Maximum output of Schneider XW+ 6848

DickyDck
DickyDck Registered Users Posts: 164 ✭✭
in Solar Beginners Corner #1
I ordered new panels, cabling, MPPT etc.... and now I'm wondering if it was semi wasted money. The datasheet for my inverters , the XW6848, lists a maximum output of 6800. the reason I am adding the gear is to try and get more output and get my electric bill down to null and maybe even feed some back to the grid. I average about 1.6kw running 24/7 and yes I know at night my solar doesn't do jack. but during the day I feel like I should be able to feed back a little more to offset it more than I am presently. SO with all my panels at max output, it would be over the 6800w the 6848 has as output. Is my logic sound? 
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,599 admin
    #2
    What size is your solar array and battery bank?

    The XW will not feed back to the grid until the battery bank is reasonably recharged... Only "excess solar array power" (more solar than battery+loads) should be fed back to to the grid (less any AC loads used locally).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,873 ✭✭✭✭✭✭
    #3
    In grid interactive mode an XW+ can output 27A or about 6KW. You can master/slave multiple XW+ or AC couple a grid tie inverter for more current to the grid. This info is in the spec and cut sheet for XW+
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • DickyDck
    DickyDck Registered Users Posts: 164 ✭✭
    #4
    yeah, I feedback some to the grid now on clear days. Presently the array is 310w x 24 = 7440w but thats best case and I've never gotten that much out of it/ average 5-5.5kw. Batt bank at 440ah presently, and doing well, it evened out some odd behavior when I only had 220. I suppose I should look into another inverter
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,599 admin
    edited August 2019 #5
    • 7,440 Watts * 0.77 typical derating for panels and controller = 5,329 Watts about the "best" array output on cool/clear days
    • 5,329 Watts (DC bus available power) * 0.90 typical AC inverter eff = 5,156 Watts about "max" I would expect on non-freezing days
    So--What you are seeing is not out of the realm of what I would expect for a pretty much optimum noon-time AC Output.

    A 440 AH @ 48 volt FLA battery bank--I would suggest that ~4.4 kWatts as optimum continuous output (at night).
    • 1,600 Watts * ~16 hours per day (dark) = 25,600 WH overnight
    • 440 AH * 48 volts * 0.85 AC inverter eff = 17,952 WH battery bank capacity
    So, yes, expecting overnight battery bus powered AC inverter power is not possible... Ideally, you should be daily discharging the bank no more than ~25% of Battery Bank capacity (for longer battery life, and realistically recharge a FLA battery bank from solar from 75% to near 100% state of charge with just solar/sun.

    Are you cycling the battery bank daily (partial cycling), or is it just "floating" waiting for a power outage?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • DickyDck
    DickyDck Registered Users Posts: 164 ✭✭
    #6
    just floating, I dont run it at all in an off-grid mode, strictly for backup since I live far out toward the end of the grid line, and I've gone a weekend or two without power which is what prompted me to get solar with the backup. If I wasn't running crypto mining gear this would be way more than enough to bring my power bill into the flat even and possibly into the negative, but I'm addicted to mining :p
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,599 admin
    #7
    And look at your total daily harvest... Say, fixed array, around Roanoke Virginia:
    http://www.solarelectricityhandbook.com/solar-irradiance.html

    Roanoke
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 53° angle from vertical:
    (For best year-round performance)

    JanFebMarAprMayJun
    3.34
         		3.78
         		4.52
         		4.82
         		4.96
         		5.00
     
    JulAugSepOctNovDec
    5.02
         		4.83
         		4.74
         		4.74
         		3.65
         		3.11
     
    As an example, August at ~4.83 hours of sun per day:
    • 7,440 Watt array * 0.77 array and controller deratings * 4.83 hours of sun per day = 27,670 WH per day (27.7 kWH per August day)
    See if you are anywhere near average predicted output.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • DickyDck
    DickyDck Registered Users Posts: 164 ✭✭
    #8
    Thanks! I'll run this math today when I get off work!
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  • WaterWheel
    WaterWheel Registered Users Posts: 384 ✭✭✭
    #9
    As Bill pointed out in post #5 your 7400 watts in panels will rarely be putting out more than 5300 watts so at this point is seems that your panels are the limiting factor.

    Panel ratings are determined using perfect testing conditions, something rarely ever seen in the real world with humidity and dust in the air not to mention dirt on the panels and the fact that the sun is only perfectly angled to your panels for a few minutes a day at best.     Then the controller will lose a few percent along with some power loss in the wiring.     Thus the 77% efficiency factor Bill uses for a realistic panel output expectation.

    Not sure if this will work while selling to the grid but.....     If lightly cycled your batteries will last longer.     The 6848 can be programmed to use your batteries a little or a lot with the grid providing the balance of the energy.     By enabling grid support with the Grid Support Volts set fairly high (maybe 50 V) you will cycle the batteries a bit while still sending most of your power back to the grid or used in your home.      Because of battery charging inefficiency you would lose a tad of power but your expensive batteries would probably last longer.

    Conext XW6848 with PDP, SCP, 80/600 controller, 60/150 controller and Conext battery monitor

    21 SW280 panels on Schletter ground mount

    48v Rolls 6CS 27P

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  • DickyDck
    DickyDck Registered Users Posts: 164 ✭✭
    #10
    OK, so if my combox is expected to be trusted, this past day I got 37.4kw/h... plugging in the numbers from that page you linked comes out to...

    • 7,440 Watt array * 0.77 array and controller deratings * 4.98 hours of sun per day = 28,529.424 WH per day (28.5 kWH per August day)

    so today anyway I got above average, I'll check the past few days to see as well.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #11
    So does your utility 'Know' you want to back feed the grid?
    Do you have a digital meter? You could actually be charged for any extra going through a shunt at the meter...
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • DickyDck
    DickyDck Registered Users Posts: 164 ✭✭
    #12
    Yep they know, they swapped out the meter after the county came and signed off on all my stuff. I already export a bit to the grid now during the nice days, but Any savings are entirely gone in my mining gear which is a constant 1200w running 24/7. I went 4 weeks without mining and ended up with a negative bill which was great. I live by myself and hardly use any power. I even bought a 240v zwave compatible switch and remotely schedule my water Heater to only run once a day for four hours. I use so little hot water I might be able to go 2 days but haven’t experimented with it yet. Can I run 2 inverters off they same single battery bank?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,599 admin
    #13
    Yes, you can run more than one AC inverter from a single battery bank... However, they need to be wired correctly (each home run back to the battery bus with its own fuse/breaker). And the peak loads need to able to be supported by the battery bank and charging system.

    Some folks have, for example, run a 300 Watt AC inverter 24 by 7 and a second 1,800 Watt AC inverter just when needed (on a 12 volt battery bank, around 1,800 Watts is suggested maximum draw on a 12 volt FLA battery bus. And an 1,800 Watt load would require a minimum of 720 AH @ 12 volt FLA battery bank (based on 250 Watts of AC inverter per 100 AH @ 12 volt battery bank minimum).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,873 ✭✭✭✭✭✭
    #14
    And specifically on the wiring there is an extra network cable for multiple XW's to keep them in phase.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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  • DickyDck
    DickyDck Registered Users Posts: 164 ✭✭
    #15
    Dave Angelini said:
    And specifically on the wiring there is an extra network cable for multiple XW's to keep them in phase.
    Yep, that cat5 cable that runs between all my components, I forget the what schneider calls that network, but its a glorified CAN network.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,873 ✭✭✭✭✭✭
    #16
    No you are mistaken. The cable is between inverters for stacking and as I said keeping them in phase. 
    You are thinking of XANBUS. Be careful as a grid install can do some nasty things without the stacking cable. Pros have messed this up so just read it first.
    "we go where power lines don't" Sierra Nevada mountain area
       htps://offgridsolar1.com/
    E-mail offgridsolar@sti.net

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