This poses an interesting question: how to get rid of that energy? Once the battery is full, you'd need a pretty substantial resistor bank to dissipate all of that excess energy. I wonder if they intentionally start the day at a low state of charge and end fully charged? The idea of a "reverse charger" to discharge the battery into the grid every night would be hilarious and not entirely unfeasible.
> we were not able to find anything larger except the occasional electric train<p>Not sure what occasional means in this contex, hard to find a train that doesn't use the grid