Announcement

Collapse
No announcement yet.

Help, please! (reluctantly posting)

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Help, please! (reluctantly posting)

    Hello everyone,

    I'm reluctant to make my first post here one in which I am begging for help, but, well, I can't quite figure out what is plaguing my off-grid system at the moment. Any help is very much appreciated! Running the generator so much is no fun.

    **extreme PV voltage drop at charge controller, little to no current flowing into batteries


    A few weeks ago I noticed my current problem:

    -very low volts and amps flowing through the charge controller and into the battery bank
    -PV voltage drops from the expected ~130V when circuit is completed between PV array and charge controller; PV voltage in the entire system fluctuates with the sun, but isn't much higher than battery voltage



    Specs:

    -northern and relatively remote location/climate, off grid permanent residence
    -48V AGM, 510Ah, 24 x 2V cells
    -325W Canadian Solar panels (CS6U, VOC 45.5V, ISC 9.34A) https://www.wholesalesolar.com/cms/c...31.1930006.pdf
    -Panels wired in series, 3 per string
    -Currently I have 15 panels combined into a single charge controller
    -Charge controller Magnum PT-100
    -Magnum 4400W inverter/charger; E-panel



    The system had been working great since I set it up in the summer of 2019. I've slowly added more panels as the winter has progressed and the solar irradiance declined.

    Battery bank charges well with generator, inverter seems to be operating normally, I think that I have now ruled out that the fault is within the charge controller (got a hold of another CC, different model, and have replicated the issue).

    I've isolated different strings of panels and the problem persists.

    Where does my problem lie?
    Attached Files
    Last edited by sprucetrees; 02-14-2020, 04:39 PM.

  • #2
    Possibly this is an issue of the PV voltage dropping under load?

    Comment


    • #3
      Divide and conquer ...
      Separate the three PV strings and verify individually ...
      What is the Voc of each string ?
      What is the Isc of each string ?
      Are they nearly identical ?

      Disconnect the wire between the Charge controller and the Arrays
      Check the round-trip OHMS
      All connections are tight?

      Start proving, to yourself, what components are 100% functional, then what is remaining ... is the problem.

      Do you have an errant connection or unwanted ground loop between the battery / output side of the Charge Control and the PV / input side?
      Verify the + /- polarity of everything - assume nothing.
      Do you need to connect the CC to battery bank first, before connecting the PV array?

      Verify that your: Disconnects, Fuses, and Circuit Breaker are low ohms.
      Last edited by NEOH; 02-14-2020, 05:33 PM.

      Comment


      • #4
        NEOH,

        Thanks for the response and some new ideas. I'll start working my way through what I can, and update/give more information about what I find. Too bad the sun has already set here...


        What is curious is that I don't believe I made any changes to the system from when it was functioning properly to now. So, I doubt the issue is an errant connection, however something could have come loose or been damaged - wiring or a component. Several feet of ice and snow on top of everything doesn't exactly make anything easier!

        Comment


        • #5
          Originally posted by sprucetrees View Post
          NEOH,

          Thanks for the response and some new ideas. I'll start working my way through what I can, and update/give more information about what I find. Too bad the sun has already set here...


          What is curious is that I don't believe I made any changes to the system from when it was functioning properly to now. So, I doubt the issue is an errant connection, however something could have come loose or been damaged - wiring or a component. Several feet of ice and snow on top of everything doesn't exactly make anything easier!
          I think you are on the right track to determine the issue. By isolating each string you should be able to identify the problem. I will bet my hat there is a water or ice issue at one of the connection points.

          Comment


          • #6
            Originally posted by SunEagle View Post

            I think you are on the right track to determine the issue. By isolating each string you should be able to identify the problem. I will bet my hat there is a water or ice issue at one of the connection points.
            Would you still say this knowing that I can measure correct PV voltage inside the house, but it drops only when it is allowed to flow into the charge controller?




            Also, each string has good voltage, I haven't checked ISC on each panel though, or each string (too high amperage for my multimeter...)
            Last edited by sprucetrees; 02-14-2020, 06:03 PM.

            Comment


            • #7
              Originally posted by sprucetrees View Post

              Would you still say this knowing that I can measure correct PV voltage inside the house, but it drops only when it is allowed to flow into the charge controller?




              Also, each string has good voltage, I haven't checked ISC on each panel though, or each string (too high amperage for my multimeter...)
              It is hard to say what your issue is based on the data you have given us. Maybe you have exceeded the max DC input voltage of your CC due to the cold temperatures.

              Something is putting a drain on the pv voltage and that means some type of additional resistance in the wiring or components.

              Comment


              • #8
                Panels coated in ice or snow, are not well illuminated, and will suffer.

                What is your panel Voc ? You have 3 in series ? How did you calculate the cold temp Voc , and is it within the charge controllers voltage limit ?
                Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
                || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
                || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

                solar: http://tinyurl.com/LMR-Solar
                gen: http://tinyurl.com/LMR-Lister

                Comment


                • #9
                  Originally posted by Mike90250 View Post
                  Panels coated in ice or snow, are not well illuminated, and will suffer.

                  What is your panel Voc ? You have 3 in series ? How did you calculate the cold temp Voc , and is it within the charge controllers voltage limit ?
                  VOC - 45.5 x 3 = 136.5V, charge controller is rated for 200VDC+, so I am okay there -- I'm aware that the cold can cause issues in this regard. Today was -35C



                  I've isolated a bunch of stuff. The issue has to be connections outside at the panels. Will follow up tomorrow. Thanks everyone.

                  Comment


                  • #10
                    Do you have a combiner box at the panels? As HEOH mentioned Verify polarity at each string into the combiner.
                    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                    Comment


                    • #11
                      Well, I haven't been able to isolate the problem.

                      But, back to basics - should voltage drop when the charge controller begins to pull a load from the panels?

                      For example, I've taken a new MPPT charge controller and connected it to a 12V battery, new cabling straight to two new panels. Before connecting to CC the voltage is an expected 91V. Once connected to charge controller, and it pulling a few amps, voltage drops to ~70-80V.

                      Overcast day, not much sunlight.



                      Voltage is reported by the CC is the same as if it is measured from +/- PV terminals on CC.



                      Is this normal?

                      Comment


                      • #12
                        Yes. Open circuit voltage vs. voltage @ max power point. What do the data labels say is the Voc. and Vmp.? Keep in mind that warm panels will read lower than spec.
                        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                        Comment


                        • #13
                          Originally posted by littleharbor View Post
                          Yes. Open circuit voltage vs. voltage @ max power point. What do the data labels say is the Voc. and Vmp.? Keep in mind that warm panels will read lower than spec.
                          Ah, yes, of course.

                          Voc 45.5
                          Vmp 37.0

                          In the above described example I should expect around 74V @ max power. Currently the little 12V set up is coming in at 62V under load.

                          Cold weather currently.
                          Last edited by sprucetrees; 02-15-2020, 02:22 PM.

                          Comment


                          • #14
                            Of course, with an MPPT controller your output voltage will be around battery voltage. You are saying the input voltage at the CC is wrong but each string is looking correct? Sounds like a string is reversed polarity or there's maybe a blown fuse/breaker at the combiner.
                            2.2kw Suntech mono, Classic 200, NEW Trace SW4024

                            Comment


                            • #15
                              Originally posted by littleharbor View Post
                              Of course, with an MPPT controller your output voltage will be around battery voltage. You are saying the input voltage at the CC is wrong but each string is looking correct? Sounds like a string is reversed polarity or there's maybe a blown fuse/breaker at the combiner.
                              Currently I have disconnected all but one string, and I have bypassed my combiner box.

                              So, currently on my main system:

                              -three panels tied together in series (positive terminal of one panel going into the negative of the other..). End point + and - running straight into the charge controller (bypassing my usual breakers). Charge controller connected directly to battery bank. Multimeter shows 136.5V before making connection to CC; drops to between battery voltage ~48V and about 70V when CC is connected.

                              Thanks/sorry...

                              Comment

                              Working...
                              X