low PV output in anything but bright sunshine

[davidwf15]

I have a system comprising 14 x 475W new this year Aiko panels in 2 strings of 7, all facing south with no shadowing at all....I am finding that early morning and late afternoon the PV falls off dramatically
example from this morning - and apologies for the disgusting state of my windows! - I am generating a lowly 345W

literally 10 minutes later and I am generating 2.8kW....same apparent level of sun, no cloud, light level looked the same

In the afternoon it is the same in reverse.....plenty of sunlight left although it is not now shining on the panels, generating over 3kW, 10 mins later maybe 500W then nothing

I would have expected to see it dropping off more gradually over a longer period
In devices/inverter/ real time/ the PV is showing around 200V but the current draw is miniscule and therefore the output power is also almost nothing

Could it be something with the MPPT settings in the inverter ????

A neighbour has 20 year old 250W panels and generates WAAAAY more than we do on cloudy days .....just over half our prospective PV in fact ....I would have thought our super duper up to date state of the art panels would be better than his....obviously in full sun we produce way more than he does but thats not in question

[MaterialBarracuda48]

That tree looks like it will cause shading, cannot see the evening side of the street.

[davidwf15]

agreed that it "LOOKS" that way but the sun hadnt moved in the 10 mins between pics.....and 1o mins lated the power was down again
I appreciate that the panels wont produce anywhere near as much when not in full sun but 14 x 475W panels only producing 400W is pretty pathetic
today we have bright cloud (and now no shading) and still only around 900W
I am not convinced the MPPT settings are working as I happened to notice the specs for the inverter say the startup voltage is 75V, the MPPT input is 80 - 500V.....but even at 8am when the panels show 200V there is no no current or power draw

[MaterialBarracuda48]

Best to show a power graph for the day in question, and some previous day(s) that show the nice curved generation if you can find one. You wouldn't normally generate that much power so early in the morning, only if the panels were cold would you see the 2.8kW. Viewing the power graph would show that as being a 'Spike' I would think, and much lower either side of that time stamp.

[davidwf15]

Thanks for your prompt reply
With the greatest respect I think you have missed the point I am trying to make here....
I appreciate that there isnt much solar early in the morning but the live section in devices shows around 200V on the panels and the spec says it will start to generate at 75 - 85V ....so as I read it there should be enough to generate more than it is.....remember we are talking about 14 x 475W panels which is a vast area of PV to only be generating the few measley watts that it is

[Dave Foster]

I appreciate that there isnt much solar early in the morning but the live section in devices shows around 200V on the panels and the spec says it will start to generate at 75 - 85V ....so as I read it there should be enough to generate more than it is.....remember we are talking about 14 x 475W panels which is a vast area of PV to only be generating the few measley watts that it is

Sadly start up voltage and power are 2 distinct things and you need both to start, the inverters MPPT balances the voltage vs current to get the highest power point but if there is not enough current the voltage will collapse and the string won’t attempt to start up - that’s why you can have enough voltage but no power, the panels are effectively connected open circuit.

[MaterialBarracuda48]

I was a bit sidetracked this morning with front door, and I see Dave has replied, I will post the pictures I made to show a visual representation.


Here are my screenshots I took for readings for a few days ago (perfect solar start)
You can see the Inverter does not make Power until ~07:40, it tries to start the solar generation before this point as you will see in the Voltage picture, only when the current reaches ~0.5Amps does it generate power.

PV1 - Power

PV1 - Voltage, note the repeated attempts to start the string before 07:40

PV1 - Current

Thank you for your previous image, the overall picture was exactly what I was expecting to see (spikes)