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  1. #11
    Join Date
    Jul 2004
    Location
    Sussex-Hampshire coast
    Posts
    863

    Default Re: Sizing my solar panel

    On a similar boat also on a Chichester harbour mooring, weekend use and a couple of weeks away in the summer we have found a 50W pannel on the coach roof works well. IMHO you wont need much more. It brings the battery back up after a weekends use and allows the fridge to be left on for a few days in sunny weather at anchor without much worry.

  2. #12
    Join Date
    May 2007
    Posts
    32,692

    Default Re: Sizing my solar panel

    Quote Originally Posted by seumask View Post
    On a similar boat also on a Chichester harbour mooring, weekend use and a couple of weeks away in the summer we have found a 50W pannel on the coach roof works well. IMHO you wont need much more. It brings the battery back up after a weekends use and allows the fridge to be left on for a few days in sunny weather at anchor without much worry.
    But the OP doesn't have a fridge.
    He's just got the stuff we used to have before anyone had solar.
    The first panel I bought IIRC was 10W. That made a huge difference to keeping my old batteries afloat during the winter.

  3. #13
    Join Date
    Apr 2018
    Location
    Mooring, Faro
    Posts
    503

    Default Re: Sizing my solar panel

    Quote Originally Posted by lw395 View Post
    But the OP doesn't have a fridge.
    He's just got the stuff we used to have before anyone had solar.
    The first panel I bought IIRC was 10W. That made a huge difference to keeping my old batteries afloat during the winter.
    The OP, assuming one of his batteries is kept for engine starting, only has 110ah domestic. Whilst a small panel will top up the batteries during the week (we had 25w for that purpose when weekend sailing) , it won't keep up during a summer holiday cruise so I would suggest fitting the largest he has space for.

  4. #14
    Join Date
    Feb 2009
    Location
    Greece (Aegean)
    Posts
    2,318

    Default Re: Sizing my solar panel

    Quote Originally Posted by cpedw View Post
    That's a useful guide (about a factor of 10 from mid winter to summer) but what size is the panel it's based on and what location (does location make much difference?)?

    Derek
    Apologies, I was in a bit of a hurry earlier and forgot to add these vital details. Calculation results were for a 100W rigid panel flat on deck in Solent area. You might exceed these figures in an odd year but that's unlikely. Shading will obviously reduce the output. Other losses have already been included.

  5. #15
    Join Date
    Apr 2005
    Location
    Shropshire
    Posts
    8,155

    Default Re: Sizing my solar panel

    I had a single semi flex 20w panel for similar sailing profile and it kept the battery well charged and returned to full charged in between visits to boat. However, times change and prices have fallen so I would now install 2 x 50w panels which would allow limited use of my cool box. Get a good pmw controller too.

  6. #16
    Join Date
    Oct 2017
    Location
    solent
    Posts
    1,943

    Default Re: Sizing my solar panel

    We just bought a 50w panel, and controller for 47 from a marine supplier. Our intention is to buy another 50w panel and controller later as for our own reasons we want two stand alone systems.
    Had I realised how cheap things had become we would have done it before.
    Our boat on swing moorings on the hamble has a huge leak due yo the coachrood being hacked about, so knowing the battery stays charged is one less thing to worry about. It is just the float switches on the pumps that keep me awake at night now

  7. #17
    Join Date
    May 2009
    Location
    Wirral
    Posts
    524

    Default Re: Sizing my solar panel

    I started off with a 10w panel when prices were expensive,this kept the batteries topped up in the summer but struggled in the winter,then added another 10w panel which maintained them all year round.I have just recently purchased a 30w lensun panel
    which will replace the original 10w panel on the hatch garage so will end up with 40w total.
    The boat is 23ft with basic electronics and two 85amp batteries.
    Leisure Owners Association

  8. #18
    Join Date
    Oct 2002
    Location
    Plymouth
    Posts
    7,765

    Default Re: Sizing my solar panel

    Quote Originally Posted by FairweatherDave View Post
    .....

    So what size panel, 20W, 50W, 100W or more? I can squeeze a 100W panel in front of the spray hood. Would appreciate some opinions as you can do all the calculations based on equipment and a rigid 6 hour sail but guestimating actual usage seems more random. Think of our use as Solent pootling rather than routine cross channel raids...........

    I seem to have similar requirements to you and usually top the batteries up via a smaller Aerogen which works exceptionally well on a swinging mooring. On a marina, this season, I have swapped it for a 10W panel which has been very good but this has been a sunny season and I expect it will be of marginal use over the winter. This does not matter much as I shall be ashore.

    As noted above, you probably don't need anything at all if you use the engine regularly but it is nice to have. On long slow sunny passages the little panel halves my power consumption; I have it on a movable mount to roughly catch the best light. However I have used the engine so much, in this summer of no wind, that it hardly mattered.

    Do fit something like the Nasa Battery Monitor, if you don't have one already, a very practical piece of kit and greatly entertaining if you have an adjustable panel.

    Cutting to the chase, I would fit a 20W panel and see how I got on, I think you would probably be happy with that but, if not, it is easy to fit a second one later. The coachroof is a prime spot for a folded dinghy but if you seldom make longer passages this may not be a consideration.

  9. #19
    Join Date
    Sep 2009
    Location
    Solent
    Posts
    1,228

    Default Re: Sizing my solar panel

    This is all really helpful stuff. Thanks. Really haven't decided which way to go yet. Since we don't actually use the sprayhood the panel is not exactly hidden so ideally from an aesthetic point of view I'd like a 50w, but we can squeeze a 100w if we wanted. Need to head to the boat with my measuring tape. Wish I didn't sit on the fence so much, but a nice problem to have

  10. #20
    Join Date
    Jan 2011
    Posts
    4,917

    Default Re: Sizing my solar panel

    I have semi-flexible ones, and in the winter I find they work better hung over the dodgers than on the top because the sun is so much lower.

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