Using Relay With SCC LVD

bajasurferbajasurfer Solar Expert Posts: 30 ✭✭
Is using the LVD feature on the Morningstar SunSaver MPPT SCC controlling a relay a viable approach to automatically disconnecting power to an inverter?
LVD: 11.5V
LVR: 12.6V

Thanks in advance.


  • mike95490mike95490 Solar Expert Posts: 9,033 ✭✭✭✭✭
    Re: Using Relay With SCC LVD

    the internal contacts are low power, so an external relay would be needed as you ask.

    1) you should have "back EMF" diodes installed on the relay coil

    2) Watch what your "holding current" is. Large relays, that can switch and make/break high ampreage DC currents, can consume a lot of power, if they are on 24/7 There may be a good solid state relay to perform this function.
    Powerfab top of pole PV mount | 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

    gen: ,

  • BB.BB. Super Moderators, Administrators Posts: 31,070 admin
    Re: Using Relay With SCC LVD

    Some inverters have a low voltage on/off control line--you might be able to wire up your LVD from the solar charge controller from that...

    Of course, it won't be as accurate as a battery meter--but for you needs--it may work well enough for now (battery voltage under load, and under charge, is not a good indicator of state of charge--which we try to keep above 50%).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • n3qikn3qik Solar Expert Posts: 741 ✭✭
    Re: Using Relay With SCC LVD

    If you are disconnecting the DC of inverter, watch out for the inrush at startup. Most have some good size caps that need to charge at first power up.

    If inverter has a on/off switch, I would wire into that.
Sign In or Register to comment.