PV Glitch???

[North of 56]

I've noticed lately that the gremlins have come by to pay a visit. I must be due for a visit with them, LOL. Occasionally, I get a reduction in my PV input to about 1/3 of normal and my Classic controller indicates PV Shading. Input voltage also drops dramatically, from around 90 volts, to about battery voltage. This occurs only for a brief period, 30 seconds typically, and then returns to normal. I noticed this in the past, but thought it was due to cloud cover, when the PV shading was indicated. That or a very large bird that lands on my panels. I have 2 strings of 3 panels, so it sounds like their may be a temporary short circuit somewhere. I also have a Midnite surge arrestor, but it appears to be functioning OK.

A poster from another site thinks that my Classic controller (150) may need a firmware update. Mine indicates it has FW 11/10/10.

I've also disconnected the Midnite SPD and haven't noticed the problem since, but also the clouds just rolled in, so it could turn into a waiting game to try and diagnose.

Any suggestions?

[Watt]

I've noticed lately that the gremlins have come by to pay a visit. I must be due for a visit with them, LOL. Occasionally, I get a reduction in my PV input to about 1/3 of normal and my Classic controller indicates PV Shading. Input voltage also drops dramatically, from around 90 volts, to about battery voltage. This occurs only for a brief period, 30 seconds typically, and then returns to normal. I noticed this in the past, but thought it was due to cloud cover, when the PV shading was indicated. That or a very large bird that lands on my panels. I have 2 strings of 3 panels, so it sounds like their may be a temporary short circuit somewhere. I also have a Midnite surge arrestor, but it appears to be functioning OK.

A poster from another site thinks that my Classic controller (150) may need a firmware update. Mine indicates it has FW 11/10/10.

I've also disconnected the Midnite SPD and haven't noticed the problem since, but also the clouds just rolled in, so it could turn into a waiting game to try and diagnose.

Any suggestions?

I hate gremlins.  Truth is, I'm usually the only gremlin on this site.

What is your series panel voltage and what voltage SPD do you have on the output of your array?  Have you put a current meter on the SPD to see if it is conducting?

[North of 56]

Series panel voltage is between 85 and 100 volts usually. I have strings of (3) 24 volt panels in series. The SPD is the Midnite 115 which has a MCOV of 180 volts. I also notice that the problem never seems to happen in the first few hours of the early morning, when panel voltages are typically higher. Always seems to occur later in the day when things are warm.

I haven't measured the SPD for current, but I did try disconnecting only the ground wire (while operating and I took personal precautions to avoid a shock, and not recommended for novices or the nervous!) and noticed sparking, on occasion when reconnecting the ground wire (to ground). Perhaps an indication that it temporarily does conduct.

[Westbranch]

you might find  something on a similar problem here.  I remember a problem(s) someone had with an early SN Classic.

http://midnitesolar.com/smf_forum/index.php?topic=229.0
hth

[Vic]

Hi North,

I did post in that other Thread on wind-sun.

I had a very early Classic 150.  Received it in Dec 2010.

As noted elsewhere,  this FW DID have a PV Shading loop that it would get into,  at least on 48 V systems,  would drag down the PV in voltage,  and kinna get stuck there.

I would STRONGLY suggest that you upgrade your Classic and MNGP FirmWare.

There is nothing obviously beneficial  that you would loose with more recent FW.  I do believe that the FW that your Classic is running was the version in my Classic that had a very similar situation on my 48 V system.

What U got to loose?  Good Luck,   Vic

[Vic]

There is this Thread,  which notes a similar issue with 12 V Banks:

http://midnitesolar.com/smf_forum/index.php?topic=606.0

FWIW,  BUT,  the suggested remedy was still  Update FW,   Vic

[Watt]

Series panel voltage is between 85 and 100 volts usually. I have strings of (3) 24 volt panels in series. The SPD is the Midnite 115 which has a MCOV of 180 volts. I also notice that the problem never seems to happen in the first few hours of the early morning, when panel voltages are typically higher. Always seems to occur later in the day when things are warm.

I haven't measured the SPD for current, but I did try disconnecting only the ground wire (while operating and I took personal precautions to avoid a shock, and not recommended for novices or the nervous!) and noticed sparking, on occasion when reconnecting the ground wire (to ground). Perhaps an indication that it temporarily does conduct.

I was going to mention that I had a 115v spd on my array combiner with upwards of 146voc.  The story as to why is a long one but an oversight nonetheless.  Anyway, I'd to recommend a FW update and go from there.  The spark you see is similar to mine when I monkey around with the SPD. haha

[Halfcrazy]

Yes definitely do a firmware update. The old code would at random times get stuck momentarily at the bottom of its sweep. Also just an FYI that number is not the firmware date. The firmware date is found by repeatedly pressing status.

Ryan

[North of 56]

There is this Thread,  which notes a similar issue with 12 V Banks:

http://midnitesolar.com/smf_forum/index.php?topic=606.0

FWIW,  BUT,  the suggested remedy was still  Update FW,   Vic

That explains it right there. I will be updating the FW this evening. Thanks so much for the replies!

[boB]

Sorry about that, North !

Please let us know if you have any problems updating.  We're on here during the weekend too, normally.

boB

[North of 56]

No problem Bob. I was successful with the FW update last evening. I'm doing another EQ this morning as I'm having a bit of an issue with my batteries, but otherwise will be back to normal. Thank you!