Solar Panel Problem

[Widge]

Hi,

My Solar system appears to have stopped working, I have a Multisol P6 230w panel and a cheap and nasty T20 MPPT controller, my initial reaction was that the controller had packed up, which I wasn't too upset about as it really needed replacing with something better. But it is looking like the solar panel its self.

According to the specs the open circuit voltage should be 37.1v, I am getting about 35v, so I am happy about that, but the short circuit current should be about 8A, but I am only reading about 240mA, I have some inline connectors on the roof, so I disconnected them and measured it again there, same results.

Now I presume that there are more connectors on the back of the panel, but I cannot get to them without removing the panel, this is where the next problem starts.

The panel has 6 mounting brackets, I presume that whoever fitted it, bolted the brackets to the panel, then used mastic to glue the whole thing down, in its self I have no problem with that, but the idiot that did it just used nuts and bolts, so there is no way I can get any sort of tool onto the rear of the bolts to hold them while they are undone.

So the questions are:

Has anyone any suggestions of something I might be doing wrong or missed while testing the panel? (I did try two different meters)

How I might go about ungluing the panel, or a suggestion on how I might hold the rear of the bolts?

If I get the panel off, is there anything that might be repairable on the back of the panel?

Thanks in advance.

Dave

 

[Jimbohorlicks]

Pictures may help.
Plus have you tried to get a current reading at the first junction joint in the cables,it may be just a bad connection or down to corrosion.

 

[Guigsy]

Are you measuring on a cloudy December day in the UK?

My 185w panel makes about 10w at this time of year.

 

[Widge]

Pictures may help.
Plus have you tried to get a current reading at the first junction joint in the cables,it may be just a bad connection or down to corrosion.

Hi thanks for the reply, but I did say that I checked at the first connections on the roof.

 

[Widge]

Are you measuring on a cloudy December day in the UK?

My 185w panel makes about 10w at this time of year.

Bright clear sunny 10C here in france, so i would expect to get a lot more than 280mA short circuit current out of it.

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[Guigsy]

I think in Saint-Étienne-d'Albagnan, France, even at midday, the sun only reaches about 24 degrees above the horizon. A panel facing straight up is going to generate very little. The shadows are pretty weak in that photo too, suggesting it isn't very bright. PV panels need a minimum amount of light before they produce anything significant.

 

[Widge]

I think in Saint-Étienne-d'Albagnan, France, even at midday, the sun only reaches about 24 degrees above the horizon. A panel facing straight up is going to generate very little. The shadows are pretty weak in that photo too, suggesting it isn't very bright. PV panels need a minimum amount of light before they produce anything significant.

I took the photo, just before I posted it so it was actualy dusk at the time, but it was in full sun earlier, i appreciate the sun is low this time of year but i would still expect a little bit more power than i am getting, forcast is for sun again tomorrow, so i will do some more measuring.

 

[Guigsy]

I took the photo, just before I posted it so it was actualy dusk at the time, but it was in full sun earlier, i appreciate the sun is low this time of year but i would still expect a little bit more power than i am getting, forcast is for sun again tomorrow, so i will do some more measuring.

I agree that it does sound a bit low, but it's pretty hard to test at this time of year. Also, even the shadow of a twig or an aerial cast over a cell will completely destroy the output.

 

[Widge]

I agree that it does sound a bit low, but it's pretty hard to test at this time of year. Also, even the shadow of a twig or an aerial cast over a cell will completely destroy the output.

The drive gets quite steep behind the van so i might back it up a bit in the morning, that should make the angle a bit better.
I will post again later tomorrow after i have done more tests.

 

[autorouter]

According to the specs the open circuit voltage should be 37.1v, I am getting about 35v, so I am happy about that, but the short circuit current should be about 8A, but I am only reading about 240mA, I have some inline connectors on the roof, so I disconnected them and measured it again there, same results.

I think you're right about the open circuit voltage, if there's a reasonable amount of light it will be almost up to the spec figure. However the short circuit current will be very dependent on the light intensity. Probably at half the spec intensity you will only get half the current, and so on. In other words you will be seeing way less than 8A in average winter conditions, even on a sunny day. Having said that, 240mA does sound a bit on the low side.

The panel has 6 mounting brackets, I presume that whoever fitted it, bolted the brackets to the panel, then used mastic to glue the whole thing down, in its self I have no problem with that, but the idiot that did it just used nuts and bolts, so there is no way I can get any sort of tool onto the rear of the bolts to hold them while they are undone.

I can't see enough detail in the picture to show what kind of head the bolts have, but if all else fails you could simply drill the head with a bit slightly larger than the bolt shank, and the head will fall off, Presumably the rest of the bolt can be tapped out, if it doesn't fall out first. Then fit Rivnuts to the panel frame once it is accessible. I suppose the only thing is, if you can take the panel off easily, so can anybody else

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[Widge]

Thanks for all your replies, I think I was chasing a red herring, it started with the habiton battery not charging and went realy low, the battery connection was a bit corroded but I didnt think it was that.

Which made me look at the panel and charge controller, on measurement it appeared to me that the panel wasn't working correctly, but I think that it was just my misunderstanding of how bad the panel can be if not at the correct angle.

I didn't do anymore measurements today, but it was all connected, and after a realy sunny morning battery voltage was fine.

I have now put better connections on the battery, so i will see how it goes over the next week or so.

Again thanks for your help.

 

[Raul]

Corroded connectors can ad very high resistance and bigger all your solar. If you can access the panel wires at the top, make sure those connections are dry and sound. Early MC4 connectors had a weak seal and corrosion was likely, taking a hole sting out for a poxy bad mc4.

 

[Guigsy]

My hab electrics have a small power draw, even when everything is off. It's enough to flatten the battery in a few weeks. Which is I think the reason the battery is very weak as it sat for sale for a while at the dealer and it was severely flattened when I got it. I've fitted a solar panel, but there's so little sunlight at this time of year, it does very little. I need to keep hooking it up on the drive. I'll fit a lithium battery soon, which should mean it lasts much longer before its dead. With occasional use, it should lasts through the worst months without assistance.