60 vs 72 vs 96 cell solar panels.

marklg said:

I would doubt everything that person said. Mono cells are make from a single crystal. Poly cells are made from multiple crystals. They are completely differently manufactured. They are not made from cutoffs. That is absolutely not true.

When you have limited space, higher efficiency cells are desirable. The highest efficiency ones I know of today commercially are Grade A Sunpower Mono cells. Some manufacturers make panels out of Grade B or lower cells, which may be rejects.

There is an advantage for poly cells when there is less than full sunlight. The power output degrades less. The type of controller also matters. An MPPT controller theoretically produced more power, but if the panels are hot or in partial sunlight, a PWM controller may actually produce more as the MPPT may even shut off as the panel voltage drops below it's minimum.

The whole thing is very complicated. You need to know what your use case and expected weather / location is to make the best decision.

Another thing I've found is Solar providers always lie about how much will be produced. The specs are for full sun, but cold temperatures, which is uncommon. In the summer you may have full sun overhead, but it is hot, reducing output. In the winter the sun is at a low angle, so there is reduced sun, resulting in lower output, but it's colder.

Regards,

Mark

Click to expand...

I'm just trying to learn more about solar before I spend on my system.
Mono crystals have the corners cut off, ergo silicon crystal cut-offs for use somewhere else. Maybe in poly panels? It's plausible.
Mono panels are more efficient than poly. We can agree on that. But the efficiency of poly panels has improved over the years and the efficiency of mono panels in degraded light conditions has improved, through use of isolating diodes I think. Making the difference less than it used to be.

I'll be using an MPPT controller because the PWM controllers don't handle as much amps as I will be making with my 300-400 watts of panel. Am I wrong here? When using multiple panels, if the end panel has a dark spot, lowering the output, the upstream panels' efficiency is affected. So it was explained by the guy. He was a master electrician and installer. And I agree claims are always measured at ideal conditions, just like gas mileage.

What is the difference between commercial and RV panels?

autostaretx said:

Umm... "energy" is watts, so amps ain't the issue (with one exception).

A 375 W panel at 37 volts is putting out 10.135 amps (before applying any temperature effects, etc).
Three 125 W panels at 19 V each can be wired in series, giving you 57 volts at 6.579 amps, or wired in parallel giving you 19 v at 19.737 amps.
Two 19v panels in series IS a 72 cell panel.
It's your MPPT controller's job to accept whatever the panels produce and tailor the output to match your battery bank.
If you've only got a 12v battery bank, the net result is 26.78 amps at (let's assume) 14 volts.
If you've got a 24v battery bank, it'll be getting 13.39 amps at 28 volts.

The only amps-related "exception" is wire size .... if you opt for the three 19v panels in parallel, you'll need a wire gauge to the controller that can handle 19.737 with minimal (or acceptable) losses.

Solar cells put out about a half volt each ... so a 36 cell panel is an 18v panel, a 60 cell is 30v, 72 cells is 36 volts.
All of the cells are in series, so if one is shaded, that significantly lowers the current flow.
Even the 18v (nominal 12v) panels usually have a couple of bypass diodes in the connection box, so a shaded cell may only throttle half of the panel. More expensive panels can put a bypass diode across each individual cell, which means you only lose the output from the actual cells that are shaded.
The "two 19v panels is a 72 cell panel" i wrote above would now have 4 bypass diodes.
For large panels, checking out how they're bypassed can make quite a difference in "dappled sun" output.

--dick
p.s. as others have written, a "poly" panel is not "cut-offs" from a mono.

Click to expand...

I always thought watts was power, hence the P in P=IV. The energy I was talking about was electricity in all its units.
And I agree with you three 125 W panels in series, but it was explained to me the if the end panel lost a few cells to shade, that loss would be multiplied by three. Maybe the guy was full of BS.
Another thing he said was if you added a portable panel (my plan) that the controller may not accept it if your fixed panels were in the shade.

Lastly, where do the crystal fragments in a poly panel come from, if not left overs/cut-offs. You can't grow a fragment of a silicon crystal. Can you?
I think of poly panels as the MDF of the solar panel industry. A product made from what was formally garbage.

Anyway, I'm not try to start a pissing match, I'm just trying to get through the myriad of information that is out there to make an informed decision.

I'm just trying to learn more about solar before I spend on my system.Mono crystals have the corners cut off, ergo silicon crystal cut-offs for use somewhere else. Maybe in poly panels? It's plausible.Mono panels are more efficient than poly. We can agree on that. But the efficiency of poly panels has improved over the years and the efficiency of mono panels in degraded light conditions has improved, through use of isolating diodes I think. Making the difference less than it used to be.I'll be using an MPPT controller because the PWM controllers don't handle as much amps as I will be making with my 300-400 watts of panel. Am I wrong here? When using multiple panels, if the end panel has a dark spot, lowering the output, the upstream panels' efficiency is affected. So it was explained by the guy. He was a master electrician and installer. And I agree claims are always measured at ideal conditions, just like gas mileage.What is the difference between commercial and RV panels?I always thought watts was power, hence the P in P=IV. The energy I was talking about was electricity in all its units.And I agree with you three 125 W panels in series, but it was explained to me the if the end panel lost a few cells to shade, that loss would be multiplied by three. Maybe the guy was full of BS.Another thing he said was if you added a portable panel (my plan) that the controller may not accept it if your fixed panels were in the shade.Lastly, where do the crystal fragments in a poly panel come from, if not left overs/cut-offs. You can't grow a fragment of a silicon crystal. Can you?I think of poly panels as the MDF of the solar panel industry. A product made from what was formally garbage.Anyway, I'm not try to start a pissing match, I'm just trying to get through the myriad of information that is out there to make an informed decision.