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.

  • psaux_grep@alien.topBEnglish
    1·
    1 year ago

    Bjørn Nyland has made several videos on the topic of AC charging, but titles are a bit vague so hard to tell which ones, but I believe this one touches on it:

    https://youtu.be/Zpp0iQC5xxc

    Obviously you might not live somewhere where it is cold during winter, peak efficiency of the on-board charger is likely to be around the 80% mark, but the more the battery heats up during AC charging the lower the internal resistance is.

    As for 11kW damaging the battery? Nope. Not even. Most EV’s to day fast charge at 100+kW, some at 200+. The battery doesn’t even get tickled at 11kW.

    At the end though it doesn’t really matter. 11kW isn’t a huge amount and your household could easily pull that around dinner time.

    What 11kW charging often enables is full off-peak (during the night) charging of the battery. So instead of taxing the grid at day you can fully charge an empty battery when the demand drops.

    Ideally chargers are smart and can help frequency balance the grid by charging when the load drops, or stop when it surges, but we have only seen the very beginning of this.