parallel wiring and shading

I'm sure this is probably covered somewhere already but I can't seem to find it.
I am installing 3 kyrocera kc130 solar panels atop my sailboat. Generally there is no shading while at anchor or at the dock, but occasional shading while we are sailing. I am wiring the panels in parallel to each other. My question is do I need additional bypass diodes or is there another way to wire thes panels.

I appreciate all the help from everyone.
I love the website and the products you carry and info you share.

Thanks again,

Jeff

Comments

  • BB.BB. Super Moderators, Administrators Posts: 32,608 admin
    Re: parallel wiring and shading

    Nope--Just wire them in parallel (usually, if you have three or more panels in parallel, there should be one fuse/breaker per string to limit feed from the 2+ panels feeding a shorted panel).

    Solar PV panels only work well in full sun and no shade... A little shade can cause fairly dramatic loss of output current (no damage, just less output).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jeff gjeff g Registered Users Posts: 4
    Re: parallel wiring and shading

    Bill,
    Thanks for the info. Here in South Florida its usually very sunny most of the time. The only shade would be from the sails on the boat.
    Do I put the fuse before the charge controller or after on the battery side.

    Thanks again,

    Jeff
  • BB.BB. Super Moderators, Administrators Posts: 32,608 admin
    Re: parallel wiring and shading

    If you have three or more panels in parallel, the fuses/breakers are usually in a combiner box where all the + leads come in, each goes to a breaker/fuse, then to a common bus to the charge controller (- wires just go to a common bus, then a larger wire back to the charge controller).

    You do not need a switch or a fuse from the array to the charge controller itself--Although, a lot of people like to use a circuit breaker so they can turn off the array when servicing the controller.

    From the controller to the battery bank, short/heavy gauge wire (ideally, less than 0.05 to 0.10 volt drop--for accurate voltage reference back to the charge controller) to the battery bank.

    A fuse in the positive lead from the battery bank to the charge controller with wire and fuse ~1.25x to 1.56x (1.252) the maximum current expected from the charge controller--And the fuse/breaker should be close to the battery bank/+ bus connections (fuses/breaker protect wiring against over current--So you want the protective device near the source of high current--the battery bank in this case). The charge controller manual should give you acceptable wire and fuse ratings for your application.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jeff gjeff g Registered Users Posts: 4
    Re: parallel wiring and shading

    Bill,
    Everything there is perfect and is what I'm doing. However, I am not using a combiner box because of the limited room for the wire run from the panels the the controller.
    Is there any problem with this?


    Regards,

    Jeff
  • BB.BB. Super Moderators, Administrators Posts: 32,608 admin
    Re: parallel wiring and shading

    I am very sorry Jeff, I missed the three panels in parallel and fixated on two for some reason. :blush:

    I did a quick search for the Kyocera 130 watt panels and did not find a "series fuse" rating.

    The KC 140 Watt panel (PDF), which should be very similar has a series fuse rating of 15 amps.

    The 130 watt panel (PDF) has an Isc=8.02 amps (short circuit rating in full sun).

    So, you can see, two panels feeding a shorted third panel (dropped winch handle through glass panel), and they can feed upwards of 16 amps--but the series fuse rating is rated at 15 amps maximum (UL/NRTL Listing ratings).

    It is very close--Would I expect a fire if you feed 16 amps into a shorted panel rated at 15 amps--Not really. But, since we are on an open forum here, and this is your boat and your family/friends (fiberglass/wood under overheating panel/wiring--could be a scary situation), we do not recommend going against safety requirements.

    If you added a fourth panel (or more)--then, for sure, you should install fusing/breakers/combiner box.

    You are looking for a simple fuse/breaker holder--But water/salt water/spray/etc. is a tough environment. Getting some sort of Marine Grade setup (and install inside a cabin/dry area) is probably mandatory unless you do some sort of in-line fuse holder (and lots of self vulcanizing tape, etc.).

    Also, remember that fuses (and many breaker) work by getting hot--So you need to watch cooling. And, simple automotive fuse holders has been seen to overheat/fail even when carrying 1/2 of rated current in an off grid solar installation.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jeff gjeff g Registered Users Posts: 4
    Re: parallel wiring and shading

    Bill,
    Taking your advice. I will find a way to run the wiring to a combiner box in the battery locker with the correct short circuit amp breaker. Then a fuse on the battery side. I don't like to cut corners on this kind of stuff.

    Thanks for all the help!

    Jeff
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