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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. Vines

    Vines Active Member

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    So I came home to a power outage last night, ah mountain living.

    As I am burning the lamp oil for light, and hating the fumes I start to wonder why I'm sitting in the dark with 40 kWh in the battery sitting in my driveway. I decided to plug a small inverter into my cigarette lighter in my Model 3 and power some lights in the house with it. Since its just a 200W inverter I wasn't too worried about draw, but I was aware that it would drain my 12v battery.

    Anyone know how often the main HV battery charges the 12v battery? Also, how many amps is the dc-dc converter able to provide safely to the 12V battery?

    If this power outage lasts longer I might get crazy and pick up a 1000w inverter and seeing if it will power my refrigerator. I just want to make sure I wont be running down my 12v battery too badly.

    If I do run down my 12v battery, what would be the effect? Would the car still be drive able? I guess the 12v systems like lights, windows ect wouldn't function, but I am not sure. Anyone with experience?
     
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  2. jsmay311

    jsmay311 Active Member

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    Someone else will have to weight in regarding the rated power of the 12V DC converter and whether or not the car needs to be on for it to run, but if you're plugging into one of the aux / cigarette lighter outlets with a higher powered inverter, you'll have to worry about tripping a fuse first.
     
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  3. Enginerd

    Enginerd Member

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    You are probably aware that this is frowned upon by Tesla. From the manual: "Caution: Do not use the Battery as a stationary power source. Doing so voids the warranty."

    I have a tiny emergency backup system that's not attached to the car. It's a 100W solar panel, charging a 100 A-hr battery, with a 1500W inverter. Cost me about $500 to set up, but it makes me very happy. I use it for all my work in the shed, including lights, drill press, miter saw, and charging my mower and trimmer batteries. Plus in a pinch I can run some circuits in the house (fridge, induction cooktop).
     
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  4. Vines

    Vines Active Member

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    Hmm, voiding the warranty wouldn't be good, I'll just stick with the cigarette lighter and small 200W inverter in that case, the draw is super low with just a few LED lights on anyway.

    Maybe I'll just setup another deep cycle battery, probably much better idea than messing with my new car. I do have a 175W panel sitting around here, just need to source a charge controller and decide on inverter.
     
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  5. Magnets!

    Magnets! Member

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    Wouldn't it be great if the wall connector could be run in reverse to power your house? Charge during offpeak and use the Tesla for house power during on-peak!
     
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  6. Vines

    Vines Active Member

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    I have always thought this should have been built in with our cars. Why buy a powerwall when you can drive your battery around?

    Bi directional power flow through electric cars would add a whole new dimension to grid stability.
     
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  7. Rocky_H

    Rocky_H Well-Known Member

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    You can run stuff through the cigarette lighter, but it's definitely going to be limited by the fuse it goes through. That is on a 15A fuse, I think, (maybe 10A?) so here's your power limit:
    12V X 15A = 180W
    If you convert that to 120V, it's only 1.5A. So you can run some small things that pull very little current, but not much--probably not a refrigerator.

    As far as running down and/or refilling the 12V battery, the car does its own monitoring and refilling of the battery automatically as needed, so you aren't really going to hurt anything from that kind of low level draw through the 12V socket. Tesla's prohibitions against using the main battery as a stationary power source are more about telling people not to try to get to the internals of the battery to tap into the main energy directly. That would be very dangerous and could damage things, but accessing low power things through this little fused socket shouldn't be any issue.
     
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  8. granto-san

    granto-san New Member

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    It’s pretty appalling that the cars are not designed to externally power anything of substance eg your house or sound system or caravan. I thought the fundamental ideology for EVs was to have the power going both ways when required.
    I’m sure I’ve seen other EVs being demo’d to do this eg The Leaf in Japan a few years ago. Charge it up when grid rates are low then plug it in as a power source during peak times....
     
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  9. electracity

    electracity Active Member

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    Tesla pickup will need to offer significant mains power out to be competitive with Rivian. Musk seems to think a lot about investor attention Rivian has recieved.

    The Nissan Leaf power out capability will also drive Tesla to do better in this area. I am sure Musk is hearing a lot about power out considering the PG&E electricity cutoffs in California.
     
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  10. Phlier

    Phlier Bluebird

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    Hopefully it'll be enough to push him over the edge and get it done.

    I think it'd be a huge selling point for a very large customer base.
     
  11. ajdelange

    ajdelange Active Member

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    Your 12 V battery is tiny as such batteries go at only 30 AH.

    A 1000 W will blow the fuse in your "cigarette lighter" socket's circuit.

    There is a lot of talk about having BEV's as standby power sources during grid outages. This is feasible but there are lots of issues to be resolved regarding things like islanding and the utilities are about as enthusiastic about it as they are about home solar installations. At this point the NEC requires that EVSE have means to prevent backflow of energy to the grid.

    The Rivian will have a couple of 120 V outlets but I don't have any idea how many amps will be behind them. Keep in mind that a 15 A circuit would deliver 1.8 kW, pull about 2 kW from the battery and discharge a 180 kWh power pack in about 85 hrs.

    Elon promises that the Tesla truck will be a real truck and include enough AC to run construction tools. I believe he has indicated that it will supply 240 VAC (and obviously 120 as well). Two kW drawn from a 100 kWh battery would discharge it in about 48 hrs.
     
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  12. electracity

    electracity Active Member

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    The minimum Rivian would have is probably 20A at 120V. That could run a refrigerator and some lights and fans for many days.

    The backfeed issue is the same for a car as it is for a genset or home backup battery. The expense issue is obviously a big inverter. The initial car to house connection may use existing powerwalls. The utility issue is already solved in a house with powerwalls.

    Tesla has shown some extremely sophisticated electrical engineering in their products. I'm sure they have beed designing for car to house.

    Tesla has to be extremely careful with battery warranty issues. They need to avoid any design that would significantly reduce the lifespan of car batteries.
     
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  13. Darmie

    Darmie Supporting Member

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    Always found it odd to consider using energy from your transportation when you are in a cautionary state just for convenience at home.
     
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  14. jsight

    jsight Member

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    There are a lot of other potential uses for bidirectional power, though. A lot of utilities offer time of use rates. These cars have a large enough power reserve that they could practically eliminate home energy usage during the peak billing periods.

    With my utility that could save somewhere between 25-30% yearly. Of course, the extra load on the battery would likely kill the savings...
     
  15. user212_nr

    user212_nr Active Member

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    #15 user212_nr, Oct 22, 2019
    Last edited: Oct 22, 2019
    The Tesla battery is expensive and not designed for such usages. Neither is the included 12v battery. You are not only ruining your battery but you will be stealing from Tesla if you later submit a warranty claim for battery degradation. They offer a long 8 year warranty.

    "Vehicle to grid" is not economical right now because they are not designed for such heavy cycles (maybe because of being packed so tightly) and are not cheap enough to ruin.
     
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  16. user212_nr

    user212_nr Active Member

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    Also, blackouts are going to be the new norm in California - better stock up on Solar and whatever kind of batteries (people use USED Tesla batteries, probably from salvage cars, to power their homes sometimes).

    PG&E didn't cause the wildfires, but they got sued and bankrupt anyways. Now they need to either put all their lines near trees underground or turn off the power.

    Maybe this will be California's big push towards Solar + Batteries.
     
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  17. Rocky_H

    Rocky_H Well-Known Member

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    o_O Wow. The way you state something false so authoritatively is just breathtaking!

    California investigators confirmed that it was PG&E equipment failures that caused the huge "Camp" fire, and PG&E themselves also confirmed it. (See links below) Let's stick to what is true, OK? However, it's a separate issue that I don't necessarily think that I agree that they should have been held liable for that accident. The lawsuit conclusion was that it was negligence which led to the accident, and I just don't know if there was enough basis for that.

    California Says PG&E Power Lines Caused Camp Fire That Killed 85

    Investigators confirm that PG&E power lines started the deadly Camp Fire

    PG&E details power line damage near ignition of Camp Fire
     
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  18. Vines

    Vines Active Member

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    From living in this area I can say that PGE negligence did in my observation allow the trees over the power lines to become a big problem.

    While taking millions in bonuses as recently as 2017, the board of directors also did not allocate enough resources over the years to trimming.

    Every few years they would get called out on it, pretend like it is some insurmountable issue, and spend a bunch of resources when storms come. Then power is out and they all are scrambling.

    However when the weather is good and there is much opportunity to trim trees proactively thyeyspend very little energy doing so. This cycle has repeated over and over, and its not rocket science.

    Dollars spent in emergency trimming and power restoration are less than half as effective as those spent proactively on trimming during more mild months.
     
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  19. n2mb_racing

    n2mb_racing Active Member

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    You can connect a big inverter directly to the 12V battery terminals under the hood.

    The DC/DC converter in the car will provide up to 2500W and will keep the 12V battery charged with the car off. I don't recommend doing it all the time, since Tesla could see it and void your battery warranty, but in an emergency, I doubt there would be a problem.
     
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  20. Vines

    Vines Active Member

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    In looking at it more, a Powerwall would be a much better solution.

    Running a single lightbulb and maybe a laptop from the cigarette lighter in an emergency I am sure is not a problem, a 2500W inverter would be significantly more draw.
     
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