Used Panels - Worth it?

[String]

A friend is setting up a new off grid system: EG4 wallmount batteries, EG4 AIO inverters (not sure which), and has come across some used panels that appear to be a great deal, if they're any good. 40 panels at $20 each seems too good to pass up, but he will if they're a waste of time. Any opinions on 230W Q-Cells? I'm guessing they're about 10 years old ....

TIA!

 

[sunshine_eggo]

I vote yes provided you're willing to spend $50 on a legit MPPT panel tester and are willing to lose 10% of them.

 

[Mattb4]

You likely will also want a MC4 crimper and a bunch of replacements. What do you base your guess on for them being ~10 years old?

 

[String]

I vote yes provided you're willing to spend $50 on a legit MPPT panel tester and are willing to lose 10% of them.

Thanks. I didn't even know they existed before now. Can you advise what he should be looking for from testing? Also, care to recommend one?

 

[String]

You likely will also want a MC4 crimper and a bunch of replacements. What do you base your guess on for them being ~10 years old?

He's not buying from this source, but I figure they're a good approximation for age(?).

Poly Qcells - QC-C05 230 Wp

Q.Cells QC-C05 230 Wp gebraucht 29 Stück

www.secondsol.com

 

[chrisski]

I will add in addition to testing them, run some numbers and see how it works. I'm not sure which AIO your friend is getting, but the numbers would need to be ran to be sure that it does not exceed the Max Isc per MPPT and the max cold adjusted voltage for VOC.

This EG4 600XP has two inputs and here's the specs:



Often, it's a numbers game and math problem to get over 100 volts when the MPPT is operating at full load in the warmest day of the year to exceed 100 volts to start and be sure you don't exceed the cold adjusted output for voltage on the coldest day of the year.

My GUESS without doing the math and not knowing your cold adjusted panel output and if Vmp would be made on a hot day is each MPPT can support 7S2P, and if additional panels are good that means they can be added in groups of 7 parallel to an MPPT. Series of 5 would be needed to make minimum operating voltage.

For me, knowing strings of 7, now it's a game to place them in usable groups of 7. On my odd shaped, gabled roof, 7S would not work. I ended up getting an inverter charger an MPPT is added for each set of panels. 32 panels total split amongst 4 MPPTs as 8 X 4S and 2 X 5S.

 

[sunshine_eggo]

I would say they're likely a little older than 10 years. Datasheet:

Loading…

www.secondsol.com

This datasheet has a copyright date of either 2002 or 2010. I can't tell based on the format. Furthermore, the dimensions of the panels puts them at just under 14% efficient.

This tester is pretty popular:

https://www.aliexpress.us/item/3256806775149919.html

 

[Hedges]

Newer (but still used) panels can be 20% and higher efficiency. That means 150% as much power in same area, on same mounting hardware.

$20/230W = $0.087/W, about half the lowest we've been seeing for new panels.
Some new panels cost more, and premium used panels do too.

I think Q-Cells, REC, SunPower are among the premium brands.
Some will fade more slowly. Polysilicon may fade faster.

Something important to consider is whether panels are "PID Free".
Some older panels degrade rapidly if biased to a voltage below ground. Some older SunPower panels degraded if biased above ground (e.g. negative grounded.)

Most inverters these days are transformerless, non-isolated. Half the PV string is biased above ground, half below ground. At least each is biased to only half the string voltage. But still, could degrade.

Cost of his system may be dominated by batteries, panel mounting hardware, and inverter.
He could start with these panels for $800, see how well things work out, plan to buy better ones if necessary some years down the road. But NOW is a great time to grab a good deal, due to disruption in the market. So consider new or premium (newer) used panels.

He should mount panels in a manner that easily allows replacement with different size. e.g. rails and top clamps if roof mount, NOT L-feet screwed to panel frame and roof.

 

[reader2580]

Used is not always bad, but I would think twice about 230 watt panels for new installs these days. You're using more space, more mounting brackets, and more of everything. If your inverter has a limitation on panels per string that can also be an issue. Most of the panels I bought were used, but I went with 305 watt 72 cell in 2017 or 2018. My used panels are still working just fine.

I know where you can get used 300 watt panels for the same price, but unfortunately not close to you at all.

 

[Suijkerbuijk]

You can always try to lower the prive.
Personal its cheap vs what i have to pay for use panels here.

Panels today are more effective but than again if fits what you need .
That panels age fine with that .
But test panels that are set over the world that are easy 30/40 old still almost run the same specs like the day it come from the factory.
So no i do not think that the panels are ware down .

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A 10 kW PV system has been feeding electricity into the Swiss power network since 1982. A research team has investigated the performance of the array’s first 35 years of life and has found that solar modules can target – at least in temperate climates – service lifetimes of 35 years, and that...

www.pv-magazine.com

 

[String]

Thanks very much for all the help! He's going to get them, but not for powering his main house. He (and I) can use them for other things.