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First post, issues with a PV system on a van!

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  • First post, issues with a PV system on a van!

    Hello all, I have something of a conundrum for you!

    I have a 12V solar system set up on a van, consisting of:

    2x100W 12V semi-flexible back-contact panels connected in parallel.

    A pwm charge controller from photonic universe (20A, PU2024B)

    2x110Ah AGM batteries connected in parallel

    A connection to the vans starter battery via a 130A voltage split relay and a manual switch

    Several weeks ago I noticed that the voltage of the batteries were staying at 12.7V, whilst the panels were in bright sunshine. The status indicator LED's on the charge controller (the only monitoring I have at the moment) were a little odd. Battery showed not full, but normal. The LED for the solar panels was flashing slowly (meaning charging as normal), but with intermittent (every 3-7 second) bursts of fast flashing (supposedly indicating that the panels were connected with incorrect polarity). All seemed a bit odd, so got the multimeter out and starting poking!

    The voltage of the solar panels (when connected to the charge controller) was fluctuating rapidly
    (several times a second) between 13-16V. Current was around 5A. Disconnecting the solar panels from the CC and reading them directly gave a voltage of 19-20V and current of 5A. Any ideas what the fluctuating voltage might mean?

    Checking the panels individually showed one panel behaving as expected (19-20V, 5A in bright sunshine), but the other giving 10V and 0A. Upon further inspection the panel with no current seemed to have a barely visible hairline crack over 3 of the cells. I then connected the normal panel to the charge controller on its own, but no luck! Same behaviour as before.

    Thinking this might be an issue with the charge controller, I managed to get hold of an identical, new charge controller, but no luck again! It behaved as before, when connected to both the panels, or to the apparently not broken one.

    The whole system is about 18 months old, I'd certainly not expect the batteries to be knackered yet (indeed I can charge them off the alternator, and they hold their charge no problem)

    It is at this point I come to you, good people of the internet, I'm stumped! Has anyone experienced anything similar? Any suggestions of other tests to try!?

    Thanks in advance!

  • #2
    12.7 volts is a full, or nearly full battery. Could it be the controller is modulating the voltage to maintain float voltage? The 'battery not full" graph shouldn't really be relied on. Try disconnecting the panel and discharging the battery to 75% full or less then reconnect the panels in full sun and see what happens.
    2.2kw Suntech mono, Classic 200, NEW Trace SW4024


    • #3
      Cracks in a cell, flexible or not, are not normal or good. I'm betting if one panel shows cracks, the other has micro-cracks that are not visible yet. When cells are cut from the bulk silicon, they require an annealing step (time & money) or they start to degrade from microcracks.

      Is there any reason the panels are repeatedly flexing that can cause the cracks ?
      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