When you charge the roadster a certain portion of the power is spent cooling the battery. If you try to do a fast charge in an hour at higher voltage and current like 50 kW ( 500 volts 100 amps? ) there will be a lot of heat to dump. Why not have a second loop through the radiator to do a higher efficiency heat exchange. This second loop is normally empty and penalizes the car with an extra couple pounds of copper or aluminum. Then you have a second umbilical that runs coolant through this heat exchanger. The car doesnt need to waste any of the juice it gets running fans, only running the pumps. If you are charging at 50 kW, then you have the charge station have a powerful cooling system to cool this fluid. Even if you are charging at a normal power, you could run fluid through a big heat sink and then you would charge faster because you dont waste power running the fans and you should be able to run the pumps less because you are getting rid of the heat more efficiently.