Inverter questions

Discussion in 'Motorhome Chat' started by Coolbeanz, Sep 4, 2013.

  1. Coolbeanz

    Coolbeanz Funster

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    If using a 1200W hairdryer is a 1200W inverter sufficient or is it better to have a larger inverter than the power of the appliance you are using?
    The price of inverters varies tremendously so has anyone bought one of the cheap eBay modified inverters for £30 and found them ok or are they best avoided for a better quality.
    Does anyone have an inverter they are using that they would be happy to recommend? :BigGrin:
     
  2. tonka

    tonka Funster Life Member

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    Its always best to have it larger than needed then it's not working out at full capacity.... Dont think your are going to get anything that big for £30. AND watch how they list the power, sometimes they list the very maximum and the inverter can only stand that for a short time...

    NOTE.. 1200 watts is 100 amps !! So even using for 5 mins will take about 8.5amps out your battery.. Cut down on the heat and use a lower setting, that will reduce the wattage required...
     
  3. irnbru

    irnbru Funster Life Member

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    Please can you explain how you work this out. I would like to know so I can work out an idea of how much I can use tv, laptop etc while wild camping. I thought I remembered it from college but now I'm confused.:Blush:
     
  4. tonka

    tonka Funster Life Member

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    It's a think called Ohm's law... Do a google search but dont cry as you read it, really it is easy..

    1200 watts of power (the amount used by the dryer) divide by the voltage.. in this case leisure battery at 12v = 100amps
    Now this figure is based on an hours use. So run that dryer for an hour and you will consume 100amps.. AND before anyone gets to technical and says "but the Inverter uses power" I am trying to keep things simple..:Wink:

    so 100amps in an hour divide by 12 (5 min sections) = 8.33 amps in 5 mins...
    Now the Inverter will consume power and have some loss, say 10% so add another .83 amps... Total use around 9.16 amps..

    Does that make sense...
    Another example.. TV... LED low power, 20watts..
    20 divide by 12v = 1.66 amps per hour...

    It's a basic formula and almost every electrical device will state its power in watts.. Big items like heaters use kw (kilowatts) 1,000 watts = 1 kw

    Here ends today lesson..
    Tomorrow.. Opening cider tins and their re-cycle uses lol
     
    Last edited: Sep 5, 2013
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  5. Bailey58

    Bailey58 Funster Life Member

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    Plenty of threads on inverters if you care to search, I installed a 2000w to run bits and pieces when off ehu. Fine for the 900 watt kettle but failed miserably to run a 1450w coffee machine. It's been said they only run at 70% of there stated wattage (if that) if I remember correctly so you're asking a bit much of it for the dryer. :Smile:

    Edit: Just re-read your post, mine's a Ring from Halfords, paid about £210 for it when on offer in May.


     
    Last edited: Sep 5, 2013
  6. JJ

    JJ Funster

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    I do believe that watts and amps calculations must be made with the voltage taken into consideration... I don't think 3 amps at 12 volts is the same as 3 amps at 220 volts!

    JJ :Cool:
     
  7. Peter & Elaine

    Peter & Elaine Funster

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  8. tonka

    tonka Funster Life Member

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    Sack him !!!!!!!!!!!
    Should be able to do it in his head or on a piece of torn off cardboard and a stubby pencil..
    :Rofl1::Rofl1:

    JJ.. Yes 3 amps at 240v and 12v are not the same..
    One will give you a "tingle" the other :cry:
     
  9. jonandshell

    jonandshell Funster

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    Our 2100 W Ring inverter achieves its rated output easily.
    Was it your inverter of battery which wasn't up to the job?:Eeek:
     
  10. Peter & Elaine

    Peter & Elaine Funster

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    Let me give you a clue our fitters nickname
    BLACKDOG
    He owns 3 tools
    14 pound hammer
    Big shifter
    Just in case 28 pound hammer
     
  11. Bailey58

    Bailey58 Funster Life Member

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    Neither, the coffee machine's a complicated bit of kit.
    T'was explained on earlier threads. My internet, phone line is about to be cut off, we're on a ship or two to the UK today.
     
  12. electricscott

    electricscott Funster

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    amps are the same, what is different is the amount of power they can generate and this down to the voltage since watts = volts x amps so:

    3 x 12 = 36 watts
    3 x 240 = 720 watts
     
  13. garlicmonster

    garlicmonster Read Only Funster

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    .... of course a hairdryer is also an inductive load, so you really need to consider the power factor

    On a.c.

    P=VI cos phi

    But that's just me being a pendant
     
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  14. oldun

    oldun Read Only Funster

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    The above is pure gobbledegook...

    For example "So run that dryer for an hour and you will consume 100amps" ---- this should be 100 amps instantaneous power and will deplete the battery by 100 amphours.

    Amps is a bit like speed, amp hours is a bit like distance.

    All in all a very misleading and confusing post.
     
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  15. Steve

    Steve Funster Life Member

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    as a quick guide I use, 1amp @ 230v = 20amp & 12v
     
  16. schojac

    schojac Read Only Funster

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    I have a 1500 watt modified sine wave inverter and it works fine with a 1200 watt hair dryer. It's not too happy on full load and on reflection would have bought a slightly higher - 2000 watt.

    The inverter cost me £30.00 but remember it's a modified sine wave inverter. People have stated that if you intend to run TV's, computers etc then yopu may need a pure sine wave inverter which costs quite a bit more.

    When connectining to the leisure batteries you will need some heavy duty(16mm2) cable to carry the load efficiently. 120 amp inline fuse and good connectors.

    The hardest part is bending the heavy duty cable so suggest that if you intend to install that you keep cable runs short and as straight as possible.
     
  17. mitzimad

    mitzimad Funster

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    with any invertor its best to keep it close to the batteries connect with fat cables and do the long run on the 240 side
     
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  18. Coolbeanz

    Coolbeanz Funster

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    So can anyone tell me if I have worked this out correctly:

    I can buy a 1500w modified sine wave inverter and it will cope fine with my hairdryer.

    I need to wire the inverter as close to the leisure batteries as possible.

    As my TV runs on 12v and my IPAD and IPhone both charge using a 12v adaptor there is no point getting a pure sine wave inverter for them.

    If I want to charge my electric toothbrush I could buy a 150w PSW inverter.

    Lastly am I right in thinking that running the TV off 12v would drain the same power from the leisure batteries as connecting an inverter and plugging the TV in to that? :Eek!:
     
  19. Steve

    Steve Funster Life Member

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    Put like that then yes it will work.
    On you last question, power is power be it at 12v or 230v but you use power to convert 12v to 230 so if you have 12v equipment then I would you it.
    Steve
     
  20. schojac

    schojac Read Only Funster

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    Hi,

    basically Yes to most of your answers.

    If you have a 12V TV then run it straight from your 12V supply; running through the inverter will not be as efficient due to power loss.

    As daft as it may sound the inverter was bought purely for the hairdryer
    "I can't do without the hairdryer" says she who must be obeyed. Carole does not use the dryer on full power and she gets 40 mins drying time easy (2 x 100amp/hr batteries)

    Expensive option but I think long term (aires, CL's etc) it will pay for itself in no time.
     
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