Adding different solar panels to system

BillyBilly Registered Users Posts: 11 ✭✭

I currently have (4) Rene Solar JC250M-24/Bb panels two strings in series hooked parallel  going to a Bus bar then to Outback Flex 80.

 

I have acquired (4) Yingli YL290P-35b panels which I would like to hook up with the others, however they have different voc’s. I thought I could hook the other 4 like the first then tie them all together in the bus bar but think that would be too much voltage and might not be a good idea in the bus bar with one breaker in control box for all 8.

 Could I take the new panels and wire all parallel and keep volts same?

Is there a way to wire these all up not to go over the flex 80’s operating max of 150 volts, or do I need another Flex 80 wired in? And do I need a combiner box to hook them in?

I have 12 GNB flooded Classic NCX-13 battery's for a 24 volt system

I'm about 60 miles south of Houston Texas

  
  
 



Comments

  • EstragonEstragon Registered Users Posts: 3,336 ✭✭✭✭✭
    Can you post the panel specs?  The general rule of thumb seems to be voltage within ~10% or so is ok.

    If I'm reading correctly, you'd be adding another 2 series strings to the parallel connection, ,in which case you'd be roughly doubling the current but at about the same voltage.  The controller would likely be ok with the extra amps, but your existing wiring and breakers should be re-evaluated and upsized if needed.

    With 4 strings, you should have a breaker on each string before parallel combining at the buss.

    Between the buss and controller, wire and breaker would need to be sized for the extra input current, and controller to bank also checked for size.
    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
  • BB.BB. Super Moderators, Administrators Posts: 28,624 admin
    Look at Vmp and Imp for the panels... You can series panels that are within 10% of Imp (i.e., 5.0 amps with 5.5 amps Imp).

    For parallel, you want the panel/strings to match Vmp within 10% (i.e,. 30+33 Volt, or if in series, 60+66 volt Vmp parallel connections).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BillyBilly Registered Users Posts: 11 ✭✭

    the Rensolar is voc-37.4 isc =8.63  The Yingli voc=45.3 and isc = 8.62

    I have Not hook the Yingli in yet.


  • BB.BB. Super Moderators, Administrators Posts: 28,624 admin
    Really need Vmp and Imp to compare... But from what you typed, Isc (and by implication Imp) is close enough to combine the two different panels in series.

    For example, if you put 1x Rensolar in series with 1x Yingli panel, and you have 4 of each, then you can make 4x parallel strings with mixed Vmp-strings very nicely.

    http://www.solardesigntool.com/components/module-panel-solar/ReneSola/2136/JC250M-24-Bb/specification-data-sheet.html
    • Imp 8.31A
    • Vmp 30.1V
    • Isc 8.83A
    • Voc 37.4V
    http://www.solardesigntool.com/components/module-panel-solar/Yingli-Solar/2084/YL290P-35b/specification-data-sheet.html
    • Imp 8.1A
    • Vmp 35.8V
    • Isc 8.62A
    • Voc 45.3V
    So, you would have Vmp-a + Vmp-B = 30.1+35.8=65.9 volts Vmp-string

    And Imp string will be ~ 8.1 amps.

    The entire array would be:
    • Vmp-array= 65.9 volts
    • Imp-array=4*8.1a ~ 32.4 amps
    • Pmp-array~65.9v*32.4a= 2,135 Watt array STD rating
    Realistic (typical cool/clear day output):
    • 2,135 Watt STD * 0.77 panel+controller deratings = 1,644 Watts typical
    • 1,644 Watts typical / 29 volts charging = 56.7 amps typical best noontime cool/clear day peak/max current (vary rare to see more except in sub freezing weather
    You cannot really combine into 2x parallel strings... the Vmp-array~130 Volts Vmp-std is too high unless you are in a very warm climate (tropical island, etc.). In cold weather, that would exceed the ~140-150 VDC max Vpanel voltage for the the Outback.

    The only reason you really would want a higher Vmp-array voltage is so you can use smaller wire gauge for longer distances... For example, say you want 100 feet (one way run) from array to charge controller/battery bank/battery shed. Typically, we suggest between 1% and 3% voltage drop. Using a generic voltage drop calculator and Vmp-array 65.9 volts with Imp-array 32.4 amps:
    https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=1.296&voltage=65.9&phase=dc&noofconductor=1&distance=100&distanceunit=feet&amperes=32.4&x=61&y=15
    6 AWG:
    Voltage drop: 2.56
    Voltage drop percentage: 3.88%
    Voltage at the end: 63.34

    https://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=0.4066&voltage=65.9&phase=dc&noofconductor=1&distance=100&distanceunit=feet&amperes=32.4&x=61&y=22

    1 AWG
    Voltage drop: 0.80
    Voltage drop percentage: 1.22%
    Voltage at the end: 65.1

    As you can see, if you can get higher voltage (around 100 Vmp-array for this controller in a cool climate), you could use much smaller AWG for longer power runs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.BB. Super Moderators, Administrators Posts: 28,624 admin
    Looking at your battery bank, it appears that they are 2 volt @ 952 AH (C8) capacity cells. Our rules of thumbs are for C(20) discharge rates (20 hours from 100% to 0% state of charge) or very roughly around 1,070 AH at the C(20) rate.

    We recommend around 5% rate of charge minimum (weekend/summer seasonal usage). And 10-13%+ rate of charge for full time year round off grid systems.

    So, the solar array suggested based on battery charging specs would be:
    • 1,071 AH * 29.0 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 2,017 Watt aray minimum
    • 1,071 AH * 29.0 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 4,934 Watt array nominal
    • 1,071 AH * 29.0 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 5,244 Watt array "cost effective" maximum
    Your 2,135 Watt 8 panel mixed array is about the minimum I would suggest for your size of battery bank. As long as you charge during the day and use energy in the evening/night, it can work OK. You do need to monitor the specific gravity (state of charge) of your battery bank to make sure you get >~90% State of Charge at least once per week (a good starting point).

    You have not told us how much energy you use per day (by season)--But with your present setup, the battery bank would "nicely" supply, based on 2 days of storage and 50% maximum discharge:
    • 1,071 AH * 24 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 5,462 WH per day
    A nice amount of power.

    Your 2,135 Watt array would produce, daily, by month:
    http://solarelectricityhandbook.com/solar-irradiance.html

    Houston
    Average Solar Insolation figures

    Measured in kWh/m2/day onto a solar panel set at a 60° angle:
    (For best year-round performance)

    JanFebMarAprMayJun
    3.53
     
    3.87
     
    4.65
     
    4.98
     
    5.20
     
    5.20
     
    JulAugSepOctNovDec
    5.40
     
    5.24
     
    5.19
     
    4.75
     
    3.93
     
    3.51
     
    So, upcoming February (long term daily average), your array would produce:
    • 2,135 Watt array * 0.52 off grid AC system eff * 3.87 hours of sun per day (Feb) = 4,296 WH per day (Feb "break even")
    And the maximum AC inverter / solar array I would suggest would be around:
    1,071 AH * 500 Watts per 100 AH (at 24 volts) = 5,355 Watts typical maximum (flooded cell batteries)

    Although, a smaller AC inverter would be nice too (1/2 that size) for planning your usage. Really depends on your energy needs (large inverter waste more energy, large battery banks need more solar panels for "proper" charging).

    Anyway, using our rules of thumb as a starting point for a "reliable" cabin/small home design (anything equal to, or over ~3,300 WH per day is a nice size system for a very energy conservation minded home with Fridge, LED lighting, Washing machine, Well pump, Laptop computer, cell charging, LED TV, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BillyBilly Registered Users Posts: 11 ✭✭

    Thank you all so much for your reply.

    If I understand, hook the two different panels in series, then add all four to a combiner box like Midnight Solar's MNPV4-MC4 to protect each series string, then to bus bar to outback 80 .Then make sure outback charges at 29 volts.

  • mcgivormcgivor Solar Expert Posts: 2,656 ✭✭✭✭✭
    Billy said:

    Thank you all so much for your reply.

    If I understand, hook the two different panels in series, then add all four to a combiner box like Midnight Solar's MNPV4-MC4 to protect each series string, then to bus bar to outback 80 .Then make sure outback charges at 29 volts.

    The 29V charging voltage is an arbitrary value  to provide a rough calculation, always use the manufacturers recommendations if available, specifically for the application, standby charging values differ significantly from cyclical use.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    900W  3 × 300W No name brand Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal as a backup system. 
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergencies and welding.
  • BillyBilly Registered Users Posts: 11 ✭✭
    Right now I have my Outback 80 at absorb @27.6v Float @ 26.0v and Rebulk @ 22.5v  If I Equalize @ 31v one hour
  • mcgivormcgivor Solar Expert Posts: 2,656 ✭✭✭✭✭
    Billy said:
    Right now I have my Outback 80 at absorb @27.6v Float @ 26.0v and Rebulk @ 22.5v  If I Equalize @ 31v one hou

    Those values seem extremely low for a flooded lead-acid bank, float should be around 27V, recharge ~25V, the bulk/absorb  would be dependent on manufacturer’s recommendations, but I'm sure they would be closer.to  29V, give or take.
    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    900W  3 × 300W No name brand Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal as a backup system. 
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergencies and welding.
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