parallel wiring and shading
jeff g
Registered Users Posts: 4
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
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
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
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
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
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
I am very sorry Jeff, I missed the three panels in parallel and fixated on two for some reason.
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
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