Why fit a diode inline from solar regulator

Discussion in 'Solar Power' started by fred flintstone, Sep 24, 2016.

  1. fred flintstone

    fred flintstone Funster

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    I have bought a van with 2 small solar panels on top, approx 40w each.
    They connect to a cheap regulator.
    Where the wire leaves the regulator, heading for the positive side of the battery, someone has put a diode inline.
    I have wired a few panels and never used a diode.
    Is it anything to do with me having a Schaudt IT268-2 control unit?
    The main thing is would it be ok to remove this diode from the system?
    Help appreciated.

    regulator.JPG
     
  2. WillH

    WillH Funster

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    It's there to prevent reverse current which may damage the panels.
     
  3. icantremember

    icantremember Funster

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    I thought they would be built into the regulator .... maybe previous owner had problem with the regulator.
     
  4. WillH

    WillH Funster

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    Depending where the diode is fitted it may also protect the regulator, doesn't do any harm and in operation will make no difference.
     
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  5. Abacist

    Abacist Funster

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    The intention is surely to prevent the reverse flow of current from the battery at night or when the panels are not producing power. As already said one would expect the regulator to do that or for their to be diodes in the box of tricks on the panels.
     
  6. Techno

    Techno Funster Life Member

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    Unnecessary
     
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  7. pappajohn

    pappajohn Funster Life Member

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    Panels normally have a diode fitted in the panels connection box under the panel.
    A 40w panel is usually such a low output it doesn't really need a diode as they are usually free standing and don't require a controller
    I don't think I ever saw a mountable 40w panel.

    Anyway, as a pair of panels (total 80w) are being used the charge current will be too high to omit a diode so it's been fitted at the easiest place.

    Leave it in place.
     
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  8. fred flintstone

    fred flintstone Funster

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    Thanks for all your replies. I think the regulator should take care of this. It looks like one more thing to go wrong IMHO.
    Thanks again
     
  9. Techno

    Techno Funster Life Member

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    Yes they simply do not make regulators that allow reverse flow of current that would be stupid
    Edit
    And not fit for purpose
     
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  10. vwalan

    vwalan Funster

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    but they did years ago . and panels didnt have diodes on the back either.
    regulators were more an on off switch thing . i have a few here .
    unfortunately uk is a bit behind and missed the early years of solar.
    diodes were the way 20 years ago.
     
  11. Techno

    Techno Funster Life Member

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    I've yet to find a regulator that says in the instructions
    And by the way you'll need to buy and fit your own diode because our regulator is a piece of junk

    Btw the one pictured can be found for sub £10 but that's no excuse
     
  12. pappajohn

    pappajohn Funster Life Member

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    That may be so Andy.....
    BUT....If you have more than one panel what's to stop current from one, in full sun, pumping current into its partner which is in full shade ?
    A regulator can't stop that, but looking at the pic that diode won't stop that happening either.
     
  13. Techno

    Techno Funster Life Member

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    Correct we're only concerned with the diode in question which is unnecessary
     
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  14. vwalan

    vwalan Funster

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    yes that is a modern one . but certainly years ago regs bought needed a diode.
    like i said they reached a voltage in batteries and switched off when battery voltage fell they came on again .
    panels were hundreds and regs in maroc cost about 5quid .
    anyone starting on solar then would possibly stil think fit a diode.
    i fitted one of the junk regs14 years ago . still have it it still works . but not in my trailer . i use it ona spare panel as a battery charger at home .
    things have moved on i admit.
     
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  15. Wildbill

    Wildbill Funster

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    dose it work yes is it broken no dont try to fix something that works
    bill
     
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  16. Techno

    Techno Funster Life Member

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    The most likely scenario is the previous owner read some misinformation on a forum about why his batteries were going flat overnight :LOL:
    Yes mate you should always fit your own diode don't you know
     
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  17. vwalan

    vwalan Funster

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    or is it your lack of older knowledge ?
    i,m not knocking you really you do a grand job of helping people . a credit to you.
    but years ago it was normal to fit diodes . . yes today not necessary but a bit of allowance.
    some may be just following the old way.
    i remember seeing batteries boiling over years ago before even the simplest of regulators were around .
    whole villages in morocco relied on just what ever batteries they could muster.
    came back to uk and hardly anyone knew solar really worked .
    how times have changed . uk is filling fields with solar and in morocco thety are turning the desert into green fields . solar is almost a thing of the past there.
     
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  18. Gromett

    Gromett Funster

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    There are two places you can fit a diode for a solar system, one is called a blocking diode and the other a bypass diode.

    Blocking diodes are to stop the battery pushing current through the solar panel at night. These are essential if you don't have a regulator installed.
    Bypass diodes are fitted in parallel with the solar panel but reverse polarity. These are only of use in a multiple panel install where they are installed in series. This is to prevent a single panel being shaded limiting the output of the others.

    If you have a regulator like the one pictured above there is absolutely no use for a diode where they have one. Every circuit diagram I have seen for a PWM solar charge controller uses a mosfet output and these prevent the reverse flow of current by their very design.

    So if you have no charge controller then yes, fit a diode for solar panels over about 12 watts. Below that the solar panels are too puny to do any damage. You can probably get away without a diode up to maybe 40 watts but I wouldn't risk it. With a charge controller this is not necessary.

    I totally agree with @Techno on this one.
     
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  19. pappajohn

    pappajohn Funster Life Member

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    But at the same time it's doing no harm.
    Maybe some miniscule resistance maybe but not causing problems....until it fails.
     
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  20. Wildbill

    Wildbill Funster

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    Probably got it on her ;) I did when I fited my panel
    Bill
     
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