Generator/electrical/question

Discussion in 'Tech/Mech General' started by Heyupluv, Mar 17, 2010.

  1. Heyupluv

    Heyupluv Read Only Funster

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    This question is for you electrical technical wizards....to keep the grey matter working.
    People keep asking about these cheap generators, are they any good for the motorhome and the answer generally is no, due to sensitive equipment on the charging panel on the motorhome,. and to a inconsistent voltage on the output....of the cheap generator.
    What people have advised in the past is the generator type pure sine-wave...this converts 12v to 230v giving a constant voltage.

    The question is......
    Many people may already have one of these cheap generators.
    And many may have a 500w inverter to covert 12v to 230v already in the motorhome
    now a lot of these cheap generators have a 12v connection to charge the battery with a output of 12v 8.3a DC ...(230v 208a Ac).

    could or would it be possible(or maybe I am talking a load of rubbish if so sooooorry :Doh:) to connect the 12v output side to a 500watt inverter to connect to the input side of the motorhome......a would this give a constant voltage and a little electricity for lighting and keep the batteries charged ????????I don't know, that is why I am asking you.:Eeek:
    now this would only be any good to people who already had this equipment......because if they was purchasing new they may as well buy a 750w or a 1kw Kipor.

    (Me I have a ....1/...650w 2 stroke cheapo generator for just running a drill if down the garden and carry it on the back of the lawn tractor (and it will run all day long),....2/ ..a ..2.2kw 4 stroke large in a frame on wheels what I had for when I did property rebuilds,.....3/...A Kipor IG 2000v (2kva) for the motorhome.)

    It was just a thought that may be of some use...to other people. if it would work??????

    Mel
     
  2. JeanLuc

    JeanLuc Funster

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    Not really an option I'm afraid. Apart from the sheer fuss of connecting the whole lot together with decent heavy-gauge cable, Ohm's Law is against you.

    A 500W inverter running at full output will draw a current of 500 / 12 / 0.85 = 49 amps
    (The 0.85 factor is to allow for 85% efficiency in the inverter)

    So that's a non-starter.

    Going the other way round with 8.3 amps as the maximum DC output from the generator:

    8.3 x 12 x 0.85 = 85 watts

    You are not going to power much with a maximum power supply of 85 watts. My Schaudt Elektroblock charger draws almost 400W.

    The solution is either: buy a decent generator; use sites with mains hook-up; supplement power with a solar system (best in in summer) / power cell; or reduce your power consumption.

    Philip
     
  3. Heyupluv

    Heyupluv Read Only Funster

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    Hi Philip ...a Big thanks for your input it was just a thought......
    (to answer your solution )
    I use mains hookups when available, :thumb:
    I have a 110w solar panel (but not a lot of good in the winter):thumb:
    I have battery power, :thumb:
    I have a Kipor IG 2000w generator,.:thumb:
    I have reduced the lighting to LED,:thumb:
    I use a lot of gas cooking exterior.cadac safari .5 in one .When weather allows it:thumb:
    so I seem to meet all your criteria.........:thumb:
    it was just a thought for other people..not to worry, you win some you loose some:thumb:

    Mel
     
  4. scotjimland

    scotjimland Funster Life Member

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    Hi Mel

    Good explanation from Phiip, pretty much an non starter ..

    When we say 'cheap' gennies they normally mean gennies without inverters, but it should be remembered they actually produce a pure sine wave, irrespective of speed.
    The problem is that many have very poor governors to control the speed, hence the frequency will vary until it is on a steady load, and will fluctuate as load is added or removed.

    Power station turbine generators don't use inverters but have sophisticated speed controllers or governors to accurately control the speed to 3,000 rpm giving 50hz .. but we could hardly call them 'cheap'
    The best power comes from a plain and simple generator. This is where commercial power comes from, a rotating magnetic field in a coil that generates a nice pure sine wave.

    The point I am getting to, a non inverter genny can be used safely provided a few precautions are taken.

    Start the genny, let it warm up and settle down to a steady speed, if possible put a small load on it before connection to the van charger and don't apply heavy loads while its in use.

    .. Your own experience while using your 'cheap' genny will be your best guide as to whether it is suitable or not, how well does it cope with load changes.. does it speed up or slow down dramatically..

    In many ways a good non invertor generator is better than a cheap inverter genny ..

    see this pdf for a good explanation of inverter generators ..
    http://bellsouthpwp.net/j/o/johngd/files/rv/inverter_generator.pdf

    and this answer on another site as to using a non inverter genny,

    Inverter vs. non-inverter generator

    EDIT

    I forgot to say, inverter gennies benefit from not needing to run at full speed all the time, this saves fuel and engine wear
     
    Last edited: Mar 17, 2010
  5. JeanLuc

    JeanLuc Funster

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    Very valid point made by Jim. However as he said, a well-controlled, non-inverter generator is unlikely to be cheap. Here is an example from the Honda 'multi-purpose' range with an output of around 3 KW - I think that is the 'baby' model. It has something called AVR technology (I think it stands for Automatic Voltage Regulation). Lots of pure power, but it is noisier than a suitcase inverter model, very heavy, and at over £1,200 it is not a cheap alternative.

    >> Honda Gennie <<

    Philip
     
  6. gogocrosby

    gogocrosby Read Only Funster

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    What would thedrawbacks be then if you used the 12volt side connected directly to the leaisure battery. It wouldn't be conected to the charger and as it revived your battery you could use the inverter and other 12volt stuff also.
     
  7. Snowbird

    Snowbird Funster Life Member

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    I used to think that would work,but alas no.
    The genny will normaly trip its 12 volt tripper when the load is put on it ie the inverter.
     
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