As I've said before, Tesla has some decent engineering talent. Perhaps, not unsurprisingly, someone there has done just that. Their new generation superchargers also include a battery bank to deliver a surge of juice without aver-taxing the supply mains. In practice though, slower charging is actually easier on the current type of batteries so a 50 Amp 230V outlet will deliver plenty to charge a battery to 100% overnight. A battery bank in the form of a powerwall could be useful to let a solar array charge the EV at night when the sun isn't shining in addition to providing backup power to the home if the mains are down. I just read that Tesla has worked out a deal with the Texas grid operators to use home powerwalls to feed the grid in times of high demand and take some of the strain off. Right now, it's a small pilot project to see how much potential there is.