Skip to main content ↑ ↓
Topic: 1200 watts of Solar on the roof (Read 1248 times) previous topic - next topic

Re: 1200 watts of Solar on the roof

Reply #25 –
Re: Using two charge controllers on the same battery bank: here is a forum with a discussion about this very topic.

Can you use two separate MPPT charge-controllers?

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: 1200 watts of Solar on the roof

Reply #26 –
FAQ about uni-solar flexible panels. Since these will be mounted flat with no way of raising them, I wanted to have at least some ability to charge in dicey conditions. Hence I ordered two of these (for something like $89 last summer). I have not put them into service yet as there are some items we need to get off the roof (old roof-top carrier and an old satellite dish) to make room. Other things have gotten priority until lately.

Q) Does the panel perform as well when it has shadows on it?
A) All UNI-SOLAR flexible modules (>10 watts) are equipped with bypass diodes wired across each solar cell.  The bypass diodes provide an alternate pathway for electricity that might otherwise flow into a shaded cell.  If 10% is covered by shadow, you will only lose 10% of the module's maximum power output. This is a great advantage of the UNI-SOLAR product line.  Most competitor products have bypass diodes in the junction box where a 50-100% loss of power may occur when only 10% of the module is shaded.

From: Uni-Solar Flexible FAQ

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."

Re: 1200 watts of Solar on the roof

Reply #27 –
wa_desert_rat
I was not aware the there are solar controllers that can cooperate via cross talk, except for the very expensive Outback line. One article you mentioned indicates making one controller be primary and the other be a follower. I am curious how that is done.

I studied the uni-solar panel advantages a few years ago and concluded the their advantages came at a price. They have become much more competitive in the last few years.

Partial Shading Power lose:
I agree that Uni-solar panels continue to be more resistant than other panels to partial shading. I carefully placed my panels on the roof such that partial shading from vent covers or A/C units will not occur as long as my coach is pointed east. Also my panels are not flat on the roof and provide maximum power when my coach is pointed east. I seldom park in the shade.

Another advantage of Uni-solar which you did not mention is their ability to maintain 100% output with the sun rays at up to 15 degrees off the perfect 90 degree. Unisolar has a clear weather protection with an organized dippled surface which refracts the light. I saw an article on this where two competing panels were attached flat on the roof of a motorhome and indeed, the Uni-solar provided more amphours as the sun moved through the sky.

Uni-solar clear weather protection is also very tough and will tolerate large hail stones which will crack other panels. 





Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: 1200 watts of Solar on the roof

Reply #28 –
I think that it is a bummer that the company with an innovative products such as the Uni-Solar flexible solar panels couldn't survive in business in spite of their fantastic product. I guess they were just ahead of their time... their panels turn up a lot on eBay these days for pennies on the dollar compared to what they sold for when the company was still in business. You can find them in various stages of completion from fully completed with the self stick adhesive and the pigtailed connectors attached to just the individual cell segments. I invested in 408W worth of the finished panels for about $650 or so. I got two of the 136W panels which are almost 18 feet long by 15 inches wide and two of the 68W panels which are slightly less than 9 feet long by the same width. There is only room for two of the longer ones on our 36 coach, but I believe I could add another six of the 68W panels if I wanted to max out the available roof space for a total of 816W. The 68W panels are 12V while larger ones are 24V (nominal). The current plan is to get the midnight solar classic 150 controller and wire the 12V panels in series (in effect making them equal to one of the larger panels) and the 24V panels in parallel but until I get the controller and do a bit more research I'm not sure on that. The idea here would be to have three banks of a hundred and 136W each at 24V. I could however just put them all in series for a total of 72 V and let the midnight solar controller dole it out to the batteries as it sees fit. If and when I get the other panels, I will have to make a decision there because it will be close to the maximum capacity of the controller if I put them all in series. I know this is oversimplifying a more complex calculation, but that's just where my thinking is at the moment, subject to new information of course....

I'd certainly be interested in any comments about that scheme! Since you can walk on these panels, I'm not too concerned about restricting access to components on the roof. Although note I said walkable, not danceable ;D if I was actually working on the roof say to replace the air conditioner, I would cover them with something like an exercise mat and a piece of plywood to protect them.
Don


Quote from: P. Wyatt Sabourin –
wa_desert_rat
I studied the uni-solar panel advantages a few years ago and concluded the their advantages came at a price. They have become much more competitive in the last few years.

Partial Shading Power lose:
I agree that Uni-solar panels continue to be more resistant than other panels to partial shading. I carefully placed my panels on the roof such that partial shading from vent covers or A/C units will not occur as long as my coach is pointed east. Also my panels are not flat on the roof and provide maximum power when my coach is pointed east. I seldom park in the shade.

Another advantage of Uni-solar which you did not mention is their ability to maintain 100% output with the sun rays at up to 15 degrees off the perfect 90 degree. Unisolar has a clear weather protection with an organized dippled surface which refracts the light. I saw an article on this where two competing panels were attached flat on the roof of a motorhome and indeed, the Uni-solar provided more amphours as the sun moved through the sky.

Uni-solar clear weather protection is also very tough and will tolerate large hail stones which will crack other panels.
The selected media item is not currently available.
Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: 1200 watts of Solar on the roof

Reply #29 –
Quote from: acousticart –
I'd certainly be interested in any comments about that scheme! Since you can walk on these panels, I'm not too concerned about restricting access to components on the roof. Although note I said walkable, not danceable ;D if I actually working on the roof say to replace the air conditioner, I would cover them with something like an exercise mat and a piece of plywood to protect them.
Don

Don... my original interest in the Uni-Solar products was to place along the roof edge outboard of the refrigerator vent on one side and the external TV antenna on the other. This space, otherwise unusable, would give us some charging on sunny days depending upon the orientation of the coach. I have no idea if the glue they are provided with will keep them down at 60mph but I propose to find out.

Pierce's revelations on that high voltage MPPT controller make me think that series is the way to go as long as you can keep within the maximums for both voltage and current. I had not realized that they were even better than I had thought until Wyatt mentioned the 15-deg off 90 sun alignment advantages. Maybe I should have gotten enough to cover the coach.

Wyatt's comments about matching panels are interesting. I would have thought that putting all panels in series would make any panel differences a non-issue. Simply add up the voltages and, Viola! (grin) you have charging.

I did not do the cover-the-roof thing because I  wanted to be able to raise some panels for better charging. So the Uni-Solars would give an advantage when we were not parked perfectly or not long enough to warrant raising the 24v panels. We'd get at least some charging.

But as I get beyond the 70-year stage I find myself less eager to get up onto the roof for anything. Luckily, my wife is 13 years my junior and still nimble enough to go up without stress. So I'm wondering, like you, whether simply covering the roof with the Uni-Solar panels might not be the best way to go.

Craig
1993 U225 36' Unihome GV with PACBRAKE exhaust retarder, Banks Stinger and Solar Panels.
Toad: 1999 Jeep Wrangler 2-door soft-top.

"No one has ever had to evacuate a city because the solar panels broke."
 

Re: 1200 watts of Solar on the roof

Reply #30 –
There is an aftermarket company in Arizona that takes the Uni-Solar panels and apparently makes their own custom trim pieces and charges a premium price for the panels and installation. I plan on screwing a piece of trim on the leading edge at least and sealing around the edges with caulking or perhaps Eternabond tape. As far as I can tell, not having actually installed panels as yet, the adhesive backing seems to be very eager to stick to anything it comes into contact with... it says in the instructions that you only get one shot to stick it on where you want to go. If 3M VHB tape can hold on large solar panels with only the surface area of the bracket footprint, I don't think these panels will have a problem staying put! I do like the fact that it retains a cleaner look than panels mounted on brackets. I did some testing in the sun with a temperature probe, and the rise in temperature behind the panels seemed to be a few degrees at most... Not really significant. Perhaps the temperature will rise more when they are actually dispensing current to the controller, but that remains to be seen.
Don
Quote from: wa_desert_rat –
Don... my original interest in the Uni-Solar products was to place along the roof edge outboard of the refrigerator vent on one side and the external TV antenna on the other. This space, otherwise unusable, would give us some charging on sunny days depending upon the orientation of the coach. I have no idea if the glue they are provided with will keep them down at 60mph but I propose to find out.
Craig
The selected media item is not currently available.
Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson