New Setup

schwy
schwy Registered Users Posts: 9 ✭✭
in Off Grid Solar & Battery Systems #1
Hi. I am very new to solar and this board. Just wanted to have you guys check out the setup I have and see if it is setup correctly. My location is in northern Wisconsin. It is an off grid hunting/vaction cabin. I have two 315watt Kyocera panels wired in parrallel to an Outback FM60. The distance is 35feet. It charges a battery bank consisting of 4 6volt golf cart batteries (232aH). Batt 1 and batt 2 are in series and batt 3 and batt 4 are in series. All 4 wires (2neg 2 pos) run to a 12volt 1000watt sine wave inverter which is then tied into the cabins circut panel. The PV power and battery power are protected by DC breakers. My main question is should I be running my panels in a series or as they are? Thanks for taking a look.
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  • Desert Rat
    Desert Rat Solar Expert Posts: 147 ✭✭✭
    #2
    Re: New Setup

    What gauge wire are you running from the array to the FM60?
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  • schwy
    schwy Registered Users Posts: 9 ✭✭
    #3
    Re: New Setup

    It is the same as what the panels had wired from the factory which I believe is 10 gauge (4 wires 2 pos 2 neg). There is 8 gauge running to the batteries from the charge controller ( 2 pos 2 neg).
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #4
    Re: New Setup

    Sounds like you have 2 strings of batteries in a 12 volt configuration? 35 feet is a ways, the panels are 12 gauge leads, I'd much rather you have a combiner box near the panels or even just MC4 'Y's or Branch connectors and then a water proof box to switch to 10 or 8 gauge wire to bring a single pair to the charge controller. I'm too tired and lazy to see what the voltage drop is over 35 feet. The 39 volt VMP of the panels should be a good voltage for maximum efficiency through the charge controller.

    I'd also rather see a single pair of wires from the charge controller to the batteries. Pairs of wires going the same place can invite problems.
    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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  • AzSun
    AzSun Registered Users Posts: 13 ✭✭
    #5
    Re: New Setup

    Also, when a battery change is due, ok to series them but not a good idea to parallel. As with paralleling anything, current does not always divide evenly as you would expect. You could end up with one set being undercharged. The stronger half of the set will also be contiuously discharging into the weaker half, albiet at a low rate. You could series the panels and have less line losses, but you would be dealing with open circuit voltages just short of 100. It looks like your controller is rated up to 150. If you go this route, make sure everything is up to code as far as insulation rating, grounding, etc. Always follow manufacturers instructions. As Photowhit stated, 39 VMP looks like a good match in itself.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: New Setup

    The panel issue:

    These 315 Watt Kyoceras run a Vmp of 39.8 and an Imp of 7.9. So two in parallel would be 16 Amps @ 40 Volts. On 10 AWG over 35 Feet would work with a minimal Voltage drop over the distance. If you raise the array Voltage by wiring the panels in series the efficiency of the charge controller will drop a small amount.

    The battery issue:

    Properly wired (negative leads on one string, positive leads on the other) two battery strings in series poses no large problem with current sharing.
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  • Desert Rat
    Desert Rat Solar Expert Posts: 147 ✭✭✭
    #7
    Re: New Setup

    With the panels in parallel and 10 ga. wire, I figure a voltage drop of 2.79% over 35 feet. If it were me I would either increase the wire size or connect the panels in series.
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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #8
    Re: New Setup
    Desert Rat wrote: »
    With the panels in parallel and 10 ga. wire, I figure a voltage drop of 2.79% over 35 feet. If it were me I would either increase the wire size or connect the panels in series.

    If I read the OP's posts correctly, each panel has its own set of wires. At 70 feet and 8A, it's only 0.56V drop, less than 1.5% at 40V. This is about 4W loss - not something worth worrying about.

    Re-wiring in series would double the voltage, but leave the same drop, so savings would be only 0.7%. It is most likely less than additional losses in CC because of the higher incoming voltage.

    Therefore, I suggest leaving it as it is.
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  • Desert Rat
    Desert Rat Solar Expert Posts: 147 ✭✭✭
    #9
    Re: New Setup
    NorthGuy wrote: »
    If I read the OP's posts correctly, each panel has its own set of wires.

    I stand corrected. I was assuming both panels through one pair of 10 ga. wires.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #10
    Re: New Setup

    Well the OP said "...It is the same as what the panels had wired from the factory..." those panels have 12 gauge wires.

    I don't think he states how he's bringing the array to the CC. He does say he has the batteries wired with separate wires running to the inverter... or at least that's my read...

    ...perhaps we could get some clarification?
    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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  • NorthGuy
    NorthGuy Solar Expert Posts: 1,913 ✭✭
    #11
    Re: New Setup
    Photowhit wrote: »
    I don't think he states how he's bringing the array to the CC. He does say he has the batteries wired with separate wires running to the inverter... or at least that's my read...

    I think he does:
    schwy wrote: »
    It is the same as what the panels had wired from the factory which I believe is 10 gauge (4 wires 2 pos 2 neg).
    Photowhit wrote: »
    Well the OP said "...It is the same as what the panels had wired from the factory..." those panels have 12 gauge wires.

    ...perhaps we could get some clarification?

    I agree. This could be #12 wire, which increases all voltage drops and power losses 1.5x. It's always better to know the exact wire size. Must be printed on a side of the wire.
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  • schwy
    schwy Registered Users Posts: 9 ✭✭
    #12
    Re: New Setup

    Thanks for all the replies. Learning a lot. I just checked my receipt from Alt . E and the wire is 10 gauge. The parallel connection for the panels is made in the charge controller which is approximately 35 feet from the panels. Each panel has its own set of DC breakers.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #13
    Re: New Setup

    So each of the two panels has its own 10 AWG wire set running to the controller? That will be no problem handling the current and Voltage drop issues.
    Each panel has its own set of DC breakers.

    In this context "set" implies more than one, indicating each panel has two breakers on it. With only two panels you don't actually need any breakers, much less two per panel.
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  • schwy
    schwy Registered Users Posts: 9 ✭✭
    #14
    Re: New Setup

    Yes each panel has a set of 10 gauge wires.I know a set of breakers per panel is overkill but I thought it might be an advantage if one panel was damaged then I could shut it off at the breaker and still keep the other one in service.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #15
    Re: New Setup

    If you have two panels in parallel the only situation that could cause a problem is if one shorts and thus pulls current from the other (this is the reason for CP on parallel panels).

    It won't hurt to have a circuit breaker on each panel. But one per; don't make the mistake some do and put a breaker on each positive and each negative lead.
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  • schwy
    schwy Registered Users Posts: 9 ✭✭
    #16
    Re: New Setup

    I currently have all my wires from my PV on seperate breakers. 4 breakers. 2 for positive and two for negative. If I understand your reply this is incorrect. I should not have my negative wires breakered. Correct? If so what problems does this cause?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #17
    Re: New Setup
    schwy wrote: »
    I currently have all my wires from my PV on seperate breakers. 4 breakers. 2 for positive and two for negative. If I understand your reply this is incorrect. I should not have my negative wires breakered. Correct? If so what problems does this cause?

    It is a waste of breakers.
    An electrical circuit is a loop consisting of a power source, a load that makes use of that power, and the wires connecting the two. The purpose of the circuit breaker or fuse is to prevent an excess current state from causing a fire by being the first part of the circuit to "give up" if the current goes too high. A breaker on the positive wire between the power source and the load will accomplish this; another breaker on the negative wire is redundant as the power flowing through it is the same as flows through the positive side.

    It is not the same as with a 240 VAC circuit or 'floating' AC/DC circuit which utilize dual (common trip) breakers to shut down both sides of power to prevent any further risk of short-circuit.

    Note that arrays which make use of the new NEC ground-fault and/or arc fault regulations will have these dual breakers as well for the same purpose.

    But two individual breakers or fuses, one on positive and one on negative, serves no purpose.
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  • schwy
    schwy Registered Users Posts: 9 ✭✭
    #18
    Re: New Setup

    Got it. Thanks a ton for your help.
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