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Recommended Solar Panels

petebridge

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Jul 2, 2022
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Hi all,

I'm looking for some solar panels to charge my home backup system.

I purchased the Zendure's Superbase V system on Kickstarter, as it seemed the easiest for me as a total beginner to have all the components in one unit.

I got 2 x the Superbase V4600 base units (the LiFePO4 version) and 2 x the B4600 expansion batteries. So chaining that together I will have 7600W output at 240v and 18.432 kWh capacity.

Each unit can accept 3000W solar input at 10-150Voc. Realistically I can probably only afford on 3000W array to start.

I'm in southern Ontario, Canada.

I've done some research on panels as a next step but still feeling baffled by the variety of options out there.

Two options I've considered so far, based on brands I saw cited as being reputable + good ratio of cost per watts:
Am I headed in the right direction? Appreciate any guidance.
 
Says 3000W, 10-150VDC input. Need to know the current limit.

Manual?

Both panels are 72 cell meaning you're limited to 2 in series to stay under the 150V limit. To get near the 3000W limit, you'd need 2S3P arrays for both.

You might get more optimal results with 60 cell panels as you can go 3S with those and drive to higher voltage.
 
@sunshine_eggo

Thanks a lot for the response - super helpful.

Need to know the current limit.

I don't have that unfortunately - will see if I can find it. I don't have the manual yet as the units are still in production and I don't have them yet.

For my education, what is the difference between the current limit differ and the Voc limit?

Both panels are 72 cell meaning you're limited to 2 in series to stay under the 150V limit. To get near the 3000W limit, you'd need 2S3P arrays for both.

That's an amazing tip - I never would have realized. I'll do some more digging. Thanks!

EDIT: Actually I may not understand the link between the # of cells and having 2 or 3 panels in series.

For example, the LONGi has 49.3v, and that x3 = 147.9, so less than 150. Would that not work?

I'm sure I'm missing something.
 
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i would say the 147.9 volts is probably a little too close to 150vmax. in colder temps the voltage can climb and that doesnt leave much wiggle room.
 
For my education, what is the difference between the current limit differ and the Voc limit?

Current and voltage are two completely different things. Drawing an analogy to water flowing in a pipe:

Voltage, Volts, is the water pressure.
Current, Amps, is the amount water flowing.
Resistance, Ohms, is the friction slowing the water in the pipe.

Summarized in this image:

Fig-3-Electricity-Explained.jpg


The PV input Amps is the maximum amount of current that the unit can receive from the array. Many solar generators are excessively restrictive in this area, and in some cases, while the unit may quote a high maximum solar power, the combination of voltage and amps prevent you from getting there.

EDIT: Actually I may not understand the link between the # of cells and having 2 or 3 panels in series.

For example, the LONGi has 49.3v, and that x3 = 147.9, so less than 150. Would that not work?

I'm sure I'm missing something.

The most common cell counts are 36 (12V), 60 and 72 (24V) cell panels. The number of cells determines the total voltage.

Panels put out higher voltages at colder temperatures. 3S of that panel would exceed 150V in the 60°Fs

Generally accepted max # of panels in series for panel type.
5S 36 cell panels (180 cells)
3S 60 cell panels (180 cells)
2S 72 cell panels (144 cells)

You may also encounter panels labeled as 120 or 144 cells. Those are typically half cut or split cell panels. They're basically two 60 cell or two 72 cell panels connected in parallel as one panel.

@ImAnIdiotPleaseBePatient

Got it - thanks!

Is there a benchmark for how much buffer you should leave between your max Voc and the rated Voc of the array?

Yes.

There are official NEC numbers:


Example, at freezing, you would multiply the array Voc by 1.08 to get your adjusted Voc.

You can also calculate this for your specific panels. Many panel datasheets list a temperature coefficient like -0.3%/°C. You can use that number to calculate your adjusted Voc.
 
Rule of thumb seems to be 20%. Fuses and breakers at 20% overhead, run SCC's at 20% under limit, keep the VoC 20% under the limit for cold weather, etc. When in doubt use 20% until you do lots of hard math, but it'll keep you on paper.
 
@sunshine_eggo @Rednecktek Thank you both for the helpful info.

I did some more research and I think I have a better understanding of amps, volts, and series/parallel configurations than I did before.

I also managed to find the manual for the Superbase V, which confirms solar charging is max 3000w 150V 25A per unit:

Superbase V Solar Recharging.png

So to make sure I understand this correctly, let's say I got this LONGi panel which per the spec sheet here has an open circuit voltage of 41.1 volts and a max current of 10.84 amps.

And let's say I create an array of 2 groups of panels in parallel, with each group containing 3 panels wired in series.

Each group of 3 panels wired in series would then have 123.3V (41.1 + 41.1 + 41.1) and 10.84A, since with panels in series you add the volts.

And then the two groups in parallel would have 123.3V and 21.68A (10.84 + 10.84), since with panels in parallel you add the amps.

(I'm basing my logic here on this video.)

Since each panel has 375W, I'd be getting 2250W (6x375) in total while staying under the max volts/amps for my input. (And presumably I could duplicate this setup so I could power each Superbase V unit).

Am I thinking about this the right way?

Obviously I'd do a bit more research to see how I could get closer to maxing out my 3000W per unit but just want to know if my mindset is correct here.
 
Yup! You've got the right idea. As for maxing out your SCC, it's almost impossible to do because 1: solar panels are NEVER even perfect numbers and 2: voltages change based on temperature.

Your 3s2p plan above is about perfect.
 
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