Question about solar combiner box.

[EMD360]

I’m designing a small solar system for the RV roof. I have room for 3 100 watt panels which I have already ordered from Northern Arizona Wind and Sun. I know this company from when I lived in Arizona and have confidence they stock quality materials at reasonable prices. The panels are 52x20 so they can be shipped UPS.
I can’t wire 3 panels in parallel and I want the panels to be shade tolerant. I’m considering wiring them individually to a combiner box on the roof. I can’t find information about this wiring setup. I assume it would be the same as using a combiner box for more than one string. Each panel would be its own string. So has anyone wired their panels like this? Does it make sense to keep them as separate “strings”?

[time2roll]

EMD360 wrote:
Except I think I’ll use thicker wire to the controller.

#8 is also readily available.

[StirCrazy]

EMD360 wrote:
Pianotuna: it’s interesting to note that I’ve read that plain monocrystalline cells perform better under test conditions but recommendations for the best low light panels include both poly and mono types. So a lot to be said for the manufacturing.

alot has to do with the actuyal design of the panel also. split cell mono panels give better low light preformace than non split cells, 24v panels have better low light preformance than 12V. also how many bypass diods are they using and so on. a mono panel should out preform a poly if they are built to the same specs, its when you start comparing cheep mono to quality poly panels that things get skewed.

basickly poly panels are made from the reject wafers that were suposed to be mono panels, that why they need a larger size for the same output, are less efficent and so on. but weather its a poly or a mono if its sized properly they will both have the same result.

Steve

[EMD360]

Pianotuna: it’s interesting to note that I’ve read that plain monocrystalline cells perform better under test conditions but recommendations for the best low light panels include both poly and mono types. So a lot to be said for the manufacturing.

[EMD360]

time2roll wrote:
Do they have MC4 connectors? Just get a 3-1 MC4 connector to combine in parallel. Use an MC4 extension cable (#10 wire) to pull wire down to the controller. Plug and play.

Yes that is what I have decided to do. Except I think I’ll use thicker wire to the controller.

[time2roll]

Do they have MC4 connectors? Just get a 3-1 MC4 connector to combine in parallel. Use an MC4 extension cable (#10 wire) to pull wire down to the controller. Plug and play.

[pianotuna]

EMD360 wrote:
Monocrystalline are supposed to be better in low light but it’s probably a toss up with some other desirable characteristic. Polycrystalline are supposedly cheaper.

It is not quite that simple.

Mono produce more power per square inch.

Poly are larger and that makes them a tiny bit better in poor light. (i.e. shade tolerant)

We had a member here iirc that had one poly and one mono from the same company with the same wattage. The poly consistently out performed the mono.

Q cells are making a poly with a reflecting surface on the bottom--that causes light to bounce back out through the active layer and gathers a bit more energy.

[CA_Traveler]

If you don't have bypass diodes then wire them in parallel.

[2oldman]

Unless there's some new magic in panels, low light and shade are not the places you normally want to be.

[EMD360]

Monocrystalline are supposed to be better in low light but it’s probably a toss up with some other desirable characteristic. Polycrystalline are supposedly cheaper.

[EMD360]

Well thanks. I see that wiring them separately is essentially wiring them in parallel. I would increase the amps instead of the volts. These are 12 volt panels at 17.2 volts and 5.81 amps. I don’t think they have bypass diodes although they are described as high efficiency monocrystalline panels that are resistant to wind, hail and snow and have low light performance. I have on order a midnight solar baby box and the correct breakers. I know parallel vs series is a hot topic. Generally series for smaller systems and MPPT controller. Not sure why I want to complicate matters with another component except it does avoid using 10 ga wire or splicing to a larger gauge wire. I’d have three screw downs for each side and one larger wire down the refrigerator vent to the breaker box. Extra wire is negligible maybe three 10ft mc4 cut in half. Im still learning and planning for this install. Thought I had it figured out then I start thinking and maybe overthinking. Seemed like wiring them in parallel like this would act as a sort of bypass diode as each panel would have direct input to the controller. I ordered a Victron 100/30 MPPT controller.

[wa8yxm]

You know I just heard a presentation by Gordon West about the difference between Polychrystaline and mono chrystaline.... And that was the difference (Shade tollerant) alas. Did not pay attention to which.

Likely Ham Nation episode 499 but might have been500 or 498

He covers it often.

[pianotuna]

Ca,

Thanks.

[CA_Traveler]

Wops - Was trying to refer to the above links. :S

[2oldman]

CA Traveler wrote:

And this thread contains some incorrect statements or understanding of bypass diodes.

I don't see them.