Isn't it really as simple as the EV being charged communicating with EVSE (charger) to determine the current rating of the available electricity supply?

There can be additional protection built into the EVSE, but not always. 

A similar question would be, why do electricians spend four hundred pounds or more on an EVSE testing adapter to fool the EVSE into thinking the electrician is plugging in an EV to charge rather than their installation tester to carry out tests?

I was starting to wonder why I wasted my hard-earned money on the course, the COP, the EV socket adaptor and a new megger !

Sparkingchip said:

A similar question would be, why do electricians spend four hundred pounds or more on an EVSE testing adapter to fool the EVSE into thinking the electrician is plugging in an EV to charge rather than their installation tester to carry out tests?

That's a good question for the most part ... although protective devices such as RCDs can be built into EV charging equipment ... having said that, in designs like the "cabinet" type approach with DIN-rail mounted components, the RCD could possibly  be tested using Test Method 2 (upstream'/downstream) from GN3 9th Ed (2022) ...

I think, however, fault-finding and commissioning are the answers to why you really need an EV  simulator/adaptor.

There must be more than this, even in a simple granny lead, as the thing was clicking on and off and I can't find out what could have been making it do this.

The granny lead will contain relays to disconnect the power from the car until it is satisfied that it has established a data connection over the pilot wire.  The same relays are probably also used to implement the RCD function.  The whole thing will be controlled by a microporcessor, because everything is these days.

If the microprocessor is faulty, or the lead is damaged, then anything could be happrning inside.

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.

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.

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.