dstance panels and inverter

robocop
robocop Registered Users Posts: 115 ✭✭
Hi
like to know the type of wire to connect between solar panels to inverter.

Do have 8pcs  500w each panels 12 pcs  250ah batteries and a 5.5kw rated hybrid  inverter.

The distance panel to inverter is about 135 feet using mc4 connects.


system voltage is  48v

Awaiting your reply and thanks

Bob   

Comments

  • mcgivor
    mcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    Well it depends on the voltage allowable by the inverter, higher voltages results in lower current therefore smaller conductors, how are the panels configured, what are the specs of both the panels and inverters charger? Assuming the hybrid inverter has a MPPT charger built-in.
    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.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,402 admin
    Bob,

    What are you using for the connection from the solar array to the battery bank (MPPT charge controller or GT Inverter or what)?

    Basically, need to know the Vmp-array / Imp-array configuration (x series * y parallel connections). What is the Vmp/Imp of the panel?

    For example, a 150 Vpanel max input MPPT controller, you can run Vmp-array ~ 100 VDC max, possibly more? (are you in Curaçao, Caribbean Sea?).

    For a Vpanel input of 600 volts, a Vmp-array of 400 volts or so is possible... Higher the voltage, lower the current, smaller diameter wire you have to use...

    -Bill

    PS: I have closed your other discussion... Keep everything in one location. -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • robocop
    robocop Registered Users Posts: 115 ✭✭
    hi Bill
    panel vmp is 58.95  imp is 10.87 voc 48.63
    inverter : max  panel array is 4000w   pv array mppt voltage is 130vd  max pv array open circuit voltage is 145vd

    inverter is MUST hybrid 5.5kw  and I do live in curacao.

    What about the inter panel connections ?  Should I use less panel? And what will the thickness  be for 35 meter lengt 

    I do have 12pcs  250ah batteries  to form 48v  and  750 ah


    Thanks for you attention and have a nice day

    Bob
  • MichaelK
    MichaelK Registered Users Posts: 234 ✭✭✭
    edited May 2020 #5
    Here are some specifications I see for your unit
    Max Voc =145VDC
    PV array voltage 64-130VDC
    Max current 80A

    I think you have your panel voltage backwards.  Voc is always higher than Vmp.  Are they Voc=58.95 and Vmp=48.63?  Something else is not right.  If the panel is 500W, then 500W/48.63V = 10.28A (Imp).  Is your amperage actually Isc=10.87?
    If the Voc is 58.95, that means you can only have two panels in series to get a Voc of ~118 VDC.  Three panels in series would be >176VDC which would exceed the 145V limit of your box. 

    It's doable to wire these panels in series/parallel, but your unit is limited to 4000W, meaning four strings of 2 panels (2S4P).  So 8 total is maximum.  Because your working voltage is rather high (118VDC) you can get by with using 10 gauge solar wire.  In my own system, I'm going 125' with 10 gauge at 120VDC, and I measure virtually no voltage drop.

    Now each of your batteries is 12V?  A 250AH 12V battery is very large?  I'm guessing that each battery must weigh about 65kg?  To wire them for 48V you need to wire them in a 4S3P configuration.  You'll need to read up on how to proper wire up three strings so they do not become unbalanced.  Assuming each string needs about 25amps to charge, you are looking at 25A x 3 x 52+ volts = 3900Watts, so the panels are in the right ballpark.

    I'm interested in hearing about how one of these Chinese all-in-one units actually performs out in the real-world.  Please keep us posted on how things turn out?
    System 1) 15 Renogy 300w + 4 250W Astronergy panels,  Midnight 200 CC, 8 Trojan L16 bat., Schneider XW6848 NA inverter, AC-Delco 6000w gen.
    System 2) 8 YingLi 250W panels, Midnight 200CC, three 8V Rolls batteries, Schneider Conext 4024 inverter (workshop)
  • robocop
    robocop Registered Users Posts: 115 ✭✭
    Hi Bill
    Checked with the manufacturer and the label was wrongly  printed so you are right
    You will hear from me when system is working

    thnks and regards

    bob
  • robocop
    robocop Registered Users Posts: 115 ✭✭
    Hi Bill
    Another question about cables
    Intent using 16mm/ 6awg  between each string of batteries ( 4x 12v/250ah) .
    each length of cable will be about 8 -9 inhes long.
    To interconnect to each string will used 4 awg  and from the batteries to the inverter 48v will use 2awg as lengt of 3 meter.
    Plse let me know if ok

    HAve a nice saterday

    Bob
     
  • BB.
    BB. Super Moderators, Administrators Posts: 33,402 admin
    The maximum continuous current from a 5.5 kWatt AC inverter on a 48 volt battery bank would be:
    • 5,500 Watts * 1/0.85 AC inverter eff * 1/42.0 volts batt cutoff = 154 Amps (pretty much worst case)
    From a 250 AH battery, the typical maximum current you can draw (reliably over time/state of charge) is around C/5 discharge rate (5 hour rate):
    • 250 AH * 1/5 hour rate = 50 Amps typical max current draw (2x that for a few second surge like starting a well pump)
    • 3x parallel strings * 50 amps = 150 Amps max continuous (math check)
    Using the NEC code (relatively conservative):
    https://lugsdirect.com/WireCurrentAmpacitiesNEC-Table-301-16.htm

    6 AWG is "good" for ~55 to 75 Amps using the North American Electrical code

    4 AWG is "good" for 70-95 Amps... (are you using battery to battery at 6 AWG, and each "string of batteries" at 4 AWG?)

    Using a voltage drop calculator... I would suggest around ~2 volts maximum drop (48 volt bus, i.e., 46 volt battery under load - 2 volt drop = 44 volts at load) on all the wiring... For example, 2 feet (one way) of 4 AWG @ 50 Amps:
    https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.1608&voltage=48&phase=dc&noofconductor=1&distance=2&distanceunit=feet&amperes=50&x=0&y=0

    Voltage drop: 0.0098
    Voltage drop percentage: 0.020%
    Voltage at the end: 47.9902

    And 10 feet (3m) @ 150 Amps @ 2 AWG:
    https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.5127&voltage=48&phase=dc&noofconductor=1&distance=10&distanceunit=feet&amperes=150&x=54&y=18

    Voltage drop: 0.47
    Voltage drop percentage: 0.98%
    Voltage at the end: 47.53

    2 AWG is a bit small for 150 amps (NEC 95-130 Amps)--But with exposed cable (not in conduit), I am sure it will not overheat...

    2 feet @ 6 AWG @ 48 volts @ 50 amps (battery interconnect):
    https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=1.296&voltage=48&phase=dc&noofconductor=1&distance=2&distanceunit=feet&amperes=50&x=30&y=12

    Voltage drop: 0.079
    Voltage drop percentage: 0.16%
    Voltage at the end: 47.921

    So, your numbers (as I guess at them), look fine.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • robocop
    robocop Registered Users Posts: 115 ✭✭
    Hi bill 

    I do have cables awaiting for the las 4 batteries.

    concern 12 batteries  of 12v 250ah 

    making 1 string of 4 batt  in parrallel/series   connecting to  another  ai 24v 250ah connecting to another string  of same 
    batt  parrallel/series to form  48v 500ah  and then again to a third string of same batt in parrallel to form  48v 1000ah.
    Can you give me  in picture how to connect to see if I do have it ok?
    Awaiting your reply

    Regards

    Bob  


  • BB.
    BB. Super Moderators, Administrators Posts: 33,402 admin
    Personally, I like to run 4x 12 volt batteries in series for 48 volts as a string. 48 volts @ 250 AH capacity per string.

    Then take the 3 (?) strings of 48 volts, and connect in parallel. 48 volts @ 750 AH total for bank.

    I am not sure your battery connections... Series connections add Voltage (only).

    Parallel strings add Amp*Hour (only).

    https://engineeringengineashar.wordpress.com/2015/08/23/how-to-make-series-and-parallel-connection/
    series and parallel connection

    To parallel battery strings, use this website's suggestion:

    http://www.smartgauge.co.uk/batt_con.html

    A DIY solar setup--The battery bus (one way to parallel):

    http://2manytoyz.com/battbank.html

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