Originally Posted by Eleven
The comment about rigid celss being dependant on direct sunlight explains alot. My flexis worked right up 'till sunset and during cloudy weather
. Some loss but still useful amps.
I have had my conventional glass covered single
onboard, for 15 years now. (Not counting my two previous boats). They charged me back through thousands of days spent "on the hook". I also have installed these, as well as many other things, professionally.
It is absolutely NOT true that they, (glass single
cell panels), need direct sunlight! ANY light will produce power. People who perpetuate such myths are not actually taking a reading, they are just noticing that their battery
didn't get charged that day. We have A meters on each one, on the group of four together, and a Link 10 Monitor
counting the Ah gained that day.
We need about 40 Ah / day to bring our batteries back to 100%, which we do every day. On a good sunny day, or BRIGHT white overcast day... In either case, our panels produce about twice that. By having this necessary "X2" ratio... we get back to 100% fully charged, EVEN on VERY cloudy days.
If it is SO cloudy that it's almost DARK out, it might be close, so we tilt the aft panel toward the setting Sun for the last little bit.
The production in Ah going into the batteries, on cloudy, overcast days, seems to be around HALF of the maximum rating.
Regarding testing an old panel to see if it is up to specs... This doesn't tell much. The specs are not often correct, and their is more to it than Max A. If it is high A but V has gone down for example, it will not charge as well. One would have to test the panel's ability to charge a battery
when new, and with exactly the same conditions AND battery, test it again X number of years later. Not easy!
All panels have declining performance from cell breakdown, and the plastic or vinyl covered ones from UV degradation of the cover as well. A little bit of hazing cuts more than you think. Our glass panels can see a measurable boost by wiping off the pollen! Glass is easily refurbished to as clear as day one. Not so with plastic/vinyl.
We also mount all of our deck
panels on side rails of Starboard. this prevents rope
snags, and keeps air movement under them, boosting V.
Having used & studied these for 35 years, my observation, and that of MOST testing entities like Practical Sailor is:
Flexible panels have their place, but they are MUCH larger than single cell glass type, for a given power output, and for single cell glass panels, that output is consistently produced for about twice as long (on average), as the flexible kind. If you compare apples to apples... Ah produced over 20 + years, the flexible units cost more as well.
This is the consensus of opinion in the VAST majority of the industry, and should be considered in ones decisions.
Hopefully, a breakthrough is just around the corner. Perhaps this will no longer be true some day? For now... It is still the case.