solar pre-wired questions

[pbitschura]

Our new rv has an outdoor two pin plug-in for solar. What do I need to take advantage of it? What are it's benefits and limitations? We don't currently have any panels.

[3_tons]

Sure Mono panels are more efficient (by about 3%), but in practice, when comparing panels of ‘equivalent wattage’ the actual power difference is equivalent, except that the poly panel will have a slightly larger footprint, while at a slightly lower cost (per watt), and as far as I can tell, I’ve seen no substantial difference in warranty…At least that’s been my perspective, and my personal priority would be (1) shape/size (efficiency may be a factor…), while (2) closely matching voltages with other panel voltages - cost advantage would be of lesser concern…JMO - leaving room for others who might view this situation somewhat differently…

https://news.energysage.com/monocrystalline-vs-polycrystalline-solar/

3 tons

[pianotuna]

CA Traveler,

see my reply to S.

The test was done by someone on rv net. They had one mono and one poly from the same maker with identical wattage.

[pianotuna]

UniSolar are no longer made. They have diodes between each cell.

However there have been reports posted on RV where some one had a poly and a mono. The poly outperformed the mono. In this example both types of panels had 3 diodes per panel, one for each "string".

There is a German company that makes a poly with diodes between each cell. However, I've been unable to source a North American dealer.
What Polycrystalline Solar Panels Are

Polycrystalline solar panels (or poly panels) are made of individual polycrystalline solar cells.

Just like monocrystalline solar cells, polycrystalline solar cells are made from silicon crystals. The difference is that, instead of being extruded as a single pure ingot, the silicon crystal cools and fragments on its own. These fragments are melted in an oven and formed into cubes which are cut into thin wafers. So, many different crystals form this amalgam, rather than the single crystal of the monocrystalline solar cell type. It’s a less exacting production process than with monocrystalline cells, so it allows for more solar cells to be produced faster and less expensively.

The blue-colored square polycrystalline cells fit neatly side by side, eliminating any empty space between the cells. Polycrystalline solar panels operate less efficiently than monocrystalline panels because the melted fragments of silicon afford less room for the electrons to move around.

[CA_Traveler]

Some smaller panels especially 12V panels don't have bypass diodes. But millions of panels have bypass diodes which protect the panel from damage due to being back biased by other series panels. And the panel still produces it's amps at the reduced voltage.

[CA_Traveler]

pianotuna wrote:
StirCrazy,
Systems with series wired panels are badly affected by shade.

Not correct or out of context. Virtually all panels today have bypass diodes and their shade tolerance is much better than parallel panels because shaded sections of the panel are bypassed for serial versus the entire parallel shade.

For example: 3 panels with 3 bypass diodes each are effectively 9 panels sections. With shade on one section the bypass diode shorts out that section and the remaining 2 sections are still producing power for that panel. So for shade on one section you still have voltage (and power) for the other 8 sections. For 30V panels you have 90V* 8/9 = 80V. And so on down to 2 sections of non shade at 20V with amps for given light conditions.

This has not been very well understood on this forum. I've posted graphs of this using collected controller data starting in the morning with leafy shade charging at 20V and increasing with 10V jumps and increasing power with the rising sun.

[Grit_dog]

:S

[StirCrazy]

pianotuna wrote:
StirCrazy,

I'll probably regret this.

Poly does better in shade. Systems with series wired panels are badly affected by shade.

My tiny system (by today's standards) produces about 17 amps in perfect conditions.

It also does 6 amps in leafy shade. Mono would produce nada if parked under a leafy tree.

Mine is a series parallel with an input of 33 volts to the controller.

My cost for parts per watt in 2005 was $5, including the charge controller, panels, wiring, fuse, shipping and tax.

haha don't regret it, I think you're using poly in a different context. polycrystalline panels are made by taking the bad crystals that were supposed to be monocrystalline panels but came out cracked or fractured. Sometimes they fractur them on purpose if there specifically making poly. all these fractured chunks are put back into a oven and melted into cubes and then cut into wafers. so they are less efficient, lower life expectancy, don't do as well with heat, but cheaper to produce, and less waist int he process. also a 300 watt poly panel will be larger than a 300 watt mono panel.

what color is the surface on your panel? I am curious to know what panel you actually have. it is possible to have a poly panel with bypass diodes on every cell also, this wouldn't be the norm but why not. if that's the case it would have better results than a mono with fewer bypass diodes.

Steve

[pianotuna]

StirCrazy,

I'll probably regret this.

Poly does better in shade. Systems with series wired panels are badly affected by shade.

My tiny system (by today's standards) produces about 17 amps in perfect conditions.

It also does 6 amps in leafy shade. Mono would produce nada if parked under a leafy tree.

Mine is a series parallel with an input of 33 volts to the controller.

My cost for parts per watt in 2005 was $5, including the charge controller, panels, wiring, fuse, shipping and tax.

[3_tons]

Bobbo wrote:

KD4UPL wrote:

3 tons wrote:

KD4UPL wrote:
#10 is a fine size if not overkill. Using an 100 amp Outback FM100 or Magnum PT-100 as an example you could hook up well over 1,000 watts of solar panels.

Sorry, not practical…

3 tons

What are you talking about? I probably install one of these a month on average.
Nobody doing any serious solar work even thinks about using a charge controller that isn't an MPPT model. PWM controllers are like black and white TVs and floppy disks.

You seem to think that your original answer, about #10 being good for 1000 watts, was sufficient for a new user. Your answer is only correct if the #10 wire is between the solar panels and the controller, and even then, at 40v or above. The new user would not know that. Following your advice and putting 1000 watts at 14v on #10 wire would be a catastrophe for a new user. Also, you assumed that the new user would KNOW to use an MPPT controller. Not a safe assumption.

Yep, thanks Bobbo, that’s what was meant by “not practical”….In fact, in retrospect I thought what I was reading might just have been a typo :h

3 tons

[Bobbo]

KD4UPL wrote:

3 tons wrote:

KD4UPL wrote:
#10 is a fine size if not overkill. Using an 100 amp Outback FM100 or Magnum PT-100 as an example you could hook up well over 1,000 watts of solar panels.

Sorry, not practical…

3 tons

What are you talking about? I probably install one of these a month on average.
Nobody doing any serious solar work even thinks about using a charge controller that isn't an MPPT model. PWM controllers are like black and white TVs and floppy disks.

You seem to think that your original answer, about #10 being good for 1000 watts, was sufficient for a new user. Your answer is only correct if the #10 wire is between the solar panels and the controller, and even then, at 40v or above. The new user would not know that. Following your advice and putting 1000 watts at 14v on #10 wire would be a catastrophe for a new user. Also, you assumed that the new user would KNOW to use an MPPT controller. Not a safe assumption.

[CA_Traveler]

I wondered if he was referring to controller to battery wire size or cost?

[KD4UPL]

3 tons wrote:

KD4UPL wrote:
#10 is a fine size if not overkill. Using an 100 amp Outback FM100 or Magnum PT-100 as an example you could hook up well over 1,000 watts of solar panels.

Sorry, not practical…

3 tons

What are you talking about? I probably install one of these a month on average.
Nobody doing any serious solar work even thinks about using a charge controller that isn't an MPPT model. PWM controllers are like black and white TVs and floppy disks.

[StirCrazy]

KD4UPL wrote:

3 tons wrote:

KD4UPL wrote:
#10 is a fine size if not overkill. Using an 100 amp Outback FM100 or Magnum PT-100 as an example you could hook up well over 1,000 watts of solar panels.

Sorry, not practical…

3 tons

What are you talking about? I probably install one of these a month on average.
Nobody doing any serious solar work even thinks about using a charge controller that isn't an MPPT model. PWM controllers are like black and white TVs and floppy disks.

yup and all the manufactures still use those black and white tv's when they install a system in the new camper. smaller controller that is easier to mount to a wall is what I figure.

[StirCrazy]

pianotuna wrote:

pbitschura wrote:

3 tons wrote:

pbitschura wrote:
Our new rv has an outdoor two pin plug-in for solar. What do I need to take advantage of it? What are it's benefits and limitations? We don't currently have any panels.

Most factory solar wiring is kinda minimalist in AWG wire gauge - you’ll be lucky if it’s #10 AWG gauge, and a lengthy roundtrip wire run (+ & -) adds to overall resistance (meaning excessive voltage drop - ugg…)…As such (if wiring panels in parallel) consider limiting your panel wattage to about 200w or so, or if more wattage is desired, consider wiring the panels in series (to help compensate for small’ish wire gauge) using an MPPT type controller that’ll exploit the higher voltage - or add a separate wiring run (of sufficiently gauge) from the roof-top down…This can often be accomplished by snaking the new wire down through the rooftop refer vent..

3 tons

As has been said, the wiring may not be heavy enough for a substantial system. I see little portable set ups. Can I then use this plug in for a battery maintainer to top it off while boondocking, maybe 100 watts or so? These, I believe come with a charge controller for a minimal system.

A pwm system runs "at the battery voltage". They are basically a switch that closes and opens. As the battery charges they shut off and on with the on time getting shorter and shorter.

Depending on the size of the bank 100 watts may be fine to run directly to a good sized bank. This is not recommended.

Get a good MPPT controller and use the highest voltage on the panel input side of the controller alows.

This allows the use of residential panels which are cheaper per watt.

My personal preference is for polycrystalline. Why? Because in the real world they do better if there is any shade--and since this system is panels in series that's a big thing.

I think you need to do a bit of reading on Polly Vs mono. here I'll sum it up for you

"Polycrystalline panels have lower efficiency rates typically in the 13-16% range. Monocrystalline panels have higher efficiencies in the range of 15-20%.

Because of the lower efficiency rate they are not as space-efficient since they produce less power per square foot.

Polycrystalline panels tend to have lower heat tolerance than monocrystalline solar panels and perform slightly worse than monocrystalline solar panels in high temperatures.

Heat can affect not only the performance of polycrystalline solar panels but is projected to substantially shorten their lifespan.

Polycrystalline panels are also less efficient in low-light condition."

in no way is a polly panel better than a Mono except in how much you pay for the panel.

I'm almost wondering if you're confusing polly for a split cell design as they are more efficient than solid cell in shading.

Steve