Solar panel problem I think

rake1

I have two solar panels on my camp 135 watts and 125 watts on a good day they put out about 17 amps. But lately only 7 amps, so I took my clamp meter and only one panel is putting out power. While disconnected I checked the Volts and they read 20.66 on a panel that says VOC 21.9 amps were 3.1 amps. The other which shows nothing on the clamp meter showed 21.3 volts VOC says 22.3, amps were 3 amps. So it looks like the panels work but when connected only one shows any amps coming out of it. Any Ideas what is wrong? I took the MC4 connectors apart and plugged the panels in every way possible and the panel that works keep working regardless which connector it is hooked up to. The other panel dosen't put out power when hooked up, even though it shows volts and amps when disconnected. Any Ideas? This is a 12 volt system and panels are 3 ears old.

Cariboocoot

Re: Solar panel problem I think

If you check the Isc on the panels you should see nearly 8 from the 135 Watt one and slightly less from the 125 Watt one. Instead you are reading around 3 Amps each? That's either an error or a problem.

Voc is irrelevant as broken panels can output that but still produce little or no current.

I suspect the one panel has a bad bypass diode or shorted cell segment. If you can measure the current flow through it when it is connected to the other you may find the direction is reversed.

rake1

Re: Solar panel problem I think

Cariboocoot wrote: »

If you check the Isc on the panels you should see nearly 8 from the 135 Watt one and slightly less from the 125 Watt one. Instead you are reading around 3 Amps each? That's either an error or a problem.

Voc is irrelevant as broken panels can output that but still produce little or no current.

I suspect the one panel has a bad bypass diode or shorted cell segment. If you can measure the current flow through it when it is connected to the other you may find the direction is reversed.

The 3 amps was with it disconnected but when hooked up it is putting out around 8 amps. The other does nothing. I am no electrician how would I go about testing for the bad bypass diode? and I assume it is inside the black box on the back of the panel? I didn't open the box up as I was afraid to break it. Does it just pop open?

rake1

Re: Solar panel problem I think

I opened up the Junction box but nothing I can do there it is encased in silicone and I cannot do anything with it. I guess I may need a new panel

BB.

Re: Solar panel problem I think

Probably--You can try digging out the the silicon and see if you can access the diodes. If you can, the bypass diodes can be pretty easy to replace.

-Bill

rake1

Re: Solar panel problem I think

Thanks I have the Panel down now I am at my camp so I think I will tak it home with me. Is there usually warranty on panels that are only about two years old. I thought most had warranty on them for some time. Am I wrong or is that warranty I see advertised just for efficency.

Cariboocoot

Re: Solar panel problem I think

Warranty would depend on what the panels actually are, how good the company is with warranty claims, and whether or not the company is still in business.

I don't know how you were measuring current but Isc could not be 3 Amps if the panel is working. The fact it puts out higher when connected in a circuit shows something was done wrong, and it may be a change in insolation. You'd be amazed how much current drops off with a change in angle.

rake1

Re: Solar panel problem I think

as mentioned I have the panel down now how do you suggest I measure the current. I used a clamp meter on the good one I get 7 to 8 amps nothing on the other one doing the same thing. I have access to the positive and negitive leads now how should I measure current. Thanks

BB.

Re: Solar panel problem I think

Sounds like you are doing it right.

Sometimes there is a 5 year workmanship warranty (panel fails, after 5 years it may not get replaced???). Not sure how that may work.

Sometimes it is possible for Voc and Isc (short circuit current) to be "OK", but Vmp/Imp to be bad. If you have a panel that passes Voc/Isc, try connecting to your car battery (watch polarity) or a few DC lamps to get Vpanel up towards Vmp with current flowing--This is the 100% good/bad test.

-Bill

rake1

Re: Solar panel problem I think

BB. wrote: »

Sounds like you are doing it right.

Sometimes there is a 5 year workmanship warranty (panel fails, after 5 years it may not get replaced???). Not sure how that may work.

Sometimes it is possible for Voc and Isc (short circuit current) to be "OK", but Vmp/Imp to be bad. If you have a panel that passes Voc/Isc, try connecting to your car battery (watch polarity) or a few DC lamps to get Vpanel up towards Vmp with current flowing--This is the 100% good/bad test.

-Bill

Good info, here is what I did I happen to have a battery here at the camp. I put the panel in good sun ran a wire from the neg on panel to neg on battery then positive left open I used my meter and ran the pos from the meter to the pos of the solar panel and neg from meter to pos on battery no current showed on meter. I have to assume from this test that the panel or diode are gone am I right.

BB.

Re: Solar panel problem I think

Yep... If a diode is sorted--Just clipping the diodes from the circuit/j-box would fix. If you do not have series connected panels (i.e., 60 Vmp on a 12 volt battery bank/MPPT charge controller), then you really do not even need the bypass diodes (they are not need on a "12 volt/18 Vmp panel" charging a 12 volt battery bank, or a 24 volt/35 Vmp array charging a 24 volt battery bank).

-Bill

rake1

Re: Solar panel problem I think

Yea mine are 1mp 17.9 and Voc 22.3 and 21.9 If I can fix this one and I add another panel how high a vmp and Voc can I use to compliment this system.

Cariboocoot

Re: Solar panel problem I think

rake1 wrote: »

Yea mine are 1mp 17.9 and Voc 22.3 and 21.9 If I can fix this one and I add another panel how high a vmp and Voc can I use to compliment this system.

You need to stay in the 17 to 19 Vmp range for parallel panels on a 12 Volt system through a PWM type controller.

inetdog

Re: Solar panel problem I think

Cariboocoot wrote: »

You need to stay in the 17 to 19 Vmp range for parallel panels on a 12 Volt system through a PWM type controller.

Although with a PWM CC you can go higher in voltage, just at the cost of not getting the full rated power from the higher voltage panels. You will still get full power from the older panels. Just make sure that the Voc of the new panels does not exceed the maximum DC input voltage specification of the CC.

When you are using an MPPT CC, the risk if you go too high in the Vmp of additional panels is that the CC will lock in on the Vmp of the higher voltage panels and if that is above the Voc of the lower voltage panels the lower voltage panels may not contribute any power at all.

Cariboocoot

Re: Solar panel problem I think

inetdog wrote: »

Although with a PWM CC you can go higher in voltage, just at the cost of not getting the full rated power from the higher voltage panels. You will still get full power from the older panels. Just make sure that the Voc of the new panels does not exceed the maximum DC input voltage specification of the CC.

When you are using an MPPT CC, the risk if you go too high in the Vmp of additional panels is that the CC will lock in on the Vmp of the higher voltage panels and if that is above the Voc of the lower voltage panels the lower voltage panels may not contribute any power at all.

Actually if the controller selects a Voltage above the Vmp of any panels connected to it the current contribution of those panels falls off. If it is at or above Voc of any panels their contribution will be zero.

inetdog

Re: Solar panel problem I think

Cariboocoot wrote: »

Actually if the controller selects a Voltage above the Vmp of any panels connected to it the current contribution of those panels falls off. If it is at or above Voc of any panels their contribution will be zero.

Some MPPT devices that do a full sweep instead of stopping at the first local maximum they reach will still be able to find the higher local maximum where the lower voltage panels are contributing.
Whether that second local maximum is lower or higher then the first one will depend, among other things, on the ration of the total output power of the two voltage groups of panels.

rake1

Re: Solar panel problem I think

Cariboocoot wrote: »

Actually if the controller selects a Voltage above the Vmp of any panels connected to it the current contribution of those panels falls off. If it is at or above Voc of any panels their contribution will be zero.

Thanks for all the info guys it was a big help

PNjunction

Re: Solar panel problem I think

rake1 wrote: »

I opened up the Junction box but nothing I can do there it is encased in silicone and I cannot do anything with it. I guess I may need a new panel

Or just new bypass diodes. For example, when I blew out the diodes in my Sharp 80w panel, both of the oem diodes were encased in silicone. However, that casing is actually a replaceable module. I took out the module, and tested for continuity with a multimeter. Sure enough, one was blown - the giveway was the gaping air bubble hole that actually let me see down into the blown diode. I didn't look forward to digging out all the silicone, so I did the next best thing...

If a blown diode is truly the problem, and they are modular, you can see about getting a modular replacement. In my case, I took a more expedient step of just ordering some "Schottky solar-diodes" on the net, which were about double the capacity of the panel. Ie, for my 80w panel that only puts out about 4.5 / 5A ISC, I used 10A individual diodes just to beef it up a little, and purposely left the leads a little longer than usual just to act as a tiny amount of heat-sinking. I used the existing screws that the modular oem diode pack connected to (leaving the bad modular pack out of course).

Ideally I should replace it with a modular oem replacement, but for now the individual replacements work, and might be expedient if you can't find any modular replacements, if yours is in fact modular inside.

rake1

Re: Solar panel problem I think

I do notice a couple of screws in the bottom left corner maybe that will release the module like you said.

rake1

Re: Solar panel problem I think

Attachment not found.
Here is a pic of what I got after the silicone came out. I checked continuity everywhere I could and I get all places I try it . I tried It from one side of diode to the other side all ok, I get it coming out the main + and - leads. The only problem I saw was the + tab was not attached so I soldered it back in place. I believe I might of broke that loose when digging out the silicone. Am I testing this the right way with my multimeter? I only get continuity across the diodes when testing one way not in reverse. Still no power coming out of the panel

Aguarancher

Re: Solar panel problem I think

You might put it in the sun and test for voltage on the - and + tabs before the + goes through the diodes.

inetdog

Re: Solar panel problem I think

On my computer anyway, your image is so pixellated that it does not give me any idea how your box is wired.

rake1

Re: Solar panel problem I think

Attachment not found.

inetdog wrote: »

On my computer anyway, your image is so pixellated that it does not give me any idea how your box is wired.

Here is a better pic. Sorry for the late reply I was away

rake1

Re: Solar panel problem I think

BB you mentioned Just clipping the diodes from the circuit/j-box would fix it. If I am getting continuity will this make any difference if I do clip them now.

BB.

Re: Solar panel problem I think

These are bypass diodes. If they show continuity in both directions, they will short out the cells.

-Bill

rake1

Re: Solar panel problem I think

BB. wrote: »

These are bypass diodes. If they show continuity in both directions, they will short out the cells.

-Bill

Bill the Diode on the left shows continuity in one direction BUT the one on the right shows Continuity in both directions.
Should I clip the diode on the right and remove it? The only reason I haven't yet is I am in discussion with the sell for warranty.
I have to go out now but will reply ASAP. THANKS

BB.

Re: Solar panel problem I think

rake1 wrote: »

Bill the Diode on the left shows continuity in one direction BUT the one on the right shows Continuity in both directions.
Should I clip the diode on the right and remove it? The only reason I haven't yet is I am in discussion with the sell for warranty.
I have to go out now but will reply ASAP. THANKS

The one on the right--I would remove (if you are not going for warranty replacement).

Of course, it is always possible that something else is shorted elsewhere in the panel electrical/solar cell connections.

Then there is the question of what may have caused the diode to fail shorted.

http://electronics.stackexchange.com/questions/77712/can-a-diode-fail-to-open-position

A diode fails closed due to overvoltage. This is called punch-through. This is is the principle used in ESD diodes. If they can't handle the voltage the PN juntion fails and short to ground, protecting any circuitry after them. On the image you see a small black dot where the voltage went through the junction.
pictures in above link
A diode typically fails to open happens due to over current. This is called metallization burnout and can occur from things like EOS (Electrical Over Stress). Image shown bellow. Over current causes excessive heating and literally burns the metal away. As mentioned above this is easy to demonstrate on LEDs as their current carrying capability is much lower than rectifier didoes.

And was there any damage to other components in the panel that may have caused the diode to fail.

-Bill

rake1

Re: Solar panel problem I think

OK Bill I cut the bad diode and the panel is now working thanks for your and everyone else for the help save me a ton of trouble with warranty.
with the diode out of there what are the chances of hurting the panel now if there is an over load. I assume the diode is just a safety feature.

rake1

Re: Solar panel problem I think

Here is the diode # 6A10 MIC I looked this up and it is a 6 amp diode, my panel is capable of putting out almost 8 amps isn't this a little light for an 8 amp panel? I realize there are two so maybe that makes the difference does it? Just curious

inetdog

Re: Solar panel problem I think

rake1 wrote: »

Here is the diode # 6A10 MIC I looked this up and it is a 6 amp diode, my panel is capable of putting out almost 8 amps isn't this a little light for an 8 amp panel? I realize there are two so maybe that makes the difference does it? Just curious

The two diodes are not in parallel, they are connected across different halves of the panel.
And if the Isc of the panel is 8A, then it is not at all surprising that a 6A diode would fail. However, it would not be conducting any current at all unless there was partial shade on the panel or one of the cells in the panel is defective.

rake1

Re: Solar panel problem I think

The ISC is actually 8.60 amps should I put a larger on in