Buying Solar Panel - SailNet Community
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post #1 of 32 Old 08-08-2011 Thread Starter
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Question Buying Solar Panel

I am in the market to purchase a solar panel but I find the choices and specifications confusing. My needs are simple I have a 30 ft S-2 Sailboat
inboard diesel and two batteries which operate the usual lights, small fan, radio and possibly a DC cooler. I want the correct size panel to keep the batteries charged to operate these items when the engine is not running and keep the batteries trickled charged when the boat is not being used for several months. Any suggestions with brand name, model and/or specifications I should be looking for to purchase this item. Thank you calmharbor
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post #2 of 32 Old 08-08-2011
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Quote:
Originally Posted by calmharbor View Post
I am in the market to purchase a solar panel but I find the choices and specifications confusing. My needs are simple I have a 30 ft S-2 Sailboat
inboard diesel and two batteries which operate the usual lights, small fan, radio and possibly a DC cooler. I want the correct size panel to keep the batteries charged to operate these items when the engine is not running and keep the batteries trickled charged when the boat is not being used for several months. Any suggestions with brand name, model and/or specifications I should be looking for to purchase this item. Thank you calmharbor
Do an accurate energy budget for your longest sailing period and come back with the results. EG so many amp hours a day.

Your question can not be answered at the moment.
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post #3 of 32 Old 08-09-2011
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TQA makes a good point about starting with your amp/hr usage estimates. In figuring out the solution, remember that usable amps will be less then the rating on the label. I've been told that cutting it in half is a good estimate to be conservative. Solar panels rarely put out the rated power.
I tackled this project on my boat from a different angle - buy as much solar as your budget or available space allows. You really can't have too much. Put a regulator in line if connecting directly to the batteries so you can't overcharge, or wire it through the battery switch so it's only charging when you are on board.
You can purchase the solid panels and mount them on swiveling brackets for a maximum amps per square inch installation. Or you can purchase soft panels and put them on your cabin top or bimini for a more 'set it and forget it' type of installation. This was my choice. I've checked the output a few times, never when the sun was at an optimal angle. The panels put out 30-60% of their rated power. They are very thin, just glued to the cabin top and you can walk on them without damaging anything. I also prefer the aesthetics as they virtually disappear lying flat.
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post #4 of 32 Old 08-10-2011
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calm, in order to keep the batteries topped up when not in use you don't need much power. Something likely 30mAH per battery per day, so one or two (keeping things separate, one to each battery, is a simple robust way to go) small 10W panels would do that job.

Keeping the batteries charged when you are using the boat is something entirely different. Yes, an energy budget is the right way to do it. But in practice I've never heard of anyone being able to afford more panel than they could really use, and following that logic you just buy as much panel as you can reasonably install on the boat. On a 30' boat that might be one or two 2x3 panels. Finding a place to install it (or them) where it won't be shaded or stepped on is the big trick.

At that point you work the other way: Buy the panel you can afford and accomodate, then deal with that much power as being all you're going to get. Switching to LED lighting and running lights (if you sail much at night) can be a very cost-effective way to stretch your power budget, despite the high cost of them. Cheaper than adding power sources, fuel, or batteries.
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post #5 of 32 Old 08-11-2011
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Have had Kyocera panels on the boat for 12 years. Still full output. Robust panels for the cruiser. Pay proper attention to your wire size and the integrity of your connections. You may want to start out with one panel at first of say 60-80 watts for your initial needs. If you add a DC refrigerator then your talking a considerable amount of wattage, say 300+.


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post #6 of 32 Old 08-11-2011
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Quote:
Originally Posted by calmharbor View Post
My needs are simple... and possibly a DC cooler.
DC refrigeration changes things considerably--not so simple. Up until that point you're talking using pretty much any 10 - 20w panel to keep the batteries topped up. I suspect you'll need more than 10 times the wattage for that "possibility". Best to figure that out first.

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post #7 of 32 Old 08-11-2011
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I have solar panels on my boat (PO installed). My question is there a fire danger from the wire from panel to the battery charger regulator? Say my panels are 60watt and the feed wire shorts, seems like it could start a fire in the wiring, or are the panels self limiting on short circuit?
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post #8 of 32 Old 08-11-2011
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...or wire it through the battery switch so it's only charging when you are on board.
That's the LAST thing you want to do. Wire it to the house bank with a controller. It'll do a LOT of work when you're not there.

Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
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post #9 of 32 Old 08-11-2011
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I have solar panels on my boat (PO installed). My question is there a fire danger from the wire from panel to the battery charger regulator? Say my panels are 60watt and the feed wire shorts, seems like it could start a fire in the wiring, or are the panels self limiting on short circuit?
Regards

That's why they invented fuses.

Stu Jackson, C34, 1986, M25 engine, Rocna 10 (22#)
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post #10 of 32 Old 08-11-2011
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Stu beat me to it - Fuses.
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Brian
Living aboard in Victoria Harbour
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