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Using car as generator for house power

Discussion in 'Gen 3 Prius Accessories and Modifications' started by ED9593, Oct 31, 2012.

  1. szgabor

    szgabor Active Member

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    Yes that is my understanding as well. So it could be potentially dangerous ... in a kitchen or bathroom .. certainly would not do this for a full home setup. Running a TV fridge for a few hours ... should be just fine ...
     
  2. North Jersey

    North Jersey Junior Member

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    My rationale for Prius rather than a generator installation was as follows:
    1. Natural gas fixed installations seem to require a battery to start - in this climate that means running electricity to heat the battery in the winter according to the manufacturer.
    2. No great place to install a fixed installation on my small property. Hard to roll a wheel based generator from the garage to where the gas line exits the house (for a barbeque - but should be big enough for a 1000 watt unit).
    3. Got a 4 line transfer switch for $150. That is the big work to run the wires from the garage (where I will have the male plugs) to the opposite side of the house where the power enters the house (basement has been partly finished -thus a pain to run wires) and wire the transfer box. I can get a small (portable) natural gas generator if I want and hook it in to the same plug leading to the transfer switch at some future time. No work, just money.
    4. If I stay in the house, the next Prius will have an option for a built in power plug (now available in Japan).
    5. In a real big disaster, natural gas is not assured indefinately. This gives me some independent capability.
    6. I DON'T WANT CANS FULL OF GASOLINE STORED IN MY HOUSE. Heard about lots of people doing things I consider dangerous after Sandy to store gasoline for a cheap generator they bought.
    7. I can unplug from the inverter and drive to fill the tank when necessary.
    8. I can drive my other car to fill up, and then transfer gas to the Prius (got $10 hand pump).
    9. With both cars full I have a month of 300 watts net, which is probably all I need on average (heat controls, hot water electronics, refridgerator, FIOS if it still works, laptop, a few lights, sump pump occaisionally). One gallon of gas has energy value of 1500 watts for 24 hours. Figure 33% efficiency gives 500 continuous watts, less 200 watts for Prius electronics, gives 300 continuous watts for a gallon for a day.
    10. If we go camping, we now have power.

    By the way, the inverter will be grounded through the 3 wire plug through the transfer box into the main ground for the house (once that is set up).

    In answer to a previous question, I used the following (from Genuinedealz.com) to connect to the bolts on the battery post clamps:
    4 AWG Tinned Lug Cable Crimp Connector End #10 hole
    FREE SHIPPING

    GIM-91024
    It seems just fine. I used 3/8" hole for the inverter and the fuse box, but that may vary depending on which you buy.
     
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  3. North Jersey

    North Jersey Junior Member

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    My boiler electronics are hard wired on their own circuit (no plug) so if I didn't buy a transfer switch, I was going to have to put in a non-code switch to the boiler, then replace it when buyer's house inspector complained when I went to sell the house. Also, the number of extension cords I would have to run if not using fixed wiring and the transfer switch offsets some of the potential savings, not to mention the risk of tripping in the dark on an extension cord, damaging a cord, etc. I would have done that in an emergency, but with time to do it right, I think it is worth it. I got the 4 line transfer switch - only wiring 4 critical circuits, but it still gives me power in the kitchen, den, basement (and maybe a few other places).
     
  4. garylow

    garylow Junior Member

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    How do you keep the car running outside of your garage and not worry about someone driving off with your generator? I like the idea, but I am on the edge of a busy street in a corner house. Is there a way to lock the shift with the car running or the engine shuts off if the door opens the engine shuts off?
     
  5. ftl

    ftl Explicator

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    You can leave the car in Ready and lock the doors with the mechanical key.
     
  6. North Jersey

    North Jersey Junior Member

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    Not that I know of. Answers I heard were 1. lock the door, just crack the window to pass out the extension cord(s), or 2. Get an appropriate hose to channel the exhaust 15 feet away from the garage, and run the car in the garage, with the garage door open enough to pass the hose, but physically blocked from opening more.

    The car will run without the key fob in the car, so lock the door and take it away. If someone breaks in, they can drive away, but cannot restart without a keyfob.
     
  7. fuzzy1

    fuzzy1 Senior Member

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    You may want to re-figure that efficiency. That computes out to 7.2 kWh delivered AC per gallon, much higher than the 4 kWh that somebody (Bob Wilson?) documented in another thread.

    Note that the 33% efficiency is probably at or near the ICE shaft. Once you add in the generator loss, AC->DC conversion loss, battery charging/discharging loss, HV->12V inverter loss, 12V wire loss, and 12V->AC inverter loss, I doubt you will have anywhere near 33%.
     
  8. windstrings

    windstrings Certified Prius Breeder

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    Conveince is and low cost to setup is prob the best advantage.

    I've rigged up separate setups before but then your talking a 12 or 24 volt has or diesel generator to charge a notable size battery bank with a respectable inverter to produce what the prius already packages.

    The main thing I don't like is your whole car is tied up.

    Alan...
    Sent with Tapatalk 2
     
  9. szgabor

    szgabor Active Member

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    thanks for the explanation.... I am having similar issues with the heating seems like hard wired although there is a switch to turn it off or on (for summer etc) I will have to figure that out otherwise no heating for now.

    also appreciate the details on the wires...
     
  10. szgabor

    szgabor Active Member

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    Or park another car in front of it on the driveway. That what I will be doing .... will check if the mechanical key locks all the doors !!!
     
  11. fuzzy1

    fuzzy1 Senior Member

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    Half the time I'll need it, the driveway will be blocked with snow exceeding the Prius' ground clearance. The rest of the time, I can block it with another vehicle. (Despite the low CO emissions, I'm not going to run it in the attached garage.)

    I haven't yet tried the mechanical door lock for verification. For others with different parking situations, would it be practical to jack up one corner of the car, put it on blocks, and remove one wheel? Or are local auto thieves enterprising enough to bring their own spare wheel?
     
  12. szgabor

    szgabor Active Member

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    Funny, you would do this during or after a hurricane or snow storm most likely at night??? and what happens if you need to drive the car ... I would say yes this could be done but not practical ...
     
  13. ftl

    ftl Explicator

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    We need some more real numbers here. This is only rough, but when I used my C to power essentials after Sandy, I averaged around a 40 watt load on the inverter for 54 hours, so just over 2 kWh. The C reported less than a gallon of gas used when I turned it off. Neither of these numbers is very precise, but I'd estimate around 2.5 to 3.5 kWh per gallon. I suspect the efficiency would be better with a higher load.

    If I'd thought about it I would have reset my Kill A Watt power meter, which I had on the output of the inverter, and recorded the actual kWh used. I'll do it next time; I'll be using my 1 kW inverter by then.
     
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  14. fuzzy1

    fuzzy1 Senior Member

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    I wouldn't because I have better options, already listed. And if the power goes out at night, I won't need Prius-scale backup power before daylight. It will be for longer events.
     
  15. bwilson4web

    bwilson4web BMW i3 and Model 3

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    The method I use is the 'trip meter.' When setting up the car for emergency power:
    • start car, record the existing trip meter miles and MPG -> calculates the initial 'fuel burned state'
    • wait 10 minutes, record the trip meter miles and MPG -> calculates the warm-up fuel burned
    • end of outage, record the trip meter miles and MPG -> calculates the steady state fuel burned
    In parallel, a Kill A Watt can be your 'power meter' to determine how much power was delivered over what interval. Using our 2003 NHW11 and a catalog of portable generators, I was able to make this graph:
    [​IMG]
    In terms of fuel efficiency, our older, 2003 Prius is well within the range of commercial, stand alone generators.

    Bob Wilson
     
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  16. ftl

    ftl Explicator

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    Thanks, Bob, that's very helpful.
     
  17. windstrings

    windstrings Certified Prius Breeder

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    As long as you don't attempt to pull more wattage than the Prius inverter can supply you should be fine. The 12V battery is not doing any work and it's voltage shouldn't drop unless the inverter can't handle the job.

    Your prius inverter is wired in parallel with the battery and so your really running off the inverter....

    Alan...
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  18. ftl

    ftl Explicator

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    Terminology check:

    AC -> AC - transformer
    AC -> DC - rectifier
    DC -> AC - inverter
    DC -> DC - converter
     
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  19. windstrings

    windstrings Certified Prius Breeder

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    Thanks ftl for the correction and sorry for the confusion.

    I have historically known inverters for use in 24v dc to 120ac, but the prius does crazy things with electricity and the labels get blurred as the ICU wears many hats.

    Seems the term "inverter" is indeed thrown around loosely. Am I more correct to say inverter/converter?

    Special Issue: Inside the Toyota Prius: Part 5 - Inverter/converter is Prius' power broker


    " Since the Prius still needs a conventional electrical system to operate instrumentation, cabin lighting and the like, the ICU also supports step-down conversion from the 200-V NiMH battery to the 12-V subsystem, where a conventional lead-acid battery is used. Circuits for the dc/dc converter share space on the same circuit board that is believed to house the A/C compressor inverter, and TO-packaged devices are again bolted to the cooling plate of the overall ICU assembly.
    The boost converter, MG1 and MG2 inverter, dc/dc converter and A/C compressor inverter all operate under the direction of the hybrid vehicle engine control unit."

    Seems I watched a video that mentioned the same device that inverts low voltage power also turns around and converts it for the accessories, am I still off?


    Toyota Prius Engine Problems - Car Forums - Edmunds

    Alan...
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  20. ftl

    ftl Explicator

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    All the terminology is correct there, Alan - the Prius itself has a mix of AC and DC components running at various voltages between 12V and 500V, and it inverts, converts or rectifies the power as needed.

    Here's a useful page with a detailed description of the electrical systems. I've extracted some relevant bits and added my own notes to point out how and where the power flow is inverted, rectified, or converted - all quite different functions.

    "MG1 recharges the high-voltage (approximately 200-V) nickel metal hydride battery pack located in the rear of the car"
    "Diodes are used during regenerative braking to rectify the ac output of the MG1 and MG2 assemblies so that after filtering and regulation (using the boost converter circuit in reverse), the recovered energy resupplies the high-voltage battery pack."

    So the AC from MG1 is rectified to DC and charges the traction battery.

    "To create the three-phase power for the motors, the dc battery source must first be stepped from 200 to 500V DC via a boost converter."

    When the electric motors are assisting the gas engine in driving the wheels, they're fed from the traction battery via a high voltage DC to AC inverter.

    "The Prius also uses an electric air-conditioning compressor motor so that cabin cooling is maintained even when running in electric mode only. A second dc/ac inverter, with circuits located on a second ICU controller circuit board ringed with TO-packaged IGBTs, is deployed to power the electric A/C compressor from the HV battery pack."

    The A/C compressor uses AC voltage, and is fed from the traction battery by an inverter.

    "Since the Prius still needs a conventional electrical system to operate instrumentation, cabin lighting and the like, the ICU also supports step-down conversion from the 200-V NiMH battery to the 12-V subsystem, where a conventional lead-acid battery is used. Circuits for the dc/dc converter share space..."

    This DC-DC converter is what we're using to feed our little inverters for house power. As mentioned in earlier posts, there's a 100 amp fuse in this circuit which limits the power we can draw from our inverter to about 1 kilowatt.

    Hope this all make sense! I'm an EE by training so this terminology is second nature to me, but all the different technology used in the Prius can be a bit tricky to understand.

    There's lots of other stuff about the Prius that I don't understand, and PriusChat has been an amazing resource for me.
     
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