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Solar panel question

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tomh
1st Mate

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USA
83 Posts

Initially Posted - 03/06/2012 : 07:34:46

We went to West Marine yesterday to outfit Karma for our first season. (I think that buying the boat was the cheapest part of this adventure).

The one thing that I want but forgot to get is a solar panel to recharge the battery.

What size/type/wattage/etc. do I want? What concerns should I have?

Tom

1978 C25 "Karma" #790
Toledo Beach Marina
LaSalle, Michigan

Edited by - on

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 03/06/2012 : 07:59:14

Do you want to trickle charge the battery while you're away or do you want the solar panel to power other items?

Edited by - on

eguevara
Navigator

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USA
111 Posts

Response Posted - 03/06/2012 : 08:10:06

Tom... just so you know.. that link on your signature does not work...

-eddy

Edited by - on

NautiC25
Admiral

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USA
957 Posts

Response Posted - 03/06/2012 : 08:30:02

I have a cheap Coleman 9watt panel that I got from Wallyworld for $75. I also have 2 Interstate SRM29 batteries.
The 2 batteries allow me to easily run all lights and the radio for the weekend.
The 9 watt panel has the batteries charged back up by the next weekend.

9 watts is enough to recharge the batteries like I use it for, but not enough to really power anything or for more than two-night cruises.

BTW, West Marine probably isn't the best place to buy a panel. You can get better quality for a lot less elsewhere.

Edited by - NautiC25 on 03/06/2012 08:32:43

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 03/06/2012 : 08:38:10

You need to do a search. This question usually get a lot of opinions, one of which you have already seen.

How much are you going to be drawing down your batteries when you use the boat? How much time between uses (charging time)? Is your slip shaded? Are you in a traditonally cloudy area, will you have a charge controller, how many batteries, is your engine electric start? Does teh engine have an alternator, for that matter - is it an electric motor as opposed to an engine, etc. There are many variables.

A good first step is to talk to other boaters in your marina to see what they are using and how well it works for them. Then look around the boat at how you use your batteries during a weekend aboard. For the first season, you may be ahead to just lug the battery home after each use and check its charge, record it, then put it on a trickle charger until your next trip. After a few months, you will have a decent idea of how much juice you need to replenish, then you can start thinking about what to buy to do that.

we have a 3 sq ft solar panel that spends 90% of its life in the basement. I think its this one: http://tinyurl.com/7ofevdq
Although it provided some replenishment, we were non-plussed and decided that it just wasn't worth keeping aboard. We also have shore power so its not much of an issue to us.

Edited by - on

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 03/06/2012 : 08:53:05

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">BTW, West Marine probably isn't the best place to buy a panel. You can get better quality for a lot less elsewhere.<hr height="1" noshade id="quote"></font id="quote"></blockquote id="quote">

Here is a good site for reference:
http://www.solar-electric.com/

Here is a link to my solar panel. Probably overkill for most C25s, but I wanted to be able to power 12v refrigeration, radio, gps and lights for extended periods away from the dock.

http://www.catalina-capri-25s.org/forum/topic.asp?TOPIC_ID=22843& SearchTerms=solar

Type "solar" into the search function and you will see what others have done

Edited by - Davy J on 03/06/2012 08:53:45

OLarryR
Master Marine Consultant

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USA
3467 Posts

Response Posted - 03/06/2012 : 11:12:55

The above posters pretty much covered the most important things. I have a 20 watt panel for 2 batteries and enough recharge capability if I were to run the nav lights for 1-2 nights a week, fishfinder several days a week and maybe a bit more but not much addl loads. A lot depends also on how much sun you get in your area. For most areas and 1-2 batteries and light loads 9-20 watts will probably be sufficient. Bear in mind that if all you wanted to do was trickle charge a battery so it will not go dead, you would need approximately a 5 watt solar panel and with that size per battery, you would not need a solar controller because the charging rate vs the trickle rate will more or less equal each other out and you won't cook the battery. However, once you exceed 5 watts charging rate/battery, then you need to also buy a solar controller to ensure you do not cook off the water especially when you are not using the boat and the charging rate is then more than needed. My website has a section on my solar panel install. Click on the thumbnails to get the larger photo.

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tomh
1st Mate

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USA
83 Posts

Response Posted - 03/06/2012 : 12:18:49

There are a lot of variables that come into play here so more information would be helpful. Asking this question is forcing me to think more about the way I'm going to use power.

I will be using the boat for 3 - 4 day coastal cruising trips every other week on lake Erie.

Most of the power usage will be for gps, stereo, nav lighting and cabin lighting.

I now have 1 deep cycle battery but am open to getting another battery if required.

I have access to shore power when in the marina. Might want to run a laptop at night.

Edited by - on

NautiC25
Admiral

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USA
957 Posts

Response Posted - 03/06/2012 : 13:04:53

Then I would suggest you go with DavyJ's setup: http://www.catalina-capri-25s.org/forum/topic.asp?TOPIC_ID=22843&SearchTerms=solar

However, I would also suggest you buy two Interstate SRM29's. I bought them and they are far better than the WM's I had before. And they're affordable.

Edited by - on

Davy J
Master Marine Consultant

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USA
1511 Posts

Response Posted - 03/06/2012 : 13:10:56

I am using two batteries connected in parallel. This doubles the amp hours of the battery bank. In addition, it keeps each battery from discharging deeply. The downside is, if the batteries do get run down, I might have to pull-start the outboard to get running.

Also, If you use this method, you will need to purchase two new batteries and dispose of your old one. An old battery will pull a new battery down.

Edited by - Davy J on 03/06/2012 13:14:54

tomh
1st Mate

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USA
83 Posts

Response Posted - 03/06/2012 : 15:55:24

I really like Davy J's set up. I checked out Northern Arizona Solar but I need to do more research so that I "Do it right the first time"

The best idea is to talk to owners in the marina who have done similar jobs to actually see how their's is hooked up.

For those who have done this I would ask "what did you do right and what did you do wrong?"

Edited by - on

redeye
Master Marine Consultant

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3476 Posts

Response Posted - 03/07/2012 : 05:50:10

http://www.defender.com/product.jsp?path=-1|328|49497|1471367&id=1802131

Rocks...

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waterbaby
Navigator

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USA
168 Posts

Response Posted - 03/08/2012 : 03:29:59

Can I ask a really dumb question? What would be the issue with installing a solar panel flat on top of the pop-top? I know the boom/main might shade it a bit, but I don't think it would be much and since my pop-top flexes a bit I don't ever stand on it. It just seems that that would be an easy location that's out of the way. I'm sure there's something wrong with that idea - so enlighten me please.

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 03/08/2012 : 05:28:19

Waterbaby, I would step on it everytime I went forward to work on something. We will set ours out there if we are at anchor though. We do not have a permanent install.

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OLarryR
Master Marine Consultant

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USA
3467 Posts

Response Posted - 03/08/2012 : 05:48:02

Two last postings:
1) What done right/wrong ? and

2) What about on top of a pop top ?

ANS: 1) Install/setup - MY setup is perfect in that it allows even removal of the outboard without removal of the solar panel and yet solar panel is above the outboard. Setup allows tilting the panel to gain max amps in winter when best to slope the panel toward the sun to maintain it being as close as possible perpendicular to the sun. I also bought a quality panel poly cell arrangement and it gets maximum amps for it's footprint compared to other panels being sold. You would have to really search for another panel that has a smaller footprint than 14" x 20" that can put out 20 watts. Most panels are larger for that wattage. I am also quite pleased with my solar panel controller with the digital readout - Always providing amp and voltage readings. I always know the status of my batteries when the panel is not charging the batteries and also when the panel or the outboard is charging the batteries. What I possibly could have done was gone to a 30-40 watt panel, not that I need a larger panel for my normal loads, however, if I were to increase my daily loads such as get a larger boombox, install a color chartplotter and a tiller pilot...well perhaps I should have planned for future potential increase in loads. As of now, the past 6 years the panel has been the right size and charging rate and should be fine for years to come for both my battery banks.

2) Install on top of the pop top cabin poses issues. Any solar panel that has partial shading of the panel and it most likely would if on top of a pop top unless perhaps you were able to position it on one side of the pop top so the boom would never shade it during overhead sun , will reduce the charging rate significantly and possibly to zero. First of all, panels are made differently. The least expensive panels are generally a very large footprint for wattage output and that would take up more room on the pop top making more area that you could not utilize to stand on if you had to unless you get a solar panel that is made so you can stand on it but those panels have shorter warranty periods (meaning generally less reliable due to the abuse they may have to put up with) compared to a rigid panel. The other issue regarding less expensive panels is that they are generally of the mono-cell construction and when even slightly shaded, their wattage goes to zero. A poly-cell panel would produce some wattage even if partially shaded but would be considerably less than it's max rate.

In general, many panels when sizing what would be appropriate for your loads, do not consider that you will always get the max wattage. Best to consider you will get approximately 2/3 to 3/4 of the max rate for about 5+ hours on a bright sunny day and then 1/3 to 1/2 the max rate for the addl hours when the sun is high enough to produce a charging rate. If any shading, even one finger's width may reduce charging to zero on a mono-cell panel or perhaps half of the charging rate you would normally get without shading on a poly-cell panel.

The other big issue consideration for putting a panel on the pop top is that you may step on it and break it unless you get the panel type that you can walk on. Typically a rigid panel comes with a 10 or 20 year warranty. The smaller ones - 10 yrs and larger ones generally 20 years. Whereas, the flexible or the walk on panels are not only larger in footprint but due to their construction may only come with a 3 year warranty. It is not so much that length of warranty service is the driving factor as to which panel to buy but based on how long they are willing to provide a warranty kind of gives you a sense of the reliability of the unit with rigid panels having the longest warranties and proportionatly more reliable, however, rigid panels....would be more susceptible to breakage if you put it on the pop top and that is exactly where you may want to stand when lowering and flaking your main sail.

Those on larger sailboats that have extremely large bimini tops - You may see panels on those bimini tops. First, on a large sailboat you are more likely to find a location that does not get shaded and you do not stand on bimini tops so a rigid more efficient panel would probably be okay up there. But on our sailboats, hanging a panel off the stern rail winds up being probably the ideal location for many. Then there are others that find putting one on the deck and removing ti when they go sailing works for them. So, it really depends what works best for you.

My website has details of my solar panel install with a number of photos.

Edited by - OLarryR on 03/08/2012 05:55:07

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