Solar panel arrangement with varying V & A

[Korishan]

So I've gotten some panels finally, used, got a great deal on them. However they have a pretty wide spread of values.
Here's their characteristics I've been able to measure.

Panel​	V​	A​	rV​	rA​	Watt​
27​	5.10​	4.50​	​	​	9.60​
16​	6.00​	-​	​	​	#VALUE!​
24​	16.80​	-​	​	​	#VALUE!​
17​	17.00​	2.60​	18.20​	3.00​	19.60​
11​	17.30​	0.03​	​	​	17.33​
25​	18.50​	0.70​	​	​	19.20​
10​	18.70​	3.62​	​	​	22.32​
2​	19.40​	1.08​	​	2.00​	20.48​
3​	19.76​	1.30​	​	2.00​	21.06​
6​	19.78​	5.90​	20.30​	6.40​	25.68​
21​	19.80​	6.40​	​	​	26.20​
5​	20.66​	4.30​	21.20​	5.00​	24.96​
1​	27.20​	6.22​	​	​	33.42​
13​	27.30​	0.62​	​	1.40​	27.92​
20​	27.70​	5.20​	​	​	32.90​
7​	27.90​	4.90​	​	5.20​	32.80​
26​	28.14​	4.30​	​	​	32.44​
23​	28.20​	6.00​	​	​	34.20​
19​	28.30​	6.40​	​	​	34.70​
8​	28.50​	6.00​	​	​	34.50​
22​	28.70​	6.50​	​	​	35.20​
12​	28.80​	5.26​	​	​	34.06​
14​	28.80​	3.20​	​	​	32.00​
18​	29.50​	7.10​	​	​	36.60​
9​	30.30​	7.60​	​	​	37.90​
4​	-​	-​	​	​	#VALUE!​
15​	-​	-​	23.70​	1.00​	#VALUE!​

First 2 columns was first test, the 2nd pair is from a revisit after having cleaned the connectors. Values left blank if they are basically the same.

Ok so my biggest question here is how to arrange these to get the best output. My controller can handle 500V, so I know I won't get anywhere near that. I also know that panels in series will only deliver the max amps output of the lowest valued panel. So definitely not putting a <5A panel in an array that has all >6A panels.

Part of my roof where I'll be installing the first array will be able to mount 8 panels, possibly 9 panels. So my initial thinking was to go with these:

1​	27.20​	6.22​
7​	27.90​	4.90​
8​	28.50​	6.00​
9​	30.30​	7.60​
12​	28.80​	5.26​
18​	29.50​	7.10​
19​	28.30​	6.40​
20​	27.70​	5.20​
22​	28.70​	6.50​
23​	28.20​	6.00​
​	​	​
Total​	285.10​	4.90​

That's when I realized I couldn't put Panel #7 in this string. So I started looking at possible replacements, which lead me to these:

6​	19.78​	5.90​
21​	19.80​	6.40​

But these have lower voltage values compared to the others.

So I'm wondering, would it be better to have overall balanced Amps over balanced Volts when making strings?? Considering voltage is the sum of the string, and amps is the Minimum of the string.

Primary objective is to have a single string with the most possible power output as my controller only has a single MPPT input. It's a PowMr 5kW Hybrid Inverter. I do have a second "MPPT" controller, though I haven't tried it out yet to make sure it truly is MPPT or not. It's a review sample.

Any input is definitely welcome. The actual solar panel installation is all new to me and looking to the experience of the community for help on this one.

 

[grundholm]

balanced Amps

yes

My controller can handle 500V

Your MPPT start voltage is 120V - This is also important if you have shades. I think 285.10V is a sweet-spot for your MPPT / roof size. As an example. I have 6x330W on my roof (straight south, no shades) - I have configured them as 2 strings 115V and paralleled the 2 strings to double the amps. I only did this because I already had the MPPT with a max. 145V input. Here it would have been better to make one big array with 230V.
Because it can get cold here in the winter I keep the voltage low so I never exceed the 145V limit and I stay within the amps that my MPPT can handle.

My other setup is different, the panels is in my garden on my fence, they are also straight south but my house shades them all in the morning. It is 10 panels in a row, the first panel starts to get sun around 9 in the morning, next panel 9:15, next 9:30, next 9:40.... - something like that. Here I have used a micro inverter on the first panel, the remaining 9 panels is split into 3x3 strings, each string has it's own MPPT. I used the micro inverter to get use of the 10th panel and because my inverter can use the power to charge the battery.
My theory is: if I had made one big array (about 300V) - then say 9:30 I would have enough sun on the first panels to start the MPPT controller, but because the last panels would be in total shade I would end up with very low amps.

 

[OffGridInTheCity]

Agree - would balance the amps and make sure the min/max voltage of the string is in range of controller. However, if you parallel strings, the lowest voltage string will come back into play.

The other issue is physically mounting them as they're presumably difference sizes and thicknesses. So once the above is set then you might need to do some physical shuffling for best mounting - but that's OK with a few wire extenders if needed.

For example, while rebuilding my ground array I have 4 x 'different panels' than the other 18 and mounted them on each end to try for some esthetics

 

[Korishan]

The other issue is physically mounting them as they're presumably difference sizes and thicknesses

Actually these are panels that were taken down from commercial roof mounted installation. So all the panels are actually the same make and model manufacturing year and more importantly dimensions. So I don't have to worry about doing the weird shuffling for different sizes
Thanks for the tip about that though

 

[grundholm]

You could also check the bypass diodes if it is possible to open the black box on the back. Inside the box you can also measure each string of the panel.

 

[Korishan]

You could also check the bypass diodes if it is possible to open the black box on the back. Inside the box you can also measure each string of the panel.

Yeah, I'll do this on all the low valued panels. Fortunately I have enough good ones to get me just over my main power usage devices. Only thing that'd be left will be the two aircons. One is a minisplit and uses very little juice, which is really nice. I mean, the power wires that go from the inside unit to the outside (and power is supplied from the inside) is only 16awg.

I selected the top 8 panels with the highest amp output based on tests. Today I started putting up the brackets. Took a little bit to figure out how to install them properly
They came with the panels and initially I thought they were the equipment for a "railed" system. These are actually rail-less brackets. So because I hadn't known, I had already gotten some hardware (2x4's and Simpson tiedowns) to make my own rails and attach the panels to that.
Once I figured out the box of hardware contained the whole system, I pulled out the 2 2x4's I had already laid down. Glad I hadn't done more

Continued build over at: https://secondlifestorage.com/index.php?threads/solar-temporary-installation-progress.12826/

Please continue posting here for further information/ideas for panel arrangement, testing, etc. I do still need/want to replace the connectors which may actually change the values of the other panels anyways. Plus checking the diodes.