Installed .179 this morning and after the install finished it was back at 79A. Think I just had a couple lucky connections.
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Andyw2100
Well-Known Member
But just to be clear, you know that's not what we're talking about happening here, right? We're charging at 79/79. (Check the video to see what I mean if you like.)
I saw mention of 79/80 versus 80/80 and figured it wouldn't hurt to add a data point.
Andyw2100
Well-Known Member
Sure, no problem. I just didn't want you to think the thread was started with that as the issue. (There has apparently been much confusion over this in the past.)
The current is actually encoded as the duty cycle of the pulses. So, it's a matter of measuring the pulse width and the pulse period and doing a division to determine the duty cycle. So, the absolute accuracy of the oscillator used to perform the measurements isn't really a factor.
The EVSE will be designed to ensure that all cars measure a valid duty cycle, meaning that some allowance for vehicle error has to be made. According to J1172, a measured duty cycle in excess of 97% prevents charging, and the vehicle is allowed to have up to 2% measurement error.
So, to avoid no-charge issues and such, an EVSE designer could aim for 95% so that there is no argument about the pilot being valid, even with the worst case allowable vehicle measurement error. A 1% reduction in charge rate is a small price to pay, more so since it also reduces resistive heating in the EVSE wiring and contactor by ~2%.
I think you might have hit on the answer. When S detects voltage drop to something below 240 it dials back current draw assuming something is starting to stress (heat).
Anybody report this phenomenon when voltage is constantly at or above 240?
No it doesn't. I start at 248-249V and drop to 242V. That's perfectly normal, and is not the reason for 79/80.
billarnett
Member
Actually, the HPC was installed with #2 wire. When I removed it and installed the HPWC I couldn't get the #2 wire to fit into the HPWC's terminals. So I replaced it with something smaller. But I was wrong when I said above that I used #6. I just checked and while I can't read the markings on the wire it is clearly much larger than #6. So it's most likely #3 as specified in the HPWC installation instructions. That means all I need to be totally up to code is to replace the breaker with a 100A one. But that seems like a lot of bother for a circuit that can never go over 80A. Isn't a smaller breaker actually slightly safer; won't it trip sooner if there's a problem? I suppose it's more likely to fail and trip too soon but that seems unlikely and wouldn't do much harm anyway.
Got my car back from being in service. They tested it on their equipment and saw the same behavior as I have been seeing. They could not find any "service bulletins or Toolbox articles" and have opened a "toolbox case to service engineering." They don't believe that there are any problems with the cars hardware. They suspect it is a firmware issue and hope that a software update in the future will resolve it. So for now we're waiting on engineering to look into the problem.
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I installed my HPWC with #2 wire. It does fit in the lugs but it is a complete pain to make it fit. This is compounded by the limited space there is to work inside the enclosure. So I can totally understand why you'd not use #2 wire for this.
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I installed my HPWC with #2 wire. It does fit in the lugs but it is a complete pain to make it fit. This is compounded by the limited space there is to work inside the enclosure. So I can totally understand why you'd not use #2 wire for this.
davewill
Active Member
My understanding is that you could end up with a nuisance trip, and might end up with stressing the breaker by running it that close to it's trip point for extended periods. Best to just follow code instead of improvising.
Danal
electricmotorglider.com
NEC states that the "protection device" (breaker) must be sized at 125% of continuous loads. Another part of the code defines "continuous" as "over 3 hours". 80*1.25=100. Therefore, you must have a 100A breaker on an 80A HPWC to be code compliant.
Same thing applies to the wires, if only because they must match the breaker.
That's why all the charts in the US version of the HPWC install guide show 100 amp breaker for 80A DIP switch setting, and so on and so forth.
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Cottonwood
Roadster#433, Model S#S37
Correct, except that the 125% rule for continuous loads applies to conventional breakers, but not to the wires. The breaker rating must be matched to the wire rating. There is an exception for breakers that are specifically built for 100% continuous load, like the fancy electronic sensing ones used in the Supercharger Distribution Center.
I have attempted running conventional breakers continuously at 112% margin, and they tripped after an hour or so. Follow the code...
Can we try to guide this thread back to the 79A issue. I've engaged in the side discussion about bilarnett's install and code violations myself. But there is probably better threads for that discussion. The thread is getting more and more cluttered with this side discussion.
Danal
electricmotorglider.com
There seems to be some speculation the 79A issue affects all D.
Just to add a single data point:
I picked up a P85D yesterday. This car reaches 80A correctly after ramp up, and stays there. V6.1 (2.2.179), car had been outside for hours on 40F ambient, spent the prior 3 days in colder temps. Then driven 70 to 80 for 45 minutes, then sat for an hour, then charged. Beginning SOC somewhere around 1/2 to 2/3rds, charged to 90%, I did not watch every minute of the charge... as mentioned, after ramp, consistent 80A.
Just to add a single data point:
I picked up a P85D yesterday. This car reaches 80A correctly after ramp up, and stays there. V6.1 (2.2.179), car had been outside for hours on 40F ambient, spent the prior 3 days in colder temps. Then driven 70 to 80 for 45 minutes, then sat for an hour, then charged. Beginning SOC somewhere around 1/2 to 2/3rds, charged to 90%, I did not watch every minute of the charge... as mentioned, after ramp, consistent 80A.
Andyw2100
Well-Known Member
Good to have the data point. It does make me wonder more about my car, and the others that aren't working as yours does.
Congrats on the new car!
You may want to take another look at a couple of the dates in your sig! You were probably just so excited to have the car your fingers were flying!
ra-san
Member
My P85D was one of the December delivery, started first week of production cars. When charging it shows 80 amps available and typically flutters between 79 and 80 amps current. The voltage is pulled down to 220 +/- a volt, typically. I've seen it settle for a few seconds at both 79 and 80. Definitely doesn't cap at 79 nor sit cemented at 80. This may well be charger specific for me. Haven't tried another charger at 80 amps.
ra-san
Member
Yup, is what I thought too. Providing as a data point of another P85D that isn't showing a 79/79 issue as was described earlier in the thread, since there were comments that all D's were affected.
Andyw2100
Well-Known Member
I don't think anyone ever said anything about all the Ds being affected. I think I probably came closest to that. This is what I said:
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