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The car as a home battery

Discussion in 'Charging and Infrastructure' started by Slartibartfast, Oct 9, 2016.

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  1. Slartibartfast

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    I'd like to start a thread about using your vehicle as a battery for the house. With a 60kwH+ battery this could power most homes for a few days. When are we going to see the necessary electronic controls to match this with your static storage (Powerwall or similar)? Hopefully with the Model 3?
     
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  2. Jamaicaman

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    Using your car's battery to power your home during a power outage is a great idea. The question then becomes... If I do use my car's battery to power my home... How will it affect my car's battery warranty? The decision then becomes a bit more complicated.
     
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  3. MelindaV

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    Elon Musk has said in the past they will not be doing this. Too much liability when hooking up with any number of different types of home wiring systems and the vehicle batteries are not designed to be used with the type of cycling that powering a home may involve.
    Not to mention, the possibility of someone constantly driving to their local Supercharger then back home to 'download' the power to their house. Why should Tesla pay to power people's homes?
     
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  4. Slartibartfast

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    ok thanks for the feedback - that seems a shame (and a waste of a huge battery resource). I use about 6kwh per day at home and so (in my case) the battery providing a backup to the grid, or overnight power would be a minimal impact on the car battery. I guess it will have to be a power wall as well!

    Currently the cells in the power wall are the same as the Tesla cars? I indeed ex traction batteries are finding their way into static storage solutions so I'd question the assertion that they are not designed for this type of duty. It really depends on the charging/discharging algorithm.
     
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  5. Badback

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    Do you have a source for Elon's statement?
     
  6. Badback

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    In what way is powering your house different than powering the car?
     
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  7. Jamaicaman

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    #7 Jamaicaman, Oct 10, 2016
    Last edited: Oct 10, 2016
    After doing some research a few years ago... I decided the risk verses reward was way to high for my comfort. Yours may differ "Badback". Check out this site and then decide for yourself...if it may just be a better and more cost effective to buy a teslawall or a generator.
    http://www.evextend.com/Emergency-Power-Kit.php

    The d.c. to a.c. inverter can vary in cost... (Read performance) and a poor inverter and easily damage an expensive refrigerator.
     
  8. Badback

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    I am talking about a Tesla installed connector wired to the main battery and a Tesla provided inverter mounted outside of the vehicle and wired to the house's main panel via a transfer switch and connected to the car with a Tesla supplied cable. In other words, a properly engineered system designed for the intended purpose.

    While my engineering skills are more than sufficient to do these modifications myself, I do not recommend them to you or anyone else without specific knowledge of the issues involved.

    Selecting a proper inverter is a matter of proper engineering for the intended application.

    A Power Wall, which costs several thousands of dollars cannot be more "cost effective" that the battery that is already in the car that you own.
     
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  9. Jamaicaman

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    Gosh it sounds as if you are way ahead of me on the electrical portion... my concern comes with trying to save a few dollars at the expense of damaging the tesla battery and voiding the warranty... if you are confident with your awesome skills... go for it!
     
  10. Rick59

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    Interesting discussion. I'm sure that, in 10 years, people will laugh at our innonence and backwardness. We are just starting down on a very fast road into renewable energy use.
     
  11. Badback

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    I wasn't trying to sound smug, just reacting to the statements about the battery. The batteries in the car are the same as in the Power Wall, just more of them. Since Tesla already has the inverter (the one that works with the Power Wall), using it for emergency power in your house is an easy thing to do. I'm sure that they do not want to dilute sales of the Power Wall, but they might change their mind someday.
     
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  12. MelindaV

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    Couldn't readily find a EM quote, but have seen it mentioned by him a couple times.
    here's a video of JB saying essentially the same

    “If we want to actually send energy back from the car to the electricity grid, this gets much more complex, and, you know, that’s something that I don’t see being a very economic or viable solution — perhaps ever, but certainly not in the near term. You know, the additional wear and tear and degradation on your vehicle battery has a fairly high cost, and many of the people and small businesses looking at this today, you know, don’t take into account fully that degradation cost, and also the additional interconnection cost, because if you interconnect your vehicle, you do have regulations that play a part — it has to interconnect in the same way that a solar system would on someone’s home or on a business, which have different standards so that they can protect line operators and people on the grid.” (as transcribed by cleantechnica)
     
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  13. Slartibartfast

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    Well thanks again for the background. At the same time, the connection of such a large stored energy device (car!) will be essential to the grid stability...... so back to my 1st question I think it is really a question of when and how rather that will it happen. I hope Telsa realise this issue of grid/car and related stability and act to guide the market forward by leading (as it is doing so well with autopilot and superchargers).

    Watch this video - great channel btw



    thoughts/ideas?
     
  14. Badback

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    WOW! Were not talking about sending power back to the utility grid. We are talking about an alternative to a standby generator for infrequent power outages. Big difference. The transfer switch isolates the power from the battery (through the inverter) to the customers internal (household) circuits. No danger to utility workers. It's the 'infrequent' part that makes it viable. Running your household loads is no different than driving the car. Probably less power required for most people. For instance, my highest utility usage last year was 1250kW-Hr for a 30 day period. That is an average of 41.7kW-Hr per day. My utility bill does not tell me my peak usage, lets say for the sake of discussion that it is 100kW-Hrs. As is typical for standby generator systems, not all loads are served by the generator. So, during a power outage, if we keep the AC, the frig, the well pump and minimal light running, I think that we are within the capacity of the car's battery as a 2 hour outage would be about 3.5kW-Hrs. This would leave plenty of range in the car. Doing this occasionally, for us it's once or twice a year for 1-2 hours, should not be a problem. This would sure beat the price of a standby generator and it's attendant maintenance.
     
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  15. Slartibartfast

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    Well using the car battery as a backup (rather than a genset) is a 'no brainer' but I was including the car 2 grid in my thoughts also. If we project forward a few years we need to incorporate the reality that after driving home from work we can't all plug our cars in at 6pm and expect the current grid to charge all our cars at the same time..... something has to give! So, I see the alternatives as:

    1) We pay much more for our electricity because the supply companies and network companies invest sqillions making a system that can cope with the 5-8pm mega peak that happens mon-fri
    2) The car chargers are controlled by the grid and can be "load shed" as required to keep the peak demand under control
    3) The car (via a grid tie inverter) feeds back to further reduce load at peak. I really see this as a few kWh per day (way less than 10). This is not going to over-stress the battery at all and would be just the difference between driving say another 50km a day

    I guess I was making a potential poor assumption :confused: that most electric car owners are also probably solar installation owners. As such all the heavy lifting equipment is already in the garage (grid tie inverter, smart meter). All that is needed is a bit of switching gear and some software and algorithms. The economics are all there too as the cost of peak electricity here in Sydney is 6x the cost of off peak (54c vs 9c roughly). I understand that most areas around the world do not have such expensive electricity and many people still have the whirly disc meters and so are not charged peak rates but that this status quo can not be maintained if millions of cars are connected to the grid.
     
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  16. Safe Daddy Driver

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    We should at least have the option to leverage the car's battery in case of emergency as a backup power source just like today's generators. If Tesla doesn't provide this solution, a third party will.
     
  17. garsh

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    The study was an interesting read. The comments were- well, WOW. Accusations of anti-battery trolls preparing the non-peer reviewed study. Given the splatter of comments, I'm not trusting anything from the paper. But.
    BUT - I did glean a nugget - They say, charging your car twice per day is better than charging once per day. I have been using my batteries like a tank of gas. Fill up, burn it off on various daily runs until it gets down to 40%, then recharge - about twice per week.
    Should I modify my battery behavior based on this report?
     
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  19. timk225

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    Powerwall and Tesla car batteries are not the same. The chemistry is different between the two, because of their charge / discharge cycles and intended use.
     
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