EV charge times

There is a huge misunderstanding going on here. The real charging rate is controlled by the vehicle, not the charge point. The range of charge rate options depends on the vehicle and they are not all the same and some are quite simple. Reducing the mains voltage for example does not reduce the charge power, it just increases the current. Charge points do provide communication with the vehicle, but this is not usually on a completely “sliding scale” as this makes the charger (in the vehicle) much more complex.

It is a difficult problem, because changing the mains waveform to a lower average, say chopping it up into a high frequency chopped sine wave has huge snags although it is done for power factor correction, and impacts the supply system as a whole, particularly the EMC. It can be overcome by rectifying the mains and smoothing the resulting DC, but this needs large, heavy, and expensive smoothing capacitors in the car, which is a problem. 

The underlying difficulty is that the car charging specification has never been satisfactory, and we are now stuck with a system that is unsatisfactory in several ways, particularly that cars should be class 2 appliances. You will note that all the problems are passed over to the fixed installation, and some of these are very difficult and expensive to work around, typically type B RCDs and the TT supplies, and neutral loss detection.

There is a huge misunderstanding going on here. The real charging rate is controlled by the vehicle, not the charge point. The range of charge rate options depends on the vehicle and they are not all the same and some are quite simple. Reducing the mains voltage for example does not reduce the charge power, it just increases the current. Charge points do provide communication with the vehicle, but this is not usually on a completely “sliding scale” as this makes the charger (in the vehicle) much more complex.

It is a difficult problem, because changing the mains waveform to a lower average, say chopping it up into a high frequency chopped sine wave has huge snags although it is done for power factor correction, and impacts the supply system as a whole, particularly the EMC. It can be overcome by rectifying the mains and smoothing the resulting DC, but this needs large, heavy, and expensive smoothing capacitors in the car, which is a problem. 

The underlying difficulty is that the car charging specification has never been satisfactory, and we are now stuck with a system that is unsatisfactory in several ways, particularly that cars should be class 2 appliances. You will note that all the problems are passed over to the fixed installation, and some of these are very difficult and expensive to work around, typically type B RCDs and the TT supplies, and neutral loss detection.