> I'd love to know what information is "missing" from the J1772 communication protocol, the trade offs on a digital vs analogue "protocol"
I think the author is confusing the DC and AC aspects of NACS. AFAIK, NACS uses the same J1772 analog protocol for AC charging. I don't think it really matters that much, but if you were designing things from scratch today, it might be nice to have things like:
* Plug-and-charge at commercial AC chargers. Nobody has this today.
* Tell the car whether off/mid/peak energy rates apply (at home AC chargers). You could program your car to charge only at off&mid rates, unless the battery is empty, then let the EVSE figure out what rates apply.
* Send state-of-charge from car to charger, to enable smarter load balancing: Several companies make EVSEs that can supply full current when one car is present, but command the first to throttle back to half current when a second car is plugged in. You might want to adjust that split to, say, 75/25 if the new car is near empty.
> J1772 has since 2012 allows digital information to be passed using a AC power-line communication standard.
Ehh... not really. The J1772 analog protocol can tell the car "hey, I'm actually a CCS station, so let's talk CSS digital protocol". But J1772 itself doesn't define any kind of digital protocol.
> the "advantage" of 277v compared to 208v?
The advantage is that if you happen to have "480V 3-phase" service available (which is common in commercial and industrial settings), you can directly attach NACS between one phase and ground (which gives you 277V). With J1772 you need a transformer to step down to "120V 3-phase" (which gives you 208V between two phases). You also get about 30% more power for the same conductor weight, which makes the copper wiring cheaper.
The two common distribution voltages in North America are 277/480 (phase-ground and phase-phase) and 120/208 (phase-ground and phase-phase). We also have 240, which is "split phase" (two conductors 180 degrees apart).
> And why aren't the comparing agains the CCS2 standard? Surely that's the most obvious competitor?
Well, CCS2 is the DC charging "add-on" to J1772. So IMHO it doesn't really make sense to talk about it in the context of AC charging, unless you're trying to "well akshually... gotcha" someone with an obscure technical point.
If you do want compare NACS and CCS2, the biggest one is simply ergonomics: CCS2 is like mini-USB (not even micro), while NACS is lightning/USB-C. CCS2 is heavy, bulky, and sometimes fails to make a good connection. You need to get the alignment just right to insert and apply a lot of force to get the thing locked in. To remove, you again need to throw your back into it. NACS, by contrast, just pops in and out with your finger tips. NACS ports are curved to guide in a slightly misaligned plug. If you haven't tried it yet, you really owe it to yourself to rent a Model 3 for the weekend and supercharge a couple times. The ergonomics are just vastly superior.
I think the author is confusing the DC and AC aspects of NACS. AFAIK, NACS uses the same J1772 analog protocol for AC charging. I don't think it really matters that much, but if you were designing things from scratch today, it might be nice to have things like:
* Plug-and-charge at commercial AC chargers. Nobody has this today.
* Tell the car whether off/mid/peak energy rates apply (at home AC chargers). You could program your car to charge only at off&mid rates, unless the battery is empty, then let the EVSE figure out what rates apply.
* Send state-of-charge from car to charger, to enable smarter load balancing: Several companies make EVSEs that can supply full current when one car is present, but command the first to throttle back to half current when a second car is plugged in. You might want to adjust that split to, say, 75/25 if the new car is near empty.
> J1772 has since 2012 allows digital information to be passed using a AC power-line communication standard.
Ehh... not really. The J1772 analog protocol can tell the car "hey, I'm actually a CCS station, so let's talk CSS digital protocol". But J1772 itself doesn't define any kind of digital protocol.
> the "advantage" of 277v compared to 208v?
The advantage is that if you happen to have "480V 3-phase" service available (which is common in commercial and industrial settings), you can directly attach NACS between one phase and ground (which gives you 277V). With J1772 you need a transformer to step down to "120V 3-phase" (which gives you 208V between two phases). You also get about 30% more power for the same conductor weight, which makes the copper wiring cheaper.
The two common distribution voltages in North America are 277/480 (phase-ground and phase-phase) and 120/208 (phase-ground and phase-phase). We also have 240, which is "split phase" (two conductors 180 degrees apart).
> And why aren't the comparing agains the CCS2 standard? Surely that's the most obvious competitor?
Well, CCS2 is the DC charging "add-on" to J1772. So IMHO it doesn't really make sense to talk about it in the context of AC charging, unless you're trying to "well akshually... gotcha" someone with an obscure technical point.
If you do want compare NACS and CCS2, the biggest one is simply ergonomics: CCS2 is like mini-USB (not even micro), while NACS is lightning/USB-C. CCS2 is heavy, bulky, and sometimes fails to make a good connection. You need to get the alignment just right to insert and apply a lot of force to get the thing locked in. To remove, you again need to throw your back into it. NACS, by contrast, just pops in and out with your finger tips. NACS ports are curved to guide in a slightly misaligned plug. If you haven't tried it yet, you really owe it to yourself to rent a Model 3 for the weekend and supercharge a couple times. The ergonomics are just vastly superior.