Can Solar deteriorate this much?

[wingssail]

I've lost about 50% of my solar capacity this year.

I don't have a lot of solar, just two Kyocera 135 watt panels mounted in a shade free location on the stern. I've had them for 14 years but this year the output has dropped off dramatically. Instead of 10-12 amps coming from the combined panels I am getting 5-6 amps at the most. They are going through an ancient PMW controller which I had with my previous 85 watt panels which, while low in power, held up remarkably for 20 years.

I've checked these by shading each one and they each produce about 2.5 to 3 amps.

I removed the PMW controller and connected them directly to the battery, and the amps to the battery was the same.

At the controller I see an open circuit voltage of about 19.75 volts.

No connections anywhere look too bad or get hot.

The only change to my system this year has been a new on/off switch which cuts the connection between the controller and the batteries which I use to take them completely off line. This switch seems pretty ordinary and works smoothly, and does not get hot.

Yes, this is the summer and the temps here in Mexico are high (30-34) but that has been typical every year.

Can this be possible?

[Jammer]

I'm confused. Do you have the panels in series, or in parallel?

[wingssail]

Originally Posted by Jammer

I'm confused. Do you have the panels in series, or in parallel?

Two 12v 135 watt panels in parallel feeding through one heavy two conductor wire to the PMW controller, then to an on/off switch then to an ammeter then to the house side of the battery selector switch.

Yes, very primitive and old fashioned but until this year it has worked flawlessly.

[sailorboy1]

I don't know how long they will/should go. But I am pretty sure the datasheet of my last panel said output was guaranteed to be 85% during first 10 years. That suggests they start going at 10 years to me.

Open circuit voltage is meaning guess. You will get full voltage with even a partial single wire strand. The most likely a common wiring issue I e it the MC4 plugins. 8t may be worth cutting them out and seeing what happens with a new connection (if you have ever unplugged under load there is good chance of 1 being burnt)

[wyb2]

One thing to check could be the resistance in the wire run. I’ve had cheap wire start to corrode internally even though it had never been exposed directly to water. If the resistance is spread across the length of wire, you may not notice any heat like you would with a bad connection.

[Jim Cate]

Besides the open circuit voltage check you should check the short circuit current developed by each panel in full noon sun. The label on the panel should show what the rated current should be If the panel has deteriorated the current will be lower than shown on the label. Make the measurement both at the panel and at the input to the controller. A big difference in those values will show up high resistance in the connecting cable or connectors.

Jim

[GordMay]

The industry standard for most solar panels' lifespans is 25 to 30 years. Most reputable manufacturers offer production warranties for 20 ➛ 25 years.
Solar panels will naturally produce less energy over time. This reduced power output is called the degradation rate. The median solar panel degradation rate is about 0.5%, which means that a solar panel’s energy production will decrease, at a rate of 0.5% per year. After 20 years, your panels should still be working at about 90% of its original output.
NREL ➥ https://www.nrel.gov/state-local-tri...pv-panels.html

[nuku34]

To the OP:
I don't know about your ancient PMW controller, but with a modern MPPT controller it is pretty much instant death to disconnect it from the battery with current still flowing in from the solar panels.


If you ever replace that controller with a MPPT one, do NOT put an on/off switch between it and the battery. The switch, if you want one, needs to go between the solar panels and the controller. I speak from experience.


About your drop off in output: solar panels do degrade, and 14 years is a reasonable life span. Since both panels are producing the same, it would indicate that both are degrading at the same rate, so its not a defect in one panel. Can you jury-rig a new wire run directly to the battery from one panel to check if its the wiring that's the problem?

I respectfully suggest you upgrade the whole system: new panels, modern controller, new wires and connectors.

[Pete7]

Originally Posted by wingssail

The only change to my system this year has been a new on/off switch which cuts the connection between the controller and the batteries which I use to take them completely off line. This switch seems pretty ordinary and works smoothly, and does not get hot.

Since the drop in performance has appeared this year and the only change has been this switch, I would take a second look at it. Perhaps even removing it from the circuit temporarily and see what happens before splashing out hard cash on new equipment.

I disagree with Nuku, we haven't had a problem with a number of Victron controllers being disconnected from the battery first. Same for previous PWM. No experience with other MPPTs. Now that most of the Victron's are smart solar with Bluetooth, I do however, tend to use the app to shut them down before disconnecting anything.

Pete

[tanglewood]

Is it possible that your batteries just aren't accepting more?


The short circuit current test described earlier will tell you conclusively what the panels can produce. Just make the short with a properly rated switch, or cover the panel when making the final short circuit connection. Otherwise the arcing could weld the wire.