MPPSolar mppt regulator (parallel or series?)

Discussion in 'Solar Power' started by Techno, Apr 13, 2015.

  1. Techno

    Techno Funster Life Member

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    Today in good morning Sun (early April) I have connected 2x100watt monocrystaline solars to a 200 watt MPPsolar mppt regulator in both series and parallel with in clear sky and full cloud.

    The scene
    [​IMG]
    The regulator shown with battery under load and solars covered.
    [​IMG]
    The constant load
    [​IMG]
    Series connection with one panel covered.
    [​IMG]
    Output
    [​IMG]
    with both panels
    [​IMG]
    output
    [​IMG]
    connections in series
    [​IMG]
    Now changed to parallel
    [​IMG]
    Output no significant difference but if anything a tad better.
    [​IMG]
    Same sky throughout test covering around 15 minutes
    [​IMG]

    Later after discharging battery and sky completely clouded.
    [​IMG]

    Series
    [​IMG]
    Parallel
    [​IMG]
    same light throughout
    [​IMG]

    My conclusion is there is no benefit to connecting 12 volt panels in series as clearly the output is actually better in parallel with these units.
    So the only point to the spec of this regulator is that it will accept 24volt panels which can be an advantage if they are available at the right size/price but even then probably best connected in parallel.
     
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  2. hilldweller

    hilldweller Funster Life Member

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    Can't beat a bit of real world research. Nice one.
     
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  3. Techno

    Techno Funster Life Member

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    Yes Brian this is where I check and compare regulators
    [​IMG]
     
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  4. Popeye

    Popeye Funster

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    Andy, I think I have admired almost all of the work you have done and advice you have given, but sometimes fellow Funster I think.........

    ................
    This Andy needs summit to do......:rofl: :doh:
     
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  5. gus-lopez

    gus-lopez Funster

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    Could fill them plant pots ? :LOL:
     
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  6. wizzer59

    wizzer59 Funster

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    :Ta2:(y)(y)(y)(y)(y)
     
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  7. hilldweller

    hilldweller Funster Life Member

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    He would if he could find a circular panel.
     
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  8. Techno

    Techno Funster Life Member

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    I'm in the process of jet washing and re oiling the decks so no point creating more stuff to shift just yet
    [​IMG]
     
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  9. Techno

    Techno Funster Life Member

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    Usually looks like this and we can't get much further off topic although it could be regarded as Sun related :LOL:
    [​IMG]
     
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  10. John Laidler

    John Laidler Funster

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    Interesting result although why there is a significant difference when it is cloudy seems odd. Do you know what the explanation is or was it perhaps just a fluctuation in the cloud level?

    But whether putting them in parallel is right for every MH depends perhaps on whether you are going to use any existing wiring. For example, if a MH already has a panel and the wiring going to the controller is sized for that panel it may be better, if adding a second panel, to add it in series so the current remains the same. If fitting new thicker wiring perhaps parallel is better.
     
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  11. Techno

    Techno Funster Life Member

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    Probably a slight change in light level.
    Whether it is one two three or more panels most installers use a minimum of 4mm so adding a panel makes no difference. If anything wiring in series requires smaller cable than in parallel.EDIT like you said
     
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  12. Lenny HB

    Lenny HB Funster

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    Providing reasonable size cables are used I don't worry too much about cable size. On my van I have 2 x 100 Watt panels in parallel, cable run is about 5m I only used 4mm cable. Working on the theory that in mid summer I can get a max output of around 10 amps with 4mm cable about 5% loss or 0.5 amp, not worth worrying about. In winter winter with say 4 amps output the loss will be 2% or 80ma again not worth worrying about.
     
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  13. eddievanbitz

    eddievanbitz Trader - Funster

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    In a "solar farm" situation that is static, I would (if asked) advise that in series is preferable. There is a slight advantage. On a motorhome that potentially could face a new "position challenge" every time the motorhome is moved, I would resort back to parallel.

    In series, if one panel is in shade in the morning, and say the other "(assuming that there are two panels fitted) is in shade in the afternoon, you'll have a problem.

    In parallel the worst case is that you would only potentially benefit from the output from one panel.

    Great photos, and excellent advice Andy :)
     
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  14. Don Quixote

    Don Quixote Funster

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    Great post, enjoy reading and looking at pictures on this subject. Thanks
     
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  15. OldAgeTravellers

    OldAgeTravellers Funster Life Member

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    Great Post Andy, thanks very much. sorry I am a bit late to the party. Unfortunately there are obviously limitations because you only had one set-up.
    Unfortunately it does not answer the question I would have liked answered.
    I always assumed in normal conditions there was no benefit between the two except that I believe that in series the cut in voltage of the controller would be achieved sooner andcontinued longer so perhaps the series would switch on and start charging at say 8am and switch off at say 7pm whereas the parallels connection would be some time after switching on and some time earlier switching off. At a certain light level the panels would be producing say 9volts so in parallel the controller would see 9 volts and not switch on but in parallel the controller would see 18 volts so would be producing a charge. That is the only reason for my belief in parallel connection. In fact I once met a German guy parked up under a street lamp in Paris who swore that he was getting a charge from the street lamp (I didn't chech his controller) and he was sure that it was because he had an MPPT controller and his panels were wired in Paralel. It would have been good if you could have tested this point but it would of course mean two setups to be meaningful. But thanks for the, as usual, great write up. If at some point though you find yourself with four identical panels and two MPPT controllers and a couple of batteries it would be great if you could test it out until them I remain convinced that series is best if the controller can take the maximum possible voltage of the panels.
    Regards,
    Steve
     
  16. John Laidler

    John Laidler Funster

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    Following your logic, which I like, series should be better as under poor light the two 9 volts would be added to make 18, making enough for a charge?

    However, I am not sure PV cells work like that, I think under low light levels they still produce a highish voltage but they can only produce a low current.
     
  17. TheCaller

    TheCaller Funster

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    Correct, but a low current is better than no current at all. Very useful when a van is standing in winter without moving for a few weeks & no access to EHU. At least it will start when you get back to it.

    To be fair, it would be a pretty awful winter if parallel panels didn't manage this too.

    My winter use of the van is the about the worst possible - occasional short distance trips, overnight stays & no EHU.
     
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  18. OldAgeTravellers

    OldAgeTravellers Funster Life Member

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    Hi DBK,
    I am sure panels slowly increase their voltage from a switch on point which is around the 9 volts as the light level increases up to the maximum of around 17 volts which is the usual open circuit maximum, but can't find the reference to it at the moment, but of course you don't see it because the controller does not pass current until the voltage can be above the batteries. The actual benefit may be tiny which is why I would have liked to see it in Andy's tests but as I said, it would only be meaningful if there were two identical setups, one in series one in parallel to compare. But of course I may be totally wrong with the last few brain cells left finding the wrong bit of data.
    Steve
     
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  19. tonyidle

    tonyidle Funster

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    I'm not certain that the panel voltage needs to be above that of the batteries. That was always the case with simple controllers but is it the same with MPPT? There is no need for that to be the case and I thought that an MPPT controller was able to use whatever power (AxV) was available.
     
  20. bubble63

    bubble63 Funster

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    the whole idea is that a MPPT controller inverts the the DC steps it up and then rectifies it back to DC at a higher voltage to charge the battery
    electricity won't flow up hill, i.e. 11 volts won't go into a 12v battery it has to be 12.1v or more to go in
    I think o_O
    so in effect on a dull day the panel produces 10v, say, the MPPT gets it higher to go into the battery, of course OHM's law means the amperage will be less, but hey ho its charging when an ordinary charger wouldn't be.
     
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