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2 Arrays, but only 1 really charges the system

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  • 2 Arrays, but only 1 really charges the system

    Hi guys,
    In the spring I installed two 3 panel arrays on a cabin. One on the east facing roof slope, one on the west facing roof slope. They're comprised of matching Canadian Solar 310w 60 cells, connected to the batteries via Tracer 5415AN charge controllers. Aside from the physical placement, they are identical. Both charge controllers are connected to the same 4S 6V battery bank with 6awg wires.

    Ok. So during installation I ran the batteries down a bit and ran only one string at a time for a few hours. Both strings happily produced 20+ amps in sunlight. (To me this seemed good since batteries were only about 80%SoC and panels do not face south at all)

    Once i was satisfied everything was working I turned both strings on and let it run, but right away I noticed that the East facing string seemed to generate a lot more power than the West facing array did. And it's not just in the morning when the batteries are lowest (I'd expect that sort of higher charging current in the bulk phase in the AM). Even in the afternoon when the West array should be at a much better angle to the sun, the east will generate more. If I switch off the panels, the West array will jump up and start generating better.

    Both tracers are setup identically in terms of parameters/settings (I set one up, saved and then loaded the save file onto the second).

    It's been cloudy/stormy the post couple weeks and it seems like the West isn't pulling it's weight.

    Any suggestions/ideas?

    Thanks in advance for the help

  • #2
    I suspect it's more like by noon, batteries are charged. Take a day, and switch the East string off, see what the west does
    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

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    • #3
      Originally posted by Mike90250 View Post
      I suspect it's more like by noon, batteries are charged. Take a day, and switch the East string off, see what the west does
      Thanks for the input Mike. I'm heading back this weekend so that's my plan. But even in the afternoon when running loads like the fridge and inverter, the solar system should still be generating. And the West array might put out 1A and the east array is putting out 4A... The Sun should be heavily favoring the West array by 2 or 3pm...

      Think I'm just being overly worried something's not quite right?


      update:
      I just checked the current status and the east array is making 7.3A to the batter and the West array is 1A or less.
      Voltage on the west array is currently about 105VDC so seems like it's not a shading issue...
      ​​​​​
      Last edited by Xplode; 07-17-2019, 04:20 PM.

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      • #4
        In mid-day, switch off the east array (ise the PV breaker, not the controller breaker)

        You may indeed have an issue with the west, going to have to design a way to test your install.
        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


        • #5
          Ok, so I'm at the cabin now. I switched off the panels (both arrays) and last night I ran everything and even left the lights/inverter on overnight to get the batteries run down to about 50-60% SoC. This morning they were around 24.6V so good candidate to test the charging. Unfortunately it's a bit cloudy today, but the sun is peeking out occasionally.

          Waited until 20 mins before noon and switched on the west array. It rolled up to around 26A charging almost immediately. Turned on the east array and it rolled up to around 28A. The West rolled back to around 22A. Seems ok so far, the sun hasn't really peaked yet.

          Checked on and off until around 1 when the east array was still a few amps ahead of the West.

          I've noticed that the two controllers never perfectly agree on the voltage of the batteries, with the West Always being 0.07-0.15v lower. Not sure if it's related, but to see if that makes a difference I bumped the charging voltage setting 0.1V in the West controller, and now as we slide into the evening, it is outperforming the east array 10.7A to 2.6A.

          Can't quite wrap my head around WHY it was underperforming, but the small tweak seems to have helped. So I'm happy about that. I'll see what happens in the morning when the sun favors the east array again.

          If you've got any insight, or other ideas, please let me know.

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