calling solar experts( questions ??)

[Jon Vermilye]

Originally Posted by NEWYORKHILLBILLY

Jon how will it work if the roof top panel is shaded and suitcase is in full sun?
would the suit case still work to its maximum being wired to same controller?

another question is what would you recommend for connectors and extension cord for the portable panel ?
I know you spend more time boondocking than most

I hope this makes it out - I'm in Internet no man's land at Agua Caliente County Park in CA & it is taking over a minute to download each page.

I've never had a problem with paralleled panels and mixed sun & shade. It is serial panels that are a problem unless bypass diodes are added. I did have a problem with a portable that had its own controller. The shaded rooftop panels wee producing enough voltage that the controller on the portable panel "thought" the batteries were full & would not produce much output. Covered the roof panel & the current to the batteries went up. Only happened once, and the portable panel controller was an inexpensive piece of junk.

As to connectors, I'm still using SAE (Zamp) connectors because they came with my portable panel & it was the type installed by Escape on the trailer. I used #10 Landscaper's cable for my extension cables. Flexible, some UV protection, and not too expensive. It is difficult to find - mine came from a Lowes, but I've never found another that sold anything larger than #12.

If I started over, I'd probably go with the Anderson PowerPole connectors. 30 amps, both pigtail & panel mount, and more robust than the SAE connectors.

[Huck]

Originally Posted by sokhapkin

You want the trailer be in the shade but the panel in the full sunshine.

Originally Posted by NEWYORKHILLBILLY

The size of the suit case has a big advantage 21.5x21.5 . plus you can move it around

I have a 100 watt panel on the roof and another 100 watt panel that I can place wherever I want (within limits of a 20' cable). By using y cables, they both connect to the same charge controller. The roof panel is always connected and the portable panel is connected as needed.

[gordon2]

Originally Posted by NEWYORKHILLBILLY

Jon how will it work if the roof top panel is shaded and suitcase is in full sun?
would the suit case still work to its maximum being wired to same controller?
...

My two 50 watt Renogy Panels arrived today and while testing them I took a some time to do a little pseudo-scientific study of the effect of partial shading. Outside of a testing laboratory, we had nearly ideal conditions for testing - 40 degrees F and literally not a cloud in the sky.

The two panels were setup next to each other on a stand as shown. They were charging my group 27 battery which was discharged to 92% of capacity. Solar controller and power meter are the Bogart Engineering Trimetic and companion SC-2030 controller.

The Renogy panels are matched with identical electrical characteristics. Individually I measured 2.57 and 2.58 amps (within the margin of measurement error). Wired in parallel they produced 5.22 amps.

I then covered part of one or the other panel and recorded the new rate of charge.

With one cell covered, the entire panel was for all practical purposes dead. The charge rate was 2.69 amps (52% of both panels).

With one half of one cell covered, I saw 4.02 amps (77%).

With one cell on one panel covered with blue painter’s tape which allows some light through, I recorded 3.38 amps (65%).

And with one third of one panel covered, again the entire panel was effectively dead and the power output matched the single panel in full sun – 2.58 amps (49%).

These results were expected and demonstrate the need to keep the entire solar panel in direct sun for maximum output.

[NEWYORKHILLBILLY]

Originally Posted by gordon2

My two 50 watt Renogy Panels arrived today and while testing them I took a some time to do a little pseudo-scientific study of the effect of partial shading. Outside of a testing laboratory, we had nearly ideal conditions for testing - 40 degrees F and literally not a cloud in the sky.

The two panels were setup next to each other on a stand as shown. They were charging my group 27 battery which was discharged to 92% of capacity. Solar controller and power meter are the Bogart Engineering Trimetic and companion SC-2030 controller.

The Renogy panels are matched with identical electrical characteristics. Individually I measured 2.57 and 2.58 amps (within the margin of measurement error). Wired in parallel they produced 5.22 amps.

I then covered part of one or the other panel and recorded the new rate of charge.

With one cell covered, the entire panel was for all practical purposes dead. The charge rate was 2.69 amps (52% of both panels).

With one half of one cell covered, I saw 4.02 amps (77%).

With one cell on one panel covered with blue painter’s tape which allows some light through, I recorded 3.38 amps (65%).

And with one third of one panel covered, again the entire panel was effectively dead and the power output matched the single panel in full sun – 2.58 amps (49%).

These results were expected and demonstrate the need to keep the entire solar panel in direct sun for maximum output.

very nice test. its amazing how one cell covered takes out the whole 50 watt panel. I wonder if it be the same case with a 100 watt panel. would one cell covered take down the whole panel, or reduce it to 50% hmmm

My 50's will not be here untill end of week, but 15 degrees ans snow here

[gordon2]

Originally Posted by NEWYORKHILLBILLY

... wonder if it be the same case with a 100 watt panel. would one cell covered take down the whole panel, or reduce it to 50% hmmm

...

The former (100% or close to it) if the shading is complete. If there is still diffused light, such as from distant trees, there will still be some power generation

[Jon Vermilye]

Originally Posted by NEWYORKHILLBILLY

very nice test. its amazing how one cell covered takes out the whole 50 watt panel. I wonder if it be the same case with a 100 watt panel. would one cell covered take down the whole panel, or reduce it to 50% hmmm

My 50's will not be here untill end of week, but 15 degrees ans snow here

Some panels built in bypass diodes in the individual rows of cells. If those panels are partially blocked, you can still get output from the rest of the rows.

While I haven't seen one, there is no reason a bypass diode couldn't be added to each cell (other than the voltage loss, which could be made up with additional cells). I suspect the reason these are not popular is most solar panels are used where partial blockage would be unusual.

For small, portable systems like those used with our trailers, paralleled panels & PWM controllers make more sense than series wired panels and MPPT controllers. We have short enough wire runs that the need for high voltage/low current series systems isn't necessary.

Not to get into the argument as to which controller is better, but for the additional cost of an MPPT controller of the same quality, you can purchase an additional panel & probably be better off in the long run.

[NEWYORKHILLBILLY]

Originally Posted by Jon Vermilye

I hope this makes it out - I'm in Internet no man's land at Agua Caliente County Park in CA & it is taking over a minute to download each page.

I've never had a problem with paralleled panels and mixed sun & shade. It is serial panels that are a problem unless bypass diodes are added. I did have a problem with a portable that had its own controller. The shaded rooftop panels wee producing enough voltage that the controller on the portable panel "thought" the batteries were full & would not produce much output. Covered the roof panel & the current to the batteries went up. Only happened once, and the portable panel controller was an inexpensive piece of junk.

As to connectors, I'm still using SAE (Zamp) connectors because they came with my portable panel & it was the type installed by Escape on the trailer. I used #10 Landscaper's cable for my extension cables. Flexible, some UV protection, and not too expensive. It is difficult to find - mine came from a Lowes, but I've never found another that sold anything larger than #12.

If I started over, I'd probably go with the Anderson PowerPole connectors. 30 amps, both pigtail & panel mount, and more robust than the SAE connectors.

Are they same as on the go power portables? when i look them up there 50 amp

[gordon2]

Originally Posted by Raz

...The only odd thing was that my panels were not square so they don't quite line up when folded. Not a big deal, just odd. I'd be curious what you find.
..

Both perfectly matched and square (Renogy panels). I have a little problem with the MC4s but I'll work it out.

[John in Santa Cruz]

cells wired in parallel add their current together, cells wired in series add their voltage together

the cells within a panel are wired in some combination of series/parallel, each cell produces about 0.5 volts, so to get 18 volts you need 36 cells in series.

but if one cell isn't powered, then it blocks the current from the others. so when you block a series cell, you knock out the whole row.

[sokhapkin]

Originally Posted by John in Santa Cruz

the cells within a panel are wired in some combination of series/parallel, each cell produces about 0.5 volts, so to get 18 volts you need 36 cells in series..

Cells within a panel are wired in series. Most of 12V system panels have 34 or 36 cells to provide 17-18V voltage to the charge controller.

[NEWYORKHILLBILLY]

so if i understanding this right , for a rv install where very often where parked where often some of the panels get shaded. 2 50 watt panels would be better a 100 watt . that way if some of the 50 watt panel gets shaded you only be down 50 watts instead of 100 watts with the bigger panel. hmmm now i wish i went 2 50's on roof

[Byron Kinnaman]

Originally Posted by NEWYORKHILLBILLY

so if i understanding this right , for a rv install where very often where parked where often some of the panels get shaded. 2 50 watt panels would be better a 100 watt . that way if some of the 50 watt panel gets shaded you only be down 50 watts instead of 100 watts with teh biger panel. hmmm now i wish i went 2 50's on roof

The biggest question is always "How long to intend to camp at one time in one place?" Second question how power are you going to use during that time?

The answer to those questions will tell a lot about what is need and what is not needed.


EXAMPLE --- My case. I used very little with LED lights and once in a while a bit of furnace. No other power usage in the trailer. Because the tow charges the batter and it's fully charged when I arrive at my chosen campsite I can go any where from 4 days to 2 weeks without charging the battery.
Even when I had all incandescent lights and using the furnace every morning I've gone 4 days, it was getting pretty close but I managed (Not much heat on the 4th day)

[sokhapkin]

Originally Posted by Byron Kinnaman

The biggest question is always "How long to intend to camp at one time in one place?"

[NEWYORKHILLBILLY]

my figures show on a cold night i could use 60 AH of batteries . furnace and cpav machine will use most that . I like to be able to stay 2 weeks with out power. I think a need it all a 200ah battery and 200 watt solar and a Honda 2000I. is my best option .

[DougOlson]

I would not call this post either advice or recommendation but just some thoughts on my use of permanent panel plus portables. I have a 120W panel + MPPT controller fixed on trailer as well as a portable 60W suitcase type with PWM controller for when the trailer is in the shade. I connect the portables only at the battery and when the fixed trailer panels are shaded, assuming then that the charging algorithms of the two controllers won't cause trouble for each other.
If putting together the whole setup at once I would do it more like the OP but mine represents some history and evolution going from tent trailer to Scamp, but still works.

[Mike Magee]

Try to locate the rooftop panels away from rooftop protrusions. The shadow of an AC or an open vent only needs to cover one cell to knock the output way down.

[patrick crawford]

Speaking of mc4 connectors, does anyone know of a cap that I could install on mine? I’ve a panel mounted permanently on the roof of the truck’s topper and i’d Like to be able to keep them dry while underway. When I find a round toit I plan to incorporate the panel’s output into the 7 pin plug, however, that may take a while...

P@

[Alex Adams]

Originally Posted by patrick crawford

Speaking of mc4 connectors, does anyone know of a cap that I could install on mine? I’ve a panel mounted permanently on the roof of the truck’s topper and i’d Like to be able to keep them dry while underway. When I find a round toit I plan to incorporate the panel’s output into the 7 pin plug, however, that may take a while...

P@

Either use the ends cut off from a built cable (I use) or buy the mc4 connector, assemble and fill the opening with sealant. Either way makes for great plugs!

[John in Santa Cruz]

do note, MC4's are a bear to take apart if you don't have the special tool

[gordon2]

Originally Posted by John in Santa Cruz

do note, MC4's are a bear to take apart if you don't have the special tool

Some are and some are not. But of course since there is a tool for the job, there is a reason for the tool. One thing the tool does is to press-in the side locking tabs so you can pull the male connector from the female one. And $7 is not so bad. Its a good thing to have.

As I understand it, generally speaking, the MC4 connectors from the same manufacturer will work together better, since the manufacturing tolerances tend to be more consistent. Keep in mind that most solar panel installations are more or less permanent. Using portable panels while camping is a less common use.

I bought a bunch from Renogy to make up some DIY cables, and was able to separate the MC4 connectors with just my hands. But then just this week, I just got two new panels and the 2 to 1 branch connectors, all from Renogy and I could not for the life of me even get the branch connectors to go on to the cables. I shaved a little plastic and then got them were I could put them together, and with the tool and some difficulty, I could also separate them. But in this case, even with the tool its not easy and not something I plan to do often. The MC4 connectors that need to be disconnected in order for me to change panels are still easy to work. And the cable plugs into my camper and then controller with a trolling motor jack and plug, so thats real easy.