In line switch on solar feed?

Discussion in 'Solar Power' started by Petest, Jul 3, 2016.

  1. Petest

    Petest Funster

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    I've recently installed a 100w solar panel kit. It came with the cheapie PWM charge controller.

    All seems to be working fine but I'm thinking about fitting an inline switch on the feed into the controller from the panel to stop the charge.

    My thinking is that continuous charging of the leisure battery could be detrimental and lead to the battery dying prematurely.

    What are your thoughts?
     
  2. Derbyshire wanderer

    Derbyshire wanderer Funster Life Member

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    Not a good idea as the controller needs the battery voltage to set its output correctly. Switching on the battery to controller when the solar panel is already connected will end up putting too many volts into the battery.
    Left connected as it is now it will reduce the charge as the battery becomes fully charged ie no harm will come to the battery.
     
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  3. Chipster

    Chipster Funster Life Member

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    My opinion is leave as is but if you want to install a switch surely it should be on the output of the controller?
     
  4. vwalan

    vwalan Funster

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    i have been using pwm regulators for about 10 years cant see any reason to change they w0rk. you could switch power to engine battery or just add another leisure battery . but again wet truck battery better than many leisure batteries . also i find keeping batteries fully charged doesnt seem to hurt them . running them down often is what kills them .
     
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  5. John Laidler

    John Laidler Funster

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    The controller shouldn't fry the batteries as the charging current will reduce when the battery voltage rises high enough. This should happen automatically.

    I can only suggest try it without the switch and check what it is doing when the battery voltage gets up to say 13.6 or 13.7 volts. Let it settle down first of course, as the batteries might be a bit flat but after a while if it is then just putting in an amp or two you should be fine because this is the "float" voltage when it should just be maintaining a sort of equilibrium.
     
  6. Techno

    Techno Funster Life Member

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    Crazy idea. There isn't a regulator made that recommend that in the instructions.
    It's purpose is to regulate so why stop it doing its job
     
  7. seanoo

    seanoo Funster

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    other way round , you should always have the batteries connected before you connect your solar panels otherwise you could damage your regulator. so if you have a switch to shut off the batteries , the power from your panels has nowhere to go
     
  8. Stealaway

    Stealaway Funster

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    What harm does it do to the panels if they are not connected t the controller?

    What harm would come to them if left out in the sun completely unconnected?

    Isn't this what he is proposing - or am I missing something?
     
  9. Petest

    Petest Funster

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    That would be the result.

    Maybe I should rephrase the question.

    Will having a leisure battery on charge for 15-18 hours z day via solar cause any problems with the battery?

    I guess not going on the answers above.
     
  10. JockandRita

    JockandRita Funster Life Member

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    Same answer as above, ie, no, as your controller will give a float charge only, once the batteries have reached a full charge. Your solar controller does it all for you, although some do it better than others. ;)

    You could then install a battery manager, which would switch in and transfer any excess charge from the panels, to your starter battery (if your onboard charging unit doesn't already do that). That is a handy wee addition. (y)

    Cheers,

    Jock. :)
     
  11. John Laidler

    John Laidler Funster

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    We've had our van for three years and the solar has been permanently connected and the batteries are fine. Indeed, this is how all installations are as far as I know. There should be no requirement to disconnect the panels though it would do no harm to the panel(s) if they were. The only thing which could come to harm might be the batteries - by going flat. :)
     
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  12. OldAgeTravellers

    OldAgeTravellers Funster Life Member

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    No problems leaving it connected as long as the PWM controller is working as it should. My previous factory fitted controller was over charging. It damaged two sets of batteries before I realised it was a controller problem not the heat in the South of France evaporating the battery fluid. So put a volt meter on the batteries to check that it settles down to a float voltage.
    Steve
     
  13. Stealaway

    Stealaway Funster

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  14. campa cola

    campa cola Funster

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    Interestingly I think most people here have missed your point!!!
    This recommends a fuse between the panels and the controller for the following reasons......I await cries of heresy but also good reasons why you should not do this ???

    We had to report what we found, which was no safety fuse fitted between the Solar Panel and the Regulator. Had this been in place it would have blown as soon as the Solar Reg shorted so minimising the damage and preventing a Fire.
    The Solar Installation was a professionally fitted item and the Motorhome owners Insurance team are saying it is the fitters Insurance that should pay, not them. I suspect it may drag on a while?
    We almost always see a fuse has been fitted on the Battery side of the regulator, but professional installers never see the Solar Panel as the big Power source it can be.
    Can we suggest it is fused properly on both sides of the Regulator?
    We have yet to see a single professional installation with a fuse where the cables come in at the Roof. See item 1. in the Installation Suggestions section below.
    Can we also suggest a Fire Extinguisher in a Motorhome is a very worthwhile safety aid?
    Solar Installation Suggestions.
    1
    . It is standard practise to install a Fuse in any 12v power cable at the battery 'power' end. This is to protect the devices being fed by the cable but also ensures that if the cable is cut through or shorted it reduces the risk of Fire. It is a primary safety consideration. A Solar array is a big power Source, if the cables are shorted there will be amps across them. A Solar Array is a power source in the same way that a battery is. It is lower current but will still melt wires. We have seen a couple of melted/burnt Solar regulators where they developed a fault and shorted the Array. Therefore please install fuses into the cables as soon they come in through the roof. We have yet to see a professionally fitted Solar Install that builds in this electrical safety. There is always one on the battery side of the Regulator, but never one on the Solar Panel side of the Regulator when there should be both.
    Fit a 10A, or relevant sized, Fuse between the Solar panel and the regulator to allow some electrical protection, but also to allow you to isolate the Solar Panel from the regulator during maintenance work, like changing the batteries. Failure to isolate the regulator from the Solar panel during battery maintenance can lead to solar regulator failure. Consider putting a label inside the battery box on the leads to remind you/engineers to pull the Solar fuse first with information on where it can be found. Click here for a page to print off to put in the Battery box, or for suggestions on the text.

    http://www.aandncaravanservices.co.uk/solar-power.php
     
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  15. JJ

    JJ Funster

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    I don't know about your charge controller but mine doesn't go on pumping charge into the batteries when they are full. It stops charging them without any need for a switch between the panels and controller.

    Again, I can only go on about my system. My charge controller controls the charging of the batteries... I reckon that is why it is called a charge controller.

    You asked for my(our) thoughts.

    I think it is completely unnecessary to fit a switch.

    JJ :cool:
     
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  16. Abacist

    Abacist Funster

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    I think they are trying to reduce the risks of fire if the controller packs up or develops a fault.
     
  17. autorouter

    autorouter Funster

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    If you short a lead-acid battery, without fuse protection the current will be huge, enough to start a fire. Similarly with mains supply.

    If you short a solar panel, the current increase will be very modest, at most. A fuse that will permit normal solar currents will be most unlikely to blow. So it's a bit debatable whether to fit one at all. If you're worried, it would be better to fit a thermal trip on the controller box. Or get the designer to build one in to start with.

    A battery charger should have a control profile known as IUoU.
    I = constant current, until a trigger voltage is reached.
    Uo = High voltage until the current drops to a pre-defined level.
    U = float voltage, about 13.6 to 13.8V, with very little current into the battery, to keep it topped up.

    That's a minimum. If your controller doesn't do that, best to get one that does, it's cheaper than a new set of batteries every year. Better chargers, like my CTEK, have seven stages.
     
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