Several tesla superchargers near where I live have fuel cell setups, presumably to shave peak loads for the rare cases that the charging stations are all in use and all charging at peak rates.
I suspect they have batteries rather than fuel cells?
Tesla is known to colocate them for exactly the reasons you say - also to shift load to cheaper hours of the day and to get paid by the grid for balancing services.
I think the current ones don't use generators, but that one time they used a gas generator to charge Teslas, called it a "battery swap station", and got a bunch of money from California that was supposed to go to zero-emissions car projects. I doubt they'll ever live that down.
Live what down? California paid for a research and demonstration project. Tesla did that but decide for a whole number of reasons that it wasn't worth doing.
