Should I wire panels in series or parallel?

cralls
cralls Registered Users Posts: 26 ✭✭
in Solar Beginners Corner #1
Hi All,

I'm having trouble deciding whether to wire my panels in series or parallel. The system is the following:

3 Sunvia OPT330-72-4-100 330W panels
Midnite Solar Classic Lite 200 MPPT Charge Controller
4 Interstate GC2-XHD-UTL 6v 232Ah batteries wired in series/parallel = 12v 464Ah
Magnum Energy MMS1012 1000W Inverter

The Midnite Solar Sizing Tool says I can wire it either way with the 200 controller but I'm interested in hearing which way some of you might wire it and why. Should I wire in series to keep the amps down or in parallel to keep the voltage down? This controller doesn't have arc fault so I suppose that's something to consider if that even makes a difference with this setup.
:: 3 - Suniva OPT330-72-4-100 Silver Mono Solar Panels | Magnum Energy MMS1012
:: Midnite Solar Classic 200 | 4 - Interstate 6V GC2-XHD-UTL
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Comments

  • littleharbor2
    littleharbor2 Solar Expert Posts: 2,113 ✭✭✭✭✭
    #2
     IMHO You would be better off going in parallel with this setup as your 24 volt nominal (72 cell) modules are already double your battery bank nominal voltage. I have the classic 200 as well and with my array of 9 72 cell modules in 3s x 3p my controller runs pretty warm, causing a lot of fan activity in warmer months. My system is a 24 volt setup  I am contemplating adding one more module and running in a 2s x 5p configuration. Your system @12 volts would really pushing your CC MPPT circuitry to it's limits with 3 72 cell modules in series into 12 volts..

    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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  • cralls
    cralls Registered Users Posts: 26 ✭✭
    #3
    Thanks littleharbor2 for that reply. I was kind of leaning toward parallel anyway. Good to know that I can add that many panels to this charger :) 
    :: 3 - Suniva OPT330-72-4-100 Silver Mono Solar Panels | Magnum Energy MMS1012
    :: Midnite Solar Classic 200 | 4 - Interstate 6V GC2-XHD-UTL
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #4

    Hi cralls,

    Agree that parallel is probably the best string configuration,  as 3 in series would have a string Vmp of about 108 V @ STC.  This is almost a 10:1 conversion ratio on a 12 V system.

    If the PVs are a considerable distance from the CC and batteries is probably the only reason to run three PVs in series.

    If you do not already own the Classic 200,  perhaps a Classic 150 would be a better choice if the PV-to-Power room distance is not great (IMO).

    With three PVs in parallel,   each of them should have a circuit breaker or fuse,  sized at the "Maximum Fuse Size" as stated on the sticker on the back of the modules,  (or in the PV Data Sheet from the manufacturer).  These breakers are usually mounted in  a Combiner Box,  at the array,  or near the power room,  if the distance from the PVs is short.

    FWIW,   Vic

    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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