HankLloydRight
No Roads
Well, which is it? You first refuted my post by making this statement (bolding mine):
And now you're saying the complete opposite:
And now you're saying the complete opposite:
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HankLloydRight
No Roads
I'm also pretty sure that even at mileage below one mile starting out from 0, the wh/mi displayed isn't extrapolated or "instantaneous", but it is still the same average of energy used / miles driven.
I just did a short drive, starting from 0/0/0, and here are the results -- seems pretty linear to me (within a margin of error for rounding both miles and kWh used to one decimal place):
It's interesting that the most accurate number is the first one at 0.6 miles.
Images:
mknox
Well-Known Member
I was trying to say the same thing, which is that the car does not "count" energy drawn (or lost to standby losses) when the car is "Off" in the Wh/mi calculation, but it does when the car is "On". In the first quote, we were talking about energy used to run a bunch of servers, and my assumption was that the car would be "Off" as this happened, just as it is "Off" when you pre-heat via the mobile app.
Here is one final observation I've made:
If I start out in the winter with a cold-soaked car, my Wh/mi starts out incredibly high (on the Since Last Charge or Since hh:mm display) and gradually comes down as the miles rack up. A 30 mile trip may come in at, say, 450 Wh/mi in cold weather. (A short 1 or 2 mile trip may come in at 2,000 Wh/mi) This, as we know, is due to the cabin and battery heaters working like mad to warm things up at the outset.
But... often I will run the HVAC for 2 half hour sessions before setting out from work (not plugged in... just using the battery). When I do this and set out, the initial Wh/mi numbers are substantially lower than when I don't pre-heat, and the 30 mile trip may come in at 350 Wh/mi. Clearly I've used kWhrs to pre-heat the car (while it's off) but that energy is not reflected in my car's trip meters. In fact my car looks more efficient. It is the same thing that happens if I pre-heat on shore power, but then it makes sense because the pre-heating energy is made up for from the wall.
As I mentioned earlier, I see the same thing when parked for extended periods. It draws power from the wall every day to top up the battery, but the Wh/mi number doesn't change over the whole period of time even though I've been adding energy to the battery and it's been draining down the whole time.
Look, I'm not trying to be argumentative, but I'm very confident in what I'm seeing. I may not be explaining myself clearly is all. We may just have to agree to disagree.
HankLloydRight
No Roads
But if you think about it, when the car is "off" the contactors are closed.
At that point the only energy you have to power four bitcoin mining servers is the 12v battery. Which really won't last very long running that kind of heat-generating equipment. When the 12v battery is depleted, the contactors will close and recharge it.
Running that kind of equipment, that recharge cycle is going to happen every few minutes and put extreme stresses on the 12v battery which itself probably won't last very long with that kind of deep discharge and frequent recharging.
That said, I assumed that any bitcoin mining operation in a Tesla could ONLY happen using the main battery and when the car is "on".. and it follows that any and all of that energy use is fully trackable by Tesla and the API. Which was my original point.
HankLloydRight
No Roads
From the Electrek article: Tesla owner builds a bitcoin mining rig in a Model S to use free Supercharger power
He's drawing 2.8 kW of energy to power four mining rigs. No way he's using just the 12v battery for that.
He's drawing 2.8 kW of energy to power four mining rigs. No way he's using just the 12v battery for that.
mknox
Well-Known Member
The car doesn't have to be "On" for the HV contactors to be closed and supplying power. You can run HVAC (high voltage) via the mobile app with the car "Off" and when the DC-DC converter fires up to top up the 12v, that also is done with the car "Off".
In my previously mentioned experience with the car sitting for an extended period of time, it used power every day to, among other things, keep the 12v topped up, and this is done by closing the HV contactors to supply the DC-DC converter. It is not reflected in my Wh/mi values. And in my other example of running HVAC (a high voltage load) from the pack while the car sits unplugged also does not "show up" in my Wh/mi numbers.
I think it comes down to where Tesla is measuring the power flow and what they do with that data depending on the state (on/off) of the car. For instance, if I use a DCFC like a ChargePoint station that can report kWhs, I have found that if I charge with everything off in the car, the number of kWhs reported by the station very closely matches what Tesla says on the 17" screen. BUT, if I charge with my HVAC on in the winter, the car is a few kWh LESS than what the station reports. The amount it is less by is roughly what I would calculate the HVAC uses over that period of time. This suggests to me that Tesla is metering energy going into the battery pack and ignoring other HV loads, like the HVAC, in the process. For those with newer cars being billed by the kWh at Superchargers, it makes me wonder if they're only billing for power that goes into the pack and, if you sit in the car with the heat on, you get that for free. If the mining rigs are wired into the HV HVAC circuit, maybe they would get that power for free too.
deonb
Active Member
Got to love how you earn a Disagree from "Jaff" based on just your "Interesting story" comment.
Presumably he thinks it's a boring story...
mknox
Well-Known Member
More than likely he's disagreeing with the concept of "stealing" power for this purpose... which I also disagree with even though it does make for an interesting technical discussion on how it may happen
deonb
Active Member
More than likely he's disagreeing with the concept of "stealing" power for this purpose... which I also disagree with even though it does make for an interesting technical discussion on how it may happen
That's like disagreeing with CNN for reporting that Bitcoin lost 18% of its value in 24 hours.
We should maybe have a "That sucks" button. But "Disagree" means something else.
HankLloydRight
No Roads
Sorry, but that still doesn't make sense. Why would Tesla count HVAC usage when the car is "on" but not when the car is "off". It seems to me that they would measure energy usage from one single upstream point and not have it conditional based on car status. I think the differences you are seeing are because sometimes you're plugged in, and that energy isn't counted, but the car is "off".. but when you are unplugged the car is "on" and that is being counted. It's not a matter of on/off status, but rather plugged in/not plugged in that's causing the differences you're seeing.
I'm going back to your original statement:
I did charge up my car and ran the HVAC and the Wh/mi numbers changed significantly.
When I proved your assertion wrong, everything you've posted since then is trying to backpedal from that clear statement, including accusing me of not understanding the difference between "instantaneous" and "average" energy metering, and the car extrapolating 1 mile energy usage from 0.1 miles, both of which I also proved to be wrong.
So I'll be clear once again -- for bitcoin mining that requires the contactors to be closed (under any on/off scenario), Tesla can monitor that energy usage, unless the car is currently plugged in, then it's using shore power and has no need to monitor that energy usage out of the battery.
mknox
Well-Known Member
This is my guess... and it is just a guess: I think they are trying to tell the driver what the efficiency of the car is while you're under way so that it is useful for figuring out how far you can get, and how efficiently you're driving during that trip cycle. If they muddied that figure with energy that was used before you departed (i.e. when the car was off), it would skew the efficiency number making it look like you are using more Wh/mi than you actually are on that trip. In actual fact, that's useful to me. What was going on with power coming out of the pack before I hit the road is not really a piece of information that would be very helpful after I departed. I might get concerned that my energy use is really high and I might not make it to my destination at that burn rate if pre-departure energy use was mixed into the blend.
And that might be the issue. My car absolutely does NOT do this. I have verified this time and time again (like every day in the winter when I pre-heat on battery power alone). In fact, if I pre-heat on battery power alone, my Wh/mi for my trip home is lower than if I don't. Maybe a difference in firmware? Maybe a difference in Canadian vs. US firmware? I dunno.[/QUOTE]
I don't dispute that at all. As I've said, I'm sure Tesla has sensors and meters all throughout the electrical system and they know EVERYTHING that is going on. What I AM saying is that I'm convinced the car's energy displays that the user can see does not reflect it when the car is off (My example of HVAC on vs. off while L3 charging in my last post).
HankLloydRight
No Roads
It took a while, but here's the original image... it was a 2.4kW drain at 235 kWh/mi
Even though the odometer says 0.0 miles, I had driven a few hundred feet down the road (obviously the denominator wasn't zero).
post: Software block for dumb mistake?
Even though the odometer says 0.0 miles, I had driven a few hundred feet down the road (obviously the denominator wasn't zero).
post: Software block for dumb mistake?
mknox
Well-Known Member
Curious: Does your car still do this? Mine used to as well, and I'd see crazy high numbers after driving a short distance too. Now, all of the numbers stay at zero until I hit 0.1 miles no matter what. Still unrealistically high numbers until I get a few miles down the road. This morning, it was relatively mild (i.e. not much HVAC needed) and I was at something like 2,000 Wh/mi at 0.1 miles. By the time I got to work the trip came in just under 300.
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