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Flexible solar panel

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putzmeister
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Initially Posted - 01/11/2013 : 11:55:16

Last fall I shared that the timing belt on our 9.9 Yamaha jumped a tooth and we ended up bending a valve (or two!) I also explained that we tried an electric trolling motor while we were trouble shooting the Yamaha. Briefly, the trolling motor was way too easy. We're thinking we'll leave the repaired Yamaha at home and use the trolling motor this summer (we're on an inland lake.)

We're going to need a solar panel to keep the batteries topped off. I can't talk myself into mounting a rigid panel. Anyone here research/purchase a flexible panel recently?

1989 C25
Hull #5822

Edited by - on

awetmore
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Response Posted - 01/11/2013 : 12:05:42

Check the watts per square foot. Last time I checked they offered about half of what a rigid panel could offer.

Also figure out the watts consumed per minute on your trolling motor to figure out how many minutes of sun you need to get one minute of motor time. It might require a huge array of solar panels on the boat and push you towards using shore power.

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shnool
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Response Posted - 01/11/2013 : 13:51:58

I think it'd be a helluva large panel, unless you only use your trolling motor for a couple hundred feet (possible I could see that).

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putzmeister
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Response Posted - 01/11/2013 : 14:47:29

We motored probably a total of 2 miles last fall with no noticable drop in the battery (it's a really small motor!)

Thanks for the above calcs. We sail once-a-week on average. If the panel recharges the batteries in a week - that will be ample. When we take the boat on vacation someday - we will use the Yamaha.

I am interested in a brand of flexible solar panel.

Edited by - putzmeister on 01/11/2013 14:49:00

Sloop Smitten
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Response Posted - 01/11/2013 : 15:24:56

I believe Jim Baumgart used to have a couple of UniSolar 11W flexible panels he used on his C25 for extended voyages. You might check them out.

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redviking
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Response Posted - 01/11/2013 : 16:30:56

Flexible panels are expensive and don't put out as much juice. Why not get three rigid 15 watt panels for $100 or so and then just throw them in the cockpit when you leave the boat? 'Tis what we used to do with our C25 while on a ball for the season in New England.

Sten

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Steve Milby
Past Commodore

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Response Posted - 01/11/2013 : 16:51:25

I'd like to put a solar trickle charger on my 2 12 volt wet cell batteries during the winter. Is a 5 volt solar panel enough, or should I get a 10 volt panel?

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redviking
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Response Posted - 01/11/2013 : 17:41:45

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Dave5041
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Response Posted - 01/11/2013 : 20:22:28

Guessing you mean watts. I would go with 10 W. That is only about 0.8 amps under optimal condition, probably 0.5 realistically.

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OLarryR
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Response Posted - 01/11/2013 : 22:30:33

Steve,

Most resources would indicate that for just trickle charge maintaining of a battery, you need a solar panel that puts out about 5 watts per battery. The way they figure that is a 5 watt panel ideally puts out about .3 Amps/hr. But no one has ideal conditions (exactly perpendicular to the sun) nor do they maintain a max charge rate throughout the main overhead sun hours each day and so you get something less than that (figure ~.15 Amps/hr for about 5 daytime hours and then probably for an average of about 4.5 days figuring at least 2.5 days it may be raining or significantly overcast. So...figure .15 Amps x ~ 5 hours/day x 4.5 days = 3.4 amps/week. Meanwhile, a battery will self discharge about .4 amps/day in the summer time and .25 amps/day during the winter months (cooler months). So that means discharging about 7 days x .4 = 2.8 amps/week in the summer and about 1.75amps/week in the winter. If you have 2 batteries, then you need to trickle charge at least 5.6 amps/week in the summer and at least 3.5 amps in the winter. Also, if it snows in the winter, the panel could be out of commission for a lot longer than 2.5 days and this also assumes that the panel stays fairly clean during the winter months when you may not be down regularly to ensure the panel is not dirty (bird splats, etc). Also, the sun is out full bast less hrs in the winter and at a lower angle. So, only having a panel that puts out about 3.5 amps may not be sufficient during the winter months and probably better to use the 5.6 amps/week summer month trickle charge requirement as a basis to shoot for when sizing the panel. So, based on the above that a 5 watt panel will conservatively provide about 3.4 amps/week, you would need a 10 watt panel conservatively putting out 6.8 amps/week to meet the 2 batteries self-discharging 5.6 amps/week.

One thing, though, that throws the whole above thing into more complexity......The above is all based on what was the normal standard years ago which was figuring you have flooded batteries. AGMs, for example, self-discharge at a lower rate/day compared to flooded batteries. Also, Gel and AGM batteries also have a slightly different charging voltage need compared to flooded batteries (which are not as sensitive to high voltage charging rates.

I have seen resources indicate that if you trickle charge with a 5 watt/battery solar panel, you generally do not need a solar controller. That is usually the case, because the charging rate of the solar panel pretty much equals or not that much greater than the rate the battery(ies) self-discharge. Whatever addl charge the panel provides would probably be lost at night when the panel actually reverses and slightly discharges the battery(ies). So, there is little chance of a 5 watt panel cooking a battery.

In my case, I have a 20 watt panel rated at 1.2 amps (ideally). It will start initially charging my batteries at about .2 - .4 amps/hr and at mid-day it charges at around .8 to .9Amps/hr and then later drops back down to about .4 - .2amps/hr. Since my 20 watt panel would overcharge my batteries except perhaps when I use loads onboard, I have a solar controller and solar controllers also prevent reverse discharge during night-time hours, so they are also efficient. My solar controller also has separate settings for flooded, Gel or AGM batteries because as I indicated earlier, the charging voltage needs are different for each of those batteries.

Edited by - OLarryR on 01/12/2013 06:15:54

Steve Milby
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Response Posted - 01/12/2013 : 05:06:37

Thanks, Larry. Storage space is a big problem for me, since I live on the boat during the summer. I want a compact charger that doesn't take up much storage space when not in use, but that is easy to install when I'm storing the boat for the winter, and that is the right size to do the job without damaging the batteries. 10 watts with a controller sounds like it will meet all those goals, and, having shopped around, shouldn't be very expensive. Thanks for the sound advice.

Edited by - on

binky
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Response Posted - 01/15/2013 : 04:20:41

I'm completely confused now...not from this post but from everything I have read about solar panels/chargers. I found my battery discharged this weekend and had to pull out the shore-power cable, hook up the battery charger, worry about the whole thing overnight and then pack it all up. I have to share the power pole with a couple other boats....I want something easier...SOLAR. I am contemplating this purchase, "NOCO iMOB ISC400" http://www.chargingchargers.com/noco-solar-charger/isc400-noco-imob-5.5-watt-solar-charger.html. For $50-60, it is 5 watts, waterproof, 5 year warranty...so on and so forth. Any thoughts? My brain is fried from reading about all the solar panel opportunities...help.

Edited by - on

Voyager
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Response Posted - 01/15/2013 : 05:25:41

Ken
My single group 24 battery needs a 20W panel to keep it topped up all the time based on my usage. While it sounds like overkill, it starts the job recharging at a good rate, and finishes the job within 1-3 days. Panels get shaded, often get dust or crud on them, aren't pointed toward the sun, never ideal.
You can't count on ratings either: my panel is rated at 20W, so you'd expect it to output 20/12 or 1.67A. But noooooo!
As the battery charges, the difference between the panel voltage and the battery reduces, so charging current can be cut to 1/3 of that, or about 0.6-0.8A.
Older amorphous silicon panels are large compared to an equally rated crystalline silicon panel. Sunforce brand is based on the older technology and are a bad deal. Check RV sites or Amazon for better deals. Some of the sites listed above offer good deals on crystalline panels.
Bottom line: got with more power - you'll be surprised how efficient it can be.

Edited by - on

redeye
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Response Posted - 01/15/2013 : 05:57:08

Defender sells some really nice panels for a good price. I agree with Voyager.. go for a 20w or more. ( my own fabricated mount )

Mine Still working... Ganz GSP-12 12 watts for about $150

Edited by - redeye on 01/15/2013 11:01:17

DaveR
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Response Posted - 01/15/2013 : 07:06:35

I believe "overkill" would be the optimal word here. Get the largest wattage you can afford. I had a 45 watt panel and it did a fine job for what I needed but I'll bet if I were on board every night with lights, TV, stereo, etc. it could have made it difficult for it to keep up.

Edited by - DaveR on 01/16/2013 06:55:37

redeye
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Response Posted - 01/15/2013 : 07:22:28

<< overkill >>
I don't know.. my experience was it was relatively easy to setup a 12w panel, and so far it rocks.

Solar is normally just a float kinda charge.. you are gonna need a bit more power to charge up a battery drained in order to run a trolling motor.

Edited by - redeye on 01/15/2013 11:13:43

Steve Milby
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Response Posted - 01/15/2013 : 08:39:57

I'm thinking about something like a 130w solar panel to support my autopilot and refrigeration, but for now, I just need a small trickle charger to keep the batteries topped off during long term, storage. Last summer I added ice to the refrig, and then only ran the refrig when running the engine, and occasionally before bedtime, and it worked very well. Used in that way, the refrig made the ice last much longer. I think a 130w solar panel might be enough to allow me to forego the ice and run the refrig as needed for long term cruising.

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putzmeister
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Response Posted - 01/15/2013 : 11:11:55

Discussion of high watts reminds me of a live-aboard in San Francisco. A 40'+ sailboat with a bimini made entirely of solar panels + a wind generator (or two.) Horrid but functional.

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Steve Milby
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Response Posted - 01/15/2013 : 11:26:45

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by putzmeister
 Discussion of high watts reminds me of a live-aboard in San Francisco. A 40'+ sailboat with a bimini made entirely of solar panels + a wind generator (or two.) Horrid but functional.
<hr height="1" noshade id="quote"></blockquote id="quote">One of our long-time members had his C25 rigged with both solar panels and a wind generator for extended cruising. It was a nice set-up. I don't know what he used that much power for, but I'd guess autopilot and refrigeration. There are some fairly energy efficient plug-in 12v refrigerator/coolers. If you cruise enough to make it worthwhile, it isn't unrealistic for a pocket cruiser.

Edited by - Steve Milby on 01/15/2013 11:27:49

Dave5041
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Response Posted - 01/15/2013 : 17:35:05

Steve,
I think I posted it in another thread, but there was an excellent little experiment published in Sail a few months ago. Shading crystalline panels by as little as 10% knocks a big hole in their output. The author quantified the dramatic drop, but he also tried shading part of one panel of two connected in parallel and found that the unshaded panel was unaffected and continued at its nominal output. The cells in a panel have to be connected in series to get to the rated 12-15 volts. If one cell in the stack is shaded, it kills the system.. Starting with two smaller panels in your initial system and adding panels to work you way up to your goal will not only spread the cost and labor, but will likely result in a more consistent output.

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OLarryR
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Response Posted - 01/16/2013 : 04:31:35

Ken,

That 5.5 watt solar panel - I read the marketing on it. They claim it will be sufficient to charge two batteries. The reality is that a 5 watt solar panel will only be sufficient to trickle charge one flooded cell battery. Same goes for a 5.5 watt which is basically the same. Even if they claim it works on overcast days, the fact is that solar panels only get max charging rate when sun is perfectly coming at the panel from overhead and that is only a small part of the day. But the panel probably will work fine for one battery and if all you want to do is trickle charge it to overcome what the battery normally loses just sitting on the boat each day, then that panel probably would be fine.

The issue all are getting into in this posting thread has to do with what if you want to not only trickle charge to overcome a battery's daily self-discharge rate but also to charge for any battery amps lost due to running loads while on the boat (i.e. fishfinder, autopilot, stereo). Well then you have to plan on a larger capacity solar panel and a solar controller to ensure the extra capacity of a larger solar panel (above a trickle charging rate) does not cook the battery.

So, your concern regarding the battery you had to charge using a battery charger using shore power....well, your posting did not really indicate if you just want a solar panel to maintain a battery during the off-season and times when you are not using the battery for very long periods (months) to run anything or if you want a solar panel that will not only maintain a resting battery but also a battery that is regularly being used to run a fishfinder, etc during the day/week.

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by binky
 I'm completely confused now...not from this post but from everything I have read about solar panels/chargers. I found my battery discharged this weekend and had to pull out the shore-power cable, hook up the battery charger, worry about the whole thing overnight and then pack it all up. I have to share the power pole with a couple other boats....I want something easier...SOLAR. I am contemplating this purchase, "NOCO iMOB ISC400" http://www.chargingchargers.com/noco-solar-charger/isc400-noco-imob-5.5-watt-solar-charger.html. For $50-60, it is 5 watts, waterproof, 5 year warranty...so on and so forth. Any thoughts? My brain is fried from reading about all the solar panel opportunities...help.
<hr height="1" noshade id="quote"></blockquote id="quote">

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binky
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Response Posted - 01/16/2013 : 06:09:31

Thanks Larry, this thing will do what I need it to do...and with just one battery to keep charged. For once I am trying to stay focused on what I need and not trying to go overboard (no pun intended), ie trying to solar power up the whole dock.

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Steve Milby
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Response Posted - 01/16/2013 : 06:55:44

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave5041
 Steve,
I think I posted it in another thread, but there was an excellent little experiment published in Sail a few months ago. Shading crystalline panels by as little as 10% knocks a big hole in their output. The author quantified the dramatic drop, but he also tried shading part of one panel of two connected in parallel and found that the unshaded panel was unaffected and continued at its nominal output. The cells in a panel have to be connected in series to get to the rated 12-15 volts. If one cell in the stack is shaded, it kills the system.. Starting with two smaller panels in your initial system and adding panels to work you way up to your goal will not only spread the cost and labor, but will likely result in a more consistent output.
<hr height="1" noshade id="quote"></blockquote id="quote">Good point Dave. I was thinking about buying one big panel, but it makes sense to buy two smaller ones instead.

I haven't decided for sure if I want to invest in that much solar power, because I'm more into racing than cruising and I'm more into crewing for other people than racing my own boat, but even my racing friends run their refrig during the races, and we often have a storm blow through that interrupts our shore power electric service for a few days, so, whether you race or cruise, it's nice to be independent of shore power. On balance, for a retiree/liveaboard, I'm inclined to think it's worth a few hundred dollars.

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Davy J
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Response Posted - 01/16/2013 : 07:50:15

This thread has gotten away from the original question, but I'll add my 2 cents. I have an 80 watt solar panel that I use when I go out on multiple day trips. I also have a 5 watt panel that I picked up at wally world. The 5 watt panel will get my two batteries up to about 13v in direct sun. That's with no load. The 80 watt panel has kept my batteries going with autopilot, refer, freezer, GPS and stereo running. Of course that's in Florida sunshine. I have no idea how they would perform in very cloudy conditions.

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Davy J
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Response Posted - 01/16/2013 : 08:07:16

I'll also add that I considered getting a wind generator. But I gave up on that idea when I came to the conclusion that 1) I rarely sail at night, 2) I usually try to find the least windy place to anchor for the night.

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TCurran
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Response Posted - 01/16/2013 : 09:46:55

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Davy J
 This thread has gotten away from the original question, but I'll add my 2 cents. I have an 80 watt solar panel that I use when I go out on multiple day trips. I also have a 5 watt panel that I picked up at wally world. The 5 watt panel will get my two batteries up to about 13v in direct sun. That's with no load. The 80 watt panel has kept my batteries going with autopilot, refer, freezer, GPS and stereo running. Of course that's in Florida sunshine. I have no idea how they would perform in very cloudy conditions.

<hr height="1" noshade id="quote"></blockquote id="quote">

Dave, can you send me an email at tcurran32766 at gmail dot com? I want to talk to you about your setup. Maybe even drive across state to take a look if you're open to that.

Thanks

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