Any way to see if all the panels are connected and working from the voltage or any other number?

Doggydogworld said:

You originally linked to this inverter, the S6-GR1P5K, which that reseller claims has a 60V startup voltage. But that model on the Solis web page shows 120V startup. I tend to believe the OEM web page. But voltage data you showed earlier never hit 120V, so how did it start up? Hmmm. Maybe it takes a second or two for logging to kick in after startup.


Isc for your panel is 13.68A at STC. Two panels in parallel would be 27.36A, which as you note exceeds that 17.2A spec. The S6-GR1P5K you linked earlier has a higher 22A Isc spec, but that's still not enough to parallel two of your panels. So you are limited to 1P strings. You can have two such strings, one on each MPPT. Since you only have one MPPT input hooked up, it implies 10S1P. But your voltage readings look like 3S1P.


Yes, you'd need at least 5 of your panels in series for 120V startup. I'd still prefer two 5S1P strings over a single 10S1P. Better to drag 5 panels down when one gets shaded than to drag all 10 down. But again, you only have a single string hooked up. And the voltages from that string are consistent with three panels, not 5 or 10. So something is wrong, we just don't know what.


I don't see any "best day" data in comment #39. But steady voltage and low current is what you get when the sun is low, or it's cloudy, or one panel in the string is shaded, etc. MPPT algorithms adjust voltage to maximize power, but due to the way panels work the max power point voltage tends to be pretty steady during the day (unless you see wild temperature swings or something). The MPP current tends to vary over a much wider range.

Click to expand...

It kicks in every day with 100v or so.

Once the installer calls looking for the money I will ask him to come here and review all the set up. I produced 2.3kwh others at least twice that......

I phoned the installer and explained things and it would seem that they did not connect 7 panels. I take it that it is a situation as the below photo but they didnt loop 7 panels above the 3 below.

They'll have to come back to connect the missing panels to the loop.

Wonder how much work that is to them. I imagine not a lot.

Galego said:

I phoned the installer and explained things and it would seem that they did not connect 7 panels. I take it that it is a situation as the below photo but they didnt loop 7 panels above the 3 below.

They'll have to come back to connect the missing panels to the loop.

Wonder how much work that is to them. I imagine not a lot.



View attachment 115412

Click to expand...

If they cannot get to the connectors they will have to unmount the panels to get to the wires can be a lot of work to get to the connectors.

They were pretty fast putting them in!! Obviously now we know rushing these jobs is not a thing.

Anyone can forget to plug something in. But you'd think they'd test voltages and currents before leaving.

Let us know how it turns out.

An update.

So the fitters were quick to come back! I give them credit for that!

It took them a while to figure things out! They had to lift almost all panels and start from connecting them from scratch. Anyway, all connected and then we sat for a cup of coffee and I brought the topic of the chimmey/tv aerial casting the shade in one to two panels (at some time of the day) and the electrician thought it was worth the shot of fitting one optimiser each for those two panels.

So up they went back to the roof and fitted the two optimasers. What I have now noticed is that the voltage dropped down a bit. Because I havent had the best experience with this installation now anything makes me wonder and question things.

Leaving aside whether I made the wrong decision with the optimiser (i am still thinking of calling them back and taking them off ), is there anything which i should worry about?

Panel max voltage



Voltage today.

Yep now your voltage looks normal and the power level for 5:30 pm looks good.

Galego said:

An update.

So the fitters were quick to come back! I give them credit for that!

It took them a while to figure things out! They had to lift almost all panels and start from connecting them from scratch. Anyway, all connected and then we sat for a cup of coffee and I brought the topic of the chimmey/tv aerial casting the shade in one to two panels (at some time of the day) and the electrician thought it was worth the shot of fitting one optimiser each for those two panels.

So up they went back to the roof and fitted the two optimasers. What I have now noticed is that the voltage dropped down a bit. Because I havent had the best experience with this installation now anything makes me wonder and question things.

Leaving aside whether I made the wrong decision with the optimiser (i am still thinking of calling them back and taking them off ), is there anything which i should worry about?

Panel max voltage

View attachment 115813

Voltage today.

View attachment 115812

Click to expand...

Yep, a hail storm is not good.

Galego said:

So up they went back to the roof and fitted the two optimasers. What I have now noticed is that the voltage dropped down a bit.

Click to expand...

Dropped? Your graph shows 300V vs. 75-100V before. Or do you mean it was higher than 300V when they first reconnected things, then dropped back down to 300V after they installed the optimizers? Anyway, your voltages look pretty good, depending on your particular local conditions. Let us know how production compares to those other local systems over the next week or so.

As I said before, I don't know how optimizers work. I know they first use a MPPT algorithm to optimize a shaded panel's output. That's only a minor gain, though. My guess is the real gain comes from using their DC/DC converter to reduce the voltage coming out of that panel and boost current to match the rest of the string. For example, consider a panel that produces 30V and 12A in sun but only 30V and 6A when partially shaded. That's a 50% power reduction. But with series it pulls the other 9 panels in the string down to 6A as well, so you lose 50% for the whole system (vast oversimplification, but you get the idea).

Now let's say the optimizer converts that 6A @ 30V to 12A @ 15V. That one panel is still down 50%, but your other nine panels stay at 12A instead of getting dragged down to 6A. So:

Pre-shading:
10 panels at 30V * 12A = 360W each = 3600W total

Shaded, no optimizers:
10 panels at 30V * 6A = 180W each = 1800W total

Shaded, with optimizers:
1 panel at 30V * 6A = 15V * 12 A = 180W plus 9 panels at 30V * 12A = 360W each = 180W + 3240W = 3420W total

Your system voltage drops to 285V in the last case vs. 300V, but your production under partial shade is vastly higher.

Hopefully someone who understands optimizers will chime in with corrections, but I think this is the basic idea.

This is a great topic. I have warned people putting in systems to make sure they have good monitoring capability and that the installer gives them theoretical numbers to expect.

SeaTac Airport, Seattle, WA, USA, installed a field of PV cells and all seemed well for several years. Then a local university did a drone flyover taking IR pictures. Analyzing the pictures they discovered 10% of the cells weren’t working. Further investigation discovered those cells had NEVER been connected during the install. Sorry I can’t find a link to the directors follow up report. Made for interesting reading.

Shows the importance of having good monitoring AND knowing what the numbers should read.

@Doggydogworld

Because I am a total newbie and trying to understand, learn and educate myself in the pv solar world...having had such a bad start at it makes me now doubt and question every thing. In my head it is like they may now only connect 9 instead or 10? Or the optimisers are actually bringing down the voltage?

These are the stats.
1- Please note that the first two rows is before they finally connected all panels (whichever number that turns to be).
2- In yellow colour, we are just having tea and coffee inside the house.
3- In green colour - Ater they fit two optimisers to those two panels which can potentially be shaded during the day by the chimmeny/ tv aerial.

Weather remains identical for the whole day. Sunny day with no clouds.

Generated kw was pretty good to be honest for today but as I said I am now almost paranoiac with this because my experience so far.

So my question in my head is now:
How come the voltage drop from a solid 313 to avrg 280-295v?
I see the current (a) gets better which ultimately makes more power but perhaps that could have happened regardless @ 313v?

Galego said:

@Doggydogworld

Because I am a total newbie and trying to understand, learn and educate myself in the pv solar world...having had such a bad start at it makes me now doubt and question every thing. In my head it is like they may now only connect 9 instead or 10? Or the optimisers are actually bringing down the voltage?

These are the stats.
1- Please note that the first two rows is before they finally connected all panels (whichever number that turns to be).
2- In yellow colour, we are just having tea and coffee inside the house.
3- In green colour - Ater they fit two optimisers to those two panels which can potentially be shaded during the day by the chimmeny/ tv aerial.

Weather remains identical for the whole day. Sunny day with no clouds.

Generated kw was pretty good to be honest for today but as I said I am now almost paranoiac with this because my experience so far.

So my question in my head is now:
How come the voltage drop from a solid 313 to avrg 280-295v?
I see the current (a) gets better which ultimately makes more power but perhaps that could have happened regardless @ 313v?

View attachment 115835

Click to expand...

I would leave things as is for a while you are thinking that you need more voltage that is not the thing you need to focus on power is the thing you need to focus on. You do not have enough data without the optimizers to make a decision yet and just now have some data with them.

The MPPT controller will bring the voltage down when it sees it can get more power out of the panels.

labeeman said:

The MPPT controller will bring the voltage down when it sees it can get more power out of the panels.

Click to expand...

Thanks! It makes sense.

I read the optimisers are to do some of that work today in theory, right?

Galego said:

Thanks! It makes sense.

I read the optimisers are to do some of that work today in theory, right?

Click to expand...

I am a complete idiot on those things.

Galego said:

Thanks! It makes sense.

I read the optimisers are to do some of that work today in theory, right?

Click to expand...

The voltage drop with the optimizers is perfectly normal.

What is happening that the optimizer will trade panel voltage for panel current.

The issue with shading is that in a regular string setup the current in the entire string is limited by the weakest producing panel and all other panels will reduce their production to the weakest panel's current production. Exception is when the bypass diode on a panel kicks in, in which case the panel is essentially eliminated from the circuit and all current flows through the bypass diodes, making the shaded panel zero producer and marginal voltage consumer over the bypass diodes.

Each panel produces power which is P = Voltage * Current.

On a string of panels the Current flowing through the string is constant.

But panel power generally has constant voltage so power output due to shading will be affecting current.

Optimizers are essentially buck converters which will sense the incoming current and adjust the voltage of the shaded panel down until the current for the power production of the shaded panel matches that of the incoming current.

Example: your panels are at 30V and 10A producing 300W of power each. With 10 in series you would have 300V and 10A for a total power of 3000W. But now let's say one of them is 33% shaded and only produce 6.66A but still the same 30V (that is how panels work). Now without optimizers your entire string will drop to 6.66A at 300V total for a net power of 2000W.

But with optimizers, the optimizer will sense that the other 9 panels are flowing 10A so it will buck the shaded panel to produce 10A at 20V instead for the same power as 6.66A at 30V would be. This way the entire string can be at 10A but the string voltage will be 9x30V + 1x20V for a total of 290V and a total power of 2900W. This is how optimizers work.

Now if you have parallel strings with optimizer, the strategy has to be more coordinated and requires the optimizers to talk to each other to balance the voltage between the two strings, but that is not the case in your scenario.

So seeing a drop anywhere between 0-30V for each optimized panel is the expected behavior.

I forgot to add: the chart you showed demonstrates perfectly that the system and optimizers work wonderfully and as advertised. Voltage dropping, current rising, power power out of the entire string. I'd say your panels are looking good now! Can't wait to see a daily production number from you now.

I agree that with a series array you want to look at current more than voltage. Vmp for your panels is 12.95A. Even the NOCT value is 10.42A. So why were you only getting 6.9-7.7A in the yellow rows? Something was pulling your current down. The optimizers managed to bring that up to 8.3-9.6A (I'll throw out that last 10.7A reading). That more than offset the voltage drop, producing higher power output.

We don't know for sure which panels caused the voltage drop, but it's a good guess the optimizers reduced the voltage and increased the current on the panels that were previously dragging your whole array down. It'd be fun to get panel-by-panel readings.

Just keep in mind, with a series connection low voltage on one panel only affects that panel while low current drags down the whole string. So if you have a panel that's shaded or whatever it's better to trade off voltage for current.

Parallel is the opposite, but it's less of an issue because voltages don't vary as much with shading and such. That's why people use parallel for panels that get shade or panels that face different directions.

Thanks a mill lads! Invaluable information what you all have provided. I am so excited about my Pv Solar system and now looking at getting a battery!

PS, I sent 7kw back to the grip yesterday. I need to store that in the future!

I thought I would give you all an update on my system.

I am very happy with it and it is performing as it should now. I am learning how to make the most of the electricity produced and have come to the conclusion that a battery would be very beneficial so I have purchased a Pylontech US5000. I will receive it in one month or so.

Another thing which I have noticed in my early learning curve with my system is that I dont find the eddi diverter a very efficient way to divert excess (to the hot water tank) and I would much rather store that energy in a battery and use it later on in the house loads. I think my oil boiler does a better job at heating the hot water and in a much cheaper way than the electricity cost (per kwh).

Thanks all for reading my journey in the pv solar world. More to come!