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DefinitelyMe · 17-08-2015, 09:45

I recently installed 4 semi-flexible renogy panels and figured i'd give a bit of feedback on them here. A bit of background first - i previously had a single, rigid 245-watt monocrystaline panel. This provided all the power i needed mounted in the cockpit underneath the boom. It was shaded by the boom and several lines but still performed very well. I replaced it because it was too big, heavy and got in the way a lot. So, now i have 4 x 100W semi-flexible panels mounted on 1/4" plywood and then hung on the after lifelines. My thinking was that if one side is shaded at any one time, i would still have 200W of panels facing the sun. Shading should be reduced because they're not under the boom. They can be tilted up when convenient, provide some privacy in the cockpit and should be able to handle some waves hitting them and hence provide some protection. They are wired in series to give an output voltage of somewhere around 70V, and charge regulation is by a Rogue systems MPT-3024.

First off - my initial impression was not good. The panels themselves are OK, but the attachment points are not in the same place for each panel (they must have been drilled by hand by eyeballing it) and the terminal boxes are simply glued onto the panels using some kind of flexible sealant very sparingly. The boxes themselves are plastic and two of the plastic covers had already broken despite good packaging for shipping. I beefed them up by filleting around the edges with some 3M UV4000 adhesive sealant.

Peak output - very good. I'm getting peak output of just under 20A near mid-day when both sets of panels are in a horizontal position. Most Ah so far in one day is 56, but this was sufficient that the controller went into float mode. I wouldn't be surprised to see over 60Ah in one day if the batteries were discharged sufficiently beforehand.

Partial shading - not good. First thing in the morning with the sun low on the horizon, only the side facing the sun is 'turned on'. I'm seeing about 4A in @ 33V, which gives about 9A output. Very good. However, if i then angle the second set of panels into the sun as well (so both pairs are getting light), it can take 2 or 3 minutes before anything happens. Then, the voltage shoots up to 66-70V, but the input current drops to about 1A and output to about 5A. Once all panels have 'switched on' they will remain on all day even if shaded again. I'm regularly seeing only 0.2 to 0.5A input in the middle of the day when sailing along with one side of panels in bright sunlight (with sufficiently discharged batteries that the controller is still in 'MPPT' mode). Additionally, any partial shading from a line or whatever casting a shadow over a panel has a big negative impact - far more than the old rigid panels.

Conclusion - still worth the money paid for them. If they last for 3 years i'll be happy. In the meantime, i intend to wire the two pairs of panels in parallel, as it appears that the series wiring is not working out in this instance. Perhaps the panels have some kind of bypass diode that prevents backflow of current into the panels when output is zero, but allows backflow once they have generated sufficient voltage to 'turn on'? Does this make sense? Any solar gurus out there who can explain this? If anyone's interested, i will report back once i've changed the wiring to parallel. I'm expecting a slight drop in peak output due to the increased resistance but hopefully a large increase in overall efficiency. Wire is 8AWG. Run to controller is about 20' (about 55' for the total series run, controller back to controller).

jwcolby54 · 17-08-2015, 10:00

If it were me I would go series / parallel. Wire each "side" pair in series, but then wire each "side" (series pair) parallel to each other. If that makes any sense. Each side or pair needs to be able to function independently so that if the other side is shaded you still get 1/2 of the total current available.

I am not sure about your specific panels, but what tends to happen with panels is that when wired in series, the total current is limited to the minimum current provided by any panel. Thus if each panel is capable of producing 6 amps (for example), but one of them is shaded and only producing 1 amp, then the total series set will only provide 1 amp. That is the problem with series wiring panels.

autumnbreeze27 · 17-08-2015, 10:54

We have 4 x 100 renogy panels on our bimini.

If the panels are 1 2 3 4, I've got 1 & 2 wired in series, and 3 & 4 wired in series, and then those are paralleled with the same setup on the dodger (except those are lensun panels)

I've found it extremely difficult to test them, but looking at the log on our morningstar we got 3910 watt hours 12 days ago, probably when we were at catalina with the boom swung out of the way.

jwcolby54 · 17-08-2015, 11:06

Quote:

Originally Posted by autumnbreeze27

We have 4 x 100 renogy panels on our bimini.

If the panels are 1 2 3 4, I've got 1 & 2 wired in series, and 3 & 4 wired in series, and then those are paralleled with the same setup on the dodger (except those are lensun panels)

I've found it extremely difficult to test them, but looking at the log on our morningstar we got 3910 watt hours 12 days ago, probably when we were at catalina with the boom swung out of the way.

Full power for 10 hours in a day is doing quite well. Good job!

Paul L · 17-08-2015, 11:34

We have similar Chinese flex panels. I drilled holes near the terminal blocks and ran wire ties through to beef them up. I also had to redrill the attachment points and put in non-rusting grommets. Like you, for the price they are a decent deal.

colemj · 17-08-2015, 16:25

I just finished installing two 100W Renogy hard panels (not the flexible ones). These appear to be quite well-made, and they are producing 13% more current than their rating at a higher temperature than their rating (this is measuring output directly from the panel, not the controller). Like the OP, they seem to suffer tremendously by partial shading - just a small shadow on a corner drops output to almost nothing. I checked and the bypass diodes are installed correctly.

Mark

DefinitelyMe · 18-08-2015, 05:24

Quote:

Originally Posted by jwcolby54

If it were me I would go series / parallel. Wire each "side" pair in series, but then wire each "side" (series pair) parallel to each other.

I am not sure about your specific panels, but what tends to happen with panels is that when wired in series, the total current is limited to the minimum current provided by any panel. Thus if each panel is capable of producing 6 amps (for example), but one of them is shaded and only producing 1 amp, then the total series set will only provide 1 amp. That is the problem with series wiring panels.

Yup, that's the plan for the wiring. I'll probably do that one evening this week, or maybe next weekend.

Very interesting about the minimum current thing. That would tend to be consistent with what i'm seeing, except that it seems like if two of the panels are not 'activated' at the beginning of the day, then they are bypassed entirely and i get the full current from the two that are in the sun.

DefinitelyMe · 18-08-2015, 05:28

Quote:

Originally Posted by jwcolby54

Full power for 10 hours in a day is doing quite well. Good job!

I think he means he's got 400W on the dodger and then 400W on the bimini, so that's 4.8 hours of full output. Still, that's more than i've managed so far with these panels, even with all panels facing up and minimal shading. Maybe the sun isn't so strong up here at 32N. I haven't made over 1000Wh in a day yet.

DefinitelyMe · 18-08-2015, 05:29

Quote:

Originally Posted by Paul L

We have similar Chinese flex panels. I drilled holes near the terminal blocks and ran wire ties through to beef them up. I also had to redrill the attachment points and put in non-rusting grommets. Like you, for the price they are a decent deal.

Good idea with the wire ties. I might steal that one from you :-)

autumnbreeze27 · 19-08-2015, 22:11

Quote:

Originally Posted by DefinitelyMe

I think he means he's got 400W on the dodger and then 400W on the bimini, so that's 4.8 hours of full output. Still, that's more than i've managed so far with these panels, even with all panels facing up and minimal shading. Maybe the sun isn't so strong up here at 32N. I haven't made over 1000Wh in a day yet.

You got it. I have 4 x 100W Renology on my bimini, and 4 X 100W Lensun on the dodger.

The whole angle of the dangle issue is why you want lots of panels, I knew if I had to tilt them it wouldn't happen.

I'm at 33.3N

DefinitelyMe · 20-08-2015, 07:33

Changed the wiring to series-parallel (each pair of panels in series and then the pairs paralleled) and, based on the one day of data so far i've seen a 20 to 25% increase in overall output. Yesterday wasn't as clear as some of the previous days either (cloudy, some rain and some thunder), so it all looks pretty promising for this arrangement. Moral of the story is that at least in this case, and based on minimal data, it appears that parallel wiring is preferred when the panels in question experience different light intensities and shading patterns.