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MASTER THREAD: Powering house or other things with Model 3 12V battery

Discussion in 'Model 3: Battery & Charging' started by Vines, Jan 17, 2019.

  1. ajdelange

    ajdelange Banned

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    You might be surprised. I was quite surprised to find that the same TMS320 DSP chip that we used years ago to... well I can't say what we used it for, is used in the Model 3 inverter (the more current improved version of course) and, actually, I wouldn't be too surprised to find it in the power wall inverter though, of course, I have no idea as to whether it is actually there.
     
  2. diamond.g

    diamond.g Active Member

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    As far as we all currently know the cars use NCA in the states while PowerWall uses NMC (and not NMC 811, again as far as we know).
     
  3. user212_nr

    user212_nr Active Member

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    #63 user212_nr, Nov 12, 2019
    Last edited: Nov 12, 2019
    Can you provide some photos or sources? I don't disbelieve it as I think I have read the same somewhere, but cannot find it.

    This topic and argument comes up a lot.

    Not requesting any confidential info as some have suggested you might have.
     
  4. user212_nr

    user212_nr Active Member

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    #64 user212_nr, Nov 12, 2019
    Last edited: Nov 12, 2019
  5. user212_nr

    user212_nr Active Member

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    From what I can find, the Powerwalls use NMC chemistry while the Tesla Model 3 batteries use NCA chemistry.

    Tesla Model 3 & Chevy Bolt Battery Packs Examined | CleanTechnica

    Tesla releases rare details about Model 3's battery cells, claims highest energy density and less cobalt - Electrek

    From the fool article above, "Ironically, you would be hard-pressed to find a worse chemistry for daily home energy use than NCA. Whereas high energy density means saving precious space and weight for on-the-move applications, it's less important for stationary applications. That's especially true when it comes with significant trade offs, such as one of the lowest thermal runaway temperatures for lithium-ion chemistries and a performance that deteriorates very quickly after only 500 deep cycles."
     
  6. sroh

    sroh Member

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    Agreed that solar panels and a couple of PWs are the optimal solution. We already have solar panels, but the ROI on PWs is absolutely horrible for our use case.

    So I'm looking at this as a possible solution during power outages. And to run just a refrigerator/freezer and maybe charge up laptops and phones. Rather than the 300w inverter through the cig lighter, a 1,000w or 1,500w inverter hooked up directly to the 12v battery should work.
     
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  7. focher

    focher Member

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    Note that Tesla does not recommend to connect anything directly to the 12V battery, including for jump starting a car. So an inverter directly connected might be a bad idea. An inverter in the 12V "cigarette" socket is probably nowhere near capable of powering very much beyond maybe some LED lights. I definitely wouldn't hang an appliance off of it.

    During Sandy, I had a Volt and I did put a 2500W inverter on the 12V and let the car cycle the engine to maintain a charge on the battery / provide current to the inverter. I doubt I'd do it on either of our Teslas (3P and X).
     
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  8. sroh

    sroh Member

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    Ya, this makes sense to me. It would be nice to be able to use the battery in the Model 3 in case of emergency like you did with the Volt. But you're probably right; not worth risking harming the battery for this use case. But still maybe a good idea to get a small cig lighter inverter to be able to power phones and laptops in case of power outage.
     
  9. Rocky_H

    Rocky_H Active Member

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    This has been covered a lot in some other threads. None of this would risk the main battery. But depending on how you do it, it might cause problems for the 12V battery.

    Basically, the considerations are this: through the cigarette lighter socket, that is fused at I think 15A at 12V, so that's only 180 Watts of power. If you go directly to the 12V battery, bypasses that fuse limit, but the car is still monitoring and will turn on the DC to DC converter to try to refill it. The analogy is like a small pool of water that has an input pipe and an output pipe. As long as your draw rate out of the battery is not more than the DC to DC converter can supply into it, then the car keeps up with it just fine and is just running the DC to DC converter a lot, which should generally be OK. I can't remember the threads where people have tested how much that can supply, but on the Model X and S, I think it was about 400 Watts. I don't know how much power the Model 3 version of can do.
     
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  10. GigaGrunt

    GigaGrunt Member

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    No.
     
  11. hmmwv

    hmmwv Member

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    I've done this a few times with my LEAF, hook up a 1000W pure sine wave inverter to the 12V battery, leave the car in "go" but park. It's enough power to keep a couple of lights on, charge my phone and laptop, run the fridge every few hours, and occasionally boil some hot water using a small electric water kettle.
     
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  12. Rothgarr

    Rothgarr Member

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    #72 Rothgarr, Jan 3, 2020
    Last edited by a moderator: Jan 3, 2020
    Moderator note: this post was a separate thread and was merged into this existing thread.
    ——————————————————————————————————————————-


    (I tried posting this in "Off topic" before Christmas but didn't get any replies so I hope it's OK to try reporting here...)

    Was thinking of getting something like this:
    https://www.amazon.com/BESTEK-300W-Power-Inverter-Adapter/dp/B004MDXS0U

    I have a Tesla Model 3 Dual Motor Long Range AWD. Could I use something like that to power some lights in the house, or maybe even a single refrigerator? I don't understand the technical aspects, what would be the limit of what I could plug in to something like that? Is it not even recommended to use something like this?

    It's not often that we lose power, but I thought it would be good to have something like this just in case.

    Thanks!
     
  13. ecarfan

    ecarfan Well-Known Member

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    @Rothgarr this has been discussed before but it is difficult to find those thread by searching TMC because of the variety of terminology used. I found this thread and merged your post into it.

    The short answer to your question is, you can’t directly access the Tesla battery pack to draw power from it to power something outside the car. As the discussion in this thread shows, you can access the car’s 12V battery to draw relatively small amounts of power but you have to be careful how you do it.
     
  14. Rothgarr

    Rothgarr Member

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    Thank you!

    (you are correct, I did try search, but I wasn't too successful, thank again for pointing me in the right direction!)
     
  15. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    How many amps can you get from the 12V system for emergency situations?

    Another thread here. As far as I can tell accessing the DC-DC output under the rear seat directly is the start of solving this problem. But there are some caveats to prevent inrush current from causing DC-DC shutdown, so some relays and a resistor to allow slow charging of any load capacitors and such may be needed, depending on what you are trying to power.

    And then there is the whole question of keeping it on, making sure you don’t trigger other fault detection, and not destroying your car in some other way.

    Hopefully a comprehensive solution with details can be published at some point, though it might already exist somewhere else on the internet...
     
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  16. AlanSubie4Life

    AlanSubie4Life Efficiency Obsessed Member

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    FYI:

    Pictures of a system that looks like it will work

    Thanks to @marcmerlin

    Note that the Owner's Manual says:
    "Do not use the Battery as a stationary power source. Doing so voids the warranty."

    It's unclear whether this qualifies or is enforceable, really, as it's a bit hard to make the argument that this is a lot different than Camp Mode, but have to decide that yourself.
     
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  17. sroh

    sroh Member

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    Posted this in the Tesla Energy forum, but thought I would post here also. THIS is what we need. It's still a bit expensive, but it's a lot less than the $20K that two PWs cost. For our use case of just wanting emergency power backup, I would buy this in a heartbeat.

    The founder is an ex-Tesla employee. I hope he is able to get Elon to make Teslas compatible. Problem is I don't see Elon agreeing as it will compete with the PW for some use cases. Heck, no reason why Tesla couldn't offer something similar if they wanted to.

    https://electrek.co/2020/01/06/wallbox-quasar-tesla-nissan/
     
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  18. marcmerlin

    marcmerlin Member

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    Thanks for posting me on yet another thread on the same topic.
    What I learned while doing my project is that the DC-DC system is a bit finicky in that it doesn't handle spikes like a battery would, and that may be a reason why Tesla doesn't want you to mess with it (although it was pretty well self protected, outside of the part where it shuts down and doesn't reset on its own if it senses that you shorted it, which a connection energy surge from a big inverter, will actually cause).

    For the rest, I think they were worried about the car being used to charge at superchargers back in the days that they were free, and discharged at home, or people mis-using the car (unintentionally) in ways that it would damage things, like if you connect to the small 12V battery, you will discharge it quicker that it can charge, and you will damage it by emptying it. They don't want to pay for that (understandably).

    If you wanted to do this "more safely", you could connect an external battery to the 12V cigarette lighter adapter, and limit current to 12A. This was not enough for my use, but would go through all the car's systems the way they were meant to be used. This would however still violate the broad "can't use car as power source".
     
  19. marcmerlin

    marcmerlin Member

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    I started this route for my project and I can confirm that on model3, the car only the charges the battery at a low rate. If you are using more than a few amps, the battery will actually discharge more quickly than the car can recharge it.

    This doesn't work in either direction:
    1) the CLA as you said doesn't give more than 12A, so it won't work for anything other than a very small inverter, unless you use it to recharge an external bigger buffer battery
    2) the internal car battery can provide near infinite amps to a big inverter, but will recharge so slowly, even with the car in camper mode, that you will empty it quickly.
    This is what I had to tap in to the car's DC-DC system.

    Thanks for connecting my thread here. Yes, the resistor and relay are needed to solve the inrush current problem, but once the inverter is powered up, it works fine.
    I think the only issue is if my inverter tries to use more than 200A, it will cause the DC-DC system to shut down and it may not reset on its own. Then again, the wires going to it will probably also limit the current to about that anyway, so I shouldn't have to worry about it.
    At the end of the day, I'm really only looking at powering a fridge or two. I tried a microwave just to test the system load, but I'd never use a microwave in a shutdown situation, I have gas cooking in my house and that'd be enough.

    Please note that my solution is not a whole house system, I didn't plug it back into a circuit breaker (which would only power half the house and would be quite unsafe if you forget to unplug the utility side). That's afterall what powerwall is for. It's just a shame that powerwall will not allow you to plug your car into it to extend runtime in case of a multi day outage (with the understanding that the car batteries are not meant for daily cycling like a powerwall is).
     
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  20. BrandX

    BrandX Member

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