Distances and wiring

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drsockmonkee
drsockmonkee Registered Users Posts: 12 ✭✭
in Solar Beginners Corner #1
Hi,

I have a garden shed that I am playing with solar on.

I have a

Renogy Solar Charge Controller 12V/24V Auto MPPT

with two Renogy 100w solar panels wired up (positive wires into an adapter that will allow for you to wire two panels together into the same pair of wires)  to my charge controller.

It is on top of my shed and the battery bank is two cheesy batteries from COSTCO in a toolbox in the back of the shed.

of course my neighbor planted a tree right against the fence and it is now shading my panels.

I am thinking of relocation of the panels, but I do not want to put them on my house.

How far do you think I could run the wires from the panels to the charge controller?

thanks.

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  • Wheelman55
    Wheelman55 Registered Users Posts: 251 ✭✭✭
    edited May 2022 #2
    OP. I use this app to calculate wire size needed over a specific distance. 


    You need to choose max voltage drop (3% is the norm), then plug in the distance in feet, voltage (VOC) and amperage (ISC) that you’ll be sending. The app will tell you what gauge wire you need. 

    Simple. 


    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    #3
    sorry... I am such a goof.  I do not know what to put.
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  • Wheelman55
    Wheelman55 Registered Users Posts: 251 ✭✭✭
    #4
    OP. For voltage put in the VOC and for amps put in ISC. These numbers are in the back of your Renogy panels. 

    BTW. 12 volts is quite likely not the correct ISC. 

    Question. Are you running your two panels in series?  If in series you double the VOC (voltage) number. Amps stay as listed on back of panel. 

    If you have the two panels wired in parallel you double the ISC (amps). Volts stay as listed on back of panel. 

    Clear as mud;)
    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    #5

    the wire I have is like this.

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  • Wheelman55
    Wheelman55 Registered Users Posts: 251 ✭✭✭
    edited May 2022 #6
    OP. Take a picture of the label on the back of your panels and post to this thread. 

    Or attach a link to the panels like you did for the wires. 
    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    #7
    @Wheelman55
    I have two 100 watt panels that I have in series.  (positive from both into an adapter then out of one wire onward)  then on to the solar charge controller
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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    #8
    my panels are these...

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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    #9
    found this... but....
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,696 admin
    #10
    I have another wire calculator... At least I know how to use this one.  :)

    And Costco batteries are generally pretty good for the price. Need to know which batteries you got. Normal "car batteries" should not be deeply cycled as they will not last very many years.

    6 volt @ 200 AH "golf cart" batteries are a good deal and will last 3-5+ years.

    Assumptions:
    • 2 x 100 Watt panels
    • 100 Watts / 17.5 Vmp (voltage max power) = 5.71 Amps Imp current max power (close enough for most panels)
    • 2 * 17.5 Vmp = 35 volts Vmp
    • Imp = 5.71 amps
    Normally, we aim for 1-3% voltage drop. In your case, you can have more drop (long runs with small diameter wire) if copper is "too expensive" for your project.

    For the calculator, lets say you are running 40 feet (one way run) on 10 AWG wire:

    https://www.calculator.net/voltage-drop-calculator.html?necmaterial=copper&necwiresize=2&necconduit=steel&necpf=1&material=copper&wiresize=0.4066&resistance=1.2&resistanceunit=okm&voltage=35&phase=dc&noofconductor=1&distance=40&distanceunit=feet&amperes=5.71&x=40&y=20&ctype=nec

    Result

    Voltage drop: 0.54
    Voltage drop percentage: 1.55%
    Voltage at the end: 34.46

    So, 2x panels in series, 40 feet one way run, on 10 AWG copper cable... Looks good (1.55% voltage drop).

    Generally, tilt the panels to your latitude for best year round harvest. You can use a solar calculator to estimate your average hours of usn per day by month (nearest major city)

    http://www.solarelectricityhandbook.com/solar-irradiance.html

    For example, to calculate your daily harvest... Say 5 hours of sun (good summer number for most places):
    • 200 Watt panels * 0.61 off grid DC solar system efficiency * 5.0 hours of sun = 610 WH per day
    • 610 WH per day / 14.5 volts charging = 42 AH @ 12 volt battery bus
    Some quick estimates (assuming NO SHADE on panels).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    edited May 2022 #11
    6 volt golf cart

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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    #12

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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    #13

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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    edited May 2022 #14
    the old charge controller is dead... it got replaced a couple of days back... and I am thinking of 'growing' the system..

    question is what part, and do i need to actually do some 'real' planning/learning.. the initial effort was kind of Meh...

    Grow the battery pack?
    Grow the 'Array'?
    Move the system?  (damn neighbor)

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  • Wheelman55
    Wheelman55 Registered Users Posts: 251 ✭✭✭
    #15
    OP. You are in good hands now with Mr. BB:)
    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    #16
    @Wheelman55
    Texas... East of Rockwall

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  • drsockmonkee
    drsockmonkee Registered Users Posts: 12 ✭✭
    #17
    @BB.
    Do you have an insight as to what is the most important component to pay attention to?

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  • Wheelman55
    Wheelman55 Registered Users Posts: 251 ✭✭✭
    #18
    drsockmonkee said:
    @Wheelman55
    Texas... East of Rockwall

    Texas…Terlingua..way offgrid. 
    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
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  • Wheelman55
    Wheelman55 Registered Users Posts: 251 ✭✭✭
    #19
    drsockmonkee said:
    @BB.
    Do you have an insight as to what is the most important component to pay attention to?

    Your loads…meaning what do you want to power?
    Off-Grid in Terlingua, TX
    5,000 watt array - 14 CS 370 watt modules. HZLA horizontal tracker. Schneider: XW6048NA+, Mini PDP, MPPT 80-600, SCP. 390ah LiFeP04 battery bank - 3 Discover AES 42-48-6650 48 volt 130ah LiFePO4 batteries
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,696 admin
    #20
    The battery (bank) is the "heart" of your system... So understanding how to size the battery for your needs is critical.

    You can estimate your loads (Watts * Time; Amps * Time * Working Voltage) etc... Or you can measure the loads too using different types of meters...

    DrSock. How familiar are you with Volts, Amperes (Amps), Amp*Hours, Watts, Watt*hours, and such? And are you OK with basic Math (simple algebra)?

    I have no issue with helping you learn... But I do want to understand your level of electrical experience so I don't frustrate you with too simple or too advanced for you at this point.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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