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Homeless_by_Cho's avatar
Homeless_by_Cho
Explorer
Jun 22, 2015

Please Review/Comment on my proposed solar install

I am presently mounting two solar panels on my truck camper roof, wiring them in series to a controller, and then to two deep cycle batteries (each 105 A-Hr). I plan on putting a 15 Amp fuse between the solar panels and the controller and a 30 amp fuse between the controller and the batteries.

I have read so many threads on RV.Net and other forums that I am somewhat confused and have very low confidence in what I am doing. So my question is: “Is this reasonable?” Or “Have I made a bad wiring decision?”

Two Kyocera KD140SX panels wired in series. Each panel:
Rated Power: 140 watts
Open circuit Voltage: 22.1vDC
Short circuit current: 8.68 amps
Voltage at load: 17.7vDC
Current at load: 7.91 amps
Factory installed bypass diodes: 8

One Blue Sky Energy – Solar Boost 3000i Controller
Nominal Battery voltage: 12vDC
Automatic Output Current Limit: 30.0A with 36 cell PV and 22.0A with 60 cell PV input
Max Isc/Power: 24A/400watt and 11.8A/290watt
Max Battery & PV Voltage: 50.0vDC (Recommend max PV Voc <40.0vDC)

All comments are gratefully appreciated.
LeRoy

7 Replies

  • 3_tons's avatar
    3_tons
    Explorer III
    Jun 23, 2015
    CJW8 wrote:
    Don says you may not want to bother with MPPT but I disagree. Why throw away 10-15% of your solar production by not going MPPT?


    X2, MPPT will dynamically optimize harvest by lowering the voltage while maximizing the current... With battery recovery it's all about current - voltage is the slave...
  • jrnymn7's avatar
    jrnymn7
    Explorer
    Jun 22, 2015
    CJW8 wrote:
    Don says you may not want to bother with MPPT but I disagree. Why throw away 10-15% of your solar production by not going MPPT?


    Homeless,

    If the controller cannot handle the combined Voc of the two 12v panels in series, but only in parallel, then there is very little voltage (Vmp) for the mppt to work with.

    The Tracer BN Series mppt's have a 150v Voc input rating, which easily handles 12v panels in series.

    Tracer 30a mppt c/w remote monitor

    If there is room, I would go with 24v panels for a rooftop install... for considerably more wattage. You can run them in series during cool cloudy weather, (when Vmp is higher and Imp is lower); and in parallel during hot sunny weather, (when Vmp is lower, but Imp is higher).

    12v panels are smaller and lighter, and thus make for a good portable pwm system.

    I use these for "fusing" and switching:

    high amp audio c.b's
  • CJW8's avatar
    CJW8
    Explorer
    Jun 22, 2015
    Don says you may not want to bother with MPPT but I disagree. Why throw away 10-15% of your solar production by not going MPPT?
  • Muddydogs's avatar
    Muddydogs
    Explorer
    Jun 22, 2015
    I use a fuse between my panels and controller just to have a off switch. I figured it was easier to wire in a spade fuse holder then mess with a switch. Your install might very but if you disconnect the batteries or need to do some work with the batteries and cables your solar panels will keep things charge unless you cover the panels or unhook them from the controller so I made it easy as all I have to do is pull the spade fuse from the holder which is next to the controller.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Jun 22, 2015
    Hi,

    You may wish to not bother with an mppt controller. I also would not fuse between panels and controller, but I would have a switch.

    I would use a controller that has a temperature compensation probe that goes to the battery bank.
  • Homeless_by_Cho's avatar
    Homeless_by_Cho
    Explorer
    Jun 22, 2015
    smkettner wrote:
    Manual page 8 says max 40 Voc so you need those panels in parallel or you are at 44.2 volts. Or a different controller?
    MC4 parallel connectors will make this easy. (I assume panels have MC4)
    No fuse needed from panel to controller. I would have 40 amp fuse close to battery and at least #6 wire for battery connection.


    smkettner,
    I will wire panels in parallel and drop the fuse between the panel and the controller. These panels have a terminal strip mounted on the bottom, no MC4 connectors. I will use a 40 amp fuse at the battery and 4 gage wire which I have left over from another project.

    Thank you for your comments.
    LeRoy
  • time2roll's avatar
    time2roll
    Nomad
    Jun 22, 2015
    Manual page 8 says max 40 Voc so you need those panels in parallel or you are at 44.2 volts. Or a different controller?
    MC4 parallel connectors will make this easy. (I assume panels have MC4)

    No fuse needed from panel to controller. I would have 40 amp fuse close to battery and at least #6 wire for battery connection.

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