Sourcing a few panels

I put together a 24v lifepo4 bank with 304ah cells about a month ago. Victron 24/3000. I have it currently functioning as a UPS for my server rack, fridge, and tankless propane water heater. So now the next progression would be to toss a few panels in and utilize the batteries a bit more. As is usual when I do a project, I start out small scale and work up. Usually this is detrimental but helpful in this case as the spouse was not overly impressed when I showed her the size one of the 12v panels I purchased. I think she will catch on eventually .
Turns out I did not research enough ahead of time because I bought one 12v panel that is 200w. (https://jjnsolar.com/products/jjn-b...ule-for-rv-home-battery-charging-single-piece). So as you know, to use with a smartsolar controller in a 24V system I would need to purchase a second.

After looking around signature solar, the size to watt ratio of this particular panel is a bit high compared to most other panels and most other panels are far higher voltage meaning I would only need one to get a small test case going. The size ratio isn't so much of a big deal but it would have been nice to have gotten 1.7 to 2x more wattage for the space the panel occupies. The final location of where I would put a panel system I am not certain of yet- either ground mount or on the lean to portion of my barn roof.

I have not had much success finding a decent panel that I can purchase in a quantity of one to two without seeing $200 shipping. Do any of you have any recommendation? 400w+ that is at least 28V? Or should I do something different?

Where do you live?

Have you checked craigslist?

PV technology hasnt changed much in 20 years, a 200W panel takes up a set amount of space. A 400W panel would take up twice as much space.

Supervstech said:

Where do you live?

Have you checked craigslist?

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East TN

Yea that isn't a bad idea actually. Usually I only see national listings without anything local but there are a few on there now.
Specifically these panels $70 used each --- https://documents.unboundsolar.com/media/specs-3975302543.1931060-1.pdf
$90 - https://us.qcells.com/q-peak-duo-blk-ml-g10/

I drove to east tn to grab a few panels, he sells a lot on craigslist.

Fyi

I will check them out - I had given up on CL after not seeing anything on there for a while. I don't mind driving to avoid the high shipping costs!

utkvols said:

... The size ratio isn't so much of a big deal but it would have been nice to have gotten 1.7 to 2x more wattage for the space the panel occupies. ...

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It really is a big deal. There are a lot of panels for sale with fake wattage ratings. It is fairly easy to figure it out with some simple math. STC (Standard Test conditions) is solar irradiance of 1000 watts per square meter. If you know the panels efficiency and its size all you need to do is multiply. Say it is 1 square meter (or 1550 square inches). If it is rated at 21% efficiency that would would give you a 210 watt panel. You can pretty well know if it is being marketed at 300w that the rating is fake.

Two sources for individual panels with free shipping are Amazon and Ebay. You might find some panels at a good deal locally but be wary of used ones if there is no guarantee. Lots of junk and smashed panels.

Here is an example of a fake rated 200w panel. Note the size is 20 X 26 inch aprox. That is only 520sqin. or 1/3 of a square meter. At most it could be a 75-80 watt panel.

Thanks! great points --- I will add that column to the spreadsheet to make sure theoretically possible with the sq ft. After creating this, Supervstech is right - they mostly do have a similar watts per square foot. The panel i bought actually is higher than some of the larger panels (at least in theory) 18w vs 15w per square foot. It has been too cloudy/rainy to try and see where the max is. So in this case, needing two panels in series for the 24V in theory should not take up any more space as an equivalent 24V+ single panel?

Well, with racking and frame, a single panel is smaller, but not by much, and is difficult to fit due to dimensions