Need help with Strings

[Jerryonthego]

Hi All,

I have combed through the forum and can't seem to get the answer to my question (yes googled as well). Admittedly I am extremely new to solar.... so forgive my ignorance, however I just came across a great deal on the SunPower 435w panels and picked up 10 of them. I currently have (2) LV2424 that I will be connecting the panels to. To split the max wattage (per LV2424.... being 2000w) I would need to limit the array to 5 panels. Since the VOC is 79..... putting in series is not an option as it will be above the 145v limit. So my question is would I be able to have 4 panels (2 strings of 2 in parallel) along with a fish panel (string 3) and attach them all into a 3-1 combiner. Would there be any issues with the 3rd string being a single panel at half the current? BTW for more info I am running this as a 24v system (nonsplit phase).

Another option would be to just have 2 strings of 2 panels in parallel going to each LV2424 and use another Mppt controller for the remaining panels..... however it makes tracking the power input and consumption more messy. Would prefer to run everything through the (2) LV2424 units.

Appreciate any insight

 

[rmaddy]

2000W / 435W per panel is 4.6 panels. So you can really only have 4 panels per controller.

Is the Voc really 79V per panel? If so you can’t even put two in series since that will be well over 145V.

 

[Jerryonthego]

Can i not go over the 2000w threshold slightly for an MPPT as these will likely never pull full power?

 

[rmaddy]

In many cases you can over panel a bit. But your proposal for 5 panels with 4 in 2S2P and the 5th added to that really won't work.

If each panel's Voc is really 79V then you might be able to do 5P depending on the amperage limits on the SCC.

Or use the two SCC you have and add a 3rd. Then split the 10 panels into 3 groups. Until you confirm the Voc of each panel it's hard to offer real numbers.

 

[Jerryonthego]

Panels are E20-435-COM….. VOC actually 85.6. So will go with the 4 panels per MPP inverter and then have the other 2 panels go to an extra EPEVER MPPT SCC that i have.Just will monitor that one via Graphana.

 

[rmaddy]

Verify the controllers can handle 4 in parallel. And you'll need combiner boxes.

 

[jamiko]

Those panels have an Isc of 6.43A I think looking at the Sunpower website. So 4 in parallel is 26A?

 

[Jerryonthego]

That is how i saw it. The lv2424 supports up to 80a on the SCC…. So i should be fine to run 4 panels i would think.

 

[jamiko]

That is how i saw it. The lv2424 supports up to 80a on the SCC…. So i should be fine to run 4 panels i would think.

Make sure all wiring, connectors, etc. support 30A

 

[rmaddy]

The lv2424 supports up to 80a on the SCC

Is that 80A input from the panels (seems rather high) or output to the battery?

 

[Hedges]

If wiring the panels 5p would be somewhat over-paneled, just orient some panels toward AM sun and some toward PM sun.
The reduction in area presented to the sun is approximately the reduction in peak current and wattage. You'll get more hours of good power production. You could over-panel to about 140% the PV wattage without having output clipped by SCC.

Use a fuse or breaker per panel when 3 or more are wired in parallel.