Kona as a backup battery for home power outage?

Discussion in 'Hyundai Kona Electric' started by Jgood, Nov 5, 2019.

  1. Jgood

    Jgood Member

    Has anyone done any research on this topic? I was thinking today that a 65Kwh battery is quite hefty and would be able to provide minimal power backup for house lighting, etc during a power failure. Plus it's kind of nice to know that even without any car-to-house connection we can always sit in the car to read a book, charge a phone or even heat up the seats to stay warm!
  2. FlbrkMike

    FlbrkMike Member

    It's a nice thought and, living in Southern California, it has definitely occurred to me. But configuring something like this would probably void the battery warranty. I have 7.5 kW (just yesterday installed the last 2.5 kW) of PV, an 8 kWh storage battery (currently set up only for load shifting) and a Kona EV. I'm getting ready to replace my propane furnace with an air-to-air heat pump, and my propane water with a hybrid electric unit, so the the house will be all electric. It would be wonderful to someday create a self-sustainable micro-grid using all of these components with some kind of intelligent control.
    Pobre and ehatch like this.
  3. Robbert

    Robbert Active Member

    I believe some folks on the Prius forums have a solution with an inverter that directly connects to the traction battery. The Prius would sense the battery voltage and start/stop the engine to re-charge if needed. Here's a link: http://priusgen.sandbox.org/
    I'm sure in theory you could do the same with the Kona, but to be safe, you'd have to be sitting "behind" any battery management system, so you can avoid damage to the battery pack by inadvertently discharging it to 0%.
  4. There are folks that have attached 12 volt inverters to the starter battery and have been able to pull ~1300 watts on relatively sustained basis, where the traction battery tops up the small battery when it gets low. I can see this being hard on the expensive DC to DC converter. You would likely void your warranty if Hyundai could figure it out. To tap into the traction battery directly would require some cable/connector surgery and at the very minimum a 400v to 120/240 volt transformer. This would definitely void your warranty and you should really should think twice before messing with this significant amount of potential energy. Could it be done, sure, is it a good idea on a new in warranty expensive car, probably not.
  5. More on that here:
    and here:
  6. FlbrkMike

    FlbrkMike Member

    For $500 or $600 you can purchase a 4 kW backup generator for emergency purposes.
    I'm not sure why anybody would consider doing something like this just to get 1300 W out of their car battery. Except maybe because "they can."
  7. Jgood

    Jgood Member

    For me it's all about the scale of the events that seem to be happening more frequently, whether climate change or not. I live in western MA. Five years ago there was an ice storm that left people in the eastern part of the state without power for more than two weeks. A couple of years before that a hurricane nearly wiped the south-central part of Vermont off the map. The flooding was monumental and people were stranded because roads were washed out. They couldn't get to gas stations for fuel for generators and the gas stations didn't have power to pump anyway. The rainfalls are clearly becoming more severe and the impacts have surpassed predictions...even by the 100 and 500 year levels. Put this all together and it seems foolish to not notice that there's a 65 kwh battery sitting in my garage. I have no intention of using it when we lose power due to a transformer fire down the road, but when hurricane beelzubub swings through it could be that risking my car battery warranty is the least of my problems. More than anything I'd just like to know what options may exist.
    eastpole likes this.
  8. I actually have a generator and am still considering using the Kona as a backup power supply . There are number reasons that I want a battery back up.
    First with the utilities have been shutting off for multiple days in California during times of high wind and fire danger. I would be running the generator 24/7 for five days. First i don't want to listen to a generator running all night I would prefer to have it quiet and run off the battery's during the night. I have a 5.5 kw generator which is capable of producing 100 kw hr in a day. I us about 10 kw hrs per day, and in the evening I am only using about 0.3 watts per hour hour. So my preference would be to use the generator for heavy loads like the well pump, the heat pump (if its cold) water heating, and charging the car during the day for maybe 3 or 4 hours, and then switch over to battery power. Than the generator would be running at peak efficiency for a short period rather than continuously at light load and low efficiency.
    Last edited: Nov 5, 2019
  9. FlbrkMike

    FlbrkMike Member

    I think that being able to use the 64 kWh battery for backup home power would be a great thing. In fact, it would also be great to use it to take advantage of TOU rates during non-emergency use. I just don't think that the EV manufacturers will soon be willing to warranty their equipment for this kind of use. I live in Southern California and, believe me, I've thought about this. I have about 7.6 kW of PV (just completed installation of the last 2.6 kWh yesterday and not yet energized). I also have an 8 kWh storage battery that's, for now, only configured for load shifting which does save me a lot of $$. Eventually I want to get it reconfigured for dual purpose, including backup. That 64 kWh battery in the Kona EV dwarfs the one in my garage, which was not cheap. I could probably live off the grid completely if I was able to use both batteries, unless of course we have two consecutive weeks of really cloudy weather.
    electriceddy likes this.
  10. I have been seriously looking in to using the Kona as a back up power supply. I currently have an older grid-tied solar system which means that when the grids down so are my solar panels. To change to a battery back up would require a number of changes and would easily cost a minimum of $4,000 us dollars. I also have a back up generator with an interlock system so that I can plug it in to my electrical panel and power my house, garage and guest house plus my well pump.

    As I said in my previous post I don't want a generator running continuously for minimum power times. So I have been looking at using the Kona and an inverter. (Side note: Nissan has been actually working on a unit which would allow a Leaf to plug in to a house ( don't know if it would work for other EVs https://electrek.co/2017/10/04/nissan-ev-ecosystem-free-power-leaf-vehicle-to-grid/ )).

    So I have been researching inverters that would work with my generator interlock plug. What I have found so far is that there are many types of inverters. There are the basic hook to your car battery inverter which allows you to plug items in to the inverter. These work fine for powering small items like lights phone chargers even a refrigerator ( my refrigerator uses 800 watts to start and 150 watts while running. I have my utility panel wired to monitor my loads so I know what circuit uses how much power for how long)

    Then moving up to higher powered inverters (things that will run washing machines and well pumps ) there are three types. Square wave , modified sine wave and Pure Sine wave. Of these I am only interested in the Pure Sine Wave as it has the capability to emulate the power from the grid. Since I want to tie into my house I want 120/240 volt. The inverter will need to be split phase (120 volt/ 240 volt with a zero potential between neutral and ground. Some cheaper inverters have 60volts between neutral and ground. These are a couple of the inverters I am considering

    I am considering two operating scenarios. One I would be turn off all of the higher powered loads in the evening and just run the low loads directly form the Kona in the utility mode. The second is to use the Kona in the utility mode to charge one of two battery banks and alternate battery banks as needed ( I have battery's from multiply vehicles most of which aren't being used most of the time any way(truck, tractor, motor home...).

    My next step is to finalize the inverter purchase and then run a number of test. I will post more after I start testing.
  11. Look forward to your results, just be careful, according to this thread 1000W is the limit:
  12. That's one of the reasons I was thinking of using the Kona as a charging source rather than direct connection. Just a nice even low charge current to the battery bank not being used, while the other bank takes all the fluctuations of daily use.v and then swap banks
  13. Those are pretty massive 12 volt inverters that are designed for large 12v batteries wired in parellel. At best the Kona 12 volt battery is 80 ah(i.e. its very small), it might run a few minutes assuming the battery would even power up the inverter with a large enough surge request. There is no way the Kona's DC to DC unit could even try to keep up with a 3-4 kwh load. I personally would not waist my money beyond a 1500 watt inverter.
    ehatch likes this.
  14. ehatch

    ehatch Active Member

    Nice setup.Why didn't you install a tankless water tank?Attaching it,and your [surge protected] breaker to a solar powered battery wall?

    V2H is doable,and shouldn't mess the warranty since the kWh "load"is stationary, less stressful than driving.
    System components: main charger / inverter unit, control switchboard, transformer unit, Wifi control pad.
    Utility mode on the Kona EV is great,I know I can rely on it.Charge on solar to recharge if/when necessary.
  15. I agree with you 100% but I am not sizing the inverters based on what the Kona can supply. I have two criteria one that it be split phase and two that it be able to power the well, heat, and water heat (not simultaneous). It is my plan to eventually add it on to the solar system with a separate battery system from the Kona. I am actually leaning to a 48 volt inverter. I have a 48 volt battery charger that runs on 120v ac. Its about 300 watts.

    I have not found a split phase below 3000w. I would not run the Kona with that kind of load. I am actually looking at a smaller inverter as well for the Kona. which I may use to run the battery charger for a larger battery bank when the days are cloudy and not getting full wattage from solar and the power is down. I could use the Kona to add 6 kwhr's to a battery pack during the day and then run the battery pack at an average .5 kw during the night through the 48 volt battery pack.
    Last edited: Nov 5, 2019
  16. Grego

    Grego Member

    ehatch likes this.
  17. Grego

    Grego Member

    Then again some houses are super old and less demanding than ours here in North America. My In laws house power panel is 40amps....yup a total of 40amps.
  18. I’ve been wondering why nobody has mentioned the Tesla Powerwall as a backup, but then I looked at the cost. Hmmm...
    eastpole likes this.
  19. Yep! got that one right!
  20. eastpole

    eastpole Member

    Although I understand why Tesla has a battery backup operation, ranging from household to utility-scale battery arrays, I don't understand why it's viewed as a good thing overall. The whole point of a lithium-ion battery is to be light weight (per Joule and per Watt.) The weight of a battery does not matter that much if it is stationary, bolted to a brick wall in my house.

    There are a bunch of "But actually" bullet points that come after this, like a) am I aware that overcharged lead acid batteries produce hydrogen gas or b) what about used automotive traction batteries ... and so on. All of these are secondary concerns because we are currently very short of new lithium batteries for EVs. In a future world where mining and battery manufacturing have caught up and we can make more lithium ion batteries than are needed in the complete replacement of the auto fleet worldwide, that would be an excellent time to switch stationary storage away from lead.

    Meanwhile I just bought a nice 1000 W pure sine wave inverter, anticipating that sometime during the many-year lifetime of my Kona EV, it will serve nicely to power my furnace and DC blower fans through a mid-winter power outage. I agree, it seems like flood/windstorm/ice storm/forest fire events are becoming more frequent, and I don't think most people will be prepared.

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