Series vs parallel connection on outback fm60

mahendra
mahendra Solar Expert Posts: 188 ✭✭✭
edited October 2023 in Solar Beginners Corner #1
I know this probably came up on the forum before but I am puzzled if I am missing some knowledge on mppt charge controllers and solar panels.

The system is 12v off grid .All items mentioned are on hand .It’s just a question of the 10-60w panel configuration.

I have 10 60w bp solar panels with the following specs
STC Power Rating Pmp (W)60
Open Circuit Voltage Voc (V)21.0
Short Circuit Current Isc (A)3.87
Voltage at Maximim Power Vmp (V)16.8
Current at Maximim Power Imp (A)3.56
Panel Efficiency10.8%
Fill Factor73.8%
Power Tolerance-3.00% ~ 3.00%
Maximum System Voltage Vmax (V)600

My thought are to put these in two series strings of 5 to save on wire breakers ease of installation etc.

I friend of mine however ,advised against series strings and suggested that  5 parallel strings of two in parallel(basically 10strings on 5breakers) should be done basing  his ideas that each panel would not be protected by breakers and that there would be losses due to the series configuration.

I honestly do not see much merit in this .Please share your thoughts.Are the losses due to series strings justifiable?


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Comments

  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #2
    I would do 2 strings of 5 panels, This would allow you to setup without breakers of fuses other than perhaps 1 just before the Outback to use to isolate the charge controller. The charge controller will keep the batteries from back feeding the panels, and 2 strings of the same potential shouldn't be able to over power the other incase 1 has a short. 

    These are 15-20 year old panels, I think BP got out of solar 12-15 years ago. Might do a basic check to confirm the panels have reasonable output, just a voltage check and maybe a 12 volt fan...
    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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  • mahendra
    mahendra Solar Expert Posts: 188 ✭✭✭
    #3
    Already did.These are new in box purchase some 20years or so
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  • mahendra
    mahendra Solar Expert Posts: 188 ✭✭✭
    #4
    Thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    There were a bunch of BP solar panels recalled... The recall has since expired (around 2019) and I don't think the 60 Watt panels were included... Here is a list of included panels (by part number):

    https://www.bpsolarsettlement.com/classaction/bpsolar/documents/bps-settlement-agreement.pdf

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,102 ✭✭✭✭✭
    #6
    BP took over Solarex in April of 1999. 60 watt BP panels could be relabeled Solarex.

    That's pretty cool that you have new in box panels that old.

    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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  • SteveK
    SteveK Solar Expert Posts: 387 ✭✭
    #7
    Where you might want to consider your friend's advice of 2S5P is in a case like my oddly and heavily shaded application. With mega-oaks all around down in a wide shallow valley were the array will see considerable amounts of time partially shaded. Otherwise, as Photowhit suggests 5S2P is better in every other way.

    Bring those new old stock back to the real world!
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  • mahendra
    mahendra Solar Expert Posts: 188 ✭✭✭
    #8
    No shading . Only when it actually cloudy, or sunrise and sunset period which I think is out of anyone’s control.
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