BBC News: Molten metal batteries for the grid

[Rob Seastrom]

Mike O'Dell <mo at ccr.org> writes:

> Electric kettles pull about a kilowatt - times the number
> of kettles making tea during Telly - that's a *LOT* of spike!

This effect has crossed my mind a couple of times when charging my
car.

There are actually two charger receptacles on the Leaf.

One is for the SAE J1772 cable which is basically a smart extension
cord (40a breaker, 240v single phase, and the charger on the car only
draws 27 amps).

The other is one of the DC fast charging standards: CHAdeMO.  A
display on charger tells you how much the car is ingesting.  While it
tapers off greatly as the battery approaches "full", when one starts
charging and is well under 50% full, things can really rock and roll.
The "big" chargers have a nameplate rating of 50kw; the small ones
half that.  I've personally witnessed 106A @ 391v.  AFAIK, it doesn't
ramp up gently; it's a step load on the 480v 3-phase that feeds the
charger.

That doesn't strike me as a very friendly thing to do to the grid...
I've heard stories about big cyclotrons and the like that require
coordination with the utility to turn them on and off...  but I wonder
what kind of accommodation a proliferation of these (and Tesla
Superchargers, which draw 120kW) might mean for the grid.

-r