Issue with getting expect power output (grid tie)

[noodle]

Hi - Need the team's help. New to solar setup and I'm not getting my expected output.

Setup -

Panels: 4 x 100W panels - Volts 17.1; Amps 5.9
Connectors: Parallel using bougeRV 1to4 connector (which says its cable size is 10-14 AWG)
Cables: Cable to inverter is iGreely 20 feet 10AWG cable
Inverter: Inverter is solarepic grid tie inverter (600W-18V) [it says the input is range of 11-32 VDC)
Angle: Panels are at 30% angle.

My theoretical math is 17.1 volts x 23.6 amps = 403 Watts

My max measure output is 210 (sunny day in texas); not anything close to 400 Watts.

I measured the open circuit amps and volts per panel and they are all good.
I measured input voltage at the inverter and its not to much of a drop.
I can't measure amps at the inverter since my multimeter only goes up to 10 amps.

I know the low voltage and 20 foot distance will lose some power but does it seem reasonable that I'm only getting 210 watts at my peak ?

 

[Ampster]

The issue may be what is your expectation based on? I base my expectations on PV Watts simulations or estimates of annual production. The STC ratings are under perfect conditions. Cells rarely operate under those perfect conditions. Heat also degrades output. In Texas this time of year the cells are probably significantly above test conditions.
In addition, solar panels are current sources, so you need enough load for the panels to output enough current for the load. . I am not certain, but I believe Isc is short circuit current. Shorting the panels is still not going to get you close to STC test conditions unless everything else is perfect.

 

[Zapper77]

Like this?


I didn't know this was even legal.

 

[pvgirl]

I didn't know this was even legal.

Not in the US.(simaler systems are legal in other parts of the world, including places such as Germany)

Without specs of this inverter not really easy to determine what is wrong.

 

[Mattb4]

2 potential trouble areas. Panels may not be properly rated. Those micro grid tie inverters are not terribly reliable.

 

[Zapper77]

Not in the US.(simaler systems are legal in other parts of the world, including places such as Germany)

Without specs of this inverter not really easy to determine what is wrong.

"My max measure output is 210 (sunny day in texas); not anything close to 400 Watts"

 

[Ampster]

Like this?

I am not sure what you are referring to, but the grid acts like an infinite load and assuming you are not maxing out the inverter capacity that would be a good test to measure potential output that day under the conditions existing that day.

 

[noodle]

Thanks for the replies All.

My focus is what power output is coming out of the inverter.

2 potential trouble areas. Panels may not be properly rated. Those micro grid tie inverters are not terribly reliable.

Not sure what you mean by properly rated. My measurements all were consistent and were close to the expected (about 80% since it was not full direct sun). They are Ecoflow ZMS331 panels.
My thoughts on bottlenecks are either
(a) the cable and the gauge/distance, or
(b) the 1-4 connector.
I wasn't thinking it was the inverter, but if the community has experience that these cheap inverters have quality problems than that could be something I can look at.
I did notice as I added each panel the amount of watts did go up versus hitting ceiling prior to the 4th panel.

Any suggesting on ways to test for the bottlenecks to help isolate ?

I know the 400W is a paper maximum - but was at least thinking maybe 300 watts would be possible. In systems that the community has built is there a ballpark % realized output versus paper maximum that you assume ? e.g. typically you should expect 75% of the maximum rated output ?

 

[Ampster]

e.g. typically you should expect 75% of the maximum rated output ?

Too many variables for even a ballpark estimate. I focus on annual production. In a couple of weeks we will be at the Equinox. Production typically declines since Summer Solstice in June until Winter Solstice in December.

 

[Solar Guppy]

Couple of thoughts:

You have to be in full direct sun, even a small amount of shade will drastically lower output

Running 4 panels in parallel looking at ~5% loss just there using under sized wiring for the home run

The invert is a budget low cost item, likely at best 80 to 85% efficient on converting DC to AC

Panel temperatures in Texas with 100+ temps alone will likely take 10-20% off ( typically loss of voltage is .08V per C over standard ). The panels are likely running at 60-70C or higher, that alone will sap ~15% off the STC test run at 25C ( panel, not air temperatures )