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Any advice on Solar panels or MPPT?

5K views 39 replies 17 participants last post by  travlin-easy 
#1 ·
Seems like electronics change daily so I wonders if de authority is about on this subject.
I have a Rawson 30' and welding a rack (removable), on the stern for the wind gen, radar and that will be removed when not cruising.
My question is what MPPT would serve wind generator and solar if that exists and some good panels. Maybe a package with panels and MPPT together.
Looking at two golf bats, maybe four but want simple.
Getting practice in for the long haul but not yet. My wife is a kiwi and we want to sail the boat down there or ship it to live on.
Rack would be almost 6 feet up and off the stern so 2 x 100 watt panels would rest there? Makes me nervous about the roll.
Will
 

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#2 ·
#4 · (Edited)
We use a Genasun controller . https://www.altestore.com/store/cha...ries-p10626/?gclid=CNiz2ufC_tICFYNsfgodJswFkw
And this 100w panel . 100 Watt 100W 12V 12 Volt Lightweight Solar Panel RV Boat/Sailboat/Yacht Marine | eBay
I made a frame out of oak strips and we hang it from the life line . Our batts. are 2 6v Trojan t-105s' in a series , that is our house bank . Typically we are away from shore power 2 weeks at a time . I forget the exact numbers but we maintain 12 .5 v at night and I have seen readings of 14.5 during the day . Our amp needs are low ie no reefer , so we are fine with just one panel .
 
#5 ·
This strikes me as too much stuff for a 30' boat.

I would lose the rack, radar, and wind. I doubt you need that much power (or you can design around less), and I'm sure that is too much windage.

Don't get to feeling you need all the toys, just because the other boys say you "need them." You may be better off with less on a smaller boat. I'd put panels on the dodger and call it good.
 
#8 ·
A wind generator ordinarily uses a dump regulator, very different from how an alternator is controlled. There are several devices sold as wind "gnerators" that actually are alternators (yeah!) or have mechnical brakes built in, to avoid the need for a dump regulator.

So, whether an MPPT controller (which normally does NOT service any type of wind generator) might service what you've got, depends on the specifics on the gnerator and whether you can find the oddball MPPT controller that will deal with it.

Odds are you'll do better with a separate controller for the wind generator, and you'll gain some redundancy that way in case one of the other system fails.
 
#9 ·
I found out the hard way not to try and use the same controller that manages my windmill for my solar panels. Just doesn't work very well with the way solar produces vs wind. I'm about to install a MPPT (Victron) for our 400 watt solar array, and will keep the dump controller for the windmill.

The construction you're describing does seem like over-kill for a 30' boat, although I've seen davits on similar sized boats which also double as solar panel mounts. With the windmill, I'd be worried about too much windage on the stern … but I'm sure you've thought about that.
 
#12 ·
I have a Genasun controller for my little boat. I've never used anything else so I can't compare it.

I looked up the Rawson 30, gawrsh that's a pretty boat. Does seem like it might be a shame to put all that junk on the trunk.

But you said it'd be removable, and at SA/D of 13 and D/L 503 you're probably not going supersonic anyway.
 
#13 · (Edited)
I've spent a few years studying solar and did my own 48 volt system here....which currently works perfectly.

Solar on a boat is a bit out of my realm. I might suggest youtubing the experiences of people who have mounted solar on their boat. They seem to be generally happy with their solar arrays. I have not seen a youtube video with a wind generator on a sailboat. For some reason, I have a negative feeling about that.

PWM chargers are very simple, quite inexpensive and fine for applications up to 600 watts. Beyond 600 watts, the far more sophisticated MPPT controllers are generally called for.

I would generally recommend a simple 12 volt system if maxing out at less than 800-1000 watts. Remember that a lot of people decide to expand their system and 24 volts would prove handy if that happens. I am also bringing a home solar perspective.

Golf cart batteries are excellent values in true deep cycle "solar" batteries. They just can't be touched value wise for the solar newcomer. A number of solar batteries are identical to golf cart batteries.

Refrigerators are energy hogs. It would be quite difficult to keep even a small fridge satisfied unless you sail in cold locales.

The flexible panels are very interesting. The solar experts that I consort with do not feel that current flexible panels will offer good longevity. They may be the future, not the present....according to them. Fixed solar panels offer 30-40 years of reliable output. If ~5 years is enough then flex panels may be for you. I am not a flex panel expert by the way.

Corrosion due to salt spray may be an issue. Heat shrink wrapping is known to offer good protection when properly done. Fuses will enhance safety and should lower fire risk significantly.

Solar gets complicated. It takes a very large book to cover the basics. Figure the panel output to be 25% less than rated output and that is with panels that are "pointed at the sun". Mine are mounted at a 45 degree angle since I live at 37 degrees latitude and favored winter time production due to the short, cloudy days of winter.

Schneider and Outback make exceptionally reliable solar equipment though they generally cater to the larger solar installations. I have seen the previously mentioned Victron recommended. I run a large chest freezer off of a Renogy 24 volt 40 amp MPPT and am happy to date. They run about $200. Do not try a $15-$30 charger unless you get batteries for free. PWM chargers are very simple by the way. The very cheapest $15-$30 chargers may never adjust their charge output as the batteries achieve a full charge. So they "cook" your batteries.

BP quit making panels a number of years ago. I wouldn't worry too much about the manufacturer and their warranty. Panels are very cheap these days and manufacturers tend to disappear before warranty may become an issue. Shipping is a killer for panels that are too large for UPS/FedEx. For that reason alone, it may be best to get smaller panels in the ~100-120 watt range.

I would just do solar panels. Solar is complicated enough without "frying your brain" with a more sophisticated system. Keep a fire extinguisher handy. Unlikely to need of course.
 
#14 ·
A bit of misinformation in the previous post.

*MPPT controllers suitability has zero to do with amount of wattage.
*Refrigeration systems are not "hogs". The biggest hogs on a sailboat are the autopilot, and the stereo system. Most refrigeration systems draw less than 5amps *when running*. Properly insulated, they aren't running that often. We ran a large freezer, and a whole bevy of electronics in the tropics using two 100w solar panels, and had juice to spare. Proper insulation is key.

Like you said, solar on a boat is out of your realm.
 
#15 ·
MPPT becomes advantageous on larger systems because they tend to use higher voltage panels. If you are using big grid tie panels that run at 35+ volts, you should use MPPT. If you are running little 100 watt panels designed for 12 volt, PWM is fine. The higher voltage of the big panels is properly stepped down to the system voltage, harvesting the extra current, with MPPT.

Biggest problem with solar on a sailboat is shading. Used in conjunction with the alternator, even a very small solar setup is excellent at properly topping off a battery bank...something the alternator sucks at. Alternators are better for bulk charging. I think solar is great just as a battery preserving supplement, if the boat isn't large enough for a big array.
 
#16 ·
I am also in the process of installing solar on my boat. I put a 100 watt panel on the stern rail, 1 100 watt panel on the seahood and 2 25 watt panels on the coachroof stepup area (no better way to explain it). But I am curious about autopilots being one of the biggest users of power on the boat as I thought tillerpilots generally used less than 1 amp.
 
#17 ·
Is there a downside to MPPT vs PWM? When I was shopping around for controllers I didn’t notice a big price difference between the two. MPPT was a little more expensive, but not significantly in the amp/voltage ranges that most boaters deal with.

On our boat the fridge certainly is our largest draw, but it is old and could be better insulated. Our tiller pilot only sucks major amps when working hard, but usually this is an indication that we need to balance the sail plan better. Mostly we use the windvane for self steering. Our stereo hardly draws anything at all. If a stereo is a large draw, then I sure hope you’re not anchored anywhere close by. It’s obviously too big and too loud!

A 200 watt panel system with a 12 volt system means you’re producing on the order of 12 to 15 amps x say 10 hrs per day (and that’s being pretty generous). So you’re putting ~150 ah of power into your batteries each day. That is damn impressive to be able to run a fridge, a large freezer and "a whole bevy of electronics” in the tropics on 150 ah per day.
 
#19 ·
A 200 watt panel system with a 12 volt system means you're producing on the order of 12 to 15 amps x say 10 hrs per day (and that's being pretty generous). So you're putting ~150 ah of power into your batteries each day. That is damn impressive to be able to run a fridge, a large freezer and "a whole bevy of electronics" in the tropics on 150 ah per day.
Just one freezer running as a fridge. Yep, worked great. Made water every day too. Fridge is only a huge draw when it is running, so insulation is key.

As for the stereo, unless you are running it very quiet, it is a large draw. Check your amp meter.
 
#22 ·
Do you guys budget power for your bilge pumps in terms of the amount of power you expect to draw each day even though the bilge pump is generally not run every day. Sorry for the slightly off topic question but I figured it might help the poster as determining ones power draw is important for a solar installation.
 
#23 ·
Not I. The bilge pump runs so infrequently that it would barely show up on the budget. I think if you have to budget daily power for bilge pumps, then you really have a bigger problem - or perhaps a wooden boat ;)

There are other pumps though that might be worthy of consideration, depending on usage. Certainly watermaker pumps would be a large draw, but deck wash, shower and even general cabin pressure water pumps should be considered. For my boat they're not large draws by any means, but for some boats I could see these pumps adding up.
 
#25 ·
I saw the Boat US article. Parts of it were a good primer on solar but I found a few of its assertions patently absurd:

"There's a world of difference between true high-performance marine solar panels and those used on residential and commercial properties. Prices reflect that..."​

The first sentence may be true for semi-flexible panels but with rigid panels my understanding has always been there's no such thing as a "marine grade" panel and that at this point there's really not much difference in quality or performance between a cheaper off-brand rigid panel and a rigid panel from a "name" manufacturer - other than maybe warranty. The cheap semi-flexibles have had enough issues for me not to feel comfortable using them, but I'd have no problem throwing a cheap rigid panel on my boat in the hope Solbians will come down in price in 5 years.

"While a small system designed just to stop a battery self-discharging will cost less than $300, a higher-capacity setup will cost in the thousands."​

$300 would easily put together a 50-100 watt rigid panel system. Except on boats with massive battery banks, this would do a good deal more than self-discharge prevention and is likely to be enough power on a smaller boat (assuming no refrigeration) to meet its complete electrical needs. If one wanted to go bigger, it is not hard to put together a 200 watt rigid panel system for under $500 and probably squeak in just under $1000 for 400 watts. Many cruisers have been able to achieve complete off-grid sufficiency with 200-400 watt systems, even with refrigeration.

Your goal is to get what you want within your budget and to be satisfied with the end result. Start by finding a qualified specialist for marine installation of solar-power systems​

If you have a limited budget, a marine solar installation specialist is the last person you'd want to talk to. Many people on the various sailing and RV forums have installed high performing solar systems without involving a "marine" specialist.
 
#26 · (Edited)
4arch-
There indeed are differences in panels. Just the same as a Lada or Yugo may look just like a Benz or Ferrari...it ain't the same product. There are very few companies offering actual "marine" and "vehicle" warranties on their panels, because they have found out that these environments eat solar panels. Buy a cheap panel from Horror Freight, and you'll see it says that it should not be left outdoors in the rain! Sure, they look the same, but the sealants on the junction boxes and in the panels (the glass of plastic is glued down) are not the same. Moisture at sea gets through seals. Moisture on land gets through seals. I've seen people in the industry talk about the "dirty little rumor" going around that many of the cheap panels are failing at ten years--not the 25 or 30 they were sold for.

Efficiencies might all be similar, since the underlying technologies and materials are similar. And throwing panels out in ten years might be good enough for some users. Hey, that 1794 Fiat with the rust holes in the trunk floor is still good enough for grocery shipping, right?

Same thing with costs. I'd suspect most boaters would make thir hookups with something like welding cable, not even tinned, and save gobs of money compared to proper marine battery cable. Except, what they call "solar" cable, which a professional installer will use, is a whole price bracket higher again. Fully tinned (they call it "silvered" but I'd bet that's not silver) and jacketed with a highly UV-resistant high voltage insulation, often teflon, not a rubber or typical PVC plastic.

And while a "rooftop" solar panel might have no internal blocking diodes ($$) because there will be no shadowing problems up on a roof, the panel on a boat should damn well have a blocking diode on each array of cells, because shadowing will be routine. Again, a different product but you'd never know by looking at it, unless you looked closely and knew what they looked like.

So the prices and remarks they make, while sounding incredulous, may just reflect the reality of "doing it right" with paid professional labor and products that carry written warranties--from vendors who can be expected to still be in business next year.(G)
 
#27 · (Edited)
To me, 10 years is an acceptable lifespan for an electronic item on a boat, particularly if it only costs $120 to begin with. Buying two $120 panels over 20 years is still money ahead of buying one $300 panel in the same timespan. Many of the 100 watt rigid panels in the $120 price range have been successfully installed in marine and RV applications with good results.

Usage of tinned wire and cable is a pretty well accepted dogma of this and other boating forms and almost any marine electrical book. I'd say its importance has been well enough publicized that anyone who'd use whatever was cheapest without doing any research probably isn't the type who otherwise would have hired a pro or otherwise would care about doing anything on their boat right. I believe the numbers quoted in my post above could certainly buy UV resistant tinned wire and other components for a quality installation. It's probably more the difference in panel prices and of course labor (paid vs. DIY) that drive my divergence with the author.

As for diodes, I've seen very few panels - particularly of the size appropriate for a boat - that don't have built in bypass diodes these days.

I have no problem with anyone using professional labor and buying quality products with robust warranties. My issue is with the article's implication that anything short of doing that and spending "thousands" for the privilege will result in a poor or undersized system when the reality I'm seeing is that systems "good enough" for a huge percentage of the boating population can be had for under $1000. These are not just hypothetical systems, but real installations that are out there functioning on sailboats as we speak. Not making that more clear is certainly not characteristic of the Boat US I've known in the past and makes the article read like a placement ad for the single solar supplier they interviewed. A more balanced perspective would have been appreciated.
 
#28 · (Edited)
The panel I use is a 100-watt Grape that I purchased from Home Depot 4 years ago. It still works like a champ, punches out the same voltage and current it did when I first purchased it, and it's built like a tank. That panel, because of competition, has come down $30 in price since I bought mine. http://www.homedepot.com/p/Grape-Solar-100-Watt-Polycrystalline-Solar-Panel-for-RV-s-Boats-and-12-Volt-Systems-GS-Star-100W/204211365http://

Almost forgot, they have a fantastic warranty: 5 year limited product warranty on materials and workmanship. 25 year warranty on 80% power output and 10 year warranty on 90% power output.

I also use an inexpensive controller with it, just to be on the safe side.

All the best,

Gary :cool:
 
#29 ·
I sincerely hope you're using some kind of a controller with a 100 watt panel if you don't want to boil your batteries alive.

I admit, I "nerd'd out" and bought a Victron Blue MPPT controller with Bluetooth functionality. The MPPT feature gets more efficiency out of the panel.
I haven't bought the Bluetooth dongle yet, but if I do, I'll be able to track energy production and consumption by looking at a mobile device.
 
#31 ·
That is an amazing price from a reputable retailer. Congrats on the dig. PWM controllers are really pretty simple devices. Yet it is easy to spend $120 for a larger controller from a big name.

I would like to think that West Marine would strive to carry items with a certain amount of corrosion resistance.
 
#32 ·
You may need a drink first. Here is a government run site that is easy to use:
PVWatts Calculator

That site will tell you what you should expect from panels at various locations and tilt...from month to month. I am somewhat surprised at reports of strong production from boat panels that lay flat.

Tinned cables are nice of course. For those who have not mastered heat shrink tubing, you need to get on that for your marine connections. You can shrink the tubing with a cigarette lighter if you have a little finesses.

Tinned copper lugs are supposed to be more corrosion resistant than copper lugs. Funny that they cost less.
 
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