Hi

[Resolved! Many thanks to the hawk eyes of this forum's members]

We noticed over past few days that despite the cloudless days, the batteries didn't charge fully as in the past and both Pylontechs and the inverter is new. The panels and installation however are not.

For the duration shown in the graph and display, there wasn't a cloud in the sky and no shadows from trees, but the panels deliver no to very little current despite showing a Volt supply.

Early morning around 8, I decided the panels may need a clean and although not overly dusty, I cleaned them with a towel and water in any case. Shortly after add shown in the graph, the current dropped to zero and didn't pick up again despite full Sun

When switching off the circuit breakers on the panel input circuit, the Volts dropped to zero and each of the circuits with 3 panels each independently showed a voltage too.

I don't understand why the supply started dropping over the past week or so and how all three strings can have the same problem at the same time.

[Reason and solution]

The new inverter has a minimum input volt threshold of 120V and due to the extreme heat, the combined volts from the panels dropped just below this threshold every day around 10am as shown in the graphs. 

With the 3 panel sets now in parallel, the total input Volts is now 3 times higher and still within the allowed range of the inverter. 

Everything is running smoothly now. New graphs added.

 

 

 

Edited November 26, 20232 yr by PaulNaude01
Resolved

17 hours ago, PaulNaude01 said:

When switching off the circuit breakers on the panel input circuit, the Volts dropped to zero and each of the circuits with 3 panels each independently showed a voltage too.

What are the mppt specs of the new inverter? It could be that 3 panels in series is too high or too low voltage for the new inverter.

Also, what are the specs of the panels?

It does happen every now and then someone replaces a low voltage model with a high voltage one.

The screen is fimiliar with either Kodak OG 5.6 or the Axperk MaxII 8K it does look like the mptt is switching off or throttling output. Like @jumpersuggested give as as much information possible panel specs, inverter make and model and the settings.

Maybe stating the obvious. Looks like giving the panels a wash may have dropped the temperature on the cells temporarily to cause a spike in Voc that caused generation to be started on a HV MPPT (120V-450V range), but that it could not be sustained at 116V.

At the bottom of the display, is that a time or a date? If it's 11:08pm then I would expect no PV. Maybe the inverter has some intelligence and switches off the MPPT if it thinks the sun is on the other side of the globe.(or hiding somewhere if the earth is flat😀)

23 minutes ago, Thunderdolt said:

At the bottom of the display, is that a time or a date? If it's 11:08pm then I would expect no PV. Maybe the inverter has some intelligence and switches off the MPPT if it thinks the sun is on the other side of the globe.(or hiding somewhere if the earth is flat😀)

The Axperts are many things, but not that smart. We need more info from the PV side

Thank you for all the replies. 

The panels were installed in 2018, 330watt units from ArtSolar. 3 strings of 3 panels, 9 in total, thus a total just shy of 3kW

 

The inverter details are on the image attached, a 5.6kW unit

Some of the unit status info is attached too and today's Volt and power graphs.

The issue seems indeed to be that the voltage drops below the minimum of 120v.

Edited November 26, 20232 yr by PaulNaude01
Added image

3 hours ago, Thunderdolt said:

At the bottom of the display, is that a time or a date? If it's 11:08pm then I would expect no PV. Maybe the inverter has some intelligence and switches off the MPPT if it thinks the sun is on the other side of the globe.(or hiding somewhere if the earth is flat😀)

I'll have to check!

6 minutes ago, PaulNaude01 said:

The panels were installed in 2018, 330watt units from ArtSolar. 3 strings of 3 panels, 9 in total, thus a total just shy of 3kW

 

The inverter details are on the image attached, a 5.6kW unit

As indicated on the photo with the inverter details the minimum solar voltage needs to be 120V so I suggest that the configuration of the solar panels must be changed to either 4S2P or all in series, if choosing 4S2P one panel would not be used because you cannot have one string with 4 solar panels in series and another string with 5 solar panels in series on the same input.

16 minutes ago, GerhardK83 said:

As indicated on the photo with the inverter details the minimum solar voltage needs to be 120V so I suggest that the configuration of the solar panels must be changed to either 4S2P or all in series, if choosing 4S2P one panel would not be used because you cannot have one string with 4 solar panels in series and another string with 5 solar panels in series on the same input.

This seems to be the issue, yes. I've added more graphs showing the voltage and power from the panels.

Do you think it is the current heat wave that causes more resistance and drops the voltage?

23 minutes ago, GerhardK83 said:

As indicated on the photo with the inverter details the minimum solar voltage needs to be 120V so I suggest that the configuration of the solar panels must be changed to either 4S2P or all in series, if choosing 4S2P one panel would not be used because you cannot have one string with 4 solar panels in series and another string with 5 solar panels in series on the same input.

This seems to be the easiest to implement in any case, to take the three inputs which are currently in parallel and put them in series, taking the total input Volts to a maks of 360V, which is still safely in the inverter's input range.

Can a cheap Volt meter get the DCV reading this wrong?

Measured at the solar panel supply, into the lightning arrestors, from where it goes directly to the inverter.

20 minutes ago, PaulNaude01 said:

Do you think it is the current heat wave that causes more resistance and drops the voltage?

This is most likely the case, but the fundamental problem remains that you are operating on the lower verge of the inverter's Voltage range.

Just be careful to calculate max input Voltage not as 9 x 40V Vmp, but as 9 x Voc and leave room for temperature variation as per the panel's spec sheet and expected local temperature. I expect you'll get closer to 450V than 360V. If in doubt rather use one panel less.

47 minutes ago, PaulNaude01 said:

Do you think it is the current heat wave that causes more resistance and drops the voltage?

Yes temperature plays a role in the output power, voltage and current of any solar panel.

28 minutes ago, PaulNaude01 said:

Can a cheap Volt meter get the DCV reading this wrong?

Measured at the solar panel supply, into the lightning arrestors, from where it goes directly to the inverter.

Geez something does not add up, is there an isolator between the solar panels and the inverter?

Also check the voltage on the surge arrester.

8 minutes ago, GerhardK83 said:

Geez something does not add up, is there an isolator between the solar panels and the inverter?

Also check the voltage on the surge arrester.

This must be the excuse I've been waiting for to buy a more expensive multimeter 😉

I would trust your cheap meter reading. See what it measures on your battery.Perhaps one of your connections to the inverter is loose or high resistance for some reason? Or your inverter has an internal issue?

53 minutes ago, PaulNaude01 said:

This must be the excuse I've been waiting for to buy a more expensive multimeter 😉

Yea definitely, Uni-T, Major Tech, Fluke, Gossen, Brymen, Top Tronic, Kyoritsu and some of the more expensive Chinese brands (+R500) are good quality and more than accurate enough, also have a look at an AC / DC Clamp meter then both AC and DC current can also be measured.

Most of the test instruments that I have has been purchased at pawn brokers or cash converters and I test the instrument before purchase so that I know the instrument works 100%.