Confirmation of panel wiring

KerryKerry Registered Users Posts: 9
Please confirm which of the two wiring diagrams will optimize my new small PV system.

(4) 250 w panels, (each panel is rated 32.2 Voc. 8.3 amp).
(4) 6v, 232amp deep cycle batts configured for 12v
FM-80 Charge Controller
Prowatt SW1000 Inverter
Combiner Box
10 awg wires from panels to Combiner Box (distance from panels to Combiner Box less than 10')

Thank you,

Kerry

My components:
(4) 250w Canadian Solar panels with MC4 male & female connectors on each 3' 12 awg wire. (each panel is rated 32.2 Voc. 8.3 amp).
(4) 6v, 232 amp Deep Cycle batts configured for 12v using 2/0 cables.
(2) 2 awg cables from the batts to the e-Panel lugs.
(1) Flexmax 80
(1) ProWatt SW 1000 Inverter
(1) Midnite Solar e-panel MNE125ALT
(1) Midnite Solar-MNPV6 Combiner Box with (4) 15 amp circuit breakers.
(8) 10' 10 awg extension wires from the panels to the Combiner Box.
(1) Midnite Solar Surge Protector
SnapNRack corrugated roof fastening system.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Confirmation of panel wiring

    Have you bought any of this equipment yet?

    There are some issues.

    1). A 12 Volt system. If you can go 24 Volt, do: same number of batteries (four 6 Volts) and power with lower current.

    2). An FM80 is overkill for a 1kW array on 24 Volts unless you are planning on expansion. You would get about 32 Amps there. If you were going 12 Volt that would be 64 Amps so I can see why you'd pick the 80 Amp controller. You would not need that much array for 232 Amp hours @ 24 Volt or 464 Amp hours @ 12 Volt.

    3). You don't need an MNPV6 combiner if you go 24 Volt either, as you'd only have two parallel strings of panels.

    Your two thumbnails seem to show the same thing: two parallel strings of two in series. This would work for either 12 or 24 Volt (array Vmp around 60). The controller would be slightly more efficient with all panels in parallel on a 12 Volt system but the higher array current would increase losses in wiring.
  • KerryKerry Registered Users Posts: 9
    Re: Confirmation of panel wiring

    Hi Cariboocoot,

    Thanks for the detailed explanation. As you can tell I'm a complete novice.

    I already have the equipment and it is installed and appears to working fine.

    Presently I have (4) pos and (4) neg #10 awg wires running from the panels (a distance of ten feet) down to the combiner. In the combiner I have (4) 15 amp circuit breakers one for each PV panel. The four negative 10 awg wires go to the combiner's neg bus bar.

    I told my friend, who is off-grid, that I'm getting about 32-34 volts at the Charge Controller and he thinks the system would be more efficient if I fed it about 74v rather than the present 32-34V. Even though I've already strung the eight 10' wires down to the combiner I'd change the wiring if it could be more efficient.

    Re: "...thumbnails seem to show the same thing:" One diagram shows two wires running from the roof (1) pos and (1) neg, the other shows (4) wires running from the roof. I must not be understanding something.

    I got the FM-80 in case I wanted to expand years from now. At 76 I can't envision ever tying into the grid

    The system is solely for emergencies (charging a my e-bike batt, cell phone, Kindle, laptop, and tool batts). Here on the Big Isle of Hawaii we avg 2 power outages a month (mostly from falling trees). Shipping strikes and civil unrest are always a possibility in which case I suspect neighbors will want to charge their batts as well.

    Much appreciation,

    Kerry
  • TucsonAZTucsonAZ Solar Expert Posts: 136 ✭✭
    Re: Confirmation of panel wiring
    Kerry wrote: »
    Hi Cariboocoot,

    Thanks for the detailed explanation. As you can tell I'm a complete novice.

    I already have the equipment and it is installed and appears to working fine.

    Presently I have (4) pos and (4) neg #10 awg wires running from the panels (a distance of ten feet) down to the combiner. In the combiner I have (4) 15 amp circuit breakers one for each PV panel. The four negative 10 awg wires go to the combiner's neg bus bar.

    I told my friend, who is off-grid, that I'm getting about 32-34 volts at the Charge Controller and he thinks the system would be more efficient if I fed it about 74v rather than the present 32-34V. Even though I've already strung the eight 10' wires down to the combiner I'd change the wiring if it could be more efficient.

    Re: "...thumbnails seem to show the same thing:" One diagram shows two wires running from the roof (1) pos and (1) neg, the other shows (4) wires running from the roof. I must not be understanding something.

    I got the FM-80 in case I wanted to expand years from now. At 76 I can't envision ever tying into the grid

    The system is solely for emergencies (charging a my e-bike batt, cell phone, Kindle, laptop, and tool batts). Here on the Big Isle of Hawaii we avg 2 power outages a month (mostly from falling trees). Shipping strikes and civil unrest are always a possibility in which case I suspect neighbors will want to charge their batts as well.

    Much appreciation,

    Kerry

    Going 48v from the panels and 24v with the batteries would certainly make your life easier but I see you already have an inverter and may not want to go that route. 72v down to a 12v battery bank wouldn't be more efficient it would be less in terms of the power you're converting from the solar panels to the battery bank, you would want to do 24v to 12v, 48v to 24v, 72v to 48v and try to avoid the more extreme differences like 72v to 12v.
  • vtmapsvtmaps Solar Expert Posts: 3,738 ✭✭✭✭
    Re: Confirmation of panel wiring
    Kerry wrote: »
    I told my friend, who is off-grid, that I'm getting about 32-34 volts at the Charge Controller and he thinks the system would be more efficient if I fed it about 74v rather than the present 32-34V.

    As Cariboocoot and TucsunAZ have mentioned, your friend is wrong about that. If the distance between the panels and the controller was long, and the wires too thin, there might be some advantage to making the modification.

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
  • KerryKerry Registered Users Posts: 9
    Re: Confirmation of panel wiring

    Thanks,

    Just to be sure I understand, the ideal for my components—

    (4) 6v, 232 Ah Deep Cycle batts
    Flexmax 80 Charge Controller
    ProWatt SW 1000 Inverter

    —is to configure the batts for 24v and the panels for 48v?

    If yes, I sure would appreciate a wiring diagram because I don't know how to wire the panels so that I deliver just 48v to the Charge Controller. My mind goes blank with the words series, parallel, series-parallel.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Confirmation of panel wiring
    Kerry wrote: »
    Thanks,

    Just to be sure I understand, the ideal for my components—

    (4) 6v, 232 Ah Deep Cycle batts
    Flexmax 80 Charge Controller
    ProWatt SW 1000 Inverter

    —is to configure the batts for 24v and the panels for 48v?

    If yes, I sure would appreciate a wiring diagram because I don't know how to wire the panels so that I deliver just 48v to the Charge Controller. My mind goes blank with the words series, parallel, series-parallel.

    Yes, but: you have a 12 Volt inverter already and that will not run from a 24 Volt battery bank.

    With all the equipment already in place you're best off leaving well enough alone.
  • KerryKerry Registered Users Posts: 9
    Re: Confirmation of panel wiring

    Thanks, yes, I forgot that the Prowatt SW-1000 requires a 12v bank.

    Much appreciation,

    Kerry
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