Um. Got a Gen 2 WC. No web UI. There are, however, a pair of rotary switches with which one can set the configuration of the WC. One of those configuration settings tells the WC what the amperage of the circuit it’s connected to.
At my place, that’s 60A. The car talks to the WC, then more or less sets the max charging current to 80% of 60A, or 48A. Which is correct for the LR Teslas the WC is normally connected to.
However, nothing stops me from setting the circuit limit switches to, say, 40A. In which case the cars hooked up to this WC would pull no more than 32A, that being 80% of 40A. In fact, I think the settings go from 20A to 100A, that last being for certain Model S’s that could pull 80A, back in the day.
My understanding is that the Gen 3 WC doesn’t use switches, but has a “commissioning” step on its GUI that has the same function. And would cause any car hooked up to the WC to limit the car’s current draw to a max of 80% of the limit set.
Two caveats: First, by all that’s holy, never set the WC’s circuit limit higher than the amperage of the circuit it’s actually hooked up to. That way lies madness, popped circuit breakers, and a non-zero chance of a fire, so Be Careful.
Second, if this wasn’t clear: the actual current is the lowest of what the WC says it can supply or what the car figures it can accept, the latter including any fiddling around with the max charge current setting on the car’s GUI.