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Use the car as a temporary generator during black out ?

Discussion in 'Electronic Basics' started by JW, Feb 18, 2004.

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  1. JW

    JW Guest

    Is there such a device that you can plug into your car and is capable
    of turning the car's DC 12V power into household 110V AC ? Please
    don't laugh if this is a stupid idea, I am just wondering if the power
    generated by the
    small alternator on a running car would be enough to drive a force air
    furnance during black out ?

    My neighbour is buying an expensive Honda generator as a backup power
    Since I can't afford to do the same and black out is not uncommon in
    my area,
    I am thinking if the alternator on my three cars can do the same trick
    power at least the furnance during a winter black out ?

    Appreciate if you can share your knowledge / experience.
  2. Andy Hill

    Andy Hill Guest

    Lessee...a blower motor on a furnace typically runs about 10A @ 120V...that's
    1200W continuous. I'll ignore the startup current, but it's probably pretty
    gnarly. 1200W inverters are out there (primarily for the RV crowd), but they
    ain't cheap. We're talking 100A+ out of the battery, which is quite a draw --
    you're not going to get that out of the alternator -- basically you're going to
    suck the life out the (non deep cycle) battery in short order. Now, RVers
    address this with a bank of deep cycle batteries, but you're getting into the
    range of a genset by the time you've bought the batteries and the inverter (it's
    quieter, 'tho).
  3. zxcvbob

    zxcvbob Guest

    You can buy little inverters that run off your car battery and generate
    110V AC. I bought a 400W inverter for about $50 (then found the same
    one at Sam's Club a few months later for $25. D'oh!) The size you need
    depends on the power requirement of your furnace blower. The inverter
    does not need the car to be running; just the battery charged. You'll
    have to run the engine every once in a while to top off the battery.
    You might want to buy a deep-cycle battery just for this use.

    How are you planning to wire it up?

  4. zxcvbob

    zxcvbob Guest

    My furnace has a 8.5A fuse in a fusable disconnect (I don't know why, I
    didn't wire it like that) and it doesn't blow during startup...

  5. Chris Lewis

    Chris Lewis Guest

    There are 12V inverters that you can buy quite cheaply to get 120V AC
    power[+]. However, above about 400W the price starts to jump _very_ steeply.
    Given startup surge and wave conditioning requirements for AC induction
    motors, an inverter for your furnace blower will have to be in the 2000W+
    range. Those things cost more than a consumer grade (ie: Coleman) 3500W
    gasoline generator (but not as much as a good Honda).

    Furthermore, at that power level, the vehicle's alternator may not be able
    to keep up. 60A is about the limit for ordinary cars, 75A is the usual
    "top end". Which is only about 720W. The furnace blower steady-state
    is going to use up just about all of it.

    There are "special" alternators you can install on your car that
    produce 120V AC - making your whole car a gas generator. They're
    actually quite inexpensive (years back Northern Hydraulics had them for
    around $60), _except_ that mounting them is often going to be a b**ch.

    These are able to deliver several thousand watts, _however_, they're
    not frequency regulated, and thus would not work for furnace blowers which
    need a reasonably well controlled 60Hz AC. They're more intended
    for things like electric drills and saws that don't care what frequency
    the 120V is at.

    Sorry, your cheapest option is a gas generator.

    [+] I have a couple smallish inverters, and will be building a 12V emergency
    lighting/power system in the house. But I won't be able to run motors like
    that, it is not intended to be as "capable" as a gas generator. Just simple,
    cheap, keeps the lights burning, we can watch emergency broadcasts on
    TV, and recharge the cell phone ;-)
  6. Woody

    Woody Guest

    Backtrack and think about what you are trying to do. First the Honda
    generator costs about four times any others. If you need a generator for
    high usage all the time the Honda is the way to go. You can buy a 5-6 kw
    generator for around $500. It will do everything you need and probably last
    you a lifetime at the small usage you need. I bought a 6kw generator about 8
    years ago for about $400 and have used it about a dozen times. I have it set
    up so it feeds the whole house during power failures. I had lights, TV, and
    hot food during the blackout. It won't run the air conditioner but it did
    run several fans. Check the prices at the big box stores and warehouse
    stores. You don't need state of the art for the small usage it will
  7. HLS

    HLS Guest

    My father-in-law used to buy these devices for his employees fleet cars.
    They worked in the oil patch, and needed to use drills, etc.

    He and I opened one of them one day to see what he was getting for him
    money. It was
    essentially a switch and a 110 receptacle.

    The switch cut the voltage regulator out of the circuit and ran the
    alternator on full output.
    The frequency was whatever you get out of a three phase circuit running at
    frequency x.

    Sure they worked. I don't recall him ever having burned out alternators
    because of it either. But it darn sure wasnt rocket science. And you are
    still limited to the wattage that the alternator can put out.

    Last point, if one thinks an alternator doesn't put out much at low RPM, he
    should remember the days of the generator. These things were borderline at
    best, always seemed to have voltage regulator problems.
  8. Art Todesco

    Art Todesco Guest

    There is a company called Auragen that makes this type of thing.
    They are at While
    the units are really nice, they are pretty pricey. I am
    currently looking a putting one in a mobile TV truck, about $3K.
    As others have said, a cheap gas generator goes a long way in
    an emergency.
  9. Tony P.

    Tony P. Guest

    As it is now alternators on cars are becoming more and more taxed at
    providing enough power for all the widgets and things on a car.

    This is part of the move to the 42V electrical systems in cars. I can
    understand that - takes 48V to run your phone why not something like a
    Best way to use your car as a generator is not to. You could buy a basic
    generator and then wire up your house to accept it as an input. You'd
    probably be looking at about $3000 or so.

    Other option is a truck with a PTO hooked to a generator. But even that
    isn't cost efficient.
  10. calhoun

    calhoun Guest

    I have a 2200watt continuous/4000 peak inverter wired (not a plug in) to a
    2nd, isolated, battery in my truck. It cost $310.00. I use it for running
    a skill saw, miter box etc. It is much easier than starting /stopping a
    generator much quieter, and doesn't take up any cargo space.

    I don't think it would take the place of a generator for continuous use. My
    alternator is a 135 amp upgrade but the inverter can draw over 200amps so it
    would never keep up with continuous use. Its output is small compared to
    even a cheap genset.

    It will be cheaper and better to just use a generator.
  11. Jeff Cochran

    Jeff Cochran Guest

    Inverter. Available through many mail-oder sites and most RV or four
    wheeling dealers.
    Unlikely. A space heater maybe.
    A generator is under $500, an inverter of any capacity would be close
    to as much.

    Blankets, firewood and candles, along with a propane heater, stove and
    lantern are much cheaper, more versatile and more practical.

  12. Tony Kimmell

    Tony Kimmell Guest

    I used to have an '85 Chevy diesel 4x4 that I setup to run a generator
    off the driveshaft. There was a flatbed on it and I mounted the
    generator to it. I left the front drivetrain hooked up so it was
    still driveable (front wheel drive). The rear driveshaft ran the
    generator with a small gearbox between the rear driveshaft and the
    chain that drove the generator to disengage it so the generator
    wouldn't turn when the truck was being driven. I don't remember the
    size of the genereator exactly, it's been a while since I sold it. It
    was enough to run the whole house with room to spare (it was big...
    weighed probably 800-900 lbs). It was originally a tractor PTO

    You just drive it up to the power service panel, set the emergency
    brake, pop the transfer case into 2WD, put the rear gearbox into
    gear,plug the generator in, and crank up the rpms. There were a
    couple times I had to use it for 2-3 days straight... that 6.2L diesel
    never missed a beat.

    This obviously isn't what you're trying to do, but I thought it was an
    interesting semi-related story :)
  13. John Davies

    John Davies Guest

    I use a 1000 watt generator to run my central furnace - it works
    fine,. I was unsure if it would handle the start-up current, but I
    have never experienced a problem.

    You do NOT need a 4 or 5 kW generator if all you want is to run the

    Don' try to jury-rig something to your car - just buy a cheap
    end-of-season generator in the 1500 to 2000 watt range and you will be

    John Davies
    '96 Lexus LX450
    '00 Audi A4 1.8T quattro
    Spokane WA USA
  14. *CBHVAC*

    *CBHVAC* Guest

    What kind of furnace do you have? Electric? Gas? Oil?

    I can tell you now, that if you have a heat pump, or straight electric
    resistance heat, you cant.

    Personally, I have a 25KW Coleman, with a Ford engine that runs on NG, and
    my heat pump hasnt even had to be shut down in the last two outages we
    If you are in an area that is prone to blackouts, or simply outages due to
    ice, or weather related, then you cant afford to be without one.
  15. Ed Stasiak

    Ed Stasiak Guest

    How difficult/expensive would it be convert an old yard tractor
    (10hp) into a mobile generator for use in case of blackouts and
    where would one find the necessary components?
  16. Chris Lewis

    Chris Lewis Guest

    As a FYI, some years ago there was a discussion (on this group I think),
    where I had suggested that an "alternator configured as 120V source"
    unit was limited to about the same wattage as when configured for 12V
    (ie: somewhere in the 500-800W range typically).

    An automotive engineer familiar with alternator design chimed in and said
    that, on the contrary, these things can put out vastly more power. As in,
    a 60A alternator reconfigured to drive 120V could actually deliver 60A
    at 120V (7200W at 120V instead of 720W at 12V) under the "right conditions".

    That would presuppose you're running it at high RPMs [+], and secondly
    that current draw and voltage were exactly in sync (ie: pure resistive
    loading). If there was significant out-of-phase current/voltage at
    those power levels, the thing would self-destruct in very short order
    because the thing isn't big enough to dissipate the inductive heating.

    It also supposes that the drive belt can stand up to 10 times as much

    [+] the amount of power that a given size of transformer or generator
    can generate is highly dependent on AC frequency. Ie: a PC switching
    power supply can supply 500W out of a transformer 1.5" in diameter,
    (because the transformer is being driven at anywhere from 20Khz to 50Khz),
    whereas an ordinary 60Hz transformer for that wattage often weighs 5 pounds
    or more and is bigger than an entire PC supply.
  17. Chris Lewis

    Chris Lewis Guest

    You'd need a speed governor and a generator. I was researching this
    some years ago because I thought of doing exactly that.

    I found that Northern Hydraulics (now just "Northern") and
    Princess Auto (more or less the Canadian equivalent of Northern) were
    selling brand new "bare" (motorless) 3500 and 5000W generator units for
    somewhere in the neighborhood of $200-$400.

    [I've seen Princess selling "surplus" 20Kw motor-less generators for
    ~$800CDN. Drool drool ;-)]

    The problem is finding a speed governor that detects the output
    frequency of the generator and can adjust the tractor's throttle to
    keep the frequency reasonably and consistently close to 60Hz under
    wildly varying load. These are usually custom units built into
    motor-generator units ("gensets").

    Even Northern, who also sold gensets they assembled themselves (from
    the generators and motors they also sold) didn't sell the governors

    While yard tractors usually do have a governor already (my 12HP Cub Cadet
    certainly does), I don't think they're anywhere near fast or accurate
    enough to reliably use in a generator/tractor combo. The one on my
    tractor certainly doesn't seem "quick" enough. This presupposes as well
    that you get the speed set right in the first place for the governor to

    If you _did_ manage to find the generator/governor units, then the problem
    becomes mounting it on the tractor. I had that all figured out for mine -
    it would have involved producing a customized version of the snowblower
    mount and adding belt drive to link the generator to the accessory clutch
    pulley (3/16" or 1/4" steel and some welding). The generator would have
    stuck out in front of the tractor almost between the front wheels. But
    very easy to mount/dismount.

    [The manual for the tractor did say a rear PTO was available for it just
    like the big ones on full size tractors, but the local Case-IH dealership
    just laughed at the notion that something like that had ever existed.]
  18. yes, it is called an inverter.
    it is not.
    It depends on your alternator.

    I have just such a setup.

    I own a Ferrups 1100KVA UPS.

    I connected its battery inputs to my truck's battery. (obviously, the
    connection is removable as I need the truck for other purposes).

    During blackout, I connect my truck's battery to the UPS, start the
    engine, and turn the UPS on. The inverter in the UPS produces enough
    power to power a small motor, and my truck's alternator has enough
    power to replenish the battery.

  19. Not a stupid question. I've tried it myself, using a 700 watt inverter, and
    a marine battery. Figure if I can get two hours or so of furnace time, it
    would surely be a lot more comfortable than not.

    What I found was that the lead in wires they gave me didn't supply enough
    amperage to start the fan motor on the furnace. Reaching in to spin the fan
    by hand didn't help.

    I keep thinking that someday I've got to wire a second battery onto the 12
    volt leads of the inverter, but I havn't done it yet.

    Keep the inverter as close to the battery as you can -- make the long
    distance run with 110 VAC extension cords.


    Christopher A. Young
    Join Alt-Hvac Moderated
    A free, easy to use Yahoo! group
  20. v

    v Guest

    Yes there is such a thing. My buddy used to use one to run his
    circular saw on a job site (intermittant use). I don't think your car
    would keep up for long with any continuous draw. You gonna leave the
    car running all night long?

    You could probably run your refrigerator off it, cool it down and then
    shut off the car. But not your heating system all the time.

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