What voltage should Kyocera 120-1 put out? Troubleshooting...

[sgtPluck]

Hi,
My solar controller stopped showing any amps coming out of my panel the other day. The first thing I suspected was corroded or loose connections on the line, but when I checked the panel directly with a multimeter I am getting readings that I think may be a problem.

In full view of the sun at 2pm I am seeing:
12.1 volts
4.78 amps

If I understand correctly I should be seeing somewhere between 15 and 17 volts, is that right?

The meter still says I'm getting 4.78 amps at the panel but my solar controller is not sending any power to the batteries (no amps showing up in my link 10 battery monitor) the controller is a Blue Sky Solar Boos 25i2i.) I was guessing that's because of the low voltage, but I am new to this and am not sure.

Thanks for any tips you might have.

[btrayfors]

The Kyocera 120-1 puts out 21.5 volts OPEN CIRCUIT (i.e., not connected to anything). Under load, it puts out 7.1 amps @ 16.9 volts.

I'm guessing there may be something wrong with the controller or the wiring.

You might disconnect the panel from the controller temporarily, and measure the open circuit voltage.

Bill

[sgtPluck]

Thanks,
I just tried that. Was getting 18.9 volts open circuit (at a very oblique angle to the sun this time.) I guess that means it's my controller? I just bought that thing at the boat show in October, I hope I can find the receipt!

[btrayfors]

Yep. Hope so.

Before you give up, go over all the connections once more to be sure that things are correctly wired and that the connections are clean and tight.

Good luck,

Bill

[sgtPluck]

I posted before thinking.... Yes, the first thing I'll do is check the splice that was done a few feet away from the panel. It is outdoors and subject to movement so it could be an issue.

[edit]
Um.. that took all of about 20 seconds to figure out. I cut open the splice and it is corroded to hell.

Sorry for not doing that before posting in the first place. I was being lazy, that splice looked good, covered in a rubber 'marine grade' sheath, I didn't want to cut it open for fear of having to redo it. But sure enough, that was the obvious place for there to be a problem.

[btrayfors]

Congratulations! You're a lucky guy...they're often not quite that easy :-)

Best way to splice, IMHO, is double-kill:

1. slip a 2" length of adhesive-lined heat shrink tubing over one of the wires;

2. use a 3M heat-shrink butt connector and a proper crimp tool (so you don't cut into the insulation) to join the wire ends;

3. heat shrink the butt connector with a heat gun or hair dryer; and finally

4. slide the adhesive heat shrink tubing over the butt connector and heat-shrink it with a heat gun or hair dryer.

Bill

[Tingum]

But don't it make you feel good to fix it!!

[sgtPluck]

Oh that I should be so lucky...

I did re-do the splice today, although before I read the posts here, and I did only an OK job. I might redo it. I crimped butt connectors on it and sealed it up with electrical tape and rescue tape.

Anyway, that did not fix it. I called Blue Sky and after trouble shooting with them for a while they are pretty sure it's not the controller.

I see 19.1 volts at the panel (short circuited)
When I measure the voltage at the controller (with the PV +/- wires disconnected from the controller) I see 19.1 volts and around 5 amps from the panel (varies with passing clouds etc.) If I reconnect the PV +/- to the controller and read the voltage, I only see 12.1 volts.
When I read the battery voltage at the controller it shows the current batter voltage, (around 12.5.)

Bluesky say I must have a problem in the panel or the wire causing resistance. I'm in above my head because the sum total of my electrical knowledge is from thumbing my Don Casey book. I'm not sure how I can get an accurate resistance reading on my long wire. I can try disconnecting it and clamping +/- together at the junction box and then using my ohmeter at the controller end. I am doubtful that the panel itself it the problem.

Oh well. The mystery continues.

[Paul Elliott]

Originally Posted by sgtPluck

I see 19.1 volts at the panel (short circuited)

I hope you mean "open circuited". If you are measuring any significant voltage with the panel wiring shorted, that means you have a bad connection.

When I measure the voltage at the controller (with the PV +/- wires disconnected from the controller) I see 19.1 volts and around 5 amps from the panel (varies with passing clouds etc.) If I reconnect the PV +/- to the controller and read the voltage, I only see 12.1 volts.
When I read the battery voltage at the controller it shows the current batter voltage, (around 12.5.)

This is confusing. The "PV" terminals are where you should connect the wires from the solar panel. Your house battery should connect to the "BAT" terminals. Do you have these wired backwards? I don't understand how you can measure panel current with the PV wires disconnected.

Bluesky say I must have a problem in the panel or the wire causing resistance. I'm in above my head because the sum total of my electrical knowledge is from thumbing my Don Casey book. I'm not sure how I can get an accurate resistance reading on my long wire. I can try disconnecting it and clamping +/- together at the junction box and then using my ohmeter at the controller end. I am doubtful that the panel itself it the problem.

The best way to measure wiring resistance is to calculate it by measuring the voltage drop across the wires, and the current running through the wires. Volts divided by Amps equals Ohms. You can measure as you suggest, but the resistance should be so low that the typical multimeter won't be able to accurately measure it.

[sgtPluck]

Hi,
I disconnected the wires on the panel so that the only circuit I was reading was the panel itself, and that showed 19.1 volts.

Then I read the voltage and amps at the controller by connecting my multimeter to the wires from the solar panel - which I had disconnected from the controller - I did this with the intention testing the circuit that includes the panel and the wires from the panel to the controller. I was getting 19.1 volts and around 5 amps here. (This seems to me to indicate that my panel and wiring is working, although the amp level is a little lower than I would have expected at that time of the day, maybe the Florida heat isn't helping.)

It is only after I connect the panel to the controller, and then measure again that I only see 12.1 volts when this circuit is connected to the controller. I don't understand why this is, but Bluesky were suggesting that once it is connected to the controller some problem with resistance in my panel or wiring is coming into effect.


(FYI, this installation had been working perfectly for many months until last week, it isn't a new installation.)

[ChuckSK]

It seems to me that 4 or 5 of the cells in the panel have failed. That would cause the low open-circuit voltage 19.1 vs 21.5. It would also explain the low voltage when the panel is connected to the controller.

To test this theory, remove the cover on the junction box on the panel. There you will see 4 terminals, 2 for each half of the panel. Measure the open-circuit voltage of each half panel. If they are not equal, the panel has failed cells.

Chuck

[sgtPluck]

Chuck,
That's pretty much exactly what the guy from Bluesky said, but he didn't mention that test you suggested.
That's a great tip, thanks, this way I can at least verify if it is the panel that's not working.

Of course it would have to be the most expensive thing that breaks

[sgtPluck]

hrm,
The voltage for each half of the panel is the exact same - 9.56 volts.

I wonder if the lower than rated voltage (19.1) could just be explained by this being an older panel, I'm not sure exactly how old but I think it is 8-10 years old.

Still mystified.

[Captain Bill]

It would seem to me that it doesn't matter if you do your short circuit amperage test right at the panel or at controller. The ratings on the panel are done at precise voltages and temperatures to maximize the ratings. They assume perfectly clean glass and 1000watt per meter squared light intensity, all done in the lab, not the real world. The fact that your panels are putting out slightly lower output does not terribly concern me. If you do your short circuit test at the controller end of the wires you will find out immediately if your wiring has a problem. If you still get around 5 amps at the controller end there is nothing wrong with your wires. If it is substantially less then the wires are the problem. If the wires are not the problem then continue if they are, fix the wires. It doesn't do any good to do a voltage test without significant current flowing through the wires. If you were to connect the wires directly to the battery you would see battery voltage which in your case is 12.5 V You should never see less than that at the panel side of the controller. You should never see even battery voltage on the panel side of an MPPT controller, it should always be near the maximum power point of the panel. If the voltage is lower than battery voltage then something on the power side is shorting to ground, which means it's the controller that has a problem. You can safely put an amp meter between the + side of the panel and the controller. The panel is not a battery and will never put out more than it's rated power. To drag the panel voltage down to 12.1 you woould have to be pulling substantial current out of the panel. If there was no current flow you would be seeing the 19.1 panel volts at the controller. If that current is not going into the battery then it's shorting to ground somewhere in the controller. It is not possible for it to be going into the battery with 12.5v on the battery side and 12.1v on the panel side. I used to do a lot of trouble shooting on electronics and when a voltage was lower than expected we just started unplugging components down stream of the supply starting at the furthest one away. When the voltage went back to normal we new we had found the problem module. Your system is much simpler since you really only have the wires and the controller. If your wires can carry the full output current of the panel then the problem has to be in the controller.

[sgtPluck]

Thanks Capt Bill,
I think I've gotten verifiably to the bottom of it now.
I just spoke to Blue Sky Systems (who have been very helpful by the way) They told me that the panel can still show the same voltage on both sides even if it has an impedance problem, but not the same amps. So I tested each side of the panel again and on one side I am getting a reading of 9.54 volts and 6.7 amps, on the other I am seeing 9.54 volts and 0.2 amps. So it would appear that, sadly, my panel is indeed the problem.