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beeeerock
Active Member
No worries, I think I'm tying to work out whether the on-board charger will do what it can to get the combination of volts and amps to reach the 10 kW limit, assuming the supply is large enough.
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It's the 'whichever comes first' that interests me. If the HPWC was connected to 208 volts with - say - 80 amps available, and a single charger car plugged in, would it pull more than 40 amps to maximize the 10 kW charging rate? I'm wondering if the installation I visited had been set for 40 amps, because the owner had a single charger (or the wiring wasn't quite large enough to go to 80) and the lower voltage wasn't considered.
But if the 'whichever comes first' is an issue, the 40 amps would be the limiting factor.
mknox
Well-Known Member
By way of explanation, typical household services are supplied by a split phase 120/240 volt system. There are two live conductors and a neutral. The live conductors are 180 degrees out of phase, so when you connect them together, you get 240 volts but when you connect either one to the neutral, you get 120 volts. Small commercial businesses are often serviced at 120/208 volts 3-phase, 4 wire. There are 3 live conductors each 120 degrees out of phase and a neutral. Each phase to neutral will yield 120 volts, but taking two phases will yield only 208 volts and not 240 volts because of the different phase relationship.
In either case, the EVSE is supplied by two live conductors, so on a 120/240 volt system the equipment will see 240 volts and on a 120/208 volt system, the equipment will see 208 volts. These are "nominal" voltages and will often be lower due to voltage drops caused by resistance in the system.
SteveS0353
Member
"...when you connect them together..." I think you meant when you connect between them...
mknox
Well-Known Member
Right! Something completely different happens when you connect them together :scared:
beeeerock
Active Member
Yes, I've had to learn the basics of this on projects where Hydro supplies three phase and the electrical consultant designs 120 v street lights - LOL
What I'm trying to work out is whether the on-board charger can draw more current to get to the 10 kW maximum, if the voltage is at 208 instead of 240. I'm wondering if the person setting DIP switches in the HPWC might think "the car can only accept 40 amps, so I'll set the switches accordingly, even though I've got circuit capacity for more", when in fact, the 208 source might mean the car could utilize more to maximize charge speed.
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But not for very long...
The DIP switches should be set solely based on circuit size. The car decides what amperage it can take from the HPWC (not to exceed 80% of the DIP switch settings).
If the HPWC is on a 40A breaker/circuit then the DIP switches should by set to 40A regardless of the voltage.
Mike
The charger in the car will max out at 40A or 10kW, whichever comes first. 40A at 240V = 9.6kW. If you feed >250V, the current draw would decrease to limit total power to 10kW (indications are that the chargers are rated to 277V, but who knows about the rest of the system).
The car will not (and cannot, without violating the J1772 standard) increase current draw beyond what is advertised by the EVSE to compensate for low voltage (or any other reason), without overloading the EVSE and/or its supply circuit.
The installer cannot (without violating NEC) increase the jumper settings to compensate for low voltage, without overloading the circuit.
Conductors are sized based on current flow, not power. Voltage is irrelevant (assuming you don't reach dielectric breakdown of insulation). 10ga=30A intermittent, 24A continuous at 100V, 120V, 240V, 277V, 480V, or 4800V.
Brass Guy
Active Member
I don't remember where I read it, but the Model S chargers are rated 250V 40A max. I don't know what would happen if you connect 277V. My first guess is the car would not allow charging with the voltage out of spec. If it charges at 277 though, it will probably still draw 40A and charge at about 11kW.
I'm doing this from memory, but somewhere I remember seeing a photo of a Model S charger that had a sticker on it that said "100VAC - 277VAC". But I wouldn't try to connect a car to 277 (bad things might happen).
As I recall, there was a discussion here that the original 120kW superchargers used 12 10kW Model S chargers. Even though they were fed 277V (L-N of 480 3ph), they limited the current draw to 36A for ~10kW. 36A*277V*12 chargers = 120kW stack.
The thread went on to state that the 135kW upgrade was to upgrade the chargers to pull the full 40A. 40A*277V*12 chargers = 133kW stack.
But like I said, I'm doing this all from memory, so take that for what it's worth. :smile:
Brass Guy
Active Member
From Model S Specifications | Tesla Motors
I am certain that at one time I read 250V, but nonetheless it is still shy of 277. If you could find 265 volts, you could charge at 10.6kW.
I am certain that at one time I read 250V, but nonetheless it is still shy of 277. If you could find 265 volts, you could charge at 10.6kW.
Cottonwood
Roadster#433, Model S#S37
TonyWilliams gave it a try. The car limits the max power per module to 10 kW. See My Own Supercharger?? - Page 7
He also states that the charger is placarded to 277 Volts. See My Own Supercharger?? - Page 8
Brass Guy
Active Member
I stand corrected, thanks Cottonwood. I never read that thread, maybe I'll read through it if I get enough time...
beeeerock
Active Member
I don't think I'm making my question clear. Let's say the wiring to the HPWC is capable of 80 amps continuous. Or 5,000 amps. Lots more than we can use.
Now let's assume the guy who has the Tesla and is having the HPWC installed, has a single charger. He sees comments on this forum that lead him to believe that a single charger car can only utilize 40 amps.
He doesn't know that P=ExI and doesn't make the connection that he's on a 208 circuit, not a 240 circuit. So he tells the installer to set the DIP switches for 40 amps and as a result, doesn't max out the 10 kW capability of his single charger.
So the question is, since the car decides how much power it can use to a maximum, would setting the HPWC switches to something higher (say 80 amps in case a dual charger car plugged in), allow the car to max to 10 kW, or would it stay at 208 volts times 40 amps? Or stated another way, if a single charger car plugged into a 208 volt HPWC on an 80 amp circuit, would it pull a maximum of 40 amps at 208 volts, or would it ramp up to closer to 45 amps to reach 10 kW?
GlmnAlyAirCar
Active Member
Except if you live in PA, where you take delivery, then have to go to an auto tag service, pay taxes and registration fees, then finally make an appointment with a private mechanic to inspect your brand new vehicle (Tesla isn't licensed to do it).
It's similar in Texas. I consider it a very minor inconvenience which is well worth it to avoid having to purchase a car through a dealer with all the time and sleaze that involves, and costs are lower this way regardless of what kind of "deal" someone thinks they got from a dealer (8% higher prices estimated in Dept. of Justice study by requiring dealers rather than direct sales).
Also you're paying for those steps of tags and registration at a dealer, typically $75-200.
Cottonwood
Roadster#433, Model S#S37
Each charging module will take at most 10 kW; in addition, the maximum current is the lower of 40 Amps or the current offered by the EVSE. Also, the taper will limit power draw near 100% SoC.
That means that a single charger Model S will take the following max powers if offered these currents and Voltages.
- 30A/208V J1772 — 30A x 208V = 6.24 kW
- 48A/208V J1772 — 40A x 208V = 8.32 kW
- 64A/240V J1772 — 40A x 240V = 9.60 kW
- 80A/265V HPWC — 37.7A x 265V = 10 kW
A dual charger car will accept up to 80 Amps and 20 kW, whichever comes first.
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