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Magnum 4448 PAE& Enphase M250 AC couple system- help needed

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  • Magnum 4448 PAE& Enphase M250 AC couple system- help needed

    When on grid (magnum passing thru power from main panel) the panels are producing approximately 10 amps of power @ 240 volts ac without an issue. However, when I go off grid (micro grid) the amperage from the enphase m250 inverters (coming from the solar panels) fluctuates greatly peaking at 50% of on grid power.
    Initially I thought the magnum inverter was frequency shifting to 60.5 HZ to turn off enphase inverters however I monitored the frequency during the erratic behavior and it never goes above 59.9 hz and also the amperage fluctuates immediately (not after the 5 minute wait time built into the enphase inverters)
    I did notice that while off grid (microgrid) the voltage fluctuates from 243 volts to 246 volts. During off grid operation the dump load ( 4 x 300 watt ceramic resistors) trigger repeatedly as the batteries are fully charged and the load in the sub panel is not significant
    I have spoken to magnum energy support and they seem to believe that my batteries are undersized for the amount of power coming in from the Solar panels.

    Would appreciate any help you can provide.

    Solar System Setup
    11 x 265 Watt Panels
    11x M250 Enphase Inverters
    1 x Magnum 4448 PAE Inverter (RTR remote)
    8 x 6 volt interstate 205 AMP hour batteries (wired in series for 48 volts)
    2 Gauge DC cables
    4 x 300 watt resistors (dump load)
    Attached Files

  • #2
    A guideline for 48V systems, is 100a of battery for every KW the inverter is capable of, This helps reduce clipping of the sinewave caused by battery bank performance,
    And if it takes 5 min for things to start to respond, the batteries have to be able to endure the power for that amount of time,
    And i would assume AC voltage fluctuations would be caused by some micro inverters shutting down from overvoltage, because the batteries cannot absorb it all.

    I'm totally off-grid, and only have a vague clue how a hybrid system should be working,
    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



    • #3
      Generally AC coupled systems need to have a bymofal inverter that is larger than the grid tie and the battery needs to be on the upper end of the size supported by the bymodal inverter. A 200 ah battery seems to be on the minimal size.
      OutBack FP1 w/ CS6P-250P


      • #4
        Thanks for the responses. Today I disconnected some of the panels (down to 6) and the power seemed a bit more stable. Guess I will have to get bigger batteries.

        Inverter: 4400 watts
        Solar array:2915 watts
        Battery bank: 200 ah

        I hope a 400 ah bank will stabilize the power in order to connect all 11 panels.