Solar panels,regulators, am I doing it right?

Discussion in 'General Electronics Chat' started by Winnebago Sam, Jun 6, 2009.

  1. Winnebago Sam

    Thread Starter New Member

    Jun 6, 2009
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    I've just bought three solar panels for my motorhome. They are rated at 17/18w.I've also bought a 6amp(60w) regulator. They are to charge two 110ah batteries.

    Question 1: Do I wire the solar panels in series or in parallel? At the moment I've got them wired in parallel.

    Question 2: When I put a cicuit tester on it to see what's what, I was getting 17v going into the regulator but only 9.8v going out to the batteries. So, will this fully charge my two big batteries? Surely it should output something like 13v shouldn't it?

    Question 3: I've read advisories saying don't have it wired up while the engine is running,would that be such a bad thing? I am toying with the idea of putting in a blocking diode between the regulator and the batteries. Would this prevent any possible damage to the regulator and solar panels, and do away with the need to disconnect before running the engine?
     
  2. DC_Kid

    Distinguished Member

    Feb 25, 2008
    638
    9
    for parallel panels i would seperate them from each other with diodes. this will prevent one panel from feeding into the other. what is the panel voltage rating?

    what was the battery voltage before you hooked them up to the regulator? do you have a part # for this regulator?
     
  3. radiohead

    Active Member

    May 28, 2009
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  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
    4,172
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    My post just went Poof, so I'll just give you solar panel plot to show relationship of voltage/current and power. V scale will be close to yours, & current from graph X 13 close to yours. Max. power as shown is around 13V. A voltage regulator should supply V boost , when needed, to keep panels operating near max output & charging V as needed by battery state of charge, dropping down to float at full charge.
     
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    That's a poor way to advertise your product. :(

    Do you think that someone using solar panels and regulator in his MOTOR-home will buy your solar street lights? Or are you just spamming every thread with "solar" in the title??

    edit; (my post above now makes no sense as the spammer's post was removed)
    :)
     
    Last edited: Jun 13, 2009
  6. Wendy

    Moderator

    Mar 24, 2008
    20,766
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    He went dark.
     
  7. Heaven Net

    New Member

    Jun 26, 2009
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    0
    I was recently give a Solar Regulator that had been thrown out; its made by
    Go Power! Electric Inc.
    Doing a quick check I determined that the possible reason it had been tossed
    is it had a short across the Solar inputs ... not knowing how these
    regulators work I decided to do a bit of reverse engineering. To my dismay
    it appears that this device shorts the solar panel out when the battery is
    deemed fully charged. Because they also have a pair of blocking diodes this
    would certainly stop the charging however I wonder if this is potentially
    damaging to the solar panel.

    Attempting to find an answer to that by reading specifications on PV panels;
    most specs give a short cct current, and an open cct voltage and specify
    that the operational voltage/current is somewhere in the middle of that.
    Being that they provide a Short cct spec sort of implies they can be
    shorted.

    To make a long question short;

    I am trying to understand;
    A) Why shorting a panel is an acceptible way to shut off the charging
    B) Is there a Solar Cell Equivalent CCT (similar to a battery) that can be
    used to mathematically predict the characteristics of the cell.
    C) Why shorting out a cell doesn't fry the cell

    bxdobs wrote:
    > I was recently give a Solar Regulator that had been thrown out; its made by
    > Go Power! Electric Inc.
    > Doing a quick check I determined that the possible reason it had been tossed
    > is it had a short across the Solar inputs ... not knowing how these
    > regulators work I decided to do a bit of reverse engineering. To my dismay
    > it appears that this device shorts the solar panel out when the battery is
    > deemed fully charged. Because they also have a pair of blocking diodes this
    > would certainly stop the charging however I wonder if this is potentially
    > damaging to the solar panel.



    I think it is no problem. It just adds a tiny temperature
    rise to the silicon.
    > Attempting to find an answer to that by reading specifications on PV panels;
    > most specs give a short cct current, and an open cct voltage and specify
    > that the operational voltage/current is somewhere in the middle of that.
    > Being that they provide a Short cct spec sort of implies they can be
    > shorted.
    > To make a long question short;

    > I am trying to understand;
    > A) Why shorting a panel is an acceptible way to shut off the charging



    Since the panel is completely power limited, it is cheap and
    reliable.
    > B) Is there a Solar Cell Equivalent CCT (similar to a battery) that can be
    > used to mathematically predict the characteristics of the cell.


    A current source proportional to light intensity in parallel
    with a string of silicon diode junctions. Instead of doing
    this, mathematically, I suggest you simulate it with
    LTspice, a free circuit simulator. It has built in
    functions to display voltage, current and power dissipation.
    http://www.linear.com/designtools/software/switchercad.jsp
    Count the number of cells in series in your panel and use
    that number of diodes. Set the current source to the panel
    short circuit current rating.
    > C) Why shorting out a cell doesn't fry the cell


    They are so inefficient that the electric energy is only a
    small part of the total heating caused by the absorbed
    light. If you want to eliminate that small additional
    heating, you could add a power resistor in series with the
    short that drops just enough voltage to keep the blocking
    diode from conducting. That will move that extra power to
    the resistor. A better way might be to have that resistor
    be the heating element in a water heater, so that you would
    make some use of the energy.
     
  8. DC_Kid

    Distinguished Member

    Feb 25, 2008
    638
    9
    my answers in red
     
    Last edited: Jun 27, 2009
  9. alister

    New Member

    May 23, 2009
    1
    0
    Hi,

    Individual cells are wired in series strings to increase the module's voltage and the series strings are wired in parallel to increase the module's current. The back of the module is protected by another sheet of tempered glass or a long lasting material such as Tedlar.

    The series parallel connections are passed through the protective backing and then wired to a weather proof junction box which is permanently mounted to the back of the module. The junction box is where the module's output connections are made.

    ___________________________

     
    Last edited by a moderator: Jul 1, 2009
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