It isn't straightforward however. There needs to be some switching circuitry so that if you are doing AC charging the current goes one place, and if you are doing DC charging, the current goes another. If you were to buy adapters, you would need a separate one for each use case.
As for communications, NACS is essentially just the same as CCS. If your car can do plug-and-charge at a CCS charger, then three is no technical reason why it cannot plug-and-charge at Tesla. They just need to get some backend stuff sorted out.
I think it's actually very straightforward. Tesla already figured this out and published the spec. Products are already on the market that do this, nobody is re-inventing any wheels here. On the new car side it's simply a different on-board charging unit/socket. . . . Replace the box and wiring harness engineered for a CCS socket with a box and harness for a NACS socket. You can stick it in exactly the same place, it's just a control box and some wires to a socket. If they ever produce a retro-fit kit for my NiroEV or KonaEV, I will be the first in line to get one. The AC/DC on common pins is actually kind of trivial on the on-board side, basically you either have 100 to 200-odd volts AC, behind a relay, or you negotiate 400-1000vdc detect it, and activate a shunt to the DC-DC charging circuit. Again, this box already exists in Tesla vehicles. At it's simplest, the adapter for DCFC could simply shunt the tesla pins to the CCS DC pins, and refuse AC negotiation.
The backend is not much different. Those big giant DCFC charging pedestals are big electrical boxes, with a couple of modules. NOTE:
They do not put out AC, just DC, and there are already prototype Tesla -> CCS adapters. But in reality, we are talking some minor software adjustments and a different cord and plug. When you plug into a DCFC, it only uses the control pins on the J1772 side. The AC pins are not even connected to anything. So pretty much all they need at the pedestal is a software update and a different cord and plug. What this actually means in reality is, two cords, just like Diesel and gas handles at the pump, only you don't need a bunch of extra piping, just swap it, and do a firmware update. We already have combo CHADEMO/CCS stations, short-mid term reality for Non-Tesla stations is going to be a CCS plug on one side Tesla on the other, just like the CCS/CHADEMO we have now.
If you already own or purchase a J1772/CCS vehicle before the changeover (same idea with CHADEMO for that matter), short-term you will simply need the Tesla to CCS adapter, if you want to charge from a Tesla/NACS-only station. Throw it in the frunk or trunk. I would expect to possibly see OBC conversion kits at some point as well. I have an openevse EVSE unit. It works with either Tesla or J1772 for AC charging. The only difference is the pigtail plug. I repeat, the only difference is the pigtail plug. From a home charging standpoint, you are simply going to have whatever plug you need for the car you own. If you end up with cars using both, you will either get 2 pigtails, or use an adapter, or just have two units, they are not that expensive these days, and the adapter should be under $500, likely will drop even lower over time.
I have the NACS to J1772 adapter, I keep it in the car, with a 120/240v/20A EVSE and a bag of 6-20 gender bender AC plugs, for emergency charging. I will have the NACS to CCS whenever they release them. Short term, if a Tesla station is available and more convenient on my route, I may use it instead of EA. Long term I will keep an eye out for an OBC conversion kit.
