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).