General question about electricity

chris_n

UK plugs an sockets cannot carry 10A continuously for extended periods. Something, often the sprung fuse holder in the plug will start to get a little warm.  Once something has started warming the metal in the fixtures and cable will conduct the heat away until it finds another high resistance point. This will often be the spring contacts in the socket which will start to add its own heat. Both of these points are in close proximity so will allow the heat to build further slowly weakening the sprung contacts and generating more heat before eventually something goes bang.
If you read EV forums they usually advise against using a Granny Charger unless you reduce the current to 6A.

Ectophile

Sockets for charging cars should be stamped "EV".  Of course, they look exactly the same to members of the public, who couldn't tell an EV rated socket from a normal one.

As chris_n says, plugs and sockets can get rather hot when run at high currents for hours on end.  And when that's done day after day, things eventually overheat and fail.

It may also depend on what sort of "granny lead" you used.  Some can be bumped up to 13A, but really shouldn't be.  Most have overheat detection built into the plug.  But cheap ones may not.

Qyburn

There are 13A sockets specifically rated for EV charging, for example ..
https://toughleads.co.uk/products/weatherproof-socket-compatible-with-bmw-nissan-and-jaguar-ev-chargers?srsltid=AfmBOop27lrogfiosJoF_YBCmK2gMn1LdoGR5oRiAzsWMH9xsjMnGWKd

Reed_Richards

But it was the plug that went phut.  So it looks as if the charger was faulty; nothing to do with the socket.  

Netexporter

Reed_Richards said:

But it was the plug that went phut.  So it looks as if the charger was faulty; nothing to do with the socket.  

I doubt the charger is faulty. I've had the plug warm up when, presumably, pulled the cable a bit and slightly dislodged the plug. It's not happened since as I'm now always careful to make sure the plug is fully home and that I can't accidentally snag the cable.

Reed_Richards

Netexporter said:
 

I doubt the charger is faulty. I've had the plug warm up when, presumably, pulled the cable a bit and slightly dislodged the plug. It's not happened since as I'm now always careful to make sure the plug is fully home and that I can't accidentally snag the cable.

Well the charger is indisputably faulty now because the plug has blown.  But the issue is what was the root cause.

When I was shopping around for my granny charger I found some that were rated at 10 Amps and some where you could adjust the charging current up to 13 Amps.  I steered will clear of the latter.  I got my granny charger over a year ago and I have used it to take my car over 10,000 miles and it's still going strong.  

    

Veteransaver

Has the 13A fuse on the granny charger actually blown though? It may have melted though so might be difficult to tell now.
I'd say it was unlikely though, more likely is that the socket has overheated (poor quality socket or wiring into the socket.)
It's unlikely the new storage heaters influenced anything, unless they were wired into the back of the socket you had the granny charger plugged into.
What sort of granny charger was it? There are some dodgy ones that have 3 pin plugs and draw 13Amps or more.
Decent ones should also have thermal protection in the plug, so if the plug itself starts getting hot it cuts out the power.

Veteransaver

chris_n said:

UK plugs an sockets cannot carry 10A continuously for extended periods. Something, often the sprung fuse holder in the plug will start to get a little warm.  Once something has started warming the metal in the fixtures and cable will conduct the heat away until it finds another high resistance point. This will often be the spring contacts in the socket which will start to add its own heat. Both of these points are in close proximity so will allow the heat to build further slowly weakening the sprung contacts and generating more heat before eventually something goes bang.
If you read EV forums they usually advise against using a Granny Charger unless you reduce the current to 6A.

10Amp should be fine, as long as socket and plug are good quality.
Mine doesn't even get warm to the touch.

tim_p

Mine never got warm to the touch either despite it being plugged into an extension lead through a monitoring plug device. Put about 1MWh through it (according to the monitor) and no issues. No longer use it as my Zappi does the necessary. 

Moley27272

Veteransaver said:

Has the 13A fuse on the granny charger actually blown though? It may have melted though so might be difficult to tell now.
I'd say it was unlikely though, more likely is that the socket has overheated (poor quality socket or wiring into the socket.)
It's unlikely the new storage heaters influenced anything, unless they were wired into the back of the socket you had the granny charger plugged into.
What sort of granny charger was it? There are some dodgy ones that have 3 pin plugs and draw 13Amps or more.
Decent ones should also have thermal protection in the plug, so if the plug itself starts getting hot it cuts out the power.

I think it just overheated and and burnt the fuse. I've ordered a new charger that more robust and safer 10amp. Thanks