Hello, all. I’m looking for some feedback on PV panels before embarking on the next upgrade to our electrical system.To establish the background, we will be mostly boondocking, and moving frequently, so the panels will be flat on the roof. Batteries are 600 ah AGM. I anticipate using 50-100 ah per day depending on the weather. If the batteries need some feeding we always have the gen and a PD 9280 converter to stuff some amps in. Performance in partial shade is important for us, we don’t want to select campsites without trees all the time. I would prefer to supplement with a little generator from time to time if needed.I’m thinking in terms of ~400-600w for now, with the option to upgrade later if we swap to a residential fridge or ...Q1: brands to include / exclude? I am the type to buy a Honda, so I don’t mind paying for quality, so long as it’s not just branding. I want reliability. Kyocera is uppermost in my list right now.Q2: Poly / Mono? I have read a number of times the poly respond better with partial shading. This gets complicated in my mind because I can fit a smaller mono panel between the roof obstacles at equivalent wattage… therefore the mono may get full sun more hours per day by virtue of the smaller footprint.Q3: panel size. For instance I could go with two KU265-6MCA or four KD 140SX-UFBS. The second scenario the panels cost about double (at least at the prices I was looking at today). Downside is the 265w panels are slightly longer in the longest dimension, and will be partially shaded a bit longer by the A/C units. And if I want to expand later, I will have room for more of the 140’s. Not so with the 265, I would have to mismatch panels and maybe do a second controller. I am also thinking the four panels will be somewhat more shade tolerant (more bypass diodes in total). I’m planning to run the array in series.Your comments much appreciated.

Running in series dictates amperage-matched panels. I don't know much about using two controllers... maybe someone else does.More diodes is better, and you'll probably pay for that. I too have no problem paying for quality, and Kyo has been good to me. Shade? Hard to say. I just avoid shade amap.

Sounds like you are on the right track - have fun with the project The K140 panels were my choice I have 4 of them and thinking of adding another pair. Went with a series/parallel configuration producing about 40Voc. Found this configuration allows for easy expansion in pairs and offers shade tolerance as good as can be. If shipping costs are a concern the smaller panel will save big $$A single quality 60 to 80 amp controller should do you just fine again enjoy the project

#1: Doesn't matter much. I chose quality (European). Roof panels is a long-term solution and solar is my only energy source now, so I need to be able to rely on it. #2: Poly is better overall. Performance in partial shade has nothing to do with poly/mono, it depends on the number of diodes, the more, the better. #3: Major difference between 265W and 140W is not "size" but "voltage". 265W panels are 24V, 140W are 12V. Different creatures and require different type of controllers. A long topic in itself. With that much wattage like you want, people "normally" go for 24V panels. "Occasionally" they go for 12V.24V are easier to wire, can be in series with mere #10 or #8 wire. 12V are usually wired in parallel, sometimes series-parallel. With wattage over 400 it means a beefy wire to controller AND a rooftop junction box. They cost more per watt. Once you've chosen either 12 or 24V, it's difficult to add another type into this mix later. Mismatch is a pain, and 2nd controller is more pain. Big residential fridge + parking in partial shade = daily generator, IMO.

My preference would be the mono panels over poly.They are a bit more efficient, are smaller in size for the same wattage and they are more heat tolerant (perform better when they get hot).

Thanks for the responses, everyone. Almot, I am planning at this point to go all series to MPPT. So the 140w panels will be 88.4 voc and 70.8 vpm.My thinking is the controller can make sense of it and charge even if only one panel is lit and three are shaded and in bypass. From what I understand if it's partial shading across multiple panels it's a crapshoot, and the MPPT controller may struggle to figure out which of the panels it's optimizing for.

PV panel selection? (long) | Good Sam Community

Almot
Explorer III
Feb 22, 2016
Ductape wrote:
I am planning at this point to go all series to MPPT. So the 140w panels will be 88.4 voc and 70.8 vpm.

My thinking is the controller can make sense of it and charge even if only one panel is lit and three are shaded and in bypass. From what I understand if it's partial shading across multiple panels it's a crapshoot, and the MPPT controller may struggle to figure out which of the panels it's optimizing for.

If 4*140 panels, 560W total, results in a less shading from roof A/C than 2*265, 530W total - I would go for 4*140W. A no brainer to me.

Partial shading in series can be difficult for any controller. It's all about sufficient number of diodes. I don't think MPPT will handle this any better than PWM. With this wattage you're more likely to find a decent MPPT than PWM though, not to mention #6 or #4 cable and rooftop box - in case of PWM.

Of course, there is always an argument that 4 panels in parallel will handle partial shading better than 4 panels in series - don't know how much truth there is to it ;)... Hear it from times to times.
Ductape
Explorer
Feb 22, 2016
Thanks for the responses, everyone. Almot, I am planning at this point to go all series to MPPT. So the 140w panels will be 88.4 voc and 70.8 vpm.

My thinking is the controller can make sense of it and charge even if only one panel is lit and three are shaded and in bypass. From what I understand if it's partial shading across multiple panels it's a crapshoot, and the MPPT controller may struggle to figure out which of the panels it's optimizing for.
Boon_Docker
Explorer III
Feb 22, 2016
My preference would be the mono panels over poly.

They are a bit more efficient, are smaller in size for the same wattage and they are more heat tolerant (perform better when they get hot).
Almot
Explorer III
Feb 22, 2016
#1: Doesn't matter much. I chose quality (European). Roof panels is a long-term solution and solar is my only energy source now, so I need to be able to rely on it.

#2: Poly is better overall. Performance in partial shade has nothing to do with poly/mono, it depends on the number of diodes, the more, the better.

#3: Major difference between 265W and 140W is not "size" but "voltage". 265W panels are 24V, 140W are 12V. Different creatures and require different type of controllers. A long topic in itself. With that much wattage like you want, people "normally" go for 24V panels. "Occasionally" they go for 12V.

24V are easier to wire, can be in series with mere #10 or #8 wire.
12V are usually wired in parallel, sometimes series-parallel. With wattage over 400 it means a beefy wire to controller AND a rooftop junction box. They cost more per watt.

Once you've chosen either 12 or 24V, it's difficult to add another type into this mix later. Mismatch is a pain, and 2nd controller is more pain.

Big residential fridge + parking in partial shade = daily generator, IMO.
KJINTF
Explorer
Feb 22, 2016
Sounds like you are on the right track - have fun with the project

The K140 panels were my choice
I have 4 of them and thinking of adding another pair. Went with a series/parallel configuration producing about 40Voc. Found this configuration allows for easy expansion in pairs and offers shade tolerance as good as can be.

If shipping costs are a concern the smaller panel will save big $$

A single quality 60 to 80 amp controller should do you just fine

again enjoy the project
2oldman
Explorer II
Feb 22, 2016
Running in series dictates amperage-matched panels. I don't know much about using two controllers... maybe someone else does.

More diodes is better, and you'll probably pay for that. I too have no problem paying for quality, and Kyo has been good to me.

Shade? Hard to say. I just avoid shade amap.

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