13A EV chargers

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

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