Priority of PV Usage

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WDHaskins
WDHaskins Registered Users Posts: 5 ✭✭
in Grid Tie and Grid Interactive Systems #1
96 320 watt panels, 6 Schneider Conext MMPT 80 Charge Controllers, 4 Schneider Conext XW-Pro Inverters, 48 volt 1000 kWh NiFe battery bank, being expanded to 2000 kWh, grid-tied system.  We are being told that all power must first go in battery bank from panels then back out to load, excess sold to grid.  What we want is to have PV power first power the load, then excess go to battery bank, then when at 100% SOC excess sold to grid so that we can avoid the inefficiencies of battery storage (roughly 65% loss going in and back out of batteries).   Does anyone know what settings should be used on the Schneider gear to prioritize PV powering loads first, then if in excess of load to battery storage?  Alternatively, is there an electro-mechanical device which will route mod power through inverters to load and only if in excess of load demand, to battery storage?  Since using NiFe batteries, we don't care whether they are at full charge or discharged, we want to prioritize load supply.  Thanks.
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  • WDHaskins
    WDHaskins Registered Users Posts: 5 ✭✭
    #2
    Should have said 35% loss going in and out of NiFe batteries, efficiency is 65%, not loss.  My bad, sorry.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 7,033 ✭✭✭✭✭✭
    edited February 2021 #3
    You are going to have to list your settings to even guess what is being prioritized.
     The general answer is the inverter should power loads first, then charge battery, then sell to grid. The Sell voltage being lowered should lower the amount of charge to the battery.

    "We are being told that all power must first go in battery bank from panels then back out to load, excess sold to grid."

    Who is telling you this and why?
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • WDHaskins
    WDHaskins Registered Users Posts: 5 ✭✭
    #4
    Dave:  Thanks for response.  The installer is telling us these things, and I'm being convinced he doesn't know what he is doing.  Inverters are Schneider 6848 with 3 slaved to the first.  Which of the settings do you need to see?  Right this moment, the solar production of 1.34 kV is going entirely from the charge controllers to the batteries, and none to load, which is entirely being supplied through the inverters by the grid on AC pass-through.  I can see the settings on devices through Schneider's insight cloud, I could email you my log-on so you could directly see them yourself.  I agree with you on priorities.  Our utility buys our excess PV at about 8% of the retail rate, so we don't want to sell any to grid if we can use ours to power load and charge batteries first.  Again, thanks for help.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 7,033 ✭✭✭✭✭✭
    #5
    Yes send me an e-mail below and add me to your cloud so I can take a peak. 
    AC passthru is crazy, why even have the XW's? Going for drive today so back tomorrow. Good Luck
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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