PV Glitch???

northerner
northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
in Off Grid Solar & Battery Systems #1
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. It is difficult to fault find as by the time I make it outside, it has returned to normal operation. Any ideas? I'm thinking it may be a glitch in one of the panels most likely???

I have tried turning off the strings, alternatively, but haven't duplicated the fault on 1 string due to this being very intermittent. May turn into a big waiting game. Possible suspects, a faulty panel, wiring (unlikely), surge arrestor acting up, the charge controller itself.
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  • bmet
    bmet Solar Expert Posts: 630 ✭✭
    #2
    Re: PV Glitch???
    northerner wrote: »
    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. It is difficult to fault find as by the time I make it outside, it has returned to normal operation. Any ideas? I'm thinking it may be a glitch in one of the panels most likely???

    I have tried turning off the strings, alternatively, but haven't duplicated the fault on 1 string due to this being very intermittent. May turn into a big waiting game. Possible suspects, a faulty panel, wiring (unlikely), surge arrestor acting up, the charge controller itself.


    It doesn't have to be a large bird, any shadow can drop a whole string. :grr
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #3
    Re: PV Glitch???

    Yes, even the slightest bit of shadow, If it is a suspect tree, its better if you can sit and watch for shadow lines moving across the panels if these 'glitches' happen at the same time of day, it can be occuring just in a corner of a panel
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #4
    Re: PV Glitch???
    bmet wrote: »
    It doesn't have to be a large bird, any shadow can drop a whole string. :grr

    Agreed, except in my case the pv input voltage is going down to the battery voltage. I'm starting to suspect the surge arrestor and have just disconnected it. That or a short in one of the panels is what I'm thinking. When I quickly turn the PV breaker on and off, problem is corrected.
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #5
    Re: PV Glitch???
    westbranch wrote: »
    Yes, even the slightest bit of shadow, If it is a suspect tree, its better if you can sit and watch for shadow lines moving across the panels if these 'glitches' happen at the same time of day, it can be occuring just in a corner of a panel

    There are no trees in the area.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #6
    Re: PV Glitch???

    North,

    Very early Classics on 48 V banks would get into a "PV Shading" loop.

    Have you updated to the latest FW, available on the MN Solat site?

    Am running the 6/29/12 FW on the Classics here, and do see similar thing on occasion, particularly when there are some clouds. It appears that a Classic will (probably) make an attempt to find a new MPP, and get stuck about 5 V above battery (48V) V for about 20 seconds, perhaps with a bit of a whine, and snap out of it and go about its business. It does NOT say Shading in my case, forget in what charge stage this is seen.

    The MidNite Forum is quite active, and the MN Tech and Engineering folks are frequent posters:

    http://midnitesolar.com/smf_forum/index.php

    Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #7
    Re: PV Glitch???
    Vic wrote: »
    North,

    Very early Classics on 48 V banks would get into a "PV Shading" loop.

    Have you updated to the latest FW, available on the MN Solat site?

    Am running the 6/29/12 FW on the Classics here, and do see similar thing on occasion, particularly when there are some clouds. It appears that a Classic will (probably) make an attempt to find a new MPP, and get stuck about 5 V above battery (48V) V for about 20 seconds, perhaps with a bit of a whine, and snap out of it and go about its business. It does NOT say Shading in my case, forget in what charge stage this is seen.

    The MidNite Forum is quite active, and the MN Tech and Engineering folks are frequent posters:

    http://midnitesolar.com/smf_forum/index.php

    Vic

    Thanks for that Vic, much appreciated! Mine indicates the 11/10/10 FW, definitely could use an update. I also notice a problem of the output momentarily (ie for an instant) dropping to zero, and have read that others experience the same thing.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #8
    Re: PV Glitch???

    I would check connections all the way from the panels to the controller, especially around the breaker that, if flipped, "fixes" the problem.
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #9
    Re: PV Glitch???
    NorthGuy wrote: »
    I would check connections all the way from the panels to the controller, especially around the breaker that, if flipped, "fixes" the problem.

    I wouldn't suspect a bad connection. I have checked them in any case and all appear good. Power in is dropping by one third, and voltage dropping to that of the battery. Sounds like either a short circuit (panels), clamping problem (SPD), or problem with the Classic controller. I read somewhere about a problem with an SPD that was faulty and clamping the output of the panels?

    I have disconnected the SPD and haven't seen the problem since, but the clouds have just rolled in, so may have to wait till tomorrow to do more checking. I will also update the firmware of the Classic as Vic recommended.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #10
    Re: PV Glitch???

    OK, well, one of my Classics will Rest momenatrily, and resume charging.

    BUT, why not update the FW soon.

    All connections in a power system really should be re-torqued at least once, after waiting overnight or more, IMHO.

    Battery cable connections should be re-torqued annally, and so on ...

    BUT this same problem, or a very, very similar one has been reported with the original shipping version of the Classic FW. I have seen it with the earliest FW on my first Classic. Have not seen it since updating ... and so on ...

    I do not recall you saying what your battery V is, but with that string V in the 90's would bet the system may well be 48 V.

    Seems to me that if an SPD had an MOV conducting enough for the string V to be dragged down to a bit above battery V, then, the SPD would get very hot ... it would most probably be trying to dissipate hundreds of watts ... HOT ++

    We all are mostly just guessing. ... but ... GL, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #11
    Re: PV Glitch???

    Battery voltage is 24. I disconnected the SPD in order to figure out the source of the problem. Problem with this is, it doesn't persist for very long and returns to normal. May very well be a problem with the Classic. BTW, I have re-torqued all my connections.
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #12
    Re: PV Glitch???

    This thread http://midnitesolar.com/smf_forum/index.php?topic=606.0
    referred to me by another poster sounds identical to what I've been experiencing. I will be updating the FW on the Classic. Thanks for all the assistance!
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #13
    Re: PV Glitch???

    OK norhterner,

    Hope that the FW Update does the trick! Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #14
    Re: PV Glitch???

    Yeah, the older firmware did have a possibility of doing this sometimes.
    Another option is to switch to another tracking mode such as Legacy or Dynamic.

    A FW update should fix it though.

    boB
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  • northerner
    northerner Solar Expert Posts: 492 ✭✭✭✭✭✭
    #15
    Re: PV Glitch???

    I made a successful upgrade to the FW last night. I should be back to normal soon. Just dealing with a bit of an issue with my batteries and doing a 2nd EQ today.
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