Solar Pannel for 1 battery

[walt]

Saildog, thanks for the picture. Looks like your using the rail mount only during winter yard storage where the boat does not move. Your summer much larger panels also "look" straight up but your pretty far north so no issue. The Telstar sure looks like a sweet sailboat..

Now that I have a nifty and convinent way to measure panel current (linklite), Im going to test my panel for various shade conditions - got me curious. Regarding shading, the clip below is from this site: http://www.energymatters.com.au/faqs/general_solar_power_faq.php Seems what the panel does in partial shading could vary a lot depending on if the panel has the bypass diodes which basically "bypass" a shaded cell or how the cells are arranged (ie, all serial or combination of serial and parellel). Interesting that if a cell is bypassed with a diode, for a serial set of cells, the panel current should not change but the panel output voltage will drop. So if your using a MPPT controller, you will get less "converted" output current to the battery during shading. But for a conventional cheap PWM controller (like I have), the current to the battery should be less affected by partial shading since the panel voltage drops to the battery voltage when the charge is delivered to the battery. But only true if the panel voltage remains somewhat above the battery voltage. Too many cells bypassed and you get nothing.

1. -------------------------------- (clip from referenced site)

Can solar panels work in the shade?


The output of any panel will be reduced or cut off if shaded. However, some solar panels do work better than others in the shade. If a single cell is heavily shaded, that cell is cut off.

All solar panels sold by Energy Matters have "bypass diodes", which send output from the remaining cells around that dead cell. However, you have lost the output of that cell, so the total panel voltage will drop by about 0.48 volts per cell. Most panels are in the 16 to 18 volt range, and most batteries need at least 13.5 volts to charge completely. So, if 2 or more cells are shaded, the output voltage of the panel may drop too low to charge the battery.

 

[sailingdog]

Yes, many panels are sold as shade tolerant, and are larger than the high-output panels of the same rating, since they have some extra cells to allow for loss due to shading, and also have bypass diodes.

The real concern is that a high-output panel would drop below the minimum voltage required to "charge" the batteries. I am using an MPPT-type charge controller, not a more basic PWM only controller, though I did have a PWM-type controller on the boat up until this past season. Still do, as a backup just in case.

If you could put the solar panel you have on your bow or stern rail, you'd probably get a significant improvement, due to the lack of shadowing, as well as possibly have a better angle to the sun.

The big panels are mounted to the area of the boat, and use rails going between the main hull and the aft-end of the amas to mount to.

 

[Phil V25]

Around here Jetskis...

Can't operate at night because they carry no running lights.

Yes, but jetskis and a lot of other small, relatively fast powerboats, can handle 3' of water without a problem.

 

[walt]

FYI, I did some very rough and not at all accurate measurements with my solar panel and came to the conclusion that it is significantly affected by shading. To do better measurements, Ill probably wait for a few months but I wouldnt be surprized if the shadow of the mast shading maybe 10 to 15% of the panel surface (for my application) doesnt reduce the output by 50%. But these are just very rough guesses made on some inacurate measurements and may not apply to other panels.

Speaking of some serious shading, here is where my panel is mounted http://analogengineering.com/sail/powell/moki_canyon5.jpg

Im not going to move it because for me, the solar panel is about convienence and I just dont want the panel on the rail when Im using the boat. Where I park the boat during the summer, the panel gets fairly good sunlight and this is the main application of the panel (to charge the batteries during the week when Im not using the boat) - and its been woking fine for two seasons now.

 

[sailingdog]

Walt-

I can understand your viewpoint. Just wanted to point out that with the panel there, you're losing a fair bit of its potential charging capability. As for the photo, which I've posted below....I'd be more worried about loose rocks coming down on the boat than shading...

FYI, I did some very rough and not at all accurate measurements with my solar panel and came to the conclusion that it is significantly affected by shading. To do better measurements, Ill probably wait for a few months but I wouldnt be surprized if the shadow of the mast shading maybe 10 to 15% of the panel surface (for my application) doesnt reduce the output by 50%. But these are just very rough guesses made on some inacurate measurements and may not apply to other panels.

Speaking of some serious shading, here is where my panel is mounted http://analogengineering.com/sail/powell/moki_canyon5.jpg

Im not going to move it because for me, the solar panel is about convienence and I just dont want the panel on the rail when Im using the boat. Where I park the boat during the summer, the panel gets fairly good sunlight and this is the main application of the panel (to charge the batteries during the week when Im not using the boat) - and its been woking fine for two seasons now.

 

[walt]

Every time I post that picture, I worry that "someone" will comment on the danger of overhanging rocks. And it is a concern.

Also of concern in South West warm lakes is the risk of an amoaba that gets up your nose and eats your brain. I also worry about an asteroid hitting Glen Canyon dam or an eco terrorist blowing it up while Im out on the lake.

 

[sailingdog]

Hey, its your boat and crew...if they're okay with it...that's cool.... I don't know the cliff in question, and some of the ones near where I sail, you'd be hard pressed to want to get anywhere near that close to them.

Every time I post that picture, I worry that "someone" will comment on the danger of overhanging rocks. And it is a concern.

Also of concern in South West warm lakes is the risk of an amoaba that gets up your nose and eats your brain. I also worry about an asteroid hitting Glen Canyon dam or an eco terrorist blowing it up while Im out on the lake.

 

[walt]

We probably took a lot more risk driving to Lake Powell from Denver but rocks have fallen on house boats in the past - so it is no doubt something to be concerned about. You will see a lot of house boats parked under cliffs at Lake Powell during the summer.

While your here, I beleive you said you have 260 watts of panel on a trailerable sailboat. Is that for extended cruising with a refregerator? I get by fairly easy for 4 or 5 days with the 20 watt panel and fully charged 200 amp hour of battery capacity - but my main power is used by the car stereo (not used a whole lot on these trips), the kids watching movies, ocassional laptop and a bunch of LED lights. My outboard 5 amp alternator had a blown rectifier (just fixed this season) so havent even used it in the past..

 

[sailingdog]

We probably took a lot more risk driving to Lake Powell from Denver but rocks have fallen on house boats in the past - so it is no doubt something to be concerned about. You will see a lot of house boats parked under cliffs at Lake Powell during the summer.

True, but many of the houseboats are rentals IIRC, so the people on them aren't quite as invested in keeping them afloat.

While your here, I beleive you said you have 260 watts of panel on a trailerable sailboat. Is that for extended cruising with a refregerator? I get by fairly easy for 4 or 5 days with the 20 watt panel and fully charged 200 amp hour of battery capacity - but my main power is used by the car stereo (not used a whole lot on these trips), the kids watching movies, ocassional laptop and a bunch of LED lights. My outboard 5 amp alternator had a blown rectifier (just fixed this season) so havent even used it in the past..

Yes, actually, with the addition of the small 25 watt panel I posted a photo of, it will be 285 watts. However, having an 18' beam gives me a few more mounting options than you'd have on your boat. Unfortunately, I’m still working the bugs out of the mounting system for the large panels, but think I have a solution now. The electrician who was hired originally to do the work did a really good job of botching it...and I’ve slowly fixed all of the shortcomings in his work.

 

[Mac]

Informative article written by Don Casey on charging your batteries using solar.

http://www.boatus.com/boattech/casey/30.htm

Great article!! Thanks.

Todd this is what I used all last summer and it worked great. I sailed every weekend and used a Sirrius radio, running lights and sometimes interior lighting, but always the Sirius radio. Twice, after all day using the radio and heading back late at night that my radio would go off, and my lights would dim alittle. But for the most part this fit the bill for what I use.

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[Mac]

Todd, I forgot, I only have 1 marine battery, but would like to add a second. Also if you buy this unit, buy the 20 foot extension wire. I didn't and I wish I had.