What size wires from solar to LR1218?

Discussion in 'Solar Power' started by fred flintstone, Oct 13, 2016.

  1. fred flintstone

    fred flintstone Funster

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    I have a Schaudt 268 controller in my 2001 Pilote Pacific.
    I want to connect 2 x 100w panels to it so after much reading in here I bought a LR1218 to make all the connections.
    It looks really easy on the pictures and in the fitting instructions.
    When the LR1218 arrived I was shocked by how small it was. The connections where the panel connects to it are tiny spade fittings. The wires from the panel are too thick for the spades.
    I have asked various solar experts and all they say is:

    "It is not as simple as you think to fit the schaudt solar unit, LR1218 or the MPPT. If you have 2 solar panels fitted on the roof it has to be the correct cable fitted and check that the panels are paralleled in the correct way"

    Does anyone know what size the correct cable is and where to buy it? Is it difficult to wire it all together.
    I assume paralleled means + to + and - to -
     
  2. aandncaravan

    aandncaravan Funster

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    Because voltage drop is not a major issue in your case, you won't need large size cable.
    If you are using a LR1218 that practically enforces you, via it's short output cables, to mount it near the Elecktroblock, then it doesn't matter too much what the cable size is used from the Solar Panel to the regulator.
    The cables 'just need to take account of the current', which most likely will be just a few amps so thin 1.0mm cable will be 'adequate'.

    Because the voltage from the Solar Panel is likely to be around 25v, any small voltage drop between the Panel and the Solar regulator will make little difference. So long as the regulator gets a decent charge it will still deliver 14v.

    The critical cable size is between the Solar regulator and the Elektroblock or battery, because once it leaves the Solar Regulator it can be as low as 13v, in low light, and even the slightest reduction in voltage will have an impact.
    To charge a battery the voltage has got to be well above the batteries 'fully charged' 13v.
    If the battery is at 12.7v and the charge from the Solar regulator is also 12.7v no charge will take place even if the charger has 2 amps to give.

    So if a Solar regulator is mounted high up near the roof, as most are, and there is a 1v drop by the time it reaches the Elektroblock/Battery, the charge rate can be pretty much little more than trickle.
    For example imagine a Solar regulator mounted up near the roof with a 4 metre run to the battery. In low light conditions it might be outputting 13.5v? By the time voltage drop has taken it's toll, there might be just 12.9v at the battery.

    Because Schaudt recommend a less than 0.5 metre length of cable from the Regulator to the Elektroblock and 'enforce' this with very short cables, even the thinnest cable over 0.5 metre will have negligible drop.

    However, we wouldn't recommend you actually install 1.0mm between the panel and the regulator, but you don't need 6mm as some recommend.



    If you are using a Schaudt LR1218 as the regulator, which has a 27v Solar Panel Voltage limit, your only choice is to wire the two Solar Panels Positive to Positive, Negative to Negative option.

    Obviously wiring two 21v panels to give 42v will destroy the LR1218.
    A lot more on Solar Power on our web site : http://www.aandncaravanservices.co.uk/lr-1218.php
     
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  3. fred flintstone

    fred flintstone Funster

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    Very informative and useful reply.
    I was fitting the LR1218 because Schaudt said it was compliant with my EBL 264-7 and would fit straight on with the wires supplied. I thought I had to fit the LR1218 or I would get problems with my control panel.
    I went to a solar installer for the fitting who said it would fit to my EBL but it was not a simple fitment.
    I decided to fit it with the Sunworks DB2C. This gives me a display panel and peace of mind that all is well.
    Hope I made the right decision.
    Thanks again for your educated reply.
     
  4. aandncaravan

    aandncaravan Funster

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    The EBL 264-7 doesn't have any special Solar requirements or display capability, so best off going straight to the battery, as you have.
     
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  5. fred flintstone

    fred flintstone Funster

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    Thanks for confirming I made the right decision.
     
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