How warm/hot should the 13A plug on a granny charger get?

My answer would be pretty warm but not so hot that you can’t hold the palm of your hand on it for quite a while.
However it seems to depend on make and model of granny charger and some other info which might be of interest to fellow EV drivers…

The reason I know this is my Zappi2 charger has failed after 2.5yrs. With a Relatively low amount of usage and I have been using granny chargers to soak up the excess solar we are generating.

The Zappi2 cable (tethered) has failed. The CP line (control line) has gone open circuit and hence cannot connect to the EV and start a charge. Interestingly this cable control line is a common failure for tethered and probably untethered cables (so any Type2 and others). The actual wire is just a relatively thin wire and it’s embedded with some hefty large current capable wires which are much stronger/stiffer. Seems the flexing causes the thinner wire to break anywhere along the length of the cable, so it’s not like it’s even easy to just repair at one or other end of the cable.
Seems a poor design to me and needs to be beefier.

Anyway, since I have been using the Zoe granny charger, I noticed the 13A plug seemed substantially hotter than when I had been using the Jaguar granny charger, so I did some back to back tests, since I have an infrared thermometer.

Zoe granny charger case temp 35degC
Zoe 13A plug temp 66degC

Jag granny case temp 30degC
Jag 13A plug 50degC

Only a very small sample, but my ‘engineering mode’ says that the more expensive Jag granny charger is probably a better design and more reliable product than the likely lower cost Renault one. However it could be that the internal connection inside the plug is not as fully secure as it needs to be in the Zoe one, but since it’s a sealed design, it is what it is. No way of checking. Both have 13A embedded fuses of a similar design, however the Jag one is about 30-50% thicker.

I am expecting delivery of a warranty replacement cable for my Zappi2 today, so should be back up and using the full solar excess abilities along with full rate charging later today.

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It could also be down to differences in the composition of the alloy (or plating) the pins are made from giving one a greater resistance than the other. Back in the day it was all high quality uncoated brass, of course, but with the price of copper these days, it’s possible manufacturers are exploiting as much leeway as the BS1363 standard allows to use metals which may not be 100% ideal, but meet the specification.

Pure speculation though - I’m not a metallurgist!

I’ve only used the Hyundai granny cable. The plug itself gets lukewarm. About as warm as the plug for the hoover when in use for a long period.

The socket gets hot. If I unplug the granny cable and press my palm over the socket I’d describe it as hot, but not enough to burn.

That said I’ve since moved house and had the electrics re-wired, I asked the electrician to wire in for a future EV charger but according to EGG he has wired it up wrong (cabled it up to the consumer unit as its own circuit rather than to the electricity meter via its own breaker). So I’ll be using the granny cable at some point and I’m curious how it performs on brand new wiring

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It’s not technically wrong, providing the consumer unit is suitable, has sufficient capacity in terms of physical space and load and, if required, an appropriate RCD.

However, a lot of the companies who install purely EV chargers like to splice in to the meter tails with what are termed as “Henley Blocks” and install their own consumer unit (and PEN fault detection device, where appropriate) as what is effentively an entirely separate installation.

This allows them to avoid touching any of the incumbent installation and thus avoid having to certify anything which isn’t their work, or ending up with any inferred responsibility for pre-existing problems. i.e. “I never touched any of that mess, guv” :slight_smile:


Ah okay that makes sense. Presumably though as there is a cable running from the consumer unit to the driveway, they can just disconnect that cable from the consumer unit and wire it in how they want?

I say this as I paid £250 for that cable to be installed. But EGG want to charge £249 because they put it down as needing to run the cable over 10m even though it’s already in place just wired up differently

As you say above, nothing wrong with an EV charger wired up from a modern consumer unit. Mine is like that, but I had a new consumer unit installed at the same time as my Zappi2 and Powerwall2. There are good reasons to have it separate though and that would be so that the Powerwall2 (or other solution) doesn’t see the EV charger as a house load and therefore doesn’t supply elecy from the battery store. Not an issue for me as the Powerwall2 understands the cheap rate times for charging both battery and EV.

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Handy to know it can work this way.

To be honest even without the £249 install I’m hesitant. £30 a month just to lease the charger then the cost of the electricity on top doesn’t make any sense when we have free public charging.

If we didn’t get free public charging then I’d splash out on a charger either flat up front fee or monthly installments. Can justify it for the convenience and potentially cheaper electric. (Well, was cheaper. We moved house so had to get a new supplier and leave our fixed term. So now pay 30p/kWh :frowning: )

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I got an Ohme charger through the Octupus discount scheme for £200 a year or so ago, and requested the one with a 32A Commando connector on it.

Then I got an electrician to install a 32A commando socket in the garage with Type A RCBO and PEN fault protection. It means I can plug the charger in when I choose to charge at home, and also use the 32A socket to supply power for other purposes (i.e. brewing beer).

It was far cheaper than a dedicated EV charger installation and, for my purposes, more flexible!

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Never know my hoover plug to get warm, but then again I have a Dyson cordless :laughing:


Commando socket is a great low cost option, with maximum flexibility.

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Lol, only the older hoovers/vacuums will get warm as the EU made them all less powerful so they don’t work properly and take twice as long to clean the house.

Cordless is the way forward these days for sure as they are very powerful for the size.
Indeed I’m waiting for all manner of electrical items to die and then I can replace with cordless.
The petrol lawnmower, elecy hedge trimmer and other items hopefully soon, but they were made to last, unlike most of todays products.

We have a hand-me-down Dyson from several years ago that pre dates the reduction in power. By the time I’ve hoovered an entire floor, the plug is noticeably warm

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