Solar panels giving trouble

[Adrianlle]

Last few weeks not getting any ah from panels though generating a voltage( 200w flexi panels with Victron 75/15 mppt controller using iPhone for Bluetooth readings). 2x 85ah gel batteries a few years old. Voltage reading on controller for last few weeks only about 15v max. Readings that show some ah going to batteries was about 5 weeks ago with a panel voltage of 18v and more.

I seem to remember that the Victron controller needs a voltage from the panels at least 5v more than the battery state to operate, which may explain things. But if so wonder if that suggests panels ( about5 years old) need replacing?

I’ve tried the usual of switching off feed for from panels and to battery bank. Also tried disconnecting the connectors from panels on roof and wd40 and reconnecting. But today for instance showing 8v from the panels, Oah from panels and a battery state of 11.3 v( I dropped it down deliberately). Any thoughts appreciated as ever. Thanks

 

[SandraL]

Do you have a handheld voltmeter?
Can you disconnect panels from the solar regulator and measure, when sun is shining, the output from the panels. Should be 20 v ish if panels are wired in parrallel.
If not, then as you have more than one panel. Can you seperate the feeds from each other, and check voltage output from the individual panels when sun is shining.

 

[Adrianlle]

Thanks. Bit wet here at moment but when sunny I will get voltmeter on roof( fortunately there’s a roof bed and a heki4 above so that I can reach the connections) and do some measuring of panels in various permutations and report back.

 

[Guigsy]

At this time of year at midday, even when the sky is clear, you're only going to generate about a third of your panel's rated output.

Also, any kind of shadow, even if it's just your aerial casting a slight shadow on the very edge of the panel, will drag the whole panel down as if it was all that level of shadow. So the low sun at this time of year is particularly bad for panels facing straight up.

 

[Raul]

Best you can do, without changing the panels is to wire them in series to increase the voltage into the controller.
There are two scenarios happening: -one or both panels have cracks and high resistance, unable to deliver any amperage,
- Light very low, and the mppt is trying to extract some power by pulling the voltage down.
The thing is a faulty panel can deliver good voltage, even 22v, but OA. Voltage reading is meaningless without being under full load. You will be reading VOC voltage open circuit, and that without resistance (load), it will read ok. The way to “sort off” test is the short circuit current with the panel in the sun. If current value is low and nowhere near the ISC value, rest assured the panel is goosed.

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[Adrianlle]

Thanks. I would be surly if it’s shading because the van is parked in its usual position in the yard, same as last 5 years without a problem with solar.

I had wondered about rearranging the connections on the roof to series in order to increase the voltage - presumably the Victron 75/15 controller can handle the voltage ?

But before going down that road, how do I check the short circuit voltage to see if the panels have had it?

Thanks

 

[Raul]

Short circuit current, not voltage. It implies a multimeter with the dial to ADC, and the probes to ADC. Then panel in the sun, touch both ends of the solar wires, of each panel.
If you not sure google the procedure how is done, not hard to do, but it needs to be fairly sunny for the test to be conclusive.
There are other ways to diagnose a duff panel but it takes some knowledge and understanding of how a panel works.
A solar panel is a current source, compared to a battery that’s a voltage source. I know for some this don’t make sense, but that’s another story.

 

[Adrianlle]

Well today there was a bit of sun at 2pm ( Somerset). The voltage from the panels either singly or in parallel has been c 8v so not enough to cause the Victron mppt to kick in as that needs to be 5v above panel voltage. So swapped the connections around on roof to wire the panels in series. With the bit of sun at 2pm that gives a voltage from panels c 20v and c 5ah. Controller has cut in and charging batteries.
So Victron seems ok and the issue seems to be the panels producing a weak voltage ( though appreciate not the best of conditions). So back to wondering whether the panels need replacement? Any thoughts?

 

[Lenny HB]

Fairly certain your panels have had it, they have done well most people only get about 2 years out of semi-flexable panels before they die.
Your best option would be to replace them with ridge panels.

 

[Adrianlle]

Thanks Lenny. Alas space is limited on top of curved roof of Westfalia James Cook but can get 2 100w flexis in but even then have to be no wider than 505mm ( which is unusually narrow I think). But with a big compressor fridge ( which is a good one) the panels are a necessity for our sort of off grid camping.

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[Pausim]

Are the panels mounted horizontally? Perhaps the November sun is too low on the horizon for them to work properly. I had some portable flexible panels and their output was virtually nothing by this time of year when laid horizontally, they did a bit better propped up nearly vertical.

Solar Angle Calculator

The solar angle calculator tells you by location the optimum angle to get the best out of your system.

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[Lenny HB]

Thanks Lenny. Alas space is limited on top of curved roof of Westfalia James Cook but can get 2 100w flexis in but even then have to be no wider than 505mm ( which is unusually narrow I think). But with a big compressor fridge ( which is a good one) the panels are a necessity for our sort of off grid camping.

I would have thought you make some brackets to fit ridgid panels on your roof.

 

[Adrianlle]

Are the panels mounted horizontally? Perhaps the November sun is too low on the horizon for them to work properly. I had some portable flexible panels and their output was virtually nothing by this time of year when laid horizontally, they did a bit better propped up nearly vertical.

Solar Angle Calculator

The solar angle calculator tells you by location the optimum angle to get the best out of your system.

www.solarelectricityhandbook.com

Yes - horizontal but we camp all year round without hook up as well as compressor fridge have webasto heating which draws current when cutting and out. In the past have usually managed to get some charge from the panels even with the winter sun low in the sky. So something not right at moment and there are only a limited number of suspects- hence my thinking that the panels are on their way out.