Solar charging

[FlyWright]

Here are some shots from last summer during my install and testing for optimum solar system form and function. I have 2x100W adjustable panels on the port rail and 2x100w stationary panels on the foredeck (temporarily). I don't have the numbers with me but they ran similar to Frank's findings. Adjusted panels with low sun makes a difference. If you're gonna lay them flat, just buy more panels. I made some adjustable struts out of PVC that seem to work OK for now. I expect that as I gain experience with it, they may be modified for better form and function.

In these photos, I was still working out the adjustable strut vs. fixed panel ideas so you can see the prototype supports I was then using. Ultimately, I mounted the other 200W on the stbd rail and have the installation Phase I completed. Phase II will involve rerouting the cabling for shorter runs that minimize runs along the fwd rails.

I used these rail mounts from Sea Dog...2 per panel. Adjacent panels are fixed together so they move in unison as one panel so only one adjustment needed per side, not two. They can be easily removed when conditions warrant but for normal docking, they lay down vertically outside and against the rail stanchions. If I need to, I can also flip them to vertically inside the rail stanchions.

If I had mounted the panels at the mid-width point, I wouldn't need the struts but the panels would protrude into the side deck walking area. I just knew if I did that, I'd end up with much more boat rash than normal. When they're 'deployed', they look a bit like wings for FlyWright. Maybe they need flamingo pink wingtips, huh?

I think my MPPT controller can handle another 100W if I need to expand but so far, it doesn't look like it'll be needed unless I want to run the second fridge full time in the summer.

IMO, I think it's much better to build your system to your specs with quality components and not rely on the kits put forth pushing last year's panels and lesser controllers. I found Renogy to be easy to work with. So far, I'm very pleased with the system that came in under budget at 1 BU. My unexpectedly favorite part is the BlueTooth app on my tablet or phone that allows me to monitor all parameters and history within BT range.

Like Frank said, electrical budget and conservation in advance is critical. Years ago, I shifted to LED throughout and fridge upgrade and ventilation/insulation mods with the help of a NovaKool engineer.

My recommendation would be to get a good handle on your electrical system before adding solar. The best place to start is with a State Of Charge (SOC) meter. My electrical system was optimized years ago to include upgrading all large cables, 6x220AH golf cart batteries and a Balmar 120A alternator (with cooling fan) on the stbd engine. Also, I carry a Honda eu2000i for electric cooking purposes mostly.

I rely on my SOC meter over the Renogy value on the tablet since the solar does not monitor other charging sources and doesn't know the battery capacity. It seems to be only voltage related.

I'm looking forward to my first full summer with solar in 2021. I'm thinking about keeping a ledger so I can track its performance throughout the months afloat. If I actually follow through with that, I'll share it here on TF.

 

[skipgundlach]

As to adjustable angle of attack/exposure of panels, I cannot see people constantly adjusting during the day. As the boat rotates or swings on anchor or mooring,optimal positioning keeps changing. There are large land based solar farms where panels adjust to changing sun positioning, either automatically or manually, but it`s hard to see that working in practice on a boat,unless it`s in a slip. Seems easier to accept that fixed panels will, at times, be sub-optimally positioned.

We have ours mounted flat, no way in hell am I getting up on the roof to try and adjust 9 panels.

Any inefficiency or loss is made up for with extra panels
Panels are cheap, adjustable mounting brackets are not.

The problem is, almost everyone we saw while cruising, who had adjustable solar panels, had become tired of constantly adjusting them and just put them in the optimum position and left them there.

^^^^^^^^^^^^^^

What they said...

If you are a cruiser, your panels will be alone for great deals of time as you explore your locale/s. If you're traveling, presuming you to be a trawler as the forum name infers, your alternator/s should take care of the charging.

That leaves you in the uncomfortable position of mostly not having optimal angles for solar gain - at least not without some very interesting cost and construction and intelligence (machine) to enagle hands-off tracking.

So, you takes your best shot for the most possible watts in the least possible space. There are endless erudite and knowledgeable discussions in many places about expected gain in amphours related to fixed panel wattage. It's a great deal less than you'd want.

If you calculate a third of optimal as your typical average gain, likely you'd be too high, and I expect you know all the reasons for more than one controller for high wattage installations, all MPPT.

That said, if, in fact, you never leave the boat, and have the space and ability (physical space and time) to adjust your panels in a 360° arc, through a 90° inclination, in both cases without shading, it's true that your solar gain will be impressive compared to fixed panels. But most cruisers don't fit that description. Short of having multiple iterations of likely attitudes of sun to over those eventualities, fixed is the usual best.

N.B. mounting at least 10° will allow for better runoff and better rain-cleaning. Otherwise, and maybe even (as we do aboard Flying Pig, a sailboat with 720W arch mounted panels), an occasional soap and water scrub with a fresh water rinse will increase your gain...

 

[Nepidae]

We installed solar at the end of last season.

I was going to use our sundeck roof until I noticed that the radar arch threw a shadow there, so move up to the bridge, Hard to Top roof and attached 3, 220W Xantrex Flex panels. I used a Victron Smart MPPT charge controller and also added a Victron Smart BMV battery monitor.

Our house batt bank is 6-L16 6V AGM batts, wired in parallel & series. They provide 600AH of useable power. Before the addition of solar, we were able to arrive at a wall, w/o power or an anchorage around 1-2PM and stay that night, the next day and the day after and leave by 10AM the day after and still be within our the discharge parameters.

The panels are connected to each other in series and then connected to the batts. I have the appropriate breakers in the system. I'd post pictures but haven't yet figured out how to do it on this forum.

In Sept of '20 after the installation and some land travel, we were able to get out to test the install. We are in KY where we waited out the COVID last season and went to a little cove several miles from our marina. We anchored from a Monday to a Friday to avoid the weekend crowds.

We experienced ranges around 400Wh while in our open slip, covered on each side.

When we went out to the anchorage, the panels really kicked in. We saw production rise to 2.7kWh per day. The Smart BMV gauge provides SOC (State of Charge) for the batts. It also provides a Time remaining for batt life. During that period we didn't drop below 85% SOC and Time remaining started at 3d 22h and went up to 4d 17h and then to Infinite.

The only way that I could see the angle of the panels really mean anything is if the angle could change as the boats movement changes. At anchorage a boat can swing and only some sort of intelligent configuration could change to keep the best angle, that is without a continual amount of human intervention.

I might add that panels made today have the ability to capture the most sunlight due to the cells and how they are made. Xantrex states, "the Max panel can harvest up to 20% more energy during the day in low light or shaded conditions compared to a standard solar panel". This is due to cell construction. This also increases the high sun capture.

The right size wiring and a quality charge controller are more important items in the build of your solar set up, as well as quality solar panels. Don't expect a $100 panel to perform at a level of the more expensive brands and construction methods.

Here (Xantrex Solar Max Flex Kits) is a link to the Xantrex Flex panels. I have no interest in Xantrex other than my extreme pleasure in their performance.

 

[Simi 60]

You sir, are running a small ship
Just having enough real estate to put 9 panels down is out of my tax bracket ��

You run several boats and I assume park them somewhere, run vehicles to get to them and sleep in a house at might.

We run one boat and dont use marinas, or pay for and maintain road vehicles and don't sleep in a house at night.

I would be thinking it is you who is in the higher tax bracket.

I’m just trying to keep my fridge/freezer going without starting the generator..

As are we, just a few more of them.

 

[Curiosity]

You can get LED bulbs for darn near any light fixtures, so no need to change them just to get LED's. Which ever way you go be aware that incandescent bulbs don't care about polarity but most LED's do. If an LED bulb doesn't work when you first plug it in, you'll have to reverse the polarity. If it's a festoon bulb, those are the ones with contacts on either end, just turn it around. If it has a socket you'll have to drop the fixture and reverse the wires. Some people doing this found the the lights were wired with all the same color wire so you couldn't even tell which was positive or negative. With the original bulbs it just didn't matter.

I did not know I could just change bulb. Figured I would be changing all fixtures.

 

[motion30]

I often hear about making an energy budget. so my question is how do you calculate the summer output as opposed to the winter output on your solar panels?. And on small boats that we have I don't think an energy budget is really that important because generally you don't have the real estate to put up enough solar panels anyhow. My opinion is to fit as much solar as you have room for, there is always use for additional power. Run a water maker a hot water heater anything that makes your life easier.

 

[mvweebles]

As I pursue the solar idea.
Does anyone have a solar worksheet they like to use? Is it better to try to buy a system in a kit or buy the pieces and put it together.

There are many solar suppliers for off grid and RV. I have used two and they were sort if good, sort of not. The best help I've received is from CruisersForum, the sail oriented sister site to this TF. They have a few solar wonks who are extremely knowledgeable. I will say it's not too difficult. Panel selection is driven by available space. From there you have to decide whether to run series or parallel, which is a good question for CF once you get there. And then select the controller which is a function of power. Whether you have one large controller or two or more smaller controllers depends on whether your panels all receive identical exposure without shading. For me, with four panels on a curved hardtop, the two pairs - starboard and port - are at slightly different angles. So I separated into pairs with a separate controller for each. Attached is my wiring diagram.

I have designed two other solar systems. One for off grid construction power of a friend's cabin in Wyoming. The other for a condo with roof deck in Yucatan. For the latter - a 16 panel grid-tie system, I used software from a US energy department designed for professional use. It's a bit difficult to use and I do not recommend it for small systems like this, though have included the link if anyone would like. I you're with angling the panels for the Mexico system. The natural install location - atop a pergola - was tilted 3 degrees in the wrong direction. I was really worried. Until I ran the numbers in the NREL software. Actual difference in annual production was under 5% hit, and was actually better in the summer months. My conclusion? At least in lower latitudes, I'm not worried about titling the panels.

https://www.nrel.gov/buildings/sunrel.html

Attached also is my solar system wiring diagram - 800w power will generate around 325 AH @ 12v per day. Will not power A/C, but will provide indefinite power for all else off grid.

Peter

 

[mvweebles]

I often hear about making an energy budget. so my question is how do you calculate the summer output as opposed to the winter output on your solar panels?. And on small boats that we have I don't think an energy budget is really that important because generally you don't have the real estate to put up enough solar panels anyhow. My opinion is to fit as much solar as you have room for, there is always use for additional power. Run a water maker a hot water heater anything that makes your life easier.

There are a couple rough rules in solar system design sizing. One that has been remarkably accurate is to take the system rating and multiply by five hours to get the average daily power production. Importantly, this the annual average. Many boats are used primarily in one season - Florida based cruising boats in the winter, PNW boats in the summer. So figure about 10% reduction in winter, increase in summer, maybe more at higher latitudes.

For most boats, available space is the limiting factor. I found square panels that are 200w each. I have four of them for a total of 800w per hour of production. Using the 5x rough calculation cited above, my system will generate 4000wh per day on average, which works out to around 310-320 AH@12v per day. I have a high insulation fridge with remote compressor, and a similarly constructed separate freezer. Together they consume around 80-100 AH per day. So plenty of power, though I caution that leaving MFDs running for anchor watch or similar is a deceptively large power draw, as is recharging PCs. It adds up.

Peter

 

[skipgundlach]

clip...

For most boats, available space is the limiting factor. I found square panels that are 200w each. I have four of them for a total of 800w per hour of production. Using the 5x rough calculation cited above, my system will generate 4000wh per day on average, which works out to around 310-320 AH@12v per day.

clip....

Peter

Have you found that to be the actual case? In Vero Beach (27N latitude), my fixed 720W panels are lucky to approach half that (2KW) and usually far less.

In the summer, it will be higher but so will the drain, as my reefer/freezer will struggle with the typical 80s low/90s high despite the 6" of extruded polystyrene insulation.

Getting the very most wattage in the smallest space is a costly venture (which I undertook), and for some years Sunpower has been the leader in efficiency. You can buy watts at as low as 50 cents, or even lower in takeouts from upgrading systems, but you need orders of magnitude more space to achieve the production of the higher efficiency panels.

And what an earlier poster has said, Cruisers Forum has a lot of very experienced folks with generally more challenging installations (sailboats hae less real estate to use, and more shading); highly recommended reading.

 

[mvweebles]

Have you found that to be the actual case? In Vero Beach (27N latitude), my fixed 720W panels are lucky to approach half that (2KW) and usually far less.

In the summer, it will be higher but so will the drain, as my reefer/freezer will struggle with the typical 80s low/90s high despite the 6" of extruded polystyrene insulation.

Getting the very most wattage in the smallest space is a costly venture (which I undertook), and for some years Sunpower has been the leader in efficiency. You can buy watts at as low as 50 cents, or even lower in takeouts from upgrading systems, but you need orders of magnitude more space to achieve the production of the higher efficiency panels.

And what an earlier poster has said, Cruisers Forum has a lot of very experienced folks with generally more challenging installations (sailboats hae less real estate to use, and more shading); highly recommended reading.

My boat bases install is not active yet, but my two other terrestrial installs using similar components have definitely supported this 5x rule of thumb. Time will tell for my boat, but there is no shading, the cabling is sized for 3% loss, and separate MPPT controllers. I'll ultimately be in St Pete, so same latitude.

I'm surprised at your low production. I would think you'd get around 3000wh in winter, 4000kwh in summer. But that's just a guess. But still, 2000 sounds low for 720w of panels

Peter

 

[skipgundlach]

My boat bases install is not active yet, but my two other terrestrial installs using similar components have definitely supported this 5x rule of thumb. Time will tell for my boat, but there is no shading, the cabling is sized for 3% loss, and separate MPPT controllers. I'll ultimately be in St Pete, so same latitude.

I'm surprised at your low production. I would think you'd get around 3000wh in winter, 4000kwh in summer. But that's just a guess. But still, 2000 sounds low for 720w of panels

Peter

I agree - but in a set which saw 50A production at ~ equinox/spring, I think it's as about efficient as it gets.

In Vero, particularly in the winter, there are extended periods of cloudy weather, and we routinely have to engage our shore power (Honda 2200i) every few days to avoid excessive battery drop.

We're off the boat currently, or I could capture my victron's history page to illustrate....

 

[mvweebles]

I agree - but in a set which saw 50A production at ~ equinox/spring, I think it's as about efficient as it gets.

In Vero, particularly in the winter, there are extended periods of cloudy weather, and we routinely have to engage our shore power (Honda 2200i) every few days to avoid excessive battery drop.

We're off the boat currently, or I could capture my victron's history page to illustrate....

You gotta love having a 50A battery charger cranking away with nothing but the sun.

You might be right about the 5x rule being optimistic. I just did the math on my 16 panel system in Yucatan, about 21 degrees latitude. For all of 2020, worked out to right at 3.9x per day. As mentioned, panels are installed flat, much the same as a trawler would normally be.

I was the one who mentioned CF as a good source. I just posted a question on cabling and fuses for final install of my system. I'll get a few bone head responses but those are pretty easy to weed out. Info will be a LOT better than what I've gotten from the solar stores that tout great customer service.

Peter

 

[rslifkin]

I'm calculating the solar install I'm planning out based on a factor of 4, rather than 5, and based on AH at 14 volts rather than 12 to be conservative. For the 820 watts of panels I'm currently planning I calculate 234 ah/day based on that. That's probably a fairly conservative estimate, so I should have no trouble reaching or possibly beating it.


In the winter up here I'd probably do worse, but the boat is stored for winter anyway, so it doesn't matter. And if we do boat through a winter at some point, it'll be somewhere further south.

 

[Frosty]

I often hear about making an energy budget...And on small boats... you don't have the real estate to put up enough solar panels anyhow. My opinion is to fit as much solar as you have room for

I thought about posting to the thread but held back because for anything I came up with, there were always so many exceptions.

But, I tend to agree with motion: On small to medium sized boats there is rarely the room to install "too many" panels. Most people can always find a use for power. Solar panels have become relatively cheap. Conditions are always variable (sun/shade/orientation).

So I'd say to just fit as many panels as you reasonably can and go from there. It's unlikely you will find you have too many. Most here do have alternative charging means (that you have been using prior to installing solar) so you can just see how much of your loads you can cover. If all, great. Some, still pretty darned good.

Nowadays the general wisdom is that with a number of panels not oriented exactly the same (getting the same insolation), it's better to run more than one controller. That somewhat mutes the previous need to get the whole system right from the start (when expanding was more of a challenge or more $$ because you were trying to fit it all into one controller, but did you get a big enough one from the get-go, etc.).

For me, the thing I think about much more than "how many panels," is just the physicality of it. Where do I put them, how do I mount them, etc. Again, it comes down to having the real estate.

If I had a big enough boat to put on over 1,000 watts (or more), I suppose I might do an energy budget. But then maybe not because with a boat that large, most have commensurately large loads, so again hard to have too much.

So to sum up, my own choice is to use as many panels as reasonably possible, wire them up for next to no voltage drop, use a good MPPT controller, and make sure I have good controller and battery monitoring so I can see just where I stand. If that were not enough then I would consider adding more panels in the more difficult or expensive locations (new hardtop or whatever).

I'm not mentioning coordinating the size or condition of the battery bank because of the assumption that most people here already have a "working size" house bank and the means to charge it in some other way. If not, then of course that would be part of the picture.

Summary: Fit as many panels as you reasonably can, wire for elimination of voltage drop, good controller, good battery monitoring. Then enjoy what you have and see if you want to (or can) add more.

 

[jerridsc]

Bi-Facial Panels

Just bought a 400watt panel that produces power on both front and back. If tilting up to any degree is doable, catching ambient light power on the back of the panel can add greatly to output, and keeping the panel cool increases efficiency. Bi-Facial.

 

[skipgundlach]

Just bought a 400watt panel that produces power on both front and back. If tilting up to any degree is doable, catching ambient light power on the back of the panel can add greatly to output, and keeping the panel cool increases efficiency. Bi-Facial.

Was that 400W including the top and bottom?

What size is that panel (efficiency determines size)?

On the water, there should be (if you have made sure not to shade it just like you did the top) plenty of added sun to the underside.

Whose panel, and cost? Does it have two efficiency ratings, one for the top and another for the bottom? Or, perhaps, combined?

Some time ago (years) in another forum, there was a manufacturer who was looking for beta testers of a single size panel which the poster was going to try to mass-market to applications which could use the back-lit situation.

I never heard the outcome of that. My panels, mounted on an arch significantly over the water (~10 feet at least), would have massively benefitted from reflected light on the underside...

 

[Group9]

I agree - but in a set which saw 50A production at ~ equinox/spring, I think it's as about efficient as it gets.

In Vero, particularly in the winter, there are extended periods of cloudy weather, and we routinely have to engage our shore power (Honda 2200i) every few days to avoid excessive battery drop.

We're off the boat currently, or I could capture my victron's history page to illustrate....

You can tell here, who has called their wife over and said, "Look at the amps! That's almost theoretical!"

And, got the look.

 

[sunchaser]

You can tell here, who has called their wife over and said, "Look at the amps! That's almost theoretical!"

And, got the look.

Or had the girls ask "When will you start the genset Dad (five daughters) so we can shower and dry our hair?"

 

[Hippocampus]

Now with microprocessors and monocrystalline panels you can get efficacy from a small space. Initially was surprised how even a very small area of shadow markly decreases output. Think that’s the most important factor. Not getting any shadowing at all( not even an antenna) and having each panel working independently. For most boats that means putting them up on a Bimini or like structure. Pragmatically you’re just not going to be constantly adjusting the angle so flat is best.
Have found cleaning them periodically makes a big difference in output. Just a haze of dried salt or dirt kills output. So the other consideration is being able to get a soft bristle brush on the end of a boat hook pole on them.
The flexible walk on panels remain very expensive for what you get for output. Also when wet slippery. They’re awkward to deploy and store. Would rather spend the money on figuring out a good permanent solution.

 

[Hippocampus]

Make them shampoo on the swim platform. Keep hair, sand and salt out of the boat ��

 

[skipgundlach]

clip

... so flat is best.
Have found cleaning them periodically makes a big difference in output. Just a haze of dried salt or dirt kills output. So the other consideration is being able to get a soft bristle brush on the end of a boat hook pole on them.

Clip...

.

Flat is going to collect junk much more quickly regardless of latitude.

Sunpower makes a specific recommendation for angling them (don't now recall the angle but it's double digit) for self-cleaning properties.

We on boats can clean our panels from time to time but solar farms (while there ARE tractors with great large rotating brushes) are challenging for cleaning, so an angle works best.

I too, despite my ~10 degree slant, occasionally get up with a microfiber and soap and water around a deck brush and clean and rinse my panels. Even slanted, it's amazing how dirty they get... As to a soft bristle brush, while that will get off more grime, it will also leave a lot of spaces untouched unless you do it many times per session. Thus the microfiber, frequently rinsed...

 

[rslifkin]

There's one big downside of a fixed angle to the panels for self-cleaning on a boat. Some days you'll be facing a direction where the angle benefits you, but other days, they'll be angled the wrong day and reducing output to worse than the flat panels would give. Personally, if the panels are in a spot that's easily reachable for cleaning, I'd want just a very slight angle for drainage and nothing more.

I'll be putting panels on my boat this spring. Plan is to mount them on the cabin top forward of the windshields (on either side of the horns shown in the picture). They'll be angled slightly forward and outwards to match the angle of the deck, but it's nowhere enough for self cleaning, just enough to drain the water off them.

 

[Hippocampus]

Good points Skip but have found with adequate water pressure a brush has sufficed. Like the idea of a microfiber towel and will try it.

 

[HeadedToTexas]

It's unlikely you will find you have too many...

For me, the thing I think about much more than "how many panels," is just the physicality of it. Where do I put them, how do I mount them, etc. Again, it comes down to having the real estate...

That is my thinking as well. The energy budget intrigues me from an engineering geek perspective, but I seriously doubt anyone regrets installing too much capacity.

 

[Group9]

There's one big downside of a fixed angle to the panels for self-cleaning on a boat. Some days you'll be facing a direction where the angle benefits you, but other days, they'll be angled the wrong day and reducing output to worse than the flat panels would give. Personally, if the panels are in a spot that's easily reachable for cleaning, I'd want just a very slight angle for drainage and nothing more.

I'll be putting panels on my boat this spring. Plan is to mount them on the cabin top forward of the windshields (on either side of the horns shown in the picture). They'll be angled slightly forward and outwards to match the angle of the deck, but it's nowhere enough for self cleaning, just enough to drain the water off them.

That's exactly where we have ours mounted now, on the cabin top. On the negative side, they do collect a lot of grime and dirt. And, we do get some minor shading from the mast (but, they are wired in parallel to minimize that). On the positive side, it's easy to clean them.

 

[stubones99]

Has anyone done the research on Micro Inverters as opposed to having a big single inverter for a string of panels? From what I see, they are saying that you get higher efficiency, lower DC line loss, and safer voltages, as well as redundancy in the event of an inverter failure... I think that's primary for dirt dwellers, not marine, even though exposed inverters at home will have lots of weather exposure, perhaps not as much salt though.

 

[Xsbank]

I use a wet towel and a squeegee for cleaning my panels. Then I do my windows too.

600 watts, an overcast day, rain, fog or snow or anytime after about the end of September, not enough energy produced. In the summer, I am "floating" by noon. Flat panels, no shadow.

 

[rslifkin]

That's exactly where we have ours mounted now, on the cabin top. On the negative side, they do collect a lot of grime and dirt. And, we do get some minor shading from the mast (but, they are wired in parallel to minimize that). On the positive side, it's easy to clean them.

Looks very similar to what I'm planning. Only differences are that I don't have a mast to worry about and I have to size and position things to leave a walkway up the middle so I can get to the windshields for cleaning.

 

[thedeltaskipper]

Looks very similar to what I'm planning. Only differences are that I don't have a mast to worry about and I have to size and position things to leave a walkway up the middle so I can get to the windshields for cleaning.

I have a light mast on my Chris-Craft 381 and we sometimes have the kayaks or SUP on the cabin top. My wife uses the cabin top as a spot to lay down her yoga mat and the kids like to hang out up there as well. With that in mind I'm installing 440W of Sunpower semi-flex panels (4) with magnet hold downs on the bimini this spring. I'm looking forward to waking up to the house batteries charging this season.

 

[rslifkin]

I have a light mast on my Chris-Craft 381 and we sometimes have the kayaks or SUP on the cabin top. My wife uses the cabin top as a spot to lay down her yoga mat and the kids like to hang out up there as well. With that in mind I'm installing 440W of Sunpower semi-flex panels (4) with magnet hold downs on the bimini this spring. I'm looking forward to waking up to the house batteries charging this season.

I thought about going that route, but with how rarely we use the cabin top for anything, I'll gladly lose that space for 800-ish watts of solar. Mine is an 86. I'm guessing yours is an earlier year, as the light masts seem more common on the early 381s.

At some point I'll build a hard top to replace the bimini, so I might put another 400 watts or so up there when the time comes.