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haroldw
haroldw Registered Users Posts: 3 ✭
in Solar Beginners Corner #1
what size breaker between battery and inverter 3500 watt 7000 surge pure sine wave inverter?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #2
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    What voltage and AH size battery bank?

    Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #3
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    haroldw said:
    what size breaker between battery and inverter 3500 watt 7000 surge pure sine wave inverter?
    7KW @ 48V = 145A   Add in some inverter overhead and loss, you will be near 200A, if you dont want it to pop at the surge.
     My 6kw inverter recommends a 250A breaker
    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

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

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  • Estragon
    Estragon Registered Users Posts: 4,496 ✭✭✭✭✭
    #4
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    Also important, what is awg size of the wire connecting to battery (which is what the breaker is protecting)?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
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  • haroldw
    haroldw Registered Users Posts: 3 ✭
    #5
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    750 ah battery bank
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  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    #6
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    @haroldw,

    more details, please, your battery voltage is the most important thing you have not stated 
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,046 ✭✭✭✭✭
    #7
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    Battery type and configuration as well.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric,  460 Ah. 24 volt LiFePo4 battery bank. Plenty of Baja Sea of Cortez sunshine.

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  • haroldw
    haroldw Registered Users Posts: 3 ✭
    #8
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    12 volts
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  • Tecnodave
    Tecnodave Registered Users Posts: 437 ✭✭✭✭
    #9
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    3500 watts at 11 volts is 318 amps , 7000 watts at 11 volts is 636 amps....A 12 volt 3500 watt. Inverter is not practical, the current required is way too high for any normal system. The biggest inverter you can expect to operate on 12 volts is 1000 watts and that will require a big battery.  Current calculations are always done at the low end of the battery voltage range. 
    2 Classic 150, 2 Kid, 5 arrays 7.5 kw total  2ea.  2S6P Sharp NE-170/NE-165, 1ea. 12P Sanyo HIT 200,  2ea. 4/6P Sanyo HIT 200, MagnaSine MS4024AE, Exeltech XP-1100,  2 Banks L-16 battery, Rolls-Surette S-530 and Interstate Traction, Shunts with whizbangJr and Bogart Tri-Metric, iCharger i208B  dc-dc buck/boost converter with BMS for small form lithium 8S 16650 or LiFePO4,
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,447 admin
    #10
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    12 VDC @ 750 AH battery bank... For a flooded cell deep cycle battery bank, suggest a maximum AC inverter rated capacity of ~250 Watts per 100 AH (~12 volts):
    • 250 Watts * 750 AH / 100 AH (at 12 volts) = 1,898 Watt suggested maximum inverter rated output...
    And that maps with ~1,800 Watts as a suggested "maximum supportable" AC inverter on a 12 volt battery bank.

    And the typical maximum continuous current rated 12 VDC battery bus for an 1,800 Watt inverter:
    • 1,800 Watt * 1/0.85 AC inverter eff * 1/10.5 volts battery cutoff * 1.25 NEC continuous current derating = ~252 Amp rated 12 VDC branch circuit and fuse/breaker (round down to 250 Amps is fine).
    Wiring wise, a basic NEC wiring chart would suggest:

    https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

    around 3/0 to 350 kcmills copper cabling (depending on ambient and insulation rated temperatures).

    And you need to look at maximum voltage drop too... Say pick 2/0 cabling and a maximum of 0.5 volt wiring drop (for 12 volt battery bus):
    • 1,800 Watts * 1/0.85 AC inverter eff * 1/10.5 volts battery cutoff = 202 amps current (12 volt 
    https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.5127&voltage=12&phase=dc&noofconductor=1&distance=8&distanceunit=feet&amperes=202&x=0&y=0

    8 feet (one way run for this calculator) of 2/0 at 202 Amps gives 0.51 volts drop.

    Voltage drop: 0.51
    Voltage drop percentage: 4.21%
    Voltage at the end: 11.49

    You can run the same calculations for a 3,500 Watt inverter... But that is 2x heavier cable and a 2x larger (AH) battery bank @ 12 volts for a "reliable" battery based system...

    Highly suggest reducing your loads, or looking at a 24 or 48 volt DC battery bus and AC inverter if you need those levels of power...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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