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Old 06-07-2018, 14:36   #1
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Troubleshooting solar setup... or troubleshooting my troubleshooting!!

OK, everyone here has been so helpful I am going to impose again. Having trouble with my solar setup and can't seem to figure out where the problem is.

Backstory: everything was "working", but around June 21st solstice at 49N I was getting ~50-55w from a nominally 200w setup, seemed weird. Asked some questions with this thread: 0 volts from panel... anything I can do? and double checked all the wiring, including replacing a few butt connectors (good ones, adhesive shrink wrap Ancor). Still no joy. One pair of panels (#3 &#4) was putting out about 50 watts, the other (#1 & #2) about 10-12w according to the Victron app.

So instead of wasting the rest of our vacation I let it lie and took everything home with me and am now testing to try to figure out if it's one or more of my panels or controller.

Original setup was 4 total Renogy 50w panels, wired in two folding pairs in series, with end result of 2 100 watt pairs putting out 24v (one on each side of boat) then wired in parallel to a single controller. Controller is Victron 75/15 MPPT with the Bluetooth dongle.

I have tested one pair of panels (numbers 3&4) together today, and also tested each panel completely separately. All the "wiring" right now is 12 gauge wire with alligator clips hooked to controller then to my 4Runner battery as a test. For each panel I tested Open Circuit Voltage (back of panel states 22.7v), Short Circuit Current (back of panels state 2.84A) and then connected to controller and read wattage off app that Bluetooths to the MPPT controller. This was all done in almost full sunlight (a light haze way up high), conditions I have gotten easily 80+ watts out of my 100w panel on my van.


Here were my results:


It seems to me that maybe panel #2 is a little weak and might have problems (voltage seems fine, short circuit amperage seems weak but maybe that was my testing methodology). For the rest of them, it seems unlikely that I got 4 bad panels, could it be my charge controller? I look at panel #4 for example, 20.53v open circuit, 2.52a short circuit, and it puts out 10-19 watts? Seems wrong.

At least two of the panels oscillated a lot outputwise according to the controller, #1 and #4 would go up to ~20w, then down to ~10w, then back up, over and over. Could this be some internal short in the controller?

Only other possibility is if my testing setup is wrong. The 12ga wiring should be plenty good voltage drop wise for the short runs I have while testing, but maybe using alligator clips for convenience (I guess I could solder everything over and over while testing, or use $3 butt connectors, but...) is causing resistance? I'm using a relatively cheap clamp on meter for amperage and regular leads on the meter for voltage.











If anyone has any feeling on this or input or can detail the many things I'm sure I'm doing wrong here, I would be very grateful.

-- Bass
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Old 06-07-2018, 16:25   #2
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

Follow up, tested one of the panels (#3) through my known working setup on my camper van (Tracer 20a MPPT controller, a little older school than the Victron) and got pretty much identical readings of 13w on both that Tracer and the Victron, so I don't THINK it's the controller.


Got 20.45 volts open circuit, 1.00a - 1.66a short circuit this time around with just one 12ga jumper connecting positive and negative.


Could I have gotten 4 bad panels??? Seriously??? Seems so unlikely (and I dread Renogy's response), but not sure where to go from here except to try to make warranty claim (which will be denied because I've drilled a bunch of holes in the frame).





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Old 07-07-2018, 13:03   #3
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

Hi Bass,

A couple of thoughts -

Good connections are key. When I was testing my setup, I used the mc4 connectors and then straight wire screwed into the controller. I have victron 100/30, but Iím not sure if you have screw down connectors that clamp the wire like mine or not. So that would be my first advice, ensure your connections are solid, no clips, using the minimum number of connections.

The other thought is when measuring power into the battery, the battery has to be capable of accepting everything the panels can put into it. So run the AC or something high load without the engine on to maximize the power you can put into your truck battery.

I like I that you are testing each panel separately.

The short circuit current of two of the panels, especially #1, do seem low. Not sure what to make of that, other than perhaps the connectors where not good enough.

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Old 07-07-2018, 14:05   #4
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

In the last row of your measurement table the battery voltage is going between 14.2 and 16V. This battery is apparently fully-charged (or damaged) and will not accept much power from the controller. This is probably why you see the oscillation. As Scott says, you should put a load on the battery for these tests.

However, the low short-circuit current on panel 2 indicates a problem. Is the panel dirty, cracked, or shadowed in any way?
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Old 07-07-2018, 14:30   #5
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

Quote:
Originally Posted by ScottMeilicke View Post
Good connections are key. When I was testing my setup, I used the mc4 connectors and then straight wire screwed into the controller.

Thanks Scott. I originally what seemed to be a very solid setup just using Ancor marine butt connectors (I cut off the MC4 connectors), have been just using the clips when testing. I will try without the clip setup and see if that makes any difference (the butt connectors and tool are onboard - and expensive - so might just solder up some test wiring for now to see if that makes any difference).



Quote:
Originally Posted by ScottMeilicke View Post
I have victron 100/30, but Iím not sure if you have screw down connectors that clamp the wire like mine or not.

Same setup, and I have been tightening the connectors as much as I dare...



So that would be my first advice, ensure your connections are solid, no clips, using the minimum number of connections.

Quote:
Originally Posted by ScottMeilicke View Post
The other thought is when measuring power into the battery, the battery has to be capable of accepting everything the panels can put into it.

Had someone else (and the next post after yours) mention this too, and now I'm thinking this is something I missed. Because my controller was only putting out 12.9v I assumed that meant it hadn't gone to an absorption or float charge (assuming those would be higher voltage) so I figured the battery would take it, but now I'm not sure, it was just the truck sitting there not running. I think tomorrow I will try again with the truck off and the high beams and driving lights on (combined ~200 watts of light draw), that should presumably create enough load to be sure that's not what's slowing me down.



Quote:
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I like I that you are testing each panel separately.

Yeah, that was the whole point of bringing them home and trying to do it right, so I'm being thorough but my test protocol might be flawed


Thanks.
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Old 07-07-2018, 14:37   #6
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

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Originally Posted by Paul Elliott View Post
In the last row of your measurement table the battery voltage is going between 14.2 and 16V. This battery is apparently fully-charged (or damaged) and will not accept much power from the controller. This is probably why you see the oscillation. As Scott says, you should put a load on the battery for these tests.

Thanks Paul, I plan to try that tomorrow, I think you and Scott are onto something (I believe the battery is fine, just needs a load like headlights and driving lights, but just in case I can try it on another truck battery as a control test.


Quote:
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However, the low short-circuit current on panel 2 indicates a problem. Is the panel dirty, cracked, or shadowed in any way?

I agree panel #2 seems like a problem child. The panel looks totally fine no cracks no shadowing and I just cleaned them all, so if it does have problems it appears they're internal. At this point if only one of the four is bad and that's my issue I can live with that at $80/panel even if Renogy doesn't want to warranty them because I drilled a bunch of holes in the frames.
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Old 08-07-2018, 10:09   #7
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

OK, no joy on further testing . Cleaned up my test setup (no more clips, direct connection between MPPT controller and battery, secure wire nut connection between wires coming off the panels and wires that go into the controller - and no I wouldn't use wire nuts onboard) and tested again with high beams and 100w driving lights on on the 4Runner, with panel pretty optimally directed at the sun, and I still only get 10-19 watts out of either of the two panels I tried (#3 and #4 from table above)... was too dispirited to try the other two panels.


Could it be a bad controller? How do I test, or do I just order another one and try it to compare?


Otherwise, what??? At least 2 possibly 4 bad panels? Bad battery on the 4Runner (unlikely, it runs, although alternator had to be replaced recently).



Here is the controller screen from panels #3 and #4, shows how loaded my 4Runner battery is so it must want to take all the power the controller should be giving it:






Testing setup:






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Old 08-07-2018, 10:25   #8
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

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Could it be a bad controller? How do I test, or do I just order another one and try it
You can connect each panel to battery directly without the controller.
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Old 08-07-2018, 10:34   #9
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

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You can connect each panel to battery directly without the controller.

How do I judge if it's working better when connected directly to battery? See how many volts I'm getting? Or check amperage while connected I guess?
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Old 08-07-2018, 10:41   #10
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

first of all, test EACH PANEL ALONE.

measure Voc AND Isc for each panel, write the results down.

Then hook one at a time to the controller and the controller to a battery, put at least as much load on the battery as you expect from the panel ( 50W, for single panel, 200W for integration test with all 4)

Write down the power / amps. Should be all in the same range.

Connect all panel in PARALLEL to the controller and put load on the battery, use a clamp DC-Ammeter and measure the currents of each panel. Select pairs of panel with the same current and wire them then in series for maximum output or keep the parallel installation.

With 2 strings of serial panels, one string may completely fail, if the other outputs a higher voltage, especially if one cell gests partially shaded. Connecting in parallel you lose only one panel (25%), in series you lose the string (50%).
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Old 08-07-2018, 10:46   #11
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

The panels look fine. When I troubleshoot the panels if I have good VOC I go forward toward the batteries.

I don't have MPPT controllers though

On my PWM Controllers, the voltage on the panel side equals the voltage on the battery side until the battery gets to the float voltage then the voltage on the panel side will start to increase as the controller decreases current flow to the battery as it approaches fully charged

Have you ever noticed / compared your Battery Voltage to your Panel Voltage at various stages of charge

I have 3 cheap controllers so swapping out to test is quick.

With that battery voltage reading so low maybe it is the controller. Does the battery voltage increase after a while? If not it's the controller.

Can't you test with your other controller and take readings with your meter which is how I have to do it. Let each panel recharge the battery and monitor the voltage

My Controllers show battery voltage only so I have to monitor with a VOM

When I test, I load the battery down for a few minutes (like down to 12.2 volts or so) to get the voltage below float then take off the load. (turn of the lights for you) then do your test and see if your battery starts to charge or charges at the same rate for each panel

Make your test simple and the same conditions for each test
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Old 08-07-2018, 10:56   #12
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

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The panels look fine. When I troubleshoot the panels if I have good VOC I go forward toward the batteries.

I don't have MPPT controllers though

On my PWM Controllers, the voltage on the panel side equals the voltage on the battery side until the battery gets to the float voltage then the voltage on the panel side will start to increase as the controller decreases current flow to the battery as it approaches fully charged

Have you ever noticed / compared your Battery Voltage to your Panel Voltage at various stages of charge

I have 3 cheap controllers so swapping out to test is quick.

With that battery voltage reading so low maybe it is the controller. Does the battery voltage increase after a while? If not it's the controller.

Can't you test with your other controller and take readings with your meter which is how I have to do it. Let each panel recharge the battery and monitor the voltage

My Controllers show battery voltage only so I have to monitor with a VOM

When I test, I load the battery down for a few minutes to get the voltage below float then take off the load. (turn of the lights for you) then do your test and see if your battery starts to charge or charges at the same rate for each panel

Make your test simple and the same conditions for each test
Its an MPPT controller, Voltages dont match there. You must test both, Voc AND Isc to tell, if the panel is ok, Voc alone is not sufficient for evaluations.
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Old 08-07-2018, 11:06   #13
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

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How do I judge if it's working better when connected directly to battery? See how many volts I'm getting? Or check amperage while connected I guess?
If directly connected the solar panel voltage will be the same as the battery voltage. The current produced should be the same for each identical panel. If you can test under very good solar conditions the current should be close to the Imp listed on the specifications.

While testing put a load on the battery equal or greater than the current produced by the solar panel.

The current can be measured with a clamp on multimeter (the easiest solution), or a conventional multimeter providing its maximium current rating (usually 10A) is greater than the panel can produce.
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Old 08-07-2018, 11:45   #14
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

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Its an MPPT controller, Voltages dont match there. You must test both, Voc AND Isc to tell, if the panel is ok, Voc alone is not sufficient for evaluations.
Of course it's not totally sufficient but usually it's a good first indicator, and I was going for simplicity and percentage. (of what the failure usually is)

Untrained troubleshooters usually compound their problems due to lack of experience and over analyzing

My panels have taken a total beating and the problem is usually wiring, batteries, connections, or the controller

If he tests each panel separately with his other controller and monitors voltage with a meter he will find out if there is a problem if he understand what he is looking at

Voltage measurements alone should be enough......
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Old 08-07-2018, 11:52   #15
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Re: Troubleshooting solar setup... or troubleshooting my troubleshooting!!

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....
Voltage measurements alone should be enough......
No, they are not, better to measure Isc.

even damaged cells can output Uoc, but the current they output in the circuit is near zero. same for batteries, generators, alternators etc. Power sources can only be vetted under load.
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