Using Relay With SCC LVD

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bajasurfer
bajasurfer Solar Expert Posts: 30 ✭✭
in Solar Beginners Corner #1
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.
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
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    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.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #3
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    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%).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #4
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    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.
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