Inverter location

Discussion in 'The Beginner' started by mark e, Mar 21, 2009.

  1. mark e

    mark e Read Only Funster

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    Bought my 600 watt inverter, 2 xmas ago and still havent put it in the motorhome.

    With the new season starting, where is the best location for it ?

    My leisure battery is under the passanger seat, so i know its got to be about there, but not sure whether to permantly put it in or temp instolation ?

    You'r views as allways are appriciated :thumb:
     
  2. hilldweller

    hilldweller Funster Life Member

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    I can't think why.

    As long as the cables will stand 600/12=50A with fuse at battery I'd say anywhere safe and cool and convenient for the 240 side too, is OK.

    And once you've fitted it see if you really can flatten a standard single battery in one hour as the theory suggests.
     
  3. scotjimland

    scotjimland Funster Life Member

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    Hi Brian

    The reason is volt drop, the longer the cable the greater the volt drop, this has to be taken into account when sizing the cable..

    for a 600 watt inverter, full load 50 A and up to 3 mt, with a max volt drop of 5% you need 25 sq.mm
    If you wanted to reduce the volt drop to 1% you would need to use 70 sq.mm. :Eek!: but if you reduced the length to 1mt and using 25sq.mm the volt drop is less than 1%

    hope that made sense

    Jim
     
    Last edited: Mar 21, 2009
  4. hilldweller

    hilldweller Funster Life Member

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    Well I did say "stand 50A"

    So the trade off is more copper for a more convenient position. I don't know the cost but 25mm2 cable is only about 6mm diameter so not as frightening in the flesh as it looks.

    Now back to your figures.

    Copper is 0.0175E/mm2/m ( I'm using E for ohms )

    So 3m of 25mm2 = 0.0175 * 3 / 25 = 0.0021E

    Voltage drop = 50 * 0.0021 = 0.1V for each wire.

    0.2/12*100 = 1.6% drop

    Have I got it wrong ?
     
  5. olley

    olley Funster

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  6. hilldweller

    hilldweller Funster Life Member

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    Very close to my figures and since they use a different cable and higher temperature they are both correct.
     
  7. scotjimland

    scotjimland Funster Life Member

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    Sounds about right ..

    The longer the cable run the heavier it needs to be to compensate for the volt drop.. and it's more critical with low voltages.. a couple of volts lost from a 230v supply is negligible but a huge loss when it's a 12v supply

    Same calculations when sizing cable for solar panels.

    For Example.
    An 80 watt panel in theory produces around 5 amps @ 17v what size cable is needed if the run is 6 mt with a max volt drop of 5% ?

    well, surprisingly the same size ... 25mm sq ..

    But how many spend hundreds of pounds on decent solar panels then skimp on the cable..
    It's only 5 amp so they think 2.5sq.mm cable is fine, . but they don't consider the volt drop .. then wonder why the panel isn't performing as it should.

    The figures I quoted are from AEI cables, there is a cable sizing wizard on their site ..
     
  8. Douglas

    Douglas Read Only Funster

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    Hi Jim,

    Nothing about volage loss, but dont forgat the venterlation for the inverter.

    Doug.
     
  9. sinbad1

    sinbad1 Deleted User

    What about earthing the unit :Smile:
     
  10. pappajohn

    pappajohn Funster Life Member

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    hi Mark'

    like yours mine is under the passenger seat,

    i tie-wrapped the inverter to the back of the seat base so keeping the wires to a sensible length.
    its well out of harms way and plenty of cooling air.
    i run an extention cable from the inverter to whatever im using but its mainly kitchen stuff so most will plug in directly.
     
  11. hilldweller

    hilldweller Funster Life Member

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    Don't you know that trawling with nets that size contravenes EU regulations ?
     
  12. sinbad1

    sinbad1 Deleted User

    Not if you throw the small fry back:Rofl1::Rofl1:
     
  13. mark e

    mark e Read Only Funster

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    Should have mentioned 85 amp/hous battery and the inverter has come with cable.
    Quite thick and about 50 cm in length. So will be using that, if that would be up to the job. No inline fuse on it though, so do i need one ?

    Like the idea of just cableting the back of the passanger seat base. Wont be using it too much, just for the 22 inch lcd tv mainly before bed.

    ( Pain having to go out of the motorhome to turn the genny off, just for the tv :Rofl1: )
     
  14. pappajohn

    pappajohn Funster Life Member

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    with a bit of calculating you could put just enough petrol in the genny for the evening and let it run out :Rofl1::Rofl1::Rofl1::Rofl1:
     
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