I think turning this thread into a discussion about an Open Source DC Fast Charger would be useful and interesting.

Tony's proposal for a higher power unit that has two handles and can charge two vehicles with variable power is very interesting. This is the way that Tesla SuperChargers work. Tesla gives the first vehicle to arrive as much power as it asks for and the second gets whatever is left over, up to its requested amount. The SuperChargers use a stack of 10kW AC to DC chargers, the same as the ones used in their cars, to leverage production volumes and provide some fault tolerance in case one fails. This is a good architecture.

For any new effort, I think the easiest path to implementing a fault tolerant system like this is to use some existing hardware and integrate it together. eMotorWerks has some DC charger hardware and could be ganged up to build this kind of system. At 25kW each, there is not as much granularity as the Tesla 10kW chargers, but they are likely cheaper and easier to inetgrate. Conceptually, the easiest way to handle the dual output for two cars is to have each charger output go into an A/B switch that can direct all of that charger's output to one of two current delivery buses, one going to each of the two CHAdeMO handles. Each charger in the system is working at the battery voltage of the connected vehicle and the current from each one is additive. As the current ramps down on one vehicle and one charger's current is no longer needed it can be switched over to the other bus and ramp up the current to that vehicle as needed.

From a system integration standpoint, cooling is probably one of the larger concerns. SuperChargers are liquid cooled, mostly because that is how the individual charger modules are cooled.

Thoughts?