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Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664
Posted: 11:45pm 29 Apr 2018
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Hi All,
Just ran the meter over the 12 panels I got the other day.
Specs are, Voc=37.5V Isc=9.0A
Pretty much getting a reading in spec with only a small variation. Getting about 7.8A on average.
Except for 1 Panel.
Think it was about 24.5V Voc & 7.8A Isc.
Nothing visually obvious, & Didn't get a chance to opened the junction box yet.
Does this behaviour sound typical of a Diode failure, possibly shorting out one of the strings on the panel?
Will open it up later & test, but curiosity needs some feedback sooner.
Cheers
Phil.
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 12:02am 30 Apr 2018
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a third of your panel is not in circuit, it sounds like it has been wired incorrectly somehow. I'm confused, no wait... maybe I'm not...
George65 Guru Joined: 18/09/2017 Location: AustraliaPosts: 308
Posted: 12:14am 30 Apr 2018
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Last panel box I opened had 3 Diodes so maybe being a 3rd is out it could be a Diode or connection there.
The Panel I opened was a 250 and I see all of yours are about that size so maybe you will be in luck and it will be an easy fix.
If the panel is buggered, still good for other uses. I have 2 Shattered panels on the roof of my shed that drive the car fans for keeping the shed cool and the light for my Aeroponic system. Soon going to put that in my little greenhouse I just bought to play with.
Being that it is outputting 24V, you could use it for battery charging or top up on the mower and other things.
Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814
Posted: 02:23am 30 Apr 2018
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Its not uncommon for diodes to fail in high temps at full capacity, and often go O/C Definitely sounds like a string has failed, and I'd bet on the diode has gone Easy to check and easy to replace if it has
Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664
Posted: 05:12am 30 Apr 2018
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Opened up the terminal block; potted in silicone.
Figured the 3rd diode must be SC, so cut it's leg.
Notice how the lead fell free.
I could measure 12V across each string, but once the diode was out I got 0V from the panel.
I can get full Voc at the top green mark, but nothing at the screw below it.
It should be present there I think?
Seems the diode may have been ok, just poorly terminated, hence the heat signs, but the real problem may have been lack of continuity between the two bits marked in green.
Will wait for the silicone solvent to work a bit & then have a better look.
Phil.
Edit, Closer view.
Edited by Phil23 2018-05-01
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 10:29am 30 Apr 2018
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Actually I think I am wrong, you should get full voltage and restricted amps with a wiring fault. so if you have a terminal with full voltage perhaps you have a high resistance connection somewhere. I'm confused, no wait... maybe I'm not...
Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664
Posted: 09:00pm 30 Apr 2018
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Nope,
Your were on the mark. The last 1/3 was out of circuit due to a very poor connection at the top green mark when the strip from the cells comes thru the slot in the terminal.
Output from the other 2 was getting there via the 3rd diode, despite the fact that it's spot weld had failed.
Phil.
Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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