Recommendations for solar panel?

A

ash2020

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Just about to launch our 20' Hunter Medina for what's left of the season but it's just occurred to me that with a DSC radio, chart plotter, autohelm and a couple of other instruments, the battery will take quite a hammering. I've always had larger boats with inboard engines so charging's never been much of an issue but now I'm thinking we need a solar panel. It'll only be for topping up in between outings but how much power are we likely to need to keep the battery up to scratch. I can work out the current draw but not sure how to calculate how much input is needed between say, weekly trips. Also any makes to avoid? Flexible would be good. Thanks.
 
a. Also lights overnight when anchored. Should be all LED. Small fans. Saving power is easier than adding generation and storage.

b. How much power will you use? Ah=Watts x hours / 12. The tiller pilot will be many times below the rated peak watts, and you don't need to run everything all the time. Don't just automatically turn everything on when you step aboard, and don't leave it on.

c. How much battery capacity? Consider that if lead you can only use 50% of it and you might have a grey day with no solar. Two group 24 batteries might be typical for a 20' boat.

d. How much solar? Take "b" and divide by 5 hours (average, including clouds, shading, and sun angle). About 100 W might be typical for a 20' boat. On a 20' boat finding room for the panels is a challenge. Maybe 50 W on the slider turtle and 50 W on the foredeck.

Don't try to pretend a 20' boat is a 40' boat by puting too much stuff on here. She will be crowded and overloaded. Keep it simple. I have a single 50W panel on my slider and a group 24 lithium battery. It's enough for my 24' trimaran. On my cruising cat (avitar) I have 3 larger batteries and 4 times as much solar, but I have a big roof, more demand, and take longer trips.
 
I have exactly the same instruments as you on my GK29 and had the same on my previous boat, a Hunter Duette. On both a 10W solar panel connected straight to the battery keeps the leisure battery topped up year round, for several day sails per week. If going off for a week or so it probably wouldn’t be enough.
 
PeterV said:
I have exactly the same instruments as you on my GK29 and had the same on my previous boat, a Hunter Duette. On both a 10W solar panel connected straight to the battery keeps the leisure battery topped up year round, for several day sails per week. If going off for a week or so it probably wouldn’t be enough.
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Same.. Hurley 20... very much will depend on the OP's definition of "outing" - day sail, extended day sail, overnighting, etcetc
 
I am going through a session of trying to decide the replacement for an old panel fitted to the deck ahead of the mast on my 38.

You would think that a 38ft boat would have loads of area to accommodate solar ... well not on mine !! Having had smaller boats 19ft and up - I understand OP's question.

So - I suggest to "Ash2020" ....

First try and imagine where on the boat you will fix the panel(s) .. with they be permanent or removable - put in place when not sailing ? Once you have that ...
Second look for the size of panel(s) you can mount and then ...
Third - how to run the cable and where you fit the controller.

I suggest try to maximise the wattage .... there's nothing worse than not having enough !

I suggest 40W as starting point ... more if possible. The reason being that brand claims are way over the real figures usually ... not only that - but the number of hours production reduces overall charge amount as well ..

There are some on YBW who post often about size of their panels (watts) - but many are in better locations to avail of sun ... ie Caribbean etc.
 
I sail once a week and have a 20w panel mounted permanently which keeps the batteries on 100% all year around. If I ever get chance to do some extended sailing I’m going to buy a flexible 40w I can mount on different areas of the boat.
 
thinwater said:
a. Also lights overnight when anchored. Should be all LED. Small fans. Saving power is easier than adding generation and storage.

b. How much power will you use? Ah=Watts x hours / 12. The tiller pilot will be many times below the rated peak watts, and you don't need to run everything all the time. Don't just automatically turn everything on when you step aboard, and don't leave it on.

c. How much battery capacity? Consider that if lead you can only use 50% of it and you might have a grey day with no solar. Two group 24 batteries might be typical for a 20' boat.

d. How much solar? Take "b" and divide by 5 hours (average, including clouds, shading, and sun angle). About 100 W might be typical for a 20' boat. On a 20' boat finding room for the panels is a challenge. Maybe 50 W on the slider turtle and 50 W on the foredeck.

Don't try to pretend a 20' boat is a 40' boat by puting too much stuff on here. She will be crowded and overloaded. Keep it simple. I have a single 50W panel on my slider and a group 24 lithium battery. It's enough for my 24' trimaran. On my cruising cat (avitar) I have 3 larger batteries and 4 times as much solar, but I have a big roof, more demand, and take longer trips.
Click to expand...
Thanks for that. All mast top lights and cabin light are LED. Nice switch panel within easy reach, so I'll only turn on the instruments I need. I'll get a LiIon when I can afford it.
 
PeterV said:
I have exactly the same instruments as you on my GK29 and had the same on my previous boat, a Hunter Duette. On both a 10W solar panel connected straight to the battery keeps the leisure battery topped up year round, for several day sails per week. If going off for a week or so it probably wouldn’t be enough.
Click to expand...
10W sounds very little. I was thinking more in the region of 50W.
Refueler said:
I am going through a session of trying to decide the replacement for an old panel fitted to the deck ahead of the mast on my 38.

You would think that a 38ft boat would have loads of area to accommodate solar ... well not on mine !! Having had smaller boats 19ft and up - I understand OP's question.

So - I suggest to "Ash2020" ....

First try and imagine where on the boat you will fix the panel(s) .. with they be permanent or removable - put in place when not sailing ? Once you have that ...
Second look for the size of panel(s) you can mount and then ...
Third - how to run the cable and where you fit the controller.

I suggest try to maximise the wattage .... there's nothing worse than not having enough !

I suggest 40W as starting point ... more if possible. The reason being that brand claims are way over the real figures usually ... not only that - but the number of hours production reduces overall charge amount as well ..

There are some on YBW who post often about size of their panels (watts) - but many are in better locations to avail of sun ... ie Caribbean etc.
Click to expand...
Thanks. I was thinking 50W if I can find the space but it may be difficult. Most seem to be monocrystalline which are more efficient than polywhatsit. Doing the cables at the moment so I will lay extra in the trunking.
 
Gixer said:
I sail once a week and have a 20w panel mounted permanently which keeps the batteries on 100% all year around. If I ever get chance to do some extended sailing I’m going to buy a flexible 40w I can mount on different areas of the boat.
Click to expand...
That sounds encouraging. Maybe I don't need anything like 50W. Thank you.
 
ash2020 said:
Thanks for that. All mast top lights and cabin light are LED. Nice switch panel within easy reach, so I'll only turn on the instruments I need. I'll get a LiIon when I can afford it.
Click to expand...

Based on your feedback and the comments of some others, I think what I have on my F-24 is probably just about right. Same inst etc.

50W semi flex solar on the slider, one battery (now lithium, but group 24 lead is OK--I went LiFePO4 because it was very hard to lift it into the weird under-steps location and because I found a good one cheap), and a simple charger with an in-line fuse to the battery. 50W was the largest that would fit the slider, which is a very convenient place to mount on a small boat. You can tuck the wires and pass through underneath, avoiding a potential leak path.

Yes, less could work, but the UK is not known for cloudless skies. Just sayin'.

simple solar

JUST FYI. You do NOT need to change the battery until it dies. I paid a little less than this; new tariffs in the US (🥴 we have a nut behind the wheel) I suppose. Drop-in for an out-board powered boat, if your changer has a lithium option (nearly all do, but check in case you change battery types).
Wattcycle
 
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As said the question is what size you can fit on the boat. Actual cost of panel is not so significant compared to mounting difficulties. I solved the problem on my small boat by only fitting the panel when I leave the boat. It sits o top of the main sail cover held down by bungees and plugged in to electrics via the main hatch. (10w although probably 20 w would not be too big.
Now you can calculate how many amp hours you will need for a voyage. Double that number for battery capacity you need.
Then calculate approximate charging by your solar panel. I would guess for 20 w panel you might get 5 amp hour on a good day. So perhaps 30 amp hours over a week. If you do sail every weekend that will probably be more than enough.
But all these figures are a variable quantity. Only your experience will tell. ol'will
 
The "standard" east coast US calculation is Ah = W x 5 hours/12V. This allows for some clouds and shading. But more clouds, higher latitude, or winter means less.

And easy to remember rule. W, A, and V are capitalized because they are named after people. Hours, feet, and meters, for example, are not, and are thus not capitalized. For example, amp-hours is Ah. (not picking--I can't spell to save my life.)
 
Northern climes ..... I live at 57.5 N ..... and have a 13.4 KW Solar array for my house ...

On a sunny day - I can see over 11KW being produced over the middle day .... with 1 - 2KW at breakfast time .. and early evening.
On a full cloudy day - I can see anything from 1 - 5KW ....

Just posting to show that just because its high latitude - does not mean low outputs.
 
Remember that you may not need a fixed panel. On a previous 23’ boat we had a 80w panel that we just left in the cockpit when not onboard, otherwise stored below.
 
I'm also looking for a panel that I can mount when not sailing, limited size on a 30' boat. What amazes me is the huge range of prices- for a 80w flexible panel from £60 to £300. I guess they're all made in China and I read somewhere that there is massive overcapacity so prices are collapsing. But how to decide which one to buy?
 
ash2020 said:
Probably mainly daysailing with the occasional overnighter.
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Then I would say 5 or 10W is plenty.. depending on your battery size you don't even need to then have to install solar charging hardware - just connect it direct to the battery (using the 10% rule of W to Ah) - makes everything far simpler.. if it turns out not to be enough, then panels are so cheap in that size you can just double it..
 
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