For the cable entering the j-box I use a waterproof cable clamp. I pick them up at my local electrical supply house for about $3.00 each.. Well worth the expense. They work best if you use a round cable. If using 4GA or larger cable each wire gets its own water tight entrance to the j-box.
Most marine wire is not UV stabilized. Despite the lack of UV inhibitors it can still last in the five to ten year range out in the sun, depending upon where you are. A UV stable SOW, STW, STOW, SEOW, or STOOW type cable can work well and can often be ordered in sizes up to 6/2. These cable types are the same or similar jacketing used in shore power cords and they hold up quite well in solar applications..
The Water Tight Cable Clamp
Here's a close up.
Series or Parallel Wiring ..?
In this photo I am getting ready to install two 140W Kyocera panels for a nice 280W array capable of delivering about 70Ah's + per day to the battery bank, in Maine. They have been wired together in parallel as evidenced by the gray duplex wire running between them for the best performance.
I get asked quite often about wiring multiple panels together. "Should I wire them in series or in parallel?" is the most often asked question I get. My answer to that question is almost always to wire them in parallel, on a sailboat..
Why? Because mono or polycrystalline panels are made up of a series or a daisy chain of solar cells. If you block one of these cells it acts much like a plugged sink drain stopping or greatly minimizing the "flow". Blocking just a small portion of one cell, with shade, can cut the output of both panels, if they are wired in series. The answer to this question is far more complex and requires actual testing on YOUR BOAT to determine the best overall performance. For the most part though you can do very, very well by wiring the panels in parallel.
By wiring the panels in parallel the shaded panels drop in output will not affect the other panels output if it is not shaded. When shading occurs across one small area of two series wired panels the output of both can be greatly affected. When shading occurs across one of the two panels in a parallel wired array the other panel still pumps out its current unaffected by the shaded one.
In a perfect lab type scenario series panels with an MPPT controller work really well. Sailboats however are any thing but perfect when it comes to shade. Parallel wiring of multiple panels is often the best scenario on a sailboat but not in every case. If you really want to know what is best on your boat for your use then it will need to be measured over time.
Shade, the big "S" word in solar systems, is a real enemy. In this short video we can see the % output drop by shading just a small corner.
Effect of Shade On Panel Performance
As can be seen in the video even a small amount of shading drastically cuts into the output performance.
Wire The Controller
A solar panel sized to actually "re-charge" a bank, not just maintain it, should ideally be routed directly to the house bank. The white jacketed wire coming into this Genasun controller is the panel feed. The connections are easy and clearly labeled on most controllers. Hooking them up is the easy part.
The black & red wires leaving the controller go to the house bank. The red wire is "switched" so the panel can be turned off if needed. Check with your controller manufacturer to see where an ON/OFF switch can be installed if you want the ability to flip the panel OFF. ON/OFF switches are normally installed on the battery/output side of a controller but this can vary from manufacturer to manufacturer.
There is also a fuse in the red wire between the battery bank and switch, that can't be seen. It is installed close to the battery + post. When connecting anything directly to a battery bank the wire should be fused. The ABYC suggestion is for the fuse to be within 7" of the + post of the house bank. While not always possible to be within 7" try to get it as close as possible.
If you have a secondary starting or reserve bank you can then use a device like an Echo Charger or an VSR type relay to charge the start or reserve bank and keep it topped up. Even without a solar panel an Echo Charger or VSR are useful devices.
Some charge controllers, such as the Morningstar SunSaver Duo PWM, can charge two banks simultaneously. This is a nice feature if you don't have an Echo Charger or VSR to charge two banks from one array.
When bringing the solar panel wires into the boat it's a good idea to enter the boat with a "drip loop". Deck and fitting leaks happen, it's just the nature of boats, and even "cable clams" can leak.
In the event of a leak the last thing you want is for the leaking water to migrate along the wire all the way to the controller, or another device near the wire that should not come in contact with water.
As always secure the wire well with wire ties on its path to the controller. This one mounted to the underside of the cockpit sole with Weld Mount tabs and wire ties.
Mounting The Panels
For mounting the panel shown in the first photo I used standard marine canvas parts. This is a standard SS deck hinge fitting. Simply drill the frame and mount two hinge fittings.
In this photo I am showing the back side of the frame mounts. I used some SS fender washers to stiffen the aluminum frame a bit and nyloc nuts so they don't work loose. A little Tef-Gel under the washers seems to prevent stainless/aluminum interface corrosion.
Articulating Deck Mount
This is a foot designed for dodger or bimini mounting on an uneven surface. They are hard to find but most any sail or canvas maker could source it. They are not cheap however. This one runs about $35.00 retail.. The nice thing about this mount is the plastic bushing that isolates it from the aluminum.
The articulating deck hinge accepts the angled 1" support bar and makes for a nice neat looking install.
Tube End Fitting
The tube end fitting simple attaches to the articulated deck hinge and accepts the 1" support bar.
It is a good idea to use TefGel or another dissimilar metals corrosion blocker, such as Lanocoat, on the SS set screws.
1" Split Rail Clamp
These rail fittings are the cats meow. They are a two piece SS clamp that fits over a 1" piece of SS tubing. They are also available to fit 7/8" tube. Clamp them over the rail and attach them to the panel deck hinges previously mounted to the panel as shown. Once everything is adjusted and aligned tighten the clamp set screw.
If you click on the photo to make it larger you can see the details of the split rail clamp a little better.
TefGel is one of the best products on the planet to prevent thread galling and seizing of stainless steel fasteners. When using TefGel I have never once had a thread galling situation with SS. Thread galling is when the stainless steel nut & bolt seize together for no apparent reason. Any one who's worked with stainless for long enough has experienced this nuisance. Coat the threads and under the screw head and they will tighten smoothly and without issue.
You can see the TefGel under the screw head here. TefGel also virtually eliminates the corrosion form
ed by using SS fasteners in aluminum!!
The Finished Panel Installation
This little 30W panel will keep this boats small bank topped up just fine. It is out of the way and easy to remove if needed. Alternatively an adjustable strut could be used to angle the panel towards the sun if you wanted. This one is fixed as the owner simply doesn't want to mess with it.