I heard something today that makes me very skeptical. A dealership claimed that charging an EV with 11 kW has higher energy efficiency than charging with 6 kW. (And they didn’t mean 3-phase vs. 1-phase!)
Even if it is somehow related to battery temperature and receptiveness, that would still be heat loss. With higher currents, resistance increases, too, no? Or is it proportional and always the same percentage?
In any case, I find it foolish to follow such advice because there are other factors involved, mainly a battery suffering more regarding longevity if charged faster, and that is a lot more expensive of a loss, eventually, also because an older battery is generally less efficient in several ways. (internal resistance, self-discharge)
Plus more load spike on the grid, external and house. But I don’t want to rant too much about the lack of reason in the world that seems to be a self-amplifying spiral of doom. Apparently house charger impatience is a thing. Three hours of charging twice a month - absolutely intolerable to some.
Different hardware might handle charging at different speeds. Given that I’ve personally never heard of a vehicle charging at 11 kW on a single phase, I’m all but certain the dealer was referring to the difference between single-phase and three-phase here.
A rough rule of thumb for charging losses is: 15% for single phase level 1, 10% for three-phase level 2, 5% for DCFC level 3.
It varies from car to car, obviously. But the hardware handling three-phase charging is always less lossy than the one handling single-phase.
The dealer meant 3-phase for both.