Solar 4x4 cell grid wiring (is this logical?)

[misfits]

John61ct, from what I've researched most panels in that voltage range are not meant for "off grid" systems. Boost chargers, you loose amps when you boost.

I've got a 48 volt bank. I've decided on 2-24 volt panels wired in series as a starting point.

[john61ct]

It is exactly the ability to use the larger higher voltage "grid-tie" panels that make modern MPPT panels so great.

Every such SC includes DC-DC voltage conversion, the extra power they extract more than compensates for its losses.

As opposed to PWM, which simply wastes, literally discards! the power output from any voltage above 16-18V. Which are irrelevant to a 48V system anyway I believe.

[Paul Elliott]

Originally Posted by misfits

Boost chargers, you loose amps when you boost.

Yes, you lose amps, but you gain volts. The power stays constant (minus the conversion efficiency factor which should be 95% or better). Boost just matches a low-voltage panel to a higher-voltage battery. There are valid reasons for wanting to use a higher voltage panel (minimizing wiring losses, for one), but a good boost converter shouldn't be any less efficient that a good buck converter.

[mitiempo]

I agree that large panels are a better choice than many smaller ones.

This is the controller I would choose. With a 48 volt bank it will handle 2000 watts.
https://www.victronenergy.com/upload...-150-35-EN.pdf


Here is a list of the Victron controllers that will charge a 48 volt bank - which requires voltages of about 58 volts by the way.

https://www.victronenergy.com/upload...verview-EN.pdf

[john61ct]

> Victron controllers that will charge a 48 volt bank - which requires voltages of about 58 volts

True for those Victrons and others with buck-only conversion

Those with boost can use even "12V" panels.

And some have both boost and buck.

_____
Too bad Victron doesn't have an inexpensive (under $100) 48V choice like their 75/15.

Putting lots of (even larger) paralleled panels per SC will cause MPPT to be less efficient in partial shade conditions.

[2big2small]

Hold your horses everybody! Before delving into the technicalities of panels and controllers I believe there’s a fundamental flaw in the OP’s reasoning that needs to be addressed. (Chastise me if I’m wrong.)

Any shadow (boom, mast, whatever) will in the vast majority of cases only cover either starboard or port. There’s no scenario (except probably only sailing wing on wing towards the sun) where you could loose more than 50% percent of your panels (if they are evenly spread over starboard and port).

With that in mind, back to the drawing board!

I personnaly have two panels on either side. Each pair is in series, which allowed me to keep the wire gauge reasonable, and has its own MPPT controller. Those were my two major considerations, YMMV.

And I overdid it. Each pair provides more than enough juice on a sunny day by itself, and both pairs together still work well enough even when it’s very overcast or rains all day.

[misfits]

Originally Posted by mitiempo

I agree that large panels are a better choice than many smaller ones.

This is the controller I would choose. With a 48 volt bank it will handle 2000 watts.
https://www.victronenergy.com/upload...-150-35-EN.pdf


Here is a list of the Victron controllers that will charge a 48 volt bank - which requires voltages of about 58 volts by the way.

https://www.victronenergy.com/upload...verview-EN.pdf

The victron 150-35 is one the controllers I've considered. If I remember correctly it turns on at 5 volts above whatever the battery bank is & turns off when it's 1 volt. Unless you want to buy more victron product or download an app to a smart phone you're relying on the idiot lights. The midnight kid is another charger I've looked at. It has a display & appears to be fairly easy to program.

When I say boost controllers I'm talking about something like the Genasun GVB 8 ? I see alot of controllers that have "boost" in their descriptions, Blue Sky comes to mind, but they are not rated for 48 volt banks.

I'd like to use a couple of 32 volt panels but they extremely large & I don't have the real estate on a 28' boat

[mitiempo]

Originally Posted by misfits

The victron 150-35 is one the controllers I've considered. Unless you want to buy more victron product or download an app to a smart phone you're relying on the idiot lights.

All Victron Smartsolar controllers will display and allow full adjustment with your smartphone. The app is free.

https://www.victronenergy.com/upload...verview-EN.pdf

[noelex 77]

Originally Posted by misfits

I've got a 48 volt bank. I've decided on 2-24 volt panels wired in series as a starting point.

Be careful many "24 v" panels are actually 60 cell panels. This is not enough to charge a 24v battery system effectively. So 2 of these panels in series is not enough voltage for a 48v lead acid bank.

Stupid I know. They should be called 21 or 22v panels, but for some reason they are labeled "24v" panels. "12v" panels do not have this problem they are nearly all 36 cell panels which is ideal for charging a 12v bank.

[noelex 77]

Originally Posted by CatNewBee

AUO BenQ Solar SunForte PM096B00 330 Watt - 96 Cells,


Power (Wp): 330
Vmp (V): 54,7V
Imp (A): 6,04A
Isc (A): 6,52A
Voc (V): 64,9V
max string Voltage (V): 1000
STC: 20,3%
Cell-Type: 96 high-efficiency back contact cells
Tolerance: 0/+3 %
Size (LxWxH) (mm): 1559 x 1046 x 46
Weight (kg): 18,6
Cells: 96
Connector: MC4 connectable

These are reasonably high efficiency panels (around 20%) which is good, but it should be rembered that high voltage panels like this are electrically identical to multiple smaller panels conected in series. Multiple 50w "12v" connected in parallel would be more shade tollerant for a 12v battery system.

Unfortunately it is very hard to find high effeciency panels in these smaller sizes. (The space taken by the framing is part of the reason). Hence high voltage panels are often the best choice, but there attraction is their better efficiency not the higher voltage.

[john61ct]

Originally Posted by noelex 77

Be careful many "24 v" panels are actually 60 cell panels. This is not enough to charge a 24v battery system effectively. So 2 of these panels in series is not enough voltage for a 48v lead acid bank.

Stupid I know. They should be called 21 or 22v panels, but for some reason they are labeled "24v" panels. "12v" panels do not have this problem they are nearly all 36 cell panels which is ideal for charging a 12v bank.

Designed back in PWM days where higher voltage output is wasted?

[john61ct]

Originally Posted by noelex 77

Hence high voltage panels are often the best choice, but there attraction is their better efficiency not the higher voltage.

Many MPPT controllers have a greater power output when they have a larger V range to work with in seeking MPP.

My understanding is the Victrons don't get much more efficient than PWM until panel V gets up to ~40V or so?

[misfits]

Originally Posted by noelex 77

Be careful many "24 v" panels are actually 60 cell panels.

Any panel I've been looking at for the science experiment are 72 cell panels.
There's a 100 watt panel from AltE, vmp 32.3, should get me 64.6 in series.
120 watt from Solarland, vmp 34.4, 68.8 in series.
I'm leaning towards the Solarland panels based upon the vmp & efficiency.
I really don't want to mount them on a bimni frame due to shading issues. I want to put them on a pole so they can be adjusted, rotated hence the smaller frame panel.

Thanks

[misfits]

Made an oops on the 100 watt 24 volt AltE panel.
The vmp is 36.23 which 2 in series should be 72 volts.

[GTom]

Originally Posted by CatNewBee

AUO BenQ Solar SunForte PM096B00 330 Watt - 96 Cells,
Power (Wp): 330
Vmp (V): 54,7V
...

That's a very nice output voltage, question is how much does an MPPT controller gain compared to a 4x parallel 17.5V (e.g. 80W) panel? With other words: how much is the advantage of a full series setup compared to parallel under perfect conditions?