Case Study: Time to Go Solar by Ed Eisen

Time to Go Solar

by Ed Eisen

It's midsummer. We're at our favorite anchorage, and it's another perfect day on the water. What makes it even better, is waking to the smell of coffee my wife started a few minutes ago. I crawl out of bed and slither up to the cockpit, cup in hand. What a view. We can see the mainland and a few boats throwing spray on a glassy blue ocean. Just as I raise my cup I think, “Damn, I forgot to start the generator.” The ole Honda 2000 is fairly quiet, but it is still not my favorite sound as I enjoy the morning. The other time I have to hear the generator is when the sun has transited to the other side of the boat, and I'm ready for happy hour. We bought the Honda when they were all the rage, and it has been a wonderful alternative to charging with the boat's diesel for the last ten years. Lately, I have felt a growing envy of my fellow boaters with solar power. So, after our typical family debate on cost versus benefits, my wife and I decided to add solar and more silence to our 2005, 43 foot Jeanneau.

We started from scratch and spent many hours studying the concepts and equipment necessary. We are far from solar experts, rather just retired boat owners who wanted a quiet way to charge batteries. If you are a first time, solar-do-it-yourselfer like us, I hope this short story of our installation will be of interest.

Sizing the system

While at the San Diego Boat Show, we visited the Sun Powered Yachts booth. We learned about their panels and reviewed a list of possible power requirements on our boat to determine how much solar wattage we needed. For us, the big items are the refrigerator and freezer. We use the freezer more as a beverage cooler, still two refrigeration units are the biggest draw on our boat. All lights are LED's so not much draw there. The other considerations were that we had easy space for two panels on our bimini and two were all we had budgeted for. With little more thought to sizing, we purchased 2x SunPower 110 Watt panels that we were optimistic would satisfy our needs.

Acquiring parts and a plan

The panels were our major single purchase, but we soon realized much more is needed to complete an installation.

1. How will the panels fasten to the bimini?

2. How to position the panels?

3. Will they connect in series or in parallel?

4. What size wire do I use

5. Where do I run the wires?

6. How do the wires enter the boat?

7. How do I switch the system on and off?

8. What kind of charge controller is best and where should it be mounted?

9. How do I protect the system from overload?

The picture shows most of the additional parts I purchased. It turned out I did not need a few.

1. Fastening the panels to the bimini

There are six grommets on each solar panel used for holding it to a surface. With two panels, I had 12 grommets. They have an inner diameter of 5/8 inch which meant I needed a ¼ inch diameter fastener. I discussed fasteners with both Sun Powered Yachts and my canvas guy, Tom Anderson (Custom Marine Canvas by Tom). Lyall at Sun Powered Yachts suggested using LOXX fasteners which appeared to be a quality and elegant solution. However, it was going to cost $75 for the 12 fasteners I needed.

Canvas Tom suggested an elegant and economical solution, a nylon bolt with rubber washers to sandwich the canvas and stainless steel washers to sandwich the panel. I liked this approach.

I bought twelve ¼ inch nylon bolts and nuts, 24 stainless steel washers (nylon was too flimsy), 24 stainless fender washers, 12 stainless locking nuts and 24 rubber washers for a total of about $20.

Any fastener will require a hole in the canvas, in this case ¼ inch diameter. Canvas Tom suggested purchasing a hobby style soldering iron for $3.99 at Harbor Freight Tools. The soldering iron is exactly ¼ inch in diameter. When heated it passes through the canvas (Sunbrella in my case) like butter and leaves the threads melted so they will not unravel. The soldering iron turned out to be a great way to achieve our holes and without removing the canvas.

The hardware goes together in the order shown in the picture above, bolt, ss washer, two rubber washers, ss washer, nylon nut, two fender washers and the lock nut. The canvas is sandwiched between the two rubber washers and bolted tight. The rubber avoids chafing on the fabric and gives additional protection to the holes to avoid fraying. The panels are sandwiched between the fender washers and held tight with the lock nut.

This picture shows two bolts fastened to the canvas and ready for a panel. (Hint: I found the rubber washers in the plumbing department of the hardware store. They are actually replacement faucet washers. I enlarged the hole to ¼ inch.)

Viewing the bolts from under the bimini, my wife and I were very pleased that they blended in well and were not obvious. In fact, only one row is visible as the others are inside a zipper channel that holds the bimini support.

With the panels mounted, you can barely see them. I took this picture holding the camera as high as I could. At normal height, you might not even notice them.

2. Positioning the Panels

We were aware that shading affects solar performance, so before mounting the panels we experimented with placement. Using a multi-meter to measure volts and amps, we shaded the panels with our double back stays, the boom, the mast and radar and a big piece of cardboard. We had watched a YouTube video showing the effects of shading being about a 40% decrease in performance Our testing (not to be confused with scientific testing) showed a decrease of only about 5 to 10%. At this point we were glad we bought SunPower solar panels because they are obviously the evolved generation. We decided that the shading effect was so small, that we would mount our two panels simply based on where we thought was the most convenient and aesthetic location.

3. Connect in Series or Parallel

We decided to connect the panels in parallel because shading has less affect this way. Potentially there is more current loss in parallel, but our wire run was short enough we didn’t think the loss was significant.

4. Wire Sizing

There are online charts we used to help calculate wire size based on various factors including length of run. Our run was short. It’s all in the back third of a boat! We used 10 gauge wire which is larger than needed, but over sizing would help eliminate current loss. It’s better to go too big than too small.

5. Running the Wires

Next the issue was how to get the wires from the panels to the boat. With two panels there are four wires, a positive and a negative from each panel. I bought a pair of “MC4 Branch Parallel Adapter Cables” from Amazon. These take the like poled wires from each panel and combine them with a single wire resulting. Picture a “Y” with two wires on the top and one on the bottom. In the picture you see both adapter cables connected to the four solar panel cables and only two wires, a positive and a negative, running into the canvas.

I was reminded that real electricity is coming through the wires from the panels, so I didn't connect to the panels until I was ready to activate the completed system. “MC4” refers to the connector on the cables. I found these are standard and are on all the solar products I bought. They are the same ones used on our SunPower panels. Notice in the picture left that the cables disappear into a hole in the bimini. I made that with the soldering iron, and it’s just large enough to fit a MC4 connector through. It goes into a zipper sleeve, so you can’t see it from below in the cockpit. Also notice the cables lay over the bimini window. We will fix that later. Next the cables needed to run down to where they will enter the boat.

In our case, it was best to run them down the back stay. I wanted to use true outdoor solar cable rated for outdoor use. On Amazon I bought two 20 foot pieces of “10AWG Solar Extension Cable with MC4 male and female connectors”. I only needed the MC4’s to make a water tight connection with the exterior wires in the previous picture, so I cut off the MC4 connectors on the ends that would be inside the boat. This also allowed me to insert the cable through a smaller hole into the boat. I could have bought one 40 foot piece and cut it in half but it was more expensive.

In this picture you can see the cable exiting the zipper sleeve on the right and going to the middle bimini support on the left. (I could have run it there from the top of the bimini but it caused additional issues with the window.)

The cable is covered with “½ inch “Expandable Braided Cable Sleeving” purchased from Amazon. This gives wire a nice finished appearance.

Here is the transition from the bimini support to the back stay. The black cover on the bimini support is a “Cable Cord Sleeve” that is a piece of neoprene with Velcro fasteners you can wrap around anything. (Amazon) It came with 50 Velcro cord straps that were handy in fastening the cable to the backstay as you can see in the next picture.

Here is the finished cable run as seen from the stern. You can see the Velcro ties and cable running down the backstay but not much else as was the plan.

6. Entering the Boat

Next the cables needed to pass through the fiberglass and into the boat. Maybe you have a convenient entry point but we did not. This meant a new hole in the boat, but with confidence in our plan I did what was emotionally very hard. The result was perfect. I used butyl putty tape to seal the cable into the hole and also to seat the “clam shell cover” that I bought at West Marine for about $4.00. Under the cockpit I connected the solar cable to #10 Ancor sheathed cable. It looks like cable they use in houses except Ancor is marine quality, tinned copper wire. For the connectors I used two Ancor heat shrink crimp connectors.

This and any wire mentioned subsequently I purchased at West Marine. I bought plenty of cable as it is not preferable to use additional connectors. I used the sheathed cable up to the solar charge controller, mostly running it through the same spaces as the original factory wiring. Cable ties and cable tie mounts were very handy to secure the new wiring to fixed surfaces or to existing wires.

7. Switching the System On and Off

I wanted an actual switch to turn the system on and off as opposed to just unplugging a cable. Switched circuit breakers are only slightly more expensive than an appropriate switch. I heard several installers say that they position a breaker on both sides of the charge controller, so that’s what I did. I bought two Blue Sea Systems 285 series switchable breakers from Amazon. The first one disconnects the panels from the charge controller and is mounted out of sight in a cabinet behind the charge controller. Push the red button and the yellow arm swings out to shut down power from the panels. Push the arm back into place and the system is back up and running.

8. Mounting the Charge Controller

There are a lot of charge controllers to choose from and after doing my due diligence, I decided to go with the Victron MTTP smart controller that was recommended by Sun Powered Yachts I bought the 100/30 model which means it can accept up to 100 volts from the panels and will charge up to 30 amps. This would give me room for future expansion if needed. ($226 on Amazon.) There are lights on the controller that indicate its stage of charging i.e. bulk, absorption, or float. To easily see the lights I mounted the unit on the outside of a cabinet close to the batteries. Being a “smart” controller it is Bluetooth and connects to an app on my phone where I can see more charging data.

From the charge controller I switched to Ancor #10 primary wire which is also marine grade and tinned copper. The charge controller is near my shore power or AC charger so I followed a similar path as the factory wiring to access the batteries. My wire run is seen on the left in a flexible plastic conduit. (Wire and conduit from West Marine.)

9. Overload Protection - Breaker or Fuse

I read a lot of discussion about whether to use a fuse or a circuit breaker to protect the system. I concluded it was a matter of preference. But again, I wanted a convenient switch so I used the second and identical Blue Sea Systems breaker. It is positioned just before the battery which is located about six inches to the right of the breaker in this picture. The charge controller stated that its minimum breaker size was 40 amps, so that’s what I went with. Everything I researched emphasized that a breaker (or fuse) is absolutely necessary between the batteries and the controller and you want to locate it as close to the batteries as possible. Whereas my shorepower charger charges the house and starting batteries independently, the solar is only connected to the house batteries. I connected the positive lead from the breaker to the closest house battery and the negative lead from the charge controller to the furthest battery. That is, I have three 12 volt batteries connected in parallel. The positive lead from the breaker is connected to the positive terminal on the number one battery located just on the other side of the partition in the picture. The negative lead goes to the negative terminal on the third battery about three feet away. Having a breaker/switch on both sides of the solar charge controller enables me to completely turn off the controller, so it is not receiving current from either the solar panels or the batteries.

10. Bimini Window

I had one more tune-up item to finish back at the bimini. My boat has a single helm on the centerline under the bimini. There is a window in the bimini that I uncover when sailing so I can see aloft. Unfortunately, the solar wires want to lie across the window. This is okay when the cover is on the window, but not when it’s off. I made a short strap with scrap webbing. It connects to the twist fastener on the bimini when the cover is removed and holds the solar cables off the window. In the picture you can see the finished strap and the soldering iron that I used to melt holes for the fasteners.

11. Testing the System

At this point I powered up the system just as the sun was about to set. As per the instructions on the charge controller, I powered the breaker on the battery side first and then the solar side. The “bulk” charging light lit immediately. I knew the system was working, but I could not see how much power was being produced. My boat has a Charge Meter in amps at the master panel but I did not connect the solar system to it. The batteries are connected to a Volt Meter on the master panel so I could see the solar panels’ effect there.

I bought the “smart” or Bluetooth version of the Victron 100/30 charge controller that allows you to see all the charge data on either an Apple or Android phone. The reviews using Apple phones were all great. Those with Android were a mixed bag of the app working well or not at all. I have a Samsung 7 Android phone, so I held my breath and downloaded the app. It immediately recognized the controller, but said it needed a firmware update. “Enter a PIN of 0000 and press continue.” I did this and got an error saying the device unexpectedly disconnected. I tried a number of variations without success. It was past happy hour, the project was becoming less fun, so I traded the app for a beer and was content, for now, to see the “bulk” light still lit.

The next morning, I found a reference on the Victron web site that said to enter 000000 as the initial PIN. The message on my phone had only showed four zeros. The six zeros worked perfectly, the system updated its firmware and displayed all the charge data on my phone.

At this point it was about 45 minutes after sunrise with a heavy cloud cover. The screen capture from my phone shows that there is not yet a lot of power from the panels, but the MPPT charge controller is doing exactly what it is designed to do. It’s taking the excess voltage and increasing the amps. The panels are producing 0.4 amps and the batteries are receiving 0.5 amps, an increase of 25%. Subsequently, I have seen this increase as high as 73%.

This is the history screen. The “Today” and “Yesterday” columns which represent March 2 and 3 are interesting. “Yesterday” it rained with thick cloud cover all day. The shorepower charger was off, and the batteries had been running the refrigerator, freezer and lights all night. The bright white bar shows the system was charging in Bulk mode, meaning it was at max for the given sun light all day. The battery did not quite charge all the way reaching a maximum of 13.75 volts. “Today” started out with thick clouds and low charging as per the previous picture. By mid-morning the sky cleared to intermittent clouds and sun. Again, the shore-power charger had been off all night with appliances running. Under these conditions the solar system charged the batteries fully by around noon as indicated by the 14.38 maximum voltage. The shaded parts of the bar show Absorption and Float modes the system transitioned to after bulk charging was completed.

We are thrilled by these initial results. If our two 110 watt solar panels can charge us up by noon in early March on a less than sunny day, we will have more than enough power come summer and longer days.

12. Things I Would Do Different In Hindsight

1. Regarding the fasteners holding the panels to the bimini, the nylon core of the lock nut flattened out the threads of the nylon bolt. Doing it again, I would use a lock washer and regular nut or wing nut.

2. Again regarding the fasteners, I would use regular washers in place of the fender washers. Regular ¼ inch washers are large enough to have perfect contact with the grommets built into the Sun Power panels and are less expensive.

3. I would buy a smaller charge controller. I thought I might need to expand the system in the future, so I oversized the charge controller. Based on our initial results, we will not need additional panels.

Happy Charging, Ed & Diane