Announcement

Collapse
No announcement yet.

PV inverter and MPPT feeding from same PV array?

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

  • PV inverter and MPPT feeding from same PV array?

    Can I connect a PV Inverter from the same PV Array of my MPPT Charge Controller to take advantage of the full potencial of the PV array when the battery are charged by the MPPT?
    I have a MX60 charging 8 Trojan batteries with 4 x 250 Watts panels but when the batteries are full the MX60 goes sleeping and I waste the rest of the energy in that day. so I'm thinking to install a Enphase M250 to each panel to AC couple to the output of my Inverter/charger.

    This way I do not use the reserve from my batteries just the exceed of my PV array.

    Theoretically it does not have anything in common because the inverter connected to the batteries has a magnetic bond to the AC output and the PV inverter will have a AC Coupling will not notice that...
    Am I right?

  • #2
    Why not have a diversion load? Some farms here use this extra energy to pump water or run other equipment and still go into the night with a full charge of their battery array. Is there anything else that you can use the excess energy for during sunlight? The Enphase will not work without grid, or what they perceive as a grid and your inverter has to be capable of AC coupling to handle and manage the additional AC input. This has been discussed before here. https://www.solarpaneltalk.com/forum...78-ac-coupling
    Last edited by ncs55; 05-14-2016, 09:47 PM. Reason: added link

    Comment


    • #3
      Assuming that by PV inverter you mean grid tie inverter, the answer is no.

      The general rule is that you cannot connect two independent MPPT input devices to the same array at the same time. Both devices will vary their input behavior assuming that they are the only load and as a result will get very confused.
      By extension you should not connect one MPPT device and one PWM device either.
      SunnyBoy 3000 US, 18 BP Solar 175B panels.

      Comment


      • Dominican Dude
        Dominican Dude commented
        Editing a comment
        Yes I meant a Grid Tie inverter.
        But keep in mind that the MPPT Charge Controller will not use the PV array. after the battery are fully charged so in that moment the PV array is not used 100%.
        So attaching a PV inverter or grid tie inverter will take advantage of the PV Array when the Charge controller is sleeping or floating stage.

        PS. Yes I know that MPPT and PWM can not be mixed.

    • #4
      If you are determined to do this... it is possible...
      1. Buy a new acceptable grid tie inverter of your choice, pay attention to your PV grounding... if grounded you need a transformer inverter...
      2. Buy appropriately rated contactors for your string voltage and current, and the right coil voltage to match to the charge controller auxiliary output relay
      3. Using the digital output from the charge controller have it shut off when bat volts are at float or your liking
      4. Using this digital output, it shuts off contactor feeding the charge controller (I assume the charge controller stays powered up, looking at bat volts after this)
      5. Wire a normally closed contact from charge controller contactor to close the coil on the grid tie contactor

      Basically the charge controller operates a contactor that feeds PV to it, once charged it opens, then closes the grid tie contactor once the charge controller contactor is open, preventing overlap. I would be hesitant about this scenario due to slamming the grid tie inverter. I would recommend a couple of high impedance resistors to bleed across the grid tie contactor terminals to keep a bit of voltage on the grid tie inverter at all times. It will work, safely, and prevent dual mppt's fighting each other due to being electrically interlocked. I would estimate $150-250 for all contactor parts and maybe 20 minutes to wire it up.

      My $0.02
      Last edited by Eleceng1979; 05-28-2016, 09:47 PM.

      Comment

      Working...
      X