Asking for help modifying existing solar array for better performance

[autumnbreeze27]

More testing, dodger array, series/parallel , 400W - array 33.4v, 2.9A = charging at 7.2A

Bimini array, series, 400W before towel test - array 43.4v 1.2A charging at 3.8A
Towel on panel #1 - 31.9v 1A charging at 2.6A
Towel on panel #2 - 32.1v 1.6A charging at 3.7A
Towel on panel #3 - 30.8v 1.3A charging at 3.1A
Towel on panel #4 - 30.1v 1.1A charging at 2.4A
No towels after test - 31v 1.5A charging at 3.5A

I'm pretty sure the panels have bipass diodes in the black box. I have replaced them before (same brand of panels, but different from these)

I'm not really sure how to analyze this, partly because I'm on benedryl to try and keep my sinuses from exploding. Looks like panel 2 is the problem still? Should I remove the bad panel from the array?

[barnakiel]

I will rethink all this while doing my evening run. maybe someone else will chime in meanwhile.

All other things equal, panel #2 would be my prime suspect. I would also consider #3 a possible cahoots, until proven innocent.

What catches my eye right off the bat is the voltage on bimini - 43.4V - this looks very low on a 4 x 12 V series. Such a series could be well above 60V (?)

Looking at the other set: you are getting 33.4V out of series/parallel - I think this translates into over 16.7 V per panel - exactly what I would consider fine. Following the same pattern a 4 x series on the bimini should/could deliver around 60V if all individual units are healthy and not shaded. 43.3V is just not good enough.

Panels 1&4 look fine IMHO.

Right?

b.

[autumnbreeze27]

I emailed Renogy about the panel, they are offering a credit towards a rigid panel or refund, but I have to get the panels to them somehow. Not sure if that will be worth the expense.

So it seems like these panels heat up, and the plastic warps, which breaks the cells. I can feel the panels are all rippled so that's definitely what happened.

[barnakiel]

I would not take neither rebate nor replacement. I would live with what there is, search the web, then buy different stuff, from different provider.

Seen plenty of trouble with flexible panels but sure there must be some good stuff out there. Look at Mini racers - they are 100% solar I think and very harsh conditions - close to water, walked on, etc.

Ourselves, we are on plain rigid panels with alloy frame. About 2 USD per Watt. Mono crystals, 36 cells. One 14 years old, one new'ish.

My next step will be black (backlinked) mono panels. About 5% more efficient than the plain mono stuff. I can get beyond 90W in our present 75W footprint.

Not sure if you can have framed panels on bimini or not. Some do.

Cheers,
b.

[socaldmax]

After reading all of this, I'm of the opinion that you don't have one defective panel.

What you have is 8 semi flexible panels that don't really put out 100w ea., one brand puts out slightly more than the other, but none of them produce 100w. Actually, no solar panel puts out advertised wattage unless conditions are perfect, which they never are. Flexible panels are even worse and mounting them directly on a flat surface makes them heat up more, which is even worse.

The bigger issue you have is where you have them mounted. You're getting a huge amount of shade due to the boom and sail, so at no point would you ever get even 50% of theoretical max. solar harvest, since the boom is shading one side, the other, or both.

You'd be better off with 2 x 400w rigid panels mounted on an arch aft of the boom.

Another point I'd like to make is that 12 awg wire is, IMHO, too small for any solar installation. Yes, I know the voltage drop is not considered excessive, but I've never designed a solar system to minimum standards, rather to the highest the customer's wallet will allow. So far, we've always used 6 awg from the panels to the controllers and 4 awg from the controllers to the bus bar. This minimizes losses so that the choice of panels and controllers also maximizes output. Between that, mounting the panels with no shading and using more panels, we've managed to harvest enough power in the winter, and more than enough in the summer.

Maximizing your solar harvest is all about minimizing all of the small losses along the way.

[autumnbreeze27]

I'm not sure what kind of sailboat you have, but my boat's boom is moveable. If I put the boom all the way over to port or starboard, the panels only get shaded by the masts when the sun is in front of the main mast or behind the mizzen.

As for the voltage, right now my dodger array is putting out 32v at 4A. I've got a 12' run, which means I've got a voltage drop of 0.19 (0.59%). If I upgraded to 6 awg wire, the voltage drop would be .05 (0.16%). So for 344% more expense I can gain 0.43% more power. My budget doesn't allow for such a huge offset in cost/benefit.

Clearly if I'm covering a panel and the voltage solar array output does not change, then the panel is not contributing any energy, and is dead. Considering the manufacturer is no longer selling these panels, and offering refunds or replacements with a different product, it's clear they are poorly designed.

The deal is I'm in Mexico cruising, I don't have any income, and I'm trying to get the most power with what I have available.

Should I put the dodger panels in series?
Should I remove the dead/low power panels?
I'm also trying to figure out replacement costs in Mexico vs. getting these replaced in the states.

Appreciate your willingness to try to help though!

Originally Posted by socaldmax

After reading all of this, I'm of the opinion that you don't have one defective panel.

What you have is 8 semi flexible panels that don't really put out 100w ea., one brand puts out slightly more than the other, but none of them produce 100w. Actually, no solar panel puts out advertised wattage unless conditions are perfect, which they never are. Flexible panels are even worse and mounting them directly on a flat surface makes them heat up more, which is even worse.

The bigger issue you have is where you have them mounted. You're getting a huge amount of shade due to the boom and sail, so at no point would you ever get even 50% of theoretical max. solar harvest, since the boom is shading one side, the other, or both.

You'd be better off with 2 x 400w rigid panels mounted on an arch aft of the boom.

Another point I'd like to make is that 12 awg wire is, IMHO, too small for any solar installation. Yes, I know the voltage drop is not considered excessive, but I've never designed a solar system to minimum standards, rather to the highest the customer's wallet will allow. So far, we've always used 6 awg from the panels to the controllers and 4 awg from the controllers to the bus bar. This minimizes losses so that the choice of panels and controllers also maximizes output. Between that, mounting the panels with no shading and using more panels, we've managed to harvest enough power in the winter, and more than enough in the summer.

Maximizing your solar harvest is all about minimizing all of the small losses along the way.

[newhaul]

Breeze for now IMO it would be best to bypass the bad panels and wire the rest in parallel on the bimini . This will mean yes less total harvest but also means that a failing/failed panel even with intermittent problems will not affect the rest of the array. I have no experience with the flex panels just the renogy 100 watt mono ridgid ones they don't weigh that much and I have been able to purchase them for $125 USD . So if they are willing to give you a good credit it may be worth a trip north to get new panels and mount them on the Bimini depending on ( possible reinforcements of the Bimini frame to support the additional weight ( rigid weigh about three times the weight of flex )

[socaldmax]

Originally Posted by autumnbreeze27

I'm not sure what kind of sailboat you have, but my boat's boom is moveable. If I put the boom all the way over to port or starboard, the panels only get shaded by the masts when the sun is in front of the main mast or behind the mizzen.

As for the voltage, right now my dodger array is putting out 32v at 4A. I've got a 12' run, which means I've got a voltage drop of 0.19 (0.59%). If I upgraded to 6 awg wire, the voltage drop would be .05 (0.16%). So for 344% more expense I can gain 0.43% more power. My budget doesn't allow for such a huge offset in cost/benefit.

Clearly if I'm covering a panel and the voltage solar array output does not change, then the panel is not contributing any energy, and is dead. Considering the manufacturer is no longer selling these panels, and offering refunds or replacements with a different product, it's clear they are poorly designed.

The deal is I'm in Mexico cruising, I don't have any income, and I'm trying to get the most power with what I have available.

Should I put the dodger panels in series?
Should I remove the dead/low power panels?
I'm also trying to figure out replacement costs in Mexico vs. getting these replaced in the states.

Appreciate your willingness to try to help though!

Yes, I realize your boom is movable. In your photo, it clearly shows your boom shading all 4 port panels. Even if you swing the boom even farther off to the side, it's still going to shade the 2 cabin panels, unless you can swing it nearly 90* to the centerline.

As for your cabling, 12' sounds pretty short, but did you count both directions? That would double everything, including losses. Maybe 6 awg would be overkill on this system, but at least 10 awg would at least match the cable used with MC4 connectors.

In your position, I'd replace all 4 of the brand that has the defective panel and get the rigid ones they make. I'd recommend keeping the panels in parallel to minimize shading losses and accept whatever power you get.

Perhaps in the future, you can afford to build an arch and move some of those panels to a better location.

For an idea what others are harvesting right now, I have a customer here in San Diego harvesting around 35-36 amps with 640 watts of panels and 2 x 20 amp MPPT controllers for most of the day.

I have a friend of mine who has 750 watts of solar panels connected to a TS-MPPT-60 controller and his installer ran the solar panel outputs through a 50 amp fuse. Unfortunately, he didn't tighten the connection well enough and it burned the fuse holder (he used 6 awg wire for about a 35' total run) to charcoal. When I look at how much heat was generated by a poor connection, I can't even imagine stuffing that much power through a 12 awg wire, and I've been an electronics technician for the last 32 yrs.

Well, I've submitted all of my ideas. Wish you were here in SD, I'd stop by and help you out. Best of luck to you!

[autumnbreeze27]

Ah, I see what threw ya off, it was that pic!

Here's a better one of how we typically look at anchor. You can see the bimini panels getting shaded by the mizzen mast and radar. We finally got a clear day today so I will watch the panels and take some readings/do some tests when I can clearly see I'm getting no shading. All the other testing was done on overcast days so no shadows.

But despite reading about shading and parallel vs series, maybe I still don't get it. If they are wired in series and are about 16v ea, shouldn't i get around 60v, and then if one panel gets shaded wouldn't it just drop 16v?

[autumnbreeze27]

Just ran a test, unshaded bimini panels
Panel Covered - Charging Amps - Array Voltage/Amps
0 - 9.7A - 48.1/2.6
1 - 6.3A - 44.3/2.0
2 - 7.5A - 42.1/2.4
3 - 7.2A - 38.5/2.5
4 - 6.9A - 38.2/2.4
0 - 8.6A - 38.6/3.0
1 - 6.5A - 39/2.3

Only thing I can think of is I had some kinda shading issue when i tested in the overcast. Hey I was sick, give me a break.

Right now it's 11:30am, and I'm in full sun on all panels, no shading.

The dodger setup is 30.89v @ 8.5A = 18.4A to the batteries
The bimini setup is 46v @ 2.8A = 9A to the batteries

So I'm still getting the same 30A I was getting before I started messing with things. The sun is at 77 degrees elevation.

I should be able to get roughly 30A out of 4 panels, so I'm basically getting 66% rated output on the dodger and 33% rated output on the bimini?

I tested the dodger panels just now, to see how the number would compare since the changes:
Panel Covered - Charging Amps - Array Voltage/Amps
0 - 19.2A - 29v/9.4A
1 - 13.5A - 29v/5A
2 - 10.7A - 29v/2.4
3 - 9.7A - 29v/4.6
4 - 9.8A - 29v/4.7

I should probably try the test again out of order to see if the results vary that way.

[socaldmax]

Originally Posted by autumnbreeze27

Ah, I see what threw ya off, it was that pic!

Here's a better one of how we typically look at anchor. You can see the bimini panels getting shaded by the mizzen mast and radar. We finally got a clear day today so I will watch the panels and take some readings/do some tests when I can clearly see I'm getting no shading. All the other testing was done on overcast days so no shadows.

But despite reading about shading and parallel vs series, maybe I still don't get it. If they are wired in series and are about 16v ea, shouldn't i get around 60v, and then if one panel gets shaded wouldn't it just drop 16v?

OK, in that pic you have no shading from the boom, but the radar and spreader is completely wiping out the stbd bimini array and it looks like the shadow partially covers 1 of the port bimini panels.

As far as parallel/series connections go, think of it like a garden hose. If you have 4 panels in series and step on the garden hose, how much water gets through? None, because it all flows through that one hose.

If you have 4 panels in parallel and step on one hose, you stopped the flow from that one panel, but the other 3 hoses are still open to flow water (power.)

That's a gross oversimplification, but that's basically how we should look at it, short of whipping out ammeters and doing a bunch of testing.

[socaldmax]

Originally Posted by autumnbreeze27

Just ran a test, unshaded bimini panels
Panel Covered - Charging Amps - Array Voltage/Amps
0 - 9.7A - 48.1/2.6
1 - 6.3A - 44.3/2.0
2 - 7.5A - 42.1/2.4
3 - 7.2A - 38.5/2.5
4 - 6.9A - 38.2/2.4
0 - 8.6A - 38.6/3.0
1 - 6.5A - 39/2.3

Only thing I can think of is I had some kinda shading issue when i tested in the overcast. Hey I was sick, give me a break.

Right now it's 11:30am, and I'm in full sun on all panels, no shading.

The dodger setup is 30.89v @ 8.5A = 18.4A to the batteries
The bimini setup is 46v @ 2.8A = 9A to the batteries

So I'm still getting the same 30A I was getting before I started messing with things. The sun is at 77 degrees elevation.

I should be able to get roughly 30A out of 4 panels, so I'm basically getting 66% rated output on the dodger and 33% rated output on the bimini?

I tested the dodger panels just now, to see how the number would compare since the changes:
Panel Covered - Charging Amps - Array Voltage/Amps
0 - 19.2A - 29v/9.4A
1 - 13.5A - 29v/5A
2 - 10.7A - 29v/2.4
3 - 9.7A - 29v/4.6
4 - 9.8A - 29v/4.7

I should probably try the test again out of order to see if the results vary that way.

So it looks like your bimini panels are producing 50% of the dodger panels, but neither set are producing quite what they should.

I prefer to do power comparisons using watts, this way it's just power and the voltage is out of the equation.

So your bimini panels are rated at 400w and actually producing 128.8w (46x2.8), your dodger panels are rated at 400w and actually producing 262.6w. At a charging voltage of 13.8v, you're getting 28.36A into your battery bank.

Have you tried swapping the sets of panels to the opposite MPPT controller, just to eliminate the possibility of a bad controller?

If both controllers are giving good results, then I'd say your dodger panels are performing about par for flexible panels, a little less than rigid panels would give you. The bimini panels are definitely not working well, if you can exchange those for rigid panels, I'd do that.

Also, excellent job of troubleshooting and documenting your results for us to see, it makes a world of difference when trying to help and you've been very thorough with all of it!

[autumnbreeze27]

Thank you all for your help.

Regarding the step on the hose analogy, I thought the panels had bypass diodes so a dead panel would still let the juice by? If the bad panels weren't letting the juice by, then I wouldn't be getting any power at all.

I'm thinking about changing the screws out that hold them down to longer ones, and putting some line underneath them so they'll get ventilation. I don't think it will help, I think the bimini panels are fubar and will just put out what they put out until they're replaced.

[barnakiel]

Yes. A bypass diode should allow juice to flow thru when a panel is kaput.

When I open the box of our rigid panels, I can see diodes too (if I remember well, two of them). I assume a 12V panel is then just a series of two 6V arrays. Etc.

Cheers,
b.

[barnakiel]

Yep.

I think one panel of the bimini set is shot. Not panel #1 though. Hence voltage only 48 V where we could expect about 60 V.

Not sure but possibly a sick panel can 'drag down' the whole set too - on the lines like one dead cell is pulling down the whole battery (?)

Isolate, dislocate, replace with something very electrically alike. Immediate reward: 1/8 gain in solar harvest.

b.