awake, will add more miles than we use (over 250 miles/week added vs under 200 miles/week used)... so if we do use granny charging as a stop-gap until the proper charger fitted (I'm expecting a quote for that today) we should be able to do so with safe-ish limits.

My gut feel is that 8A would be a good compromise for granny charging from a non 'EV' rated socket. If the plug or socket get significantly hot with an 8A load then they should be replaced - there is a clear fault with them.

Charging at 6A is, obviously, safer still. But bear in mind that there is likely to be 200W or more of quiescent vehicle electronics running when charging, so around 1A of your charge rate will be "wasted" powering the vehicle. This is in addition to the 10 to 15% inverter conversion loss from AC to DC. Hence at 6A, you will be only be putting in around 5A into the inverter (hence a loss of 16% on top of the inverter's losses).

FWIW... The power dissipated at any point of resistance (assuming a largely resistive load) is proportion to the square of the current drawn. From Ohm and Watts laws (V=IR and P=VI) you get P=I * I * R.

Hence, if you dodgy plug and socket has a resistance of (say) 150 mOhms, then the power dissipated by that connection would be:-

At 6A; power = 5.4W
At 8A; power = 9.6W
At 10A; power = 15W
At 13A; power = 25.3W

OMG he used a Tapo

Yes. Not sure how it was used, but it is never a good idea to force disconnect an inductive load through equipment that is not designed for it (such as a regular BS1363 plug/socket).

If one is using a granny charger, I'd always ensure that the charging has been terminated from the vehicle before switching off or unplugging a 13A plug - they are not designed for interrupting inductive loads.

 

[EvTek23]

If one is using a granny charger, I'd always ensure that the charging has been terminated from the vehicle before switching off or unplugging a 13A plug - they are not designed for interrupting inductive loads.

That's why one of the reasons the type 2 connector is locked into the vehicle while charging, to prevent arcing damage by disconnecting while current is flowing, and secondly security / theft.
When you terminate the charge from the car, by say unlocking the car, then the car stops drawing current and signals to the charger and unlocks the charging port so that the type 2 can safely be removed. Of course if you just unplug the granny charger 13A plug this process would not happen so the full current would be flowing at the moment of disconnection.

 

[GaryMG4]

Yes. Not sure how it was used, but it is never a good idea to force disconnect an inductive load through equipment that is not designed for it (such as a regular BS1363 plug/socket).

I set the Tapo to switch on 5 minutes before the car started the charge, and off 5 minutes after the car had terminated the charge. I found it useful to work out exactly how much energy was used and monitor the balancing process.

 

[redwood98]

A 7.5 year old house, should be perfectly safe. The car probably won't come with a Granny charger, unless you can negotiate one. The MG granny charger is 4m long.
To be honest I wouldn't use an extension.
Buy a 10m granny charger.

Oh and,

View attachment 41219

To the forum. And enjoy your new motor.

I have an extension for my 32a charger, as the place I installed it wasn't near enough. Works alright just slightly annoying having to plug it in. (mine is a type 2 extension though, I imagine a 13a socket extension could have risks involved)

 

[SteveM]

I charged mine with included granny chrager for months before I got a proper 7kW charger in the drive (which, by the way, was well worth it). I used a regular extension, rated 13A. It had a thermal cutout as many do and I was careful to weather proof it. I don't want to get into an argument with the safety enthusiasts, but I did want to mention one thing that will improve safety. Maybe it is too obvious to say, but the first time you charge be awake and at home. After half an hour, go put your hand on anything that worries you, certainly any plugs, to see if it is warm. My plug at the wall socket got gently warm but no more than that. If anything feels hot, turn it off. Check again after an hour, and, say three hours. That's probably long enough to reach equilibrium, but there's no harm in extra checks. In my view, the biggest risk comes not so much from the BS numbers on the hardware, but rather from the possibility of a poorly tightened connection. This can happen even when the installation was professional (I speak from personal experience) and the safety ratings all correct. The cables themselves are unlikely to be problem if you fully unwind the extension and don't exceed the rating.

 

[dave f]

If you use the granny charger that comes with the vehicle it will be fine. Despite the 13A UK rating and 10A for Australia and New Zealand (where I live) our outlets are not rated for this current with 100% duty cycle. The relevant standards set a safe limit for continuous duty at 80% of the design value, so that’s ten and a bit amps in the UK and 8A here.

If you have a granny that came from MG you will be fine. It will comply with these restrictions. If you have a third-party portable charger all bets are off because there are people (and some are on this board) who think nothing of turning things up to 11. But that’s another whole topic of its own.

I used a granny for years to charge both an MG ZS EV and our MG4 without issues. There is far far less chance you’ll burn your house down than you would have setting fire to it with the petrol and heat of your ICE vehicle, mower, or weed eater, etc.

same here i had a zs for 3 years and charged it weekly with the supplied mg charger and had no problems.(uk)
i now have an mg4 that is a year old and have been charging it again on the supplied granny with no issues
i dont use an extension lead and would not recommend it personally but im fortunate enough to have a driveway and garage and my cable is long enough on the supplied charger to reach from car to socket in garage there is a gap under the garage door thats big enough for the cable to comfortably sit without being trapped.

 

[Shep]

I had this EV 13amp socket from Screwfix fitted outside my porch, wired directly from a garage consumer unit fitted inside direct from the mains. Got an EIC18-3C certificate from the qualified electrician for home insurance purposes.

As no garage or nearby drive I made up a 10mt extension lead using this 'artic' 2.5mm cable and waterproof socket for the Granny charger to plug into, which I place under the car to protect from the weather. Leave it overnight to do a cell balance once a month, as advised (9hrs +) on the supplied MG granny charger (MG ZS EV).

Don't know what the car insurance company will say should it overheat and set fire to the car! No probs so far, lukewarm at most. Sparks said it'll be fine. Socket also very handy for the mower and hedge trimmer.

[NOTE: This is solely a description of what I did - not a recommendation or instruction of what you should do.]

 

[Yorkshire Hillbilly]

Tapo (OMG he used a Tapo!)

It was fine for 3 years until a software update reset the AC charging current on the vehicle. Anyways, I replaced the cable with an EV rated one, and replaced the plug socket with an EV rated one. If the Tapo wasn't tripping the in-line RCD all the time I'd still have it plugged in. It has a temp sensor built in so auto shuts off when it gets too warm. And I have the added bonus of being able to turn it off remotely when the local sally wags are stealing my power. The extension goes underneath the front hedge which is on the edge of a public car park (I rent the space outside my house) so Joe public can just plug in whenever they like.

 

[OAPs in an MG]

Hi, I ordered an MG4 (SE Long Range) on Saturday 8th, and am picking it up on Saturday 15th. We won't have a charger fitted by then, so until we do our choices are charge at public chargers (£££) or charge from a 13A socket. So...:

• is it safe to charge from a 13A socket? I've read that it's risky as they're not designed to supply anything like the rated current for a sustained period of time. If it makes a difference the wiring is modern as the the house is 7.5 years old
• Does the MG4 come with a "granny charger"?
• If so, how long is it? Our outside socket is probably just over 10m away, and while there is a socket in the garage (~2m away) that'd mean leaving the garage door open a crack, with something in front of the door to stop it swinging fully open, which isn't ideal
• If it comes with one that's not long enough, is it safe to use with an extension lead or do I need to buy a longer one?

I use a granny charger at home ( house built in 2017) as
I use about 6kWh per day (10% of a 64 kWh battery) it takes about 2 hours to top up. I am with Mercury and pay $NZ0.2258 a kWh plus $NZ0.068 per hour "Line charges"
If I use my local Jolt (used to be free for 7kws, now they charge $NZ1.61 for the first 7kw then $NZ0.47 after that), it is a 25kwh charger and I get 7kw in 18 mins.
My Local Charge net that will charge at up to 150kwh charges me $NZ0.90 a kw

So for me happy to charge at home, and it is safe if you plug directly into the wall socket, not happy with the idea of extension leads with line losses etc.

I will often use Jolt as it is time/cost-effective.

Work out what is best and SAFE for you

 

[Everest]

I made up a 10mt extension lead using this 'artic' 2.5mm cable a

2.5mm^2 Arctic cable is ideal. Though you need a suitable plug for the wires to fit - see also this posting / thread about extension cables..

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