The resistive capacity of the various gauges and carrying-ampacity of systems would cause variations in the efficiency of the charger as a system, but in such a small amount it's hardly worth doing the math.
SO and SJ cable? For what?...and two runs of 6/3 vs one run of 4/3? What are you trying to do? You don't need a */3 cable, what you going to do with the neutral wire?
Generally you set the wall connector to 80% of the circuit capacity (max safe charing rate) and then choose your rate in the car. As for efficiency, since the car takes a fixed amount to drive the various systems while charging the rule of thumb is to use higher current (power), since this minimizes the effect of this fixed overhead (and is part of the reason 120V charging is so slow).
I hope that you are not doing your calculations based on the breaker size the breaker size has no effect on the amount of power used. If I have a 15 Amp 120 volt circuit and run a 50 watt light bulb or a 100 watt light bulb there is a great deal of difference in the power consumed. Remember that when using a Continuous Load (That is a device that is anticipated to pull a load 3 hours or longer) that a 120 volt 15 Amp Circuit can only draw 12 Amps or 1,440 watts, a 120 volt 20 Amp circuit can only draw 16 Amps or 1,920 watts, a 240 volt 30 Amp circuit can only draw 24 Amps or 5,760 watts, a 240 volt 40 Amp circuit can only draw 32 Amps or 7,680 watts, a 240 volt 50 Amp circuit can only draw 40 Amps or 9,600 watts and a 60 Amp circuit can only draw 48 Amps or 11,520 watts... You should do your calculations based on the actual load on the circuit and Watts/Mile of range calculations. When you calculate the kilowatts burned/Mile of Range the 60 Amp circuit is by far the most efficient charge rate which must be credited to the efficiency of the on-board charger.
Why? 4/3 NM-B is $12 a foot and it good for 70 amps. 6/3 MC is $5 a foot and good for 75 amps.
Pretty much every charger is able to be hardwired. Unless you need the outlet for another purpose such as RV or welding, hard wiring is the way to go. Wiring a outlet has more complications such as its required to be on a GFCI breaker (depending on your local code of course).
Correct. But current code IF wiring an OUTLET a GFCI breaker is required if you want to pass inspection. Just trying to say hardwiring is the way to go.
You can buy 4/3 MC Cable for about $6.25/ft. at Wire and Cable Your Way -- 4/3 MC Cable w/ Ground
That does not yield that conclusion. 240V outlets still don't need that third wire. That is what the 6-XX series of outlets are, like 6-20, 6-30, 6-50. (And you can easily find plenty of generic J1772 charging stations that could plug into a 6-50 outlet.) They are just Hot1, Hot2, and ground and are 240V only. You would only need the /3 with the neutral if you insist you need to have a dual voltage outlet that can support both 120V and 240V, like the 14-30 or 14-50. But I wouldn't go to that trouble just for someone else's future flexibility. Just consider it a car charging circuit, and it will just never have a reason to have the extra neutral wire.
The only reason that Ovens etc. have the Neutral is for the Clock, Timing Circuits, etc... that will use 1 leg of the 240 and the Neutral for 120 volts.
OK, maximum flexibility of use is a good reason. I just didn't want that sitting out there for someone to read later, and think having a 240V outlet means it needs to have a neutral wire.
