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Boat Solar Panel 12V

Discussion in 'General Electronics Discussion' started by tse, May 26, 2013.

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  1. tse

    tse

    2
    0
    May 26, 2013
    Hi guys, new to the forums here.

    Anyways, I have a boat that I want to charge the 12 volt system with a solar panel. I have heard of people doing this before, and I was told by someone in the field who said I need both a solar panel and a voltage regulator (12 volts)?

    What are the exact specs of the solar panel and regulator that I need to be successful? And also, where is some options to buy these parts? Any electronic parts online stores that are both cheap and reputable? Links would be wonderful!
     
    Last edited: May 27, 2013
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
    2,838
    Jan 21, 2010
    You want a solar panel and a MPPT solar regulator.

    One place to get the regulator is http://futurlec.com, but they're available all over the place.

    If you're going to have multiple panels, make sure they are identical and placed in parallel. Also they should be oriented (i.e. facing) in the same direction.

    Get a regulator that is generously speced. I.E. if you have 2 panels rated at 4A short circuit current, get a 15A (or more) regulator. I don't recommend running things right up to the limit.

    Also, try to find a MPPT regulator that will drop your load if the batteries get too discharged. Batteries are expensive to replace and a short time without power may be preferable to a long time without it.

    There's lots of other considerations. But these are the basics.
     
  3. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
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    Jan 21, 2010
    Oh, the panels. If you have a 12V battery and an MPPT regulator, then you want panels with at least 18V open circuit voltage. These are often sold as "12V panels" anyway).

    For every WH you want to get out pf your batteries, you probably need to have panels with 1/2 that value rating in watts.

    e.g. a constant 10W load for 24 hours is 240 Wh, so a 120W panel is sufficient. This will allow for as little as 4 hours of equivalent full sunlight per day and for the inefficiencies of charging lead acid batteries.

    For the same 240 Wh daily load, batteries should be 480Wh at least, preferably double again to allow for a day without un (or multiplied by a larger figure if you expect more days in a row without sun). (240 Wh for a 12V battery = 20Ah -- 240/12)

    And remember that this is based on a tiny 10W load. That would be maybe enough for maybe a radio and a 1W LED light, but nothing much else.
     
  4. tse

    tse

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    May 26, 2013
    Last edited: May 27, 2013
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    I would say that looks pretty good.
     
  6. JMW

    JMW

    90
    3
    Jan 30, 2012
    Before you buy a panel and charger, you must determine what you are doing. Are you a weekend boater or liveaboard? What are your electrical demands? What is the insolation for your area or where you intend to sail? How many and what type of batteries do you have? AGM need a special charger.
    After putting together a realistic system, you can then build what is needed. Many use both solar and wind,
     
  7. woodchips

    woodchips

    43
    0
    Feb 8, 2013
    Umm, you could end up very disappointed. I don't know where you are in the world but the ratings of solar panels seem to be more to do with specmanship than reality.

    On a bright sunny day in the UK at 57 degree north I couldn't get more than 25% of the panel rating out if it.

    I would suggest buying a panel and experimenting. You might be surprised at the size of the panels needed. Buy bigger batteries and ignore the charge controller, if maximum panel output, in reality, is less than the battery trickle charge current then no problems.

    Also be aware that the panels must have 100% view of the sun, no shading at all. The panels are made from series connected solar cells, if one cell in the series is shaded, post, tree, mast etc, then that cell will be high impedance and no charge will be produced from the whole panel.

    Buy a wind generator, works 24/7.

    Bob
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    That's exactly why I mentioned "hours of equivalent full sunlight".

    It equalizes the effects of latitude, and season.

    In the UK in winter, it can drop to around 1 hour. Using that figure would give an appropriately (huge) size array to get the needed performance.
     
  9. woodchips

    woodchips

    43
    0
    Feb 8, 2013
    Full sunlight

    Still don't agree. In my experience, powering a remote building for lighting etc for four months of the winter I got no usable charge at all from the panels. I had eight panels, each 1/3 m^2 connected series parallel to give 24V, and no shading from anything.

    Just because it is light doesn't mean it is full sunlight, anything but. As I said, buy a panel and experiment, you will not be very happy. You really also need an optimum watts load, varying the load to get the best volts/amps product but I never bothered.

    Don't forget that the further north you go the thicker the atmosphere is, and the lower the sun angle also the thicker the atmosphere. Panels seem to be rated at the top of the atmosphere normal to the sunlight, a situation earth bound mortals never enjoy.

    Bob
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,497
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    Jan 21, 2010
    Perhaps you don't understand "hours of equivalent full sunlight". And for an optimum load, a MPPT charger (which I've already mentioned) is essential.

    Google "equivalent full sun hours"
     
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