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Off-grid inverter to connect hybrid vehicle to home?

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  • Off-grid inverter to connect hybrid vehicle to home?

    Many hybrid owners utilize old server UPS units to serve as an inverter to connect the high voltage battery in their car to their electrical panel for use as an emergency generator, because the hybrid system makes for an incredibly efficient system since you're drawing power from the batteries, and the car's onboard systems constantly monitor voltage and discharge levels, starting and stopping the gas engine as needed. Old UPS units can be hard to find, and aren't ideal since they require AC power to start (some folks start it after the grid has gone down by connecting it to a regular gas generator, then switching to the car as the power source), and just aren't the most simple solution. That got me thinking about inverters for medium to large off grid systems. Hybrid batteries tend to range in voltage from about 200 up to 400VDC. Just searching around it seems that there are a lot of inverters out there that will handle this much DC voltage and be able to output 5000-6000W, which is what the car can safely produce. Has anyone ever used an off grid inverter for this or could it work? Basically what I'd be looking to do is this:'

    Install the inverter near my electrical panel, connected to it via an interlocking (with the main breaker) transfer switch
    Run an appropriately sized cable from the inverter to the garage with enough to extend out into the driveway

    If the power goes out, the procedure would be this:

    Throw transfer switch on panel, opening the main breaker and closing the inverter breaker
    Connect cable to high voltage side of car (there would be preinstalled safe connectors on the HV terminals)
    Start car and leave running in driveway
    Go inside and enjoy cold beer and TV for however long the outage lasts

    Does this sound doable or am I missing something here?

  • #2
    Originally posted by Badfish740 View Post
    Go inside and enjoy cold beer and TV for however long the outage lasts

    Does this sound doable or am I missing something here?
    It is doable and has been done before, but there are two issues.

    1. Void warranty on your hybrid vehicle.
    2. There is a much better reliable way. Install a whole house generator made to do exactly what you want.

    I know of DIY EV guy's who have done exactly what you propose, but they know what they are doing and do not have a Warranty to worry about.
    MSEE, PE

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    • #3
      I agree with Sunking. Besides voiding the warranty, I would figure running a gasoline hybrid car engine through a DC to AC inverter would be more expensive than running a propane gas generator as a backup power source for your house.

      Comment


      • #4
        Originally posted by Sunking View Post
        1. Void warranty on your hybrid vehicle.
        Fair point, but there's no warranty to worry about. I'm looking at buying either a used Ford Escape or Toyota Highlander.

        Originally posted by Sunking View Post
        2. There is a much better reliable way. Install a whole house generator made to do exactly what you want.
        I would argue that there is not a single whole house generator out there, except for some kind of exotic, custom built system that will do exactly what I want or be better or more reliable. "Genverter" systems are nothing new-for years folks with off-grid power needs have used a generator in conjunction with a battery bank and inverter to supply power more efficiently. However, this requires a dedicated generator, a bank of batteries to maintain, and an inverter. Furthermore, unless you really start spending some $$$, you are going to have to start and stop the generator manually while constantly monitoring the level of charge/voltage in the batteries. In the case of a hybrid, Toyota engineers have done all of this work already, and the onboard systems in the car maintain the charge in the batteries, starting and stopping the engine as needed with no operator input needed. All one needs is an inverter capable of handling the DC voltage output by the car and convert it to 240VAC.

        Originally posted by SunEagle View Post
        I agree with Sunking. Besides voiding the warranty, I would figure running a gasoline hybrid car engine through a DC to AC inverter would be more expensive than running a propane gas generator as a backup power source for your house.
        A Prius putting out 6kW consumes about .4 GPH of gasoline. The average 6kW gasoline generator will consume anywhere from 1-1.2 GPH and make a terrible racket doing it, plus at any given time, half of the electricity generated will be wasted. I'm not trying to be argumentative, just pointing out that the whole house generators that are out there (or any regular generator) are horribly inefficient, loud, and in many cases aren't easily portable. If I find the right inverter and it's small enough, what I'll eventually do is mount it in the car so that I can simply connect the car to the house (or anything else) with a NEMA twist lock plug. For example, one future use I'd see is powering a small off-grid cabin. We could drive there, unload, open up the cabin, and simply connect the car to the distribution panel.

        Originally posted by Sunking View Post
        I know of DIY EV guy's who have done exactly what you propose
        There are examples out there on the web, but most of them are older (before solar inverters became more ubiquitous and cheaper), so the inverter used was a large server UPS, as stated before. It's a solution, but not a terribly good one. Solar inverters seem better, again, unless I'm missing something.

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        • #5
          Originally posted by Badfish740 View Post
          Fair point, but there's no warranty to worry about. I'm looking at buying either a used Ford Escape or Toyota Highlander.

          ...

          A Prius putting out 6kW consumes about .4 GPH of gasoline. The average 6kW gasoline generator will consume anywhere from 1-1.2 GPH and make a terrible racket doing it, plus at any given time, half of the electricity generated will be wasted. I'm not trying to be argumentative, just pointing out that the whole house generators that are out there (or any regular generator) are horribly inefficient, loud, and in many cases aren't easily portable. If I find the right inverter and it's small enough, what I'll eventually do is mount it in the car so that I can simply connect the car to the house (or anything else) with a NEMA twist lock plug. For example, one future use I'd see is powering a small off-grid cabin. We could drive there, unload, open up the cabin, and simply connect the car to the distribution panel.

          ...
          I believe there are "portable 6kw generators" that run propane (instead of gasoline) that are very quite and more efficient then you Prius but again it is your money and decision to make. Hopefully you find the right inverter to create your system and do not devalue or reduce the life of your Prius in the process.

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          • #6
            Originally posted by SunEagle View Post
            I believe there are "portable 6kw generators" that run propane (instead of gasoline) that are very quite and more efficient then you Prius but again it is your money and decision to make. Hopefully you find the right inverter to create your system and do not devalue or reduce the life of your Prius in the process.
            It's impossible for a generator with no battery bank to run as efficiently as a hybrid's generator/battery bank. A 6kW portable generator is an all or nothing proposal-either you get 6kW (whether you use it or not) or you get 0kW. With a hybrid, you're only drawing as much power from the battery as you need, when you need it, and the generator runs only as needed to top up the batteries. To top it off, propane is a more expensive fuel than gasoline if you compare gallons to gallons. Finally, there is nothing about this that will devalue or reduce the life of the car. As far as the charging system is concerned, the batteries are just seeing normal use as they would be when driving. If anything there is less wear and tear on the car while operating as a generator because the tires are not rolling over pavement, the engine is running at a constant speed (if it's running at all) rather than accelerating/decelerating, and the suspension, steering, and countless other systems in the car are not doing anything.

            There is already an established company that has been doing this for years with the Prius called ConVerdant-from what I gather they source some sort of inverter meant for the solar market, tweak it a bit, and sell it for use in the Prius. The problem is that I don't want a Prius-I'm looking for a larger AWD vehicle such as a Ford Escape or Toyota Highlander. The reason this is a problem is that ConVerdant's inverters will not work with either of them because the Prius' battery voltage is lower and that's all those inverters are built to handle. The Ford Escape battery pack operates around 330VDC and the Highlander around 280VDC-the Prius is somewhere in the low 200s. I've reached out to the company but they don't seem interested in producing anything beyond the Prius market, so I'm left to figure something out on my own.

            But again, I don't know what I don't know, so I can't anticipate whether or not this would work. Besides, does it really matter anyway? All I need to know is if these types of inverters can simply be hooked up to a DC power source or if there is something else involved. Obviously a grid-tied inverter would also need some kind of AC power source to "fool" it into thinking that the grid was up so as not to kick in any anti-islanding feature, so that would not work.

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            • #7
              Originally posted by Badfish740 View Post
              I would argue that there is not a single whole house generator out there, except for some kind of exotic, custom built system that will do exactly what I want or be better or more reliable.
              You would loose that debate in a heartbeat. I can name 6 companies who make them and is no custom build, right from stick. For homeowners Kohler makes an excellent line from 5 to 50 Kw using either NG, LPG, or diesel fuel at much higher efficiency than your hybrid engine. Takes no work at all to get going. Power goes out, Gen starts, ATS transfers house to gen even in your sleep.
              MSEE, PE

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              • #8
                Originally posted by Badfish740 View Post
                A Prius putting out 6kW consumes about .4 GPH of gasoline.
                What idiot would use gasoline?
                MSEE, PE

                Comment


                • #9
                  Originally posted by Badfish740 View Post
                  It's impossible for a generator with no battery bank to run as efficiently as a hybrid's generator/battery bank. A 6kW portable generator is an all or nothing proposal-either you get 6kW (whether you use it or not) or you get 0kW. With a hybrid, you're only drawing as much power from the battery as you need, when you need it, and the generator runs only as needed to top up the batteries.
                  You do not know what you are talking about. You can buy a 6Kw inverter off the shelf with built in charger and generator input. Generator can be as larger or small as you want to match the size of the batteries. Inverters run on batteries until the voltage set point is reached, then generator turns on and recharges the batteries. Generator is sized to operate at near full load and would smoke your car efficiency. At 6 Kw generaotr os a 6 HP motor. Much smaller than you car. Make it a deisel generator and you car motor could not even come close.
                  MSEE, PE

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                  • #10
                    Originally posted by Sunking View Post
                    You do not know what you are talking about. You can buy a 6Kw inverter off the shelf with built in charger and generator input. Generator can be as larger or small as you want to match the size of the batteries. Inverters run on batteries until the voltage set point is reached, then generator turns on and recharges the batteries. Generator is sized to operate at near full load and would smoke your car efficiency. At 6 Kw generaotr os a 6 HP motor. Much smaller than you car. Make it a deisel generator and you car motor could not even come close.
                    OK great-can it seat seven and carry a load of cargo? Look, I don't know why you care about what I intend to do-there are plenty of folks out there doing this with their hybrids right now for a variety of reasons. I'm just trying to find a simpler way.

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                    • #11
                      Originally posted by Badfish740 View Post
                      OK great-can it seat seven and carry a load of cargo? Look, I don't know why you care about what I intend to do-there are plenty of folks out there doing this with their hybrids right now for a variety of reasons. I'm just trying to find a simpler way.
                      At least one major manufacturer (Chevy?) has offered an option for their hybrid pickup that does essentially the same thing.
                      It was aimed at construction jobs and camping where you would otherwise be hauling the generator along with you.

                      Although I am not arguing either way on which method is more fuel efficient, I will say that for a widely varying load mix the combination of an autostart whole house generator with a battery bank and an inverter can be more efficient and more attractive than just a whole house generator.
                      But the marginal cost of getting a generator plus charger plus battery bank plus inverter is a much larger number than the cost of adding a power tap and inverter to a hybrid that you already own.
                      This is especially true for the small number of people who have already added EV range extending batteries to their existing hybrids with small traction batteries. Those guys are already into the high voltage circuitry and could care less about warranty service.
                      SunnyBoy 3000 US, 18 BP Solar 175B panels.

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                      • #12
                        Originally posted by inetdog View Post
                        At least one major manufacturer (Chevy?) has offered an option for their hybrid pickup that does essentially the same thing.
                        It was aimed at construction jobs and camping where you would otherwise be hauling the generator along with you.
                        I remember seeing something similar but I had thought it was just a concept-could be an option if they offer a four door. I need room for two adults and three kids.

                        Originally posted by inetdog View Post
                        Although I am not arguing either way on which method is more fuel efficient, I will say that for a widely varying load mix the combination of an autostart whole house generator with a battery bank and an inverter can be more efficient and more attractive than just a whole house generator.But the marginal cost of getting a generator plus charger plus battery bank plus inverter is a much larger number than the cost of adding a power tap and inverter to a hybrid that you already own.
                        Thank you-that's all I was trying to say. I get that for some people that this might not be a good option, but for someone like me who has a crappy backup generator and no hybrid, but is planning to buy a hybrid anyway, it seems like a good one. Again, it can be and has been done with a UPS, but I'm just trying to find another way.

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                        • #13
                          Check out this company for your inverter. http://www.sunfine.com/products/ Depending on battery pack voltage and inverter needs they may have a model that fits your usage. I have seen this brand used in the Philippines @ 220V 60hz. It has lasted over three years as his only electricity for his house. Just install a large DC jack and use Andersen connector based extension cord to the vehicle. Use a center tap balancing transformer to make your 220v to 110v conversion as required same as you would use on a 220v generator. Watch your grounding when using a transformer. It gets tricky. There are also other vendors on Aliexpress, but I do not know the quality or if they really output 60hz. Do not forget you can also use a DC to DC converter to make any car battery voltage into 12-48vdc. Then you could use any standard on/off grid inverter off the self. That may be the most simple. Check out the DC-DC converters used by the DIY electric vehicle market.
                          -YS

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                          • #14
                            There is a whole group devoted to Prius As A *
                            http://www.priups.com/
                            http://priusgen.sandbox.org/
                            http://www.aprs.org/FD-Prius-Power.html
                            http://www.greenbuildingadvisor.com/...se-prius-power
                            http://forum.solar-electric.com/show...as-a-generator

                            If you can manage the wiring connections safely, and have sized inverter to your loads and transfer switch,
                            it's a pretty decent system. As efficient as the Honda inverter gensets on auto-throttle, the Prius uses a
                            high efficiency alternator for the traction battery, not the 80W 12v aluminum brick on most cars.

                            But it's not seamless, you still have to manually move the car out of the garage and hook up the cable AND leave it "ON" and unattended in the driveway (I don't know if you can lock the door from the outside with system enabled)
                            Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                            || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                            || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                            solar: http://tinyurl.com/LMR-Solar
                            gen: http://tinyurl.com/LMR-Lister

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                            • #15
                              Originally posted by Mike90250 View Post
                              But it's not seamless, you still have to manually move the car out of the garage and hook up the cable AND leave it "ON" and unattended in the driveway (I don't know if you can lock the door from the outside with system enabled)

                              On 2005 models anyway, you have to lock the driver's door with the mechanical key. Otherwise neither the electronic fob nor the handle switch nor the armrest lock button will actually lock all the doors if the key is detected to be inside the car and possibly if the drive system is turned on.
                              I am not certain that the drive system being on makes a difference, so you might be able to just lock it with the engine enabled as long as you took the key with you.
                              To run a Prius through a car wash, you pretty much have to be inside the car to avoid the park function from being enabled.
                              If you do not put the car in Park the hybrid drive cannot use the engine to charge the batteries. If you switch to neutral to stop for more than a few seconds, a warning will appear on the screen telling you that the traction battery will not be charged.
                              SunnyBoy 3000 US, 18 BP Solar 175B panels.

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