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Vehicle 2 Grid

Discussion in 'Roadster 2008-2012' started by GSP, Sep 23, 2020.

  1. GSP

    GSP Member

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    Tesla’s battery day was awesome.

    Elon’s comments were skeptical of V2G, but Drew did say they plan to support V2G for selling energy and demand response for grid support.

    Elon mentioned that the Roadster had V2G support, but no one was interested. However, I don’t recall V2G ever being offered to Roadster owners. Does anyone know if the PEM hardware could support V2G if the software was available?

    GSP
     
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  2. ViperDoc

    ViperDoc Roadster 1305

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    I didn't watch the presentation, but was he referring to our Roadster or the upcoming one?
     
  3. marco2228

    marco2228 Roadster Signature #34

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    @ViperDoc
    He meant the classic Roadster. I also never heard about it.
    Comment was like:
    V2G was possible at the classic Roadster, but nobody used it..
     
  4. buckets0fun

    buckets0fun Member

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    VP10 had V2G
     
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  5. ViperDoc

    ViperDoc Roadster 1305

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    Interesting. I never heard of it either! I wouldn't have used it, but it isn't clear, even now, how I would have since it is apparently an undocumented feature!
     
  6. AEdennis

    AEdennis Active Member

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    I believe the original motors under consideration for the Roadster used AC Motors motor.. (like the T-Zero) and it was built to go bi-directionally... So, I took his statement as that
     
  7. gregd

    gregd Active Member

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    If it was in VP10, it might be buried somewhere in the 1.5's too. Same PEM, though there would need to be active firmware support, and some sort of external hardware, too.

    Highly unlikely that it made the transition to the 2.x, however. Bummer. I could use V2O (just give me one Outlet; I don't need to power the entire house) for when PG&E pulls another of their PSPS events.
     
  8. hcsharp

    hcsharp Active Member

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    My recollection of the comments were more like "We considered offering V2G on the original Roadster but nobody wanted it." It wasn't a case of "nobody used it" as much as "nobody wanted it." I'm curious what was actually in VP10 because the regular 1.5 firmware (which is what's in VP10) didn't have any remnants or hints of this anywhere.
     
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  9. gregd

    gregd Active Member

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    I guess the bigger question is how did they (plan to) do the plumbing? Where would the power come out of, and how would it be controlled? At a high level, the ESS is just a big 375v battery, which could easily power an external inverter. The one in... Ah... Wait.

    Was the idea to take the AC power that would go to the motor windings, and instead route it external? Frequency and current control is presumably already part of the normal motor control loop. Clever.

    Just be sure to disconnect the motor windings, or you'll watch your house do 0-60 in under 4 seconds.
     
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  10. slcasner

    slcasner Active Member

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    I was able to attend the Battery Day event, so I scoffed at Elon alone in my car when he made the statement that the Roadster could do V2G but nobody wanted it. As @AEdennis mentioned a few posts earlier, this capability derived from the AC Propulsion drivetrain upon which the Roadster drivetrain was based. Tom Gage, then President of AC Propulsion, told me that their AC 150 controller (PEM) could do V2G. See here also. The initial design for the Roadster was to use the AC Propulsion controller, but it was an analog device that was hard to build and maintain. JB Straubel and his team at Tesla created a digital design with the same functionality to replace the AC Propulsion unit. I never heard a direct statement from Tesla that the V2G capability was retained, but I assumed so. That's because Alan Cocconi's Reductive Charger design in the AC 150 was inherently bidirectional. Tesla licensed that design for Roadster 1.5 (see the license label on the left end of the PEM) but made a new design with a separate charging circuit for the 2.x cars to avoid the license.

    My home solar PV inverter with battery backup is similarly bidirectional. It can pull power from the DC bus where the batteries and solar panels are connected, lowering the DC voltage, and push it to the grid by raising the AC voltage above what the grid is trying to provide. That makes the meter run backwards. Or it can pull power from the grid to recharge the batteries, lowering the AC voltage (because of the load) and raising the DC voltage.

    The car could do the same. No additional plumbing is needed, but different firmware definitely would be. However, as Elon correctly said as part of his answer to the V2G question, this is not sufficient for actual use. You can't legally deliver power from the car to the grid in this manner. If the grid goes down, you'd be trying to power your whole neighborhood. If the problem was local at the transformer that feeds your house, the car might be able to handle the load. But that would energize the home side of the transformer that the utility repair person would expect not to be energized, which could cause a fatal accident.

    To avoid this, the home solar inverter has "anti-islanding" protection to detect when the grid power has gone down and stop pushing power to the grid. This happens in a fraction of a second. In order for the battery backup in the solar system to keep power going to the home loads when the grid goes down, the inverter has two AC connections, one to the grid and a second to a subpanel containing breakers for the "critical circuits" in the home, e.g. the refrigerator, lights, etc. When the grid is up and the sun is down, the inverter feeds power from the grid AC connection to the critical circuits AC connection.

    So, you might say that to allow the same functionality using V2G would require a second AC connection from the car to the critical circuits subpanel. But you don't want power to have to flow through the car to the critical circuits when the grid is up or the refrigerator would stop when you go to work. So instead that intelligence needs to be in a switching box mounted in the home and a more sophisticated control connection would be required between the car and the EVSE (wall charger).
     
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  11. Tiger

    Tiger Active Member

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    Thanks for the explanation! To put it simply: if Tesla provided an app (think "power wall app" which talked with "car charge scheduling target app"), necessary hardware, installation, and maintenance, with leasing and purhcase/SaaS options, many people would use it and it could act both as backup source for scheduled/unscheduled grid outages, and also as an autobidder node.
     
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  12. wycolo

    wycolo Active Member

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    Simple, but heavy duty, Y switch ('either/or') as devised for genset use during blackout is all that is needed to safely isolate grid from house & emergency sources.
    --
     
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  13. slcasner

    slcasner Active Member

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    Only legal (at least where I live) if there is some automatic mechanism to prevent the car from sending power toward the grid unless the switch is thrown.
     
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  14. Timothy

    Timothy Driving on Sunshine

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    No problem. Just pay Tesla $12 grand and they will put in a couple of PowerWalls that do the exact same thing!:)
     
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  15. gregd

    gregd Active Member

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    So, back to topic, but outside the box a bit... I've been wondering what sorts of ways there might be to safely - both in terms of harm to body and to the car - access that 53kwh of juice stored on board. One possibility might be to grab it, slowly, from the 12v battery on the 2.x cars. On my car, at least, it's kept at a constant 13.77v, regardless of whether the car is awake or asleep, so that means it's constantly being fed. Would the car mind if I siphoned off a bit?

    How much can be safely be pulled from that circuit? The fuse is, I think, 30 amps... 15 amps is enough to run my kitchen fridge (with a BIG battery in parallel to pick up the starting spikes).

    I'm aware of the warnings to never run an inverter, even a small one, from the car's accessory outlet, as it can damage the APS. But from the 12v battery, with it in the circuit to buffer the load at the car, and another larger battery close to the inverter, would that be safe? I already have a PowerPole connector wired in parallel to the battery (intended as a way to "jump" the 12v system if it goes flat), but APS replacements are hard to get...
     
  16. X.l.r.8

    X.l.r.8 Supporting Member

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    The APS fuse under the dash is like 120 A bit again, you want to risk the APS ?
     
  17. gregd

    gregd Active Member

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    Yeah, that's the point. How to pull energy out, but do it without risking the APS. The thought was the 12v battery might be well enough protected with the battery in the circuit, and robust enough to provide some meaningful juice.
     
  18. S-2000 Roadster

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    YouTube Closed Captioning plus filling in a few words that they missed, Musk said,
    "and we actually had - with the original roadster - we had, uh, [vehicle to grid] capabilities; nobody used it."



    I think it's possible that Musk got confused by the "dual charging" system that the Roadster has, which very few people took advantage of. The Model S was originally offered with a single charging system and an option to pay extra for a dual charging system. Lots of people complained about this because the Roadster didn't charge extra for full AC charging. I remember at the time that the amperage ratings that matched the dual charging system were rarely used by most Roadster owners. Apparently, Tesla Motors had data showing that most Roadsters were exclusively charged on no more than 30A or 40A systems. So, it's fair to say that not everybody used the full charging capabilities. Of course, more than "nobody" had the 70A/90A HPC and used it.

    I realize that there's no way of knowing what Musk was thinking, but there's only one charging feature that was underutilized in the Roadster, and it wasn't any sort of vehicle-to-grid technology.
     
  19. S-2000 Roadster

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    Um, all of the Roadster motors are AC, and are built to go bi-directionally. That's how regenerative braking works - the motor generates electricity that charges the battery, and magnetically brakes the drive train.

    The other response explain how it was the electronics outside the motor that would enable power to leave the car (as opposed to power leaving the motor while rolling outside the home).
     
  20. slcasner

    slcasner Active Member

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    I don't know if you literally meant "dual", but the Roadster has only one charger. It's just that the current limit of that charger is 70A. The Model S charger could have been designed for 70A, too.
    I'm guessing that what @AEdennis was referring to here is not that the motor could rotate in both directions, but that the PEM in the Roadster 1.5 followed the design of the AC Propulsion (not AC Motors) AC 150 controller that operated both as the inverter for driving the motor and the "reductive charger" that used the coils of the motor as the inductors in the charging circuit thereby saving weight rather than adding more heavy inductors. As I said, Tesla changed to a separate charger for Roadster 2.x to avoid the license fee to AC Propulsion.
     

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