Pros and Cons of connecting Inverter to Controller vs. Battery

d3fault
d3fault Registered Users Posts: 1 ✭
in Solar Beginners Corner #1
I'm building my first off-grid 12v solar system and was surprised when my [MPPT] solar controller arrived and had connections for "load". I was under the impression that my inverter would be connected to the batteries, not the controller. After doing a bit of research I now think either way is possible (can someone please confirm this?), but I'm wondering what the differences of each configuration would be.

I guess most importantly: Will both configurations give power to load _before_ charging the battery?

I don't want to use my controller's "load" connection because the controller's current rating is only 40A. My [also MPPT] inverter is 1000W continuous, so if I _HAVE TO_ use the controller's "load" connection then that means I wasted money on too big of an inverter, since 40A x 12v = 480W, which is much less than 1000W :(.

Thanks in advance for your replies,
d3fault
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  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    edited October 2017 #2
    Good thing you're observant, connect the inverter to the battery with a fuse or circuit breaker rated to protect the conductors between the two. The load terminals are only suitable for low current loads, some/most are rated at the amp capacity of the controller, but it's always best to connect to the battery, especially inverters. The one benifit of the load connections is the load will be disconnected at a certain voltage to prevent over discharge, so any DC loads such as lighting, is good to use the load terminals, the inverter should have low voltage disconnect, to protect itself, which in turn protects the battery. These values can be quite low, disconnecting when the battery is almost completely dead, it's better not to rely on these values on a regular basis by sizing the battery to support the anticipated loads, never dropping below 12V, or 50% depth-of-discharge, as a maximum.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery with Battery Bodyguard BMS 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah LFP 24V nominal battery with Daly BMS, used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
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  • fratermus
    fratermus Registered Users Posts: 48 ✭✭
    #3
    One could set the LVD to something sane and run loads off a relay/solonoid triggered by the LOAD output.  Works for me.
    2017 Promaster 159" offgrid campervan
    750w:100Ah LFP
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  • d3fault
    d3fault Registered Users Posts: 1 ✭
    #4
    thanks mcgivor! I wasn't going to put a fuse/circuit-breaker there either but I will now :)
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