I was thinking it might be a truck mounted diesel generator. Instead it appears to be an even bigger battery on wheels. Must draw a massive amount of electricity to charge it up. Probably need to park it next to an electricity substation.
I think they are doing some clever things with solar to keep it charged (basically constant trickle charge with whatever they can generate), but the array might be pretty massive.
https://www.porsche.com/stories/mobility/how-does-a-mobile-c...