Hacker News Reader

That's not accurate. The EVSE communicates a max current to the vehicle, but does nothing to actively control the current. It should monitor the current and kill the circuit if the vehicle attempts to draw too much, but that only happens after the vehicle has misbehaved.

View on HN

Correct. The control pilot signal from EVSE to EV is a PWM signal that indicates to the EV how much current is available.

It could drop at any time due to, for example, many chargers being connected to 1 circuit and the chargers coordinating with each-other to load-balance their connected vehicles (everyone gets their fair share), or it could be tied to solar PV generation so that charging doesn't import from the grid; the available current will change with how much excess PV is available, etc.

A well-engineered EVSE will notice when the EV is drawing more than the EVSE wants it to. It should then open the mains contactor at this point; cutting the EV's electricity supply. It will also hold the control pilot low to signal a fault to the EV.

Reply on news.ycombinator.com