isofoton I-1509S/24 half the panel is working

[joeblo22]

Hi just wondering if there is a simple fix to this panel.

Isofoton I-1509S/24

Module specs

short circuit current 4.45

open circuit voltage 43.2v

Current reading

short circuit current 3.8

open circuit voltage 21v

This panel has 8 lines of cells

I  had this panel hooked up to a 12 v motor and this is what I found

when I cover the 4 left hand lines of cells the motor doesn't drop in speed but when I cover the other half the motor dies.

Would this be a diode issue or is this a open circuit issue

[joeblo22]

Also the point at which the solder connects to the diodes/metal tabs from the panel seem to be darkened but I am not sure if this is from the flux or not.

I have a picture on my photo uploads

http://www.fieldlines.com/images/scimages/11413/IMG_0384.JPG

Thanks for you input

[TomW]

[fabricator]

That solder joint on the + terminal looks really iffy, it looks like it didn't flow very good, like it was cold.

[dnix71]

A pic of the front of the panel would have been nice. That is a monocrystalline panel, I think.

You may as well unsolder all the diodes and check them. Replacements cost very little.

If that doesn't work, you'll have to settle for using the panel on a 12v system. I don't think there would be any way to get inside to repair a broken strip.

[ghurd]

It looks like flux residue to me.

Sounds like it could be a diode issue.  Probably 2.

Measure the voltage of each diode.  It should be about 10V on that panel.

If you plan to use it on a 24V system, can just remove the diodes and see what the numbers are.

I expect the output will go up to about rated with the bypass diodes removed.

I see more many problems with bypass diodes than problems inside the panels.

G-

[joeblo22]

Thanks for the speedy tips and ideas.

Tomorrow I will take a voltage reading AGAIN from either side of the diodes and I will also take a picture of the front of the panel.

I said again because I did take readings but didn't write them down.

From memory as per the picture and from left to right I think it was

1st diode 10v

2nd       20v

3rd        0

4th        0

I will double check

I will do a little more research on diodes, but in the meantime since I'm typing anyway

is a 6 amp rectifier diode from lets say radio shack http://www.radioshack.com/product/index.jsp?productId=2062591

be equivalent to the diodes from this panel?

I was in at circuit city(aka radio shack) today and they had the above diodes. I wanted to make sure they are the same thing before I wasted some money.

Thanks again for the input.

[ghurd]

If the panel will not be on a MPPT controller, meaning just charging a 24V battery,

then can simply leave them out.

The RatShak diodes are listed as 50V which would be considered a bit low for a 24V system, depending on who you ask.

Never know what will be in the package at RatShak, they may be 100V or 200V if you check the numbers on the actual parts.

The 6A05 is 50V, 6A1 is 100V, 6A2 is 200V, 6A4 is 400V, etc.

G-

[hydrosun]

Since you still get voltage at the pos and neg terminals it seems the bypass diodes are doing their job. I've poked the sharp probe of a volt meter into the connectors of the cells through the backing to track down where the break in connections occur. Usually the break is in the junction box with corrosion eating up the leads coming from the last cell to the connecting screw. I've been able to clean them well and solder a short connecting wire. Internally it's trickier and sometimes I give up before finding the correct spot. Good luck finding the break.

Chris

[veewee77]

If it were me, the first thing I'd do is pull the diodes and check voltage again as you did.

I'll bet there are one or more shorted diodes in there. . . If you have sensitive fingers, I'd also bet that you could lay that thing in a bright sun for a few minutes and feel the diodes and see if any were hot. . . those are likely the shorted ones. Use the back of your finger between the nail and the first knuckle. . . really sensitive there. . .

Doug

[joeblo22]

O.k I will try that...

Unfortunately it has been raining for the last few days so I haven't been able to check things out.  

Fingers crossed that the sun will shine tomorrow.

[joeblo22]

Well, I finally had a chance to take some voltage readings.

Reading from left to right of upper picture

10v 10v 0v 0v

So I'm assuming the diodes for the right two readings are bypassing the other strings either because diodes are defective or there is too much resistance in the two  strings.

I will change the right two diodes and see what I come up with.

I'm obviously having a bit of trouble adding a picture to this post as well.(Thanks Tom, here is another one to fix)

I upload a picture to the website and at the bottom of my post it says

select a file/ and a drop down menu comes down with select a file but without any choice of files.

http://www.fieldlines.com/images/scimages/11413/isofotonpanel.jpg

[TomW]

[joeblo22]

Alright sorry for the long delay, summer chores took my spare time.
Thanks for the responses.
I have removed the diodes.
Reading from left to right in junction box, on a partially sunny afternoon.

between 1 and 2 10v 2.6a
             2 and 3 10v 2.6a
             3 and 4 10v 2.6a
             4 and 5 5-7v 0a
 
             1 and 5 30-35 v 0 a

therefor the diodes were performing properly
and I have a poor connection within the panel or bad cell
I guess the next decision is whether to use the panel at 50% 12v with my morning star 12v controller.
Or to try and get a volt meter through the back and see if I can detect the short (as suggested.)
1 question.
If I do find the break and repair it with success, would I be able to change the panel from a 24v to 12 volt by running 2 + and 2- into the combiner box and splitting the panel in 2
12 v lines, so that I could use the full potential of the panel.

Thanks again for the responses and sorry about my late one.