Dead or partially dead panel.

verdigo

I have a dead or partially dead panel. Grape solar 285 watt Poly Panel. The panel is under warranty but looks as though shipping it back and probably paying shipping on the replacement or repaired unit will cost as much as an out right purchase of a new unit.

The particular model is also discontinued. (Go Figure) So I am wondering if there is a common weak link that I might be able to repair my self.
Its going to be a PITA to un-mount. I will most likely buy two modules in order to replace the string to get it up and running.

How do I know I have a dead one? They are in strings of two and normally put out open voltage of 84-85 volts per string. The string in question is putting out 60 volts.

I would like to salvage the bad panel if possible and am looking for ideas of things to look for or test.

Thanks 

Dennis

BB.

If you can open the the junction box on the back of the panel. Look for shorted bypass diodes and or burned terminals.

That is about all that is easily/reasonable to repair.

-Bill

Dave Angelini

And most panels these days do not have an accessible JB.

verdigo

Thanks. Should be able to take a closer look when I get it down off the rack.

verdigo

Dragging out my older thread. Finally got around to checking individual voltage and short circuit amps on this problem string.  The panels individually put out 41 volts checking with a DMM. and both put out 6.3 amps with the DMM. However when wired back into series the string the voltage is only 65 volts while the other strings read out at 83 volts. The extension wiring to the combiner ohms out as does the circuit breaker.  This is not computing for me. Both panels check out individually but  the voltage falls off when strung together

Dennis

softdown

Sounds like a problem in the connections/wiring. Perhaps there is an abrasion that is causing a short?

Good news really. The panels are fine.

verdigo

softdown said:

Sounds like a problem in the connections/wiring. Perhaps there is an abrasion that is causing a short?

Good news really. The panels are fine.

I am ordering a new cable to make another extension to get from the string to the combiner. My DMM only goes to 10 amps so no other way to test other than through the combiner and charge controller. The wiring is a standard PV cable with MC4 connectors cut in half to make extensions to get to the combiner.

It looks fine, (no abrasions) and there is no evidence of arching on the terminals inside the MC4 connectors. Maybe I can dig up enough wire today to wire around them to the combiner for another test.

Wow. I was able to substitute a piece of PV wire from the MC4 ground connector of the panel by stuffing one end into the connector and attaching it to the combiner ground bus and it works. No visual problems after pulling the wire from the conduit.????? Oh well my faith in the panels is restored anyway..

inetdog

verdigo said:

Dragging out my older thread. Finally got around to checking individual voltage and short circuit amps on this problem string.  The panels individually put out 41 volts checking with a DMM. and both put out 6.3 amps with the DMM. However when wired back into series the string the voltage is only 65 volts while the other strings read out at 83 volts. The extension wiring to the combiner ohms out as does the circuit breaker.  This is not computing for me. Both panels check out individually but  the voltage falls off when strung together

Dennis

Are you reading the voltage of the string open circuit or under load? If you are reading a 100 open circuit (nothing but the meter connected) then it is really hard to explain. Possibly there is a short to ground in one of the panels which only causes a problem when the panels are connected in series.
But if the low voltage is under load there is a simple explanation:
In one of the panels there is a bad cell or cells which cannot deliver the same full current as the other cells.
If there is a bad cell in one bypass group (the substring of cells connected to a single bypass diode) then the open circuit voltage will measure just fine because the defective cell is not being called upon to deliver much current.
When you measure short circuit current, the good bypass group or groups will force current around the defective cell through the bypass diode.
But when you are pulling current in the area of Imp, the good cells will be delivering their nominal current but the defective cell cannot and so once again the bypass diode comes into play and the output voltage of the string while delivering Imp will be the normal string voltage minus the Vmp voltage of the bypassed section(s) plus the forward voltage drop of the bypass diode(s). The latter will be between .5 and 2 volts depending on the diodes used.

Skippy

Silly question for ya . . but instead of wiring panel 1 to panel 2
have you tried to wire panel 2 to panel 1  ?

Flip em around, and see what happens . . . just throwing out suggestions here . .  I also picked up a spray can of electrical contact cleaner . . and gave the connections on my panels all a bit of a spray before pugging em in...

Hope you can salvage it, it is a pita when that happens.