The bulges in sone "granny leads" seem to be rather small for that. I think that it is the car which has to be satisfied that the connection is sound.

There are 3 pins on the input: L, N, E. There are 7 pins on the outlet: L1, L2, L3, N, E, PP and CP. Clearly, L2 and L3 are redundant. PP tells the vehicle that it has been plugged in so for example, it cannot be driven. CP says, "I am only a granny lead" so don't draw more than 10 A please (or I am a proper EVCP, 3-phase even so you can draw more).

Back to the OP: I think that to determine what the lights (and clicking mean) you need to refer to the instructions for that particular lead.

Hi Chris, I’m curious about your background and expertise on this topic. What are your credentials? Do you work as a consultant? You seem to answer questions with a lot of confidence and authority. How much experience do you have in electrical installation?

I think it’s fair to expect that anyone who offers advice as an expert should disclose their qualifications and experience. I have the ECS registered electrician status, which is the gold standard for electrical installation work in the UK. I also have the 2391 and 2400 qualifications, which demonstrate my competence in inspection, testing and design. I hold a HNC/HND in electrical engineering, which gives me a higher level of technical knowledge. I think this information is relevant and important when discussing BS 7671, which is the national standard for electrical wiring regulations.

Harry Macdonald said:

I have not found any information on the internet as to what is inside these units.

It occurs to me that the one certain way of finding out would be to take the lid off and have a look.

The bulges in sone "granny leads" seem to be rather small for that.

The supply end certainly should keep the power off until the car asks for it (implying that all the connectors are in place) - otherwise you'd have unshuttered live parts on the car end of the lead - not ideal for domestic situations, especially where there's a decent risk of it being dropped in a puddle.

The OP's description of the unit 'clicking' would seem to suggest that there is indeed a mechanical relay inside.

There are 3 pins on the input: L, N, E. There are 7 pins on the outlet: L1, L2, L3, N, E, PP and CP. Clearly, L2 and L3 are redundant. PP tells the vehicle that it has been plugged in so for example, it cannot be driven. CP says, "I am only a granny lead" so don't draw more than 10 A please (or I am a proper EVCP, 3-phase even so you can draw more).

True, but there is a bit more to it than that - see https://en.wikipedia.org/wiki/SAE_J1772#Signaling (That wiki page is based on the Type 1 connector common in the US, but I understand the signalling system is same on the Type 2s that are more common here).

    - Andy.

seconded, And when you do, let us know, feel free to post pics of any part you cannot identify  ;-) I know what is inside all sorts of kit, including as it happens a couple of makes of the larger chargers  by exactly this method, not by some course.

M,

Chris Pearson said:

have not found any information on the internet as to what is inside these units.

It occurs to me that the one certain way of finding out would be to take the lid off and have a look.

Not sure what you're looking for exactly as to the extent of what's in there, but this site has a good brief description: https://www.rfwireless-world.com/Terminology/EV-charging-modes.html

In short, the safety features built into the lead are:

• Built-in RCD
• Circuit to monitor the resistance between PE and N to demonstrate the earthing is likely to be safe (at least will operate RCD)
• Circuit to communicate with the vehicle, so power is not applied to the vehicle connector end of the cable until the vehicle is connected. Also, removes power if the vehicle comms fails.

Ignoring the RCD, the electronics required for the above functions are not extensive. There are various circuits available on the internet, based on those in the standards for the devices.

Thank you for this.

The original question relates to my charger cycling on and off at about once per second. I am trying to resolve whether this is likely to be normal, a fault in the car, a fault in the charger or a fault with my home wiring.

The local Nissan agent has offered to run a diagnostic on the car for £100, but this may well find nothing as the fault only seems to be present within half an hour of using the car.

From all the helpful answers, I am coming to the conclusion that the charger is switching on and off because the car is requesting it to, i.e. a fault in the car, maybe it is sensing a hot battery and switching off only to say that it is OK and switch on again.

I had the idea that it might relate to a high neutral earth voltage in the house, which would only show up when the charger was on, but measuring this showed the NE voltage steady at well below 1V at the time.

Harry Macdonald said:

I had the idea that it might relate to a high neutral earth voltage in the house, which would only show up when the charger was on, but measuring this showed the NE voltage steady at well below 1V at the time.

The car itself may also be looking for a minimum neutral-earth resistance.

Have you checked loop impedance and connections at the socket-outlet to see if anything has changed?

What is the earthing arrangement, and is the solar array/inverter grid-connected when you are charging the car? I'm also assuming you've tried it in another installation?

I am trying to resolve whether this is likely to be normal, a fault in the car, a fault in the charger or a fault with my home wiring.

What about trying that car (when still "hot") in another charge point? (a friendly neighbour or a pubic one)

   - Andy.