13A EV chargers

“Granny leads” are commonly supplied with EVs.  The blob of electronics in the middle of the lead does contain some safety equipment - a software-implemented RCD at least.

It's probably exempt from BS7671 because it's (part of) a plug-in appliance.  No different from plugging in an electric lawnmower.

And, like an electric lawnmower, it will have no idea what the earthing arrangement is, and won't particularly care.

Simon Barker: 
 

“Granny leads” are commonly supplied with EVs.  The blob of electronics in the middle of the lead does contain some safety equipment - a software-implemented RCD at least.

It's probably exempt from BS7671 because it's (part of) a plug-in appliance.  No different from plugging in an electric lawnmower.

And, like an electric lawnmower, it will have no idea what the earthing arrangement is, and won't particularly care.

Presume the same for the 16A and 32A versions of these chargers? 

And, like an electric lawnmower, it will have no idea what the earthing arrangement is, and won't particularly care.

But, and it is quite a big but, the lawnmower will  be double insulated and might as well have a 2 pin plug.   The same is true of any garden appliance made in the last 30 years or so.

In contrast,  the car connects a large amount of metal to the circuit CPC. that is accessible to someone standing on the ground under/beside the vehicle. Note that  CPC may well not  be at quite  the same voltage as the terra firma in normal use, and may be quite a long way off in certain fault conditions.

The risk is very low, but not zero. (which is why chargers screwed to the wall are usually TT earthed.)  BS7671 does not care of course, it's scope  stops at the socket. and neither do the product standards, but the situation falls neatly down the gaps between them.

Mike.

mapj1: 
 

And, like an electric lawnmower, it will have no idea what the earthing arrangement is, and won't particularly care.

 

But, and it is quite a big but, the lawnmower will  be double insulated and might as well have a 2 pin plug.   The same is true of any garden appliance made in the last 30 years or so.

In contrast,  the car connects a large amount of metal to the circuit CPC. that is accessible to someone standing on the ground under/beside the vehicle. Note that  CPC may well not  be at quite  the same voltage as the terra firma in normal use, and may be quite a long way off in certain fault conditions.

The risk is very low, but not zero. (which is why chargers screwed to the wall are usually TT earthed.)  BS7671 does not care of course, it's scope  stops at the socket. and neither do the product standards, but the situation falls neatly down the gaps between them.

Mike.

 

The chargers with built in PEN fault detection don’t require rods so the issue of different voltages between PME earth and the ground below the car, would still be an issue on these units. 

A friend with a plug in hybrid with  a 13A plug found his car had not charged. He explored a little further and found his plug had melted. He replaced the plug and socket and still had problems with the plug overheating and the car not charging.

I managed to find out how he could change the charge current from a standard 10A to 6 A and it now works. 

What is strange is that in his garage, one garage per flat with a metered supply from the flat management. In the garage he has a 15A fuse suppling a standalone 30mA RCD supplying a 13A socket to which a permanently wired  extension cable about 10ft long has been connected via a 13A plug. Even when the charger plug is getting hot this plug is still cool. 

When he replaced the melted 13A plug the wiring colours in the charger cable were not standard, I think the CPC was white with a coloured line. 

Other owners of the same car have reported the plug melting. My friend has taken it up with the dealer and despite promises got no feedback. He is now taking it up with the manufacturers. 

So irrespective of all the clever protection or lack of for earthing a more fundamental problem also exists. 

I will be visiting soon to ensure that the installation is safe. 

Sounds like a poorly made lead.

Some makes of charging leads have a thermistor built into the plug, to detect overheating before the plug melts.

kfh: 
 

A friend with a plug in hybrid with  a 13A plug found his car had not charged. He explored a little further and found his plug had melted. He replaced the plug and socket and still had problems with the plug overheating and the car not charging.

I managed to find out how he could change the charge current from a standard 10A to 6 A and it now works. 

What is strange is that in his garage, one garage per flat with a metered supply from the flat management. In the garage he has a 15A fuse suppling a standalone 30mA RCD supplying a 13A socket to which a permanently wired  extension cable about 10ft long has been connected via a 13A plug. Even when the charger plug is getting hot this plug is still cool. 

When he replaced the melted 13A plug the wiring colours in the charger cable were not standard, I think the CPC was white with a coloured line. 

Other owners of the same car have reported the plug melting. My friend has taken it up with the dealer and despite promises got no feedback. He is now taking it up with the manufacturers. 

So irrespective of all the clever protection or lack of for earthing a more fundamental problem also exists. 

I will be visiting soon to ensure that the installation is safe. 

The same applies to hot tubs that constantly pull power for 13-20 hours to bring them up to temperature (referencing these portable types). 

A 13a socket should not melt under a 10a load. 

Well a shiny new 13A plug in a shiny new socket is OK, but despite the chunky pins compared to the 15 and  16A offerings in other places , the actual area of contact is not actually that great,often being little more than the thin line where the pin top meets a curved spring finger.

A similar problem afflicts the fuse holders in some designs. To make a larger contact area, the pressure has to be enough to deform something round to be slightly flat, though like train wheels, which also go slightly flat at the point they meet the track, the change in shape is minimal, and the actual area where atoms get  close enough to exchange electrons is very small indeed.

 Once the surface of the pin is oxidized a bit, or worse pitted or scratched, then as gaps of hundredths of a mm open up,  the current is funnelled into a reduced area, causing heating and accelerating further decay.

In comparison, the hard gold plated pins of some mil spec connectors manage  far more current on very spindly pins without heating, but they do not corrode, and the surfaces are shaped and conform to give an area of contact that is actually larger than the cross-section, rather than less. This is however reflected in the eye watering price.

I have often wondered if the gold plated socket merchants of the audio business were not such shysters, if there would be a market for some sort of plated non-corroding plug and mating socket for garages etc.

Certainly in outbuildings, and some damper utility/laundry rooms indoors the 13 A plug with its brass pins that go dull and then brown/black is not really the right animal. 

As an aside, I'd suggest to replace the plug and socket together when they are heat damaged, as the other half may well also have suffered - heat reduces the ‘spring’ of the socket contacts and they may then not give a good graunching contact after that.

Mike

From an electrical safety point of view, I'm wondering why a portable EV charger is any different from a good old fashioned battery charger that we have been using for years. Balance it on the radiator and clip the leads to the battery.

We never bothered about earthing it then!

My friend with the melting plug has been told by the dealer that the car manufacturer changed their instruction manual in subsequent years to say to only use the 13A charger in an emergency! That does not solve his problem or that of other users of the same charger that have not had the updated manual.