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Adding a solar panel

Discussion in 'Ask All Sailors' started by mihaso, Dec 5, 2018. Add this thread to a FAQ

  1. mihaso

    mihaso

    Joined Apr 24, 2017
    14 posts, 0 likes
    Oday 25
    CA Montreal
    Hi,
    Quick question about solar panels.
    What specs do I need for a to keep my batteries charged?
    I just need something to keep the batteries from draining when I'm not using the boat, and to replenish it if I use the boat for a weekend, and leave it idle for a week.
    I am using a car battery and an AGM 100Ah connected in parallel.
    At this point I don't have another way to charge the batteries but my outboard's alternator.
    Since I can only sail in weekends, the boat sits idle most of the time and the batteries slowly drain, and likely get damaged. I suspect the AGM is pretty much dead but need a system to keep the charge first, before I get another battery.
    Thanks,
     


  2. Charlie Jones s/v Tehani

    Charlie Jones s/v Tehani

    Joined Mar 1, 2012
    1,525 posts, 459 likes
    1961 Rhodes Meridian 25
    us Texas coast
    I lived aboard and cruised full time for almost three years with a 32 watt panel. If I was to buy a new one, I'd go to a 50 or 60 watt. But then I'm very frugal with electric. I do charge phones, and hand held GPS units plus some radio time. For what you mention, a 50 watt should be fine. Be sure to use a controller between panel and batteries so the panel doesn't over charge during the week. I have a Morningstar Sunsaver 10 in my circuit, and have been completely satisfied with it.
     


  3. mihaso

    mihaso

    Joined Apr 24, 2017
    14 posts, 0 likes
    Oday 25
    CA Montreal
    Thank you for the quick reply Charlie,
    I will definitely get a controller.
    Would 12V panel suffice? I understand I need the source to be > 12V, but I don't know if a controller takes care of that, or if the panel must be greater than 12V.
     


  4. rgranger

    rgranger

    Joined Jan 19, 2010
    5,617 posts, 1,267 likes
    Hunter 26
    US Smith Mountain Lake
    This is what I did for my H26... I think mine is a 25W panel but I honestly don't remember. My battery has stayed topped off since. IMG_2132.JPG 2016-03-07 16.02.11.jpg IMG_2139.JPG
     


  5. BarryL

    BarryL

    Joined May 21, 2004
    715 posts, 30 likes
    C&C 110
    US Mt. Sinai, NY


  6. mihaso

    mihaso

    Joined Apr 24, 2017
    14 posts, 0 likes
    Oday 25
    CA Montreal
    Great, thank for your replies.
     


  7. markwesti

    markwesti

    Joined Jun 24, 2014
    55 posts, 15 likes
    Westsail 28
    72 Us Long Beach , California
    What is the car batt.? Sealed , flood acid ? I would not mix a AGM with anything other than another AGM . Is your motor a pull start ? Take a look at this guys site https://marinehowto.com/
    Here is my set up (note Moncrystalline) https://www.ebay.com/p/HQST-12-Volt.../1252404374?iid=163028198842&var=462132347315

    And here is my controller (note MPPT) . https://www.altestore.com/store/cha...MIjfaC5a6J3wIVgqDsCh2k8gX3EAQYASABEgL3b_D_BwE
    This set up is only good for one battery , in my case 2 6v T105's in a series . There are other controllers that will handle more than one battery . For mounting the panel I made a simple frame out of Oak that clips onto the life line with a strut going down to toe rail .
     


  8. mihaso

    mihaso

    Joined Apr 24, 2017
    14 posts, 0 likes
    Oday 25
    CA Montreal
    I am debating the wisdom of having a car battery and marine battery in parallel. That's the system I inherited from the previous owner. But I don't know enough about marine electric systems yet, so I might be actually wrong about it being in parallel or badly configured.
    The batteries are connected to a 1/2/all switch. They are in parallel only in "All" position,
    My engine is pull start as well, so I could get rid of it, but still mulling the configuration.
    I'll also buy a marine electrics book with the solar panel, save on shipping costs :)
     


  9. Sailm8

    Sailm8

    Joined Feb 21, 2008
    1,565 posts, 218 likes
    Hunter 29.5
    US Punta Gorda
    Solar is very seductive. Once you get a panel you start to say "If I got another panel I could..." I would recommend a controller that can handle the amps of a larger array just i case.
     


    rgranger likes this.
  10. markwesti

    markwesti

    Joined Jun 24, 2014
    55 posts, 15 likes
    Westsail 28
    72 Us Long Beach , California
    I was asking if your motor was pull start because I like pull start . Less weight , less drain on the batts. , plus it can double as your dingy motor if it's around 6hp .
     


  11. rgranger

    rgranger

    Joined Jan 19, 2010
    5,617 posts, 1,267 likes
    Hunter 26
    US Smith Mountain Lake
    Solid advice!
     


  12. Ron20324

    Ron20324

    Joined Jan 22, 2008
    6,512 posts, 705 likes
    Beneteau 323
    US Annapolis MD
    The wisdom is DO NOT mix types and ages of batteries:badbad:. They should be the same battery, even the same age as per the sticker that should be on the case with a month/year on it.
     


  13. mihaso

    mihaso

    Joined Apr 24, 2017
    14 posts, 0 likes
    Oday 25
    CA Montreal
    That's true, I find that info everywhere I look.
    On the other hand, every single boat does have a starter battery and a battery bank, and I can't find anywhere how that is done correctly.
    I'll get a copy of "Boatowners Mechanical and Electrical Manual 4/E" maybe it will have some answers.
     


  14. Captain Larry-DH

    Captain Larry-DH

    Joined Jun 14, 2010
    496 posts, 199 likes
    Quorning Dragonfly 1200
    US home
    To answer a few of your questions:
    1) a "12v" solar panel will have an open circuit voltage around 17v if measured with a voltmeter. This is designed to charge a 12v battery (which is really 12.6+v).
    2) You can mix batteries of chemistry type and age (in parallel) but it is not optimal, because they have differing charge characteristics and charge acceptance rates. You should connect your solar panel to the "house" bank and the engine alternator to the start bank. They will be separated (and charged only from the direct-connected charge source) unless you choose to use the "both" position on your main battery switch.
    3) You can get a "battery combiner" also known as an "automatic charge relay" to combine the batteries only when one or the other is well charged. A battery that is near full charge will charge at a float voltage of about 13.2v or above. Once one battery or the other reaches that voltage level the combiner will close the relay so that both batteries are connected together, and to the charge source... thereby enabling the second battery (bank) to start receiving a charge also. If one of the batteries goes below 13.2 , or whatever the set-point threshold (this can only happen when not charging, or when discharging) the relay will open again, so if one battery is discharging heavily it will prevent both from discharging. Here's one example of such a device https://shop.sailboatowners.com/prod.php?943
     


  15. Ken Cross

    Ken Cross

    Joined Oct 24, 2010
    1,858 posts, 281 likes
    Hunter 30
    US Everett, WA
    I see confusion here. Take a look at our own MainSail's page for a good description of a properly wired battery switch.
    https://forums.sailboatowners.com/index.php?threads/1-both-2-off-switches-thoughts-musings.137615/
    Since you have a pull start motor the engine start battery is of no value. I suspect you need to replace both batteries and add the solar and charge controller. You can take your batteries to any battery shop for a load test if you are in doubt.

    I would use the battery switch just as a battery shutoff if it were me.

    Ken
     


    Captain Larry-DH likes this.
  16. mihaso

    mihaso

    Joined Apr 24, 2017
    14 posts, 0 likes
    Oday 25
    CA Montreal
    That is some excellent info, thank you guys!
     



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