Has been mentioned elsewhere somewhere. Big problem is lack of standardisation between batteries for different models of cars, and as EVs evolve, there will be newer chemistries etc, so how do you keep the BMSes up-to-date etc? Also, the vendor has to invest in a stockpile of batteries, so there's a lot of capital value tied up. And what happens if cars pile up all wanting a swap, faster that they can recharge the empty ones arriving? I can see it might work in a large city with predictable numbers of cars, but it's going to be a lot less financially viable if you try to scatter these expensive robotised-swappers in remote locations between widely-spaced cities. And who knows, may be obsoleted by super-fast-fill solid-state batteries in the blink of an (evolutionary) eye!