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Thread: Solar panels

  1. #1
    Join Date
    Aug 2013
    Location
    Felinheli, N Wales
    Posts
    249

    Default Solar panels

    Next job on my list is to fit a solar charger to keep my domestic battery topped up as it tends to run flat over the course of the season because i don't tend to motor much and i'm rarely on 240v to use my charger. I typically run my GPS, combi log/depth, VHF and wind instruments for a few hours each week and on top of that sometimes use the autohelm. The battery is 110 Ah. Would a 10w panel be enough to keep the battery topped up with occasional help from the engine charging system or do I need to go bigger? Also can anyone recommend a panel and regulator that doesn't cost an arm and a leg because I've already spent too much this year apparently.

  2. #2
    Join Date
    Nov 2009
    Location
    UK
    Posts
    2,055

    Default Re: Solar panels

    Quote Originally Posted by HenryEDM View Post
    Next job on my list is to fit a solar charger to keep my domestic battery topped up as it tends to run flat over the course of the season because i don't tend to motor much and i'm rarely on 240v to use my charger. I typically run my GPS, combi log/depth, VHF and wind instruments for a few hours each week and on top of that sometimes use the autohelm. The battery is 110 Ah. Would a 10w panel be enough to keep the battery topped up with occasional help from the engine charging system or do I need to go bigger? Also can anyone recommend a panel and regulator that doesn't cost an arm and a leg because I've already spent too much this year apparently.
    I have a 10watt Photonic Universe panel and regulator available on Amazon for about 45 which keeps my 110h battery fully charged even in this sunless Argyll 'summer'.
    http://www.amazon.co.uk/Photonic-Uni...R2K/ref=sr_1_2

  3. #3
    Join Date
    Aug 2013
    Location
    East Coast
    Posts
    1,642

    Default Re: Solar panels

    Not sure about the arm and a leg bit but I recently got (having seen it recommended) a Victron 75/15 controller.

    This is a proper MPPT controller (many on Ebay that claim they are, are not) with a defined charging system.

    I am a saddo over charging systems and voltages and watched it one sunny day ("Heath Robinson" system with a hard, framed 30W panel, the controller and linked to 3x85AH domestic bank) go through its charging regime.

    Very impressive and I would recommend one.

  4. #4
    Join Date
    Sep 2001
    Location
    Home Berkshire, Boat Hamble
    Posts
    8,127

    Default Re: Solar panels

    Quote Originally Posted by ianj99 View Post
    I have a 10watt Photonic Universe panel and regulator available on Amazon for about 45 which keeps my 110h battery fully charged even in this sunless Argyll 'summer'.
    http://www.amazon.co.uk/Photonic-Uni...R2K/ref=sr_1_2
    So many variables to take into consideration - mainly how long do you use those things for and is it every week and do you use th engine at all every week. What about domestic lighting / domestic radio etc. Excluding the autohelm you are probably using no more than 2A so assuming 10 hours of sailing that 20 Ah to replace. Assuming that the engine covers the autohelm / lights useage then it really comes down to over what period do you want to replace the 20 Ah.

    Nigel Calder says that it should be replaced in 24 hour cycle which suggests something like a 60W - 80W panel for summer use but his book is aimed more at liveaboards. It's certainly good the battery to be charged back up quickly buts that's a big panel and unless you feel the need to live off grid during a cruise might be too much.

    IF your aim is simply to replace a weekends usage by the following Friday then you are looking at replacing 2 days usage ( 40 Ah) over 5 days so will need to produce 8 Ah a day - suggests a panel of 25W-30W.

    If your use is less frequent you could probably go further down towards a 10 W panel but could take 2 weeks to recharge your battery in typical summer conditions.

    However - If you do enough motoring when come back to your mooring to recharge the battery pretty much fully then that 10W panel is probably enough to just keep you topped up and mke up the last 10%. With a 110 Ah Battery you could get away without a regulator but if you want to maximise the charge ( or if you bigger than 11W then a regulator would be needed)

  5. #5
    Join Date
    Aug 2013
    Location
    Felinheli, N Wales
    Posts
    249

    Default Re: Solar panels

    Lots of good advice there. I use the boat a lot for pottering around during the evenings so the boat is in more or less continual use rather than used for a long stint then left for a week. It might be only an hour or two of use very other day with occasional motoring onto my mooring and when the wind dies/tide is too strong. I see the advantage of having a large panel for charging quickly for the battery's sake but space is also a consideration because the boat is wee.

  6. #6
    Join Date
    Sep 2001
    Location
    Home Berkshire, Boat Hamble
    Posts
    8,127

    Default Re: Solar panels

    Quote Originally Posted by HenryEDM View Post
    Lots of good advice there. I use the boat a lot for pottering around during the evenings so the boat is in more or less continual use rather than used for a long stint then left for a week. It might be only an hour or two of use very other day with occasional motoring onto my mooring and when the wind dies/tide is too strong. I see the advantage of having a large panel for charging quickly for the battery's sake but space is also a consideration because the boat is wee.
    So realistically you will take no more than 5-10 Ah out.

    My suggestion would be to locate a suitable site on deck for the panel. You are looking for a large flat area with minimal close shading overhead. Don't bother with trying to orientate the panels as on the mooring the boat will swing anyway - just go for flat and hope for the best.

    Once you have the dimensions for your mounting location - get the biggest panel that will fit in the space. You really want a semi flexible panel - ideally that you can walk on. 10 W - 20 W panel should be fine but by getting the largest you can fit it gives you the ability to add more electrical gear later. It also means that during the spring / autumn when you may be getting a bit less charge each day your boat is still getting enough - It also should compensate for any shading you experience from mast / boom etc.

  7. #7
    Join Date
    Jul 2003
    Location
    West Australia
    Posts
    11,493

    Default Re: Solar panels

    I would suggest that a 10w panel will go a long way to replacing your usage. If not the engine should also help. As said it is all about location and mounting. I have had a fair bit of success with a panel with bungees attached mounted over my sail cover on the boom. I remove it before sailing. If you do go for a 10w then it can be connected without a controller with your big 110 AH battery. No more than 10w and not on a smaller battery.
    If at some stage you decide you want more power then additional panels can be connected in parallel and while panels are cheaper per watt in larger sizes that difference is not so huge. So 2x 10w not much dearer than 1x20w. Ultimately it will be aht you get the urge to buy. I have had some good success from China for small panels. good luck olewill

  8. #8
    Join Date
    May 2011
    Location
    Surrey
    Posts
    721

    Default Re: Solar panels

    If it helps.. from my measurements - I have a setup of a pair of 80w panels on a garden shed at home. From them on a GOOD day I will generate over a complete day about 850w/hr, my monthly total for May was 15KWh and June so far 11Kwh. A 110AH battery is around 1kw/hr of useful energy (even then to discharge that much frequently would shorten the life).
    If you really do absolutely minimal with the battery then 10w may do, but I don't think I'd be happy with anything less than 20-30. IMHO of course and based on what I typically do with batteries etc.

    If it helps here is a pretty neat and cheap MPPT charge controller
    http://www.ebay.co.uk/itm/MPPT-20A-1...item20e0d6ce55

    It's what I have (but actually don't really use it now as I'm using a small grid tie inverter instead.) but what is smart is that you can series two 12v panels to make 24v~ and the controller will step this down to 12v to charge a battery etc, this means you can keep the pv side higher voltage and get less current drop than with two parallel 12v panels (obviously at low current this is minimal).

  9. #9
    Join Date
    Sep 2006
    Location
    West Yorkshire
    Posts
    2,679

    Default Re: Solar panels

    I have a 40W panel on my Centaur with 2 x 100Ahr batteries, swinging mooring no 240V.

    My consumption is similar to yours except we tend to use the boat for a week or two per visit ie. lights, GPS, VHF, autopilot no fridge.

    When I do hook up to 240V the charger very quickly goes onto float charge.

    The little Lidl panel I had before (10W IIRC) only really prevented the battery self discharge which was useful enough, but I did need to find 240V more often to charge the battery properly.

    I think you will need something a bit bigger than 10W.
    Bob.
    Any bull in this post may be composted.

  10. #10
    Join Date
    Jun 2015
    Location
    Tarbert
    Posts
    547

    Default Re: Solar panels

    Thanks for the charge controller link above. Been looking at a similar setup to keep a 110Ah service battery topped up. We run instruments, VHF and hopefully the autopilot when it is working properly! Lights in the evening also plus small amount of water pump. I have also ordered a 50w semi flexible panel from the same seller, so total cost of 148. Seems pretty reasonable given comparative costs from other websites.

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