When I bought my 1967 Alberg 35, Maui, in early 2023, I knew I was embracing a simpler way of cruising. Overall, her systems are about as basic as they come, so inheriting a 12V refrigerator was a bit of an unexpected luxury. While I loved having cold drinks and fresh veggies onboard, I quickly realized that convenience came with a cost: power consumption. It was time to explore solar power to keep everything running smoothly without constantly relying on the engine’s alternator.
Table of Contents:
Battery Comparisons and Solar Compatibility
Solar Product Selection
Solar Education: How much do you need?
Installation Process
Reflections and Learnings
After our first off-the-grid cruise on Maui last season, it quickly became clear that my two 65 amp-hour (AH) lead-acid house batteries (supported only by a 60-amp alternator) just weren’t cutting it—especially since we were often sailing with the engine off.
By day three of that cruise, the house battery bank was noticeably drained—something that’s definitely not healthy for lead-acid batteries, which only have a 50% usable capacity. We started paying closer attention, but without running the engine for long periods, the house bank simply couldn’t keep up.
Battery Comparisons, Compatibility, and Contemplations
Before jumping into solar panel and product research, my project really started with battery contemplations. I was considering upgrading my house batteries from lead-acid to something more robust and compatible with the solar addition. As soon as I started asking boaters in my network for advice, I was flooded with strong—and often conflicting—opinions on what to do and what to avoid.
Most full-time cruisers I spoke to were all about lithium-ion batteries. To them, it was the only option. I get it— with a 98% usable capacity, you can drain those suckers down to nothing and they bounce back as healthy as ever. To put this in perspective, one 65-AH lithium battery could provide the same power as my two 65-AH lead-acid batteries (see chart 1). It’s kind of crazy when you think about it that way.
Although lithium is the eventual goal, after taking a hard look at my budget, I quickly level-set with myself—and my ‘advisors’. A lithium upgrade was out of reach this year, so the choice was either to stick with my current lead-acid batteries or ‘upgrade’ to AGM batteries.
Every boater I talked to pretty much dismissed the lead-acid option. While AGM batteries do offer some small perks over lead-acid, I had to ask myself: was the cost worth it for what felt like only a slight improvement? Or should I hold out until lithium becomes more realistic for my budget? Would adding solar even make a difference with my current led-acid setup?
At this point, the conflicting opinions from my network had me in a total chokehold. I was drowning in a sea of anecdotes from a million different boaters. I knew I needed more power, but I also knew how simple my boat’s systems were. It was time to call in the pros.
Battery Science: Enter Xantrex
After watching a good amount of YouTube videos on solar installations and battery compatibility, one from ‘Monday Never’ about installing Xantrex’s soft panels on their bimini really caught my attention. Intrigued, I decided to reach out to Xantrex's team with my questions. Shortly after, I found myself on the phone with Mary Morgan from Xantrex, explaining Maui’s situation, along with my battery compatibility frustrations and overall solar goals.
Mary walked me through the clear and concise science behind different types of batteries, explaining why lithium is considered top-tier. She knew lithium wasn’t in the cards for my budget this year, so she helped me manage expectations about what solar could realistically do for my current setup. She pointed out that while lithium batteries pair more efficiently with solar—since they’re power-hungry and offer less resistance in the absorption phase—it doesn’t mean I should hold off on solar just because I’m not ready to make the switch to lithium yet. “For a simple boat like yours, you’ve got to start somewhere!” she said.
I finally felt like I had facts to rely on rather than just opinions about battery type. I was educated enough to feel confident and content in my choice to keep my current lead-acid batteries for another year, without bottlenecking my solar goals. I was going to start simple: add solar, and monitor the results.
Solar Research, Products, and Learnings
The Limiting Factor: Physical Space
One of the biggest challenges with solar panels is finding space for them. Though Maui’s LOA is a solid 35 feet, her low lines and old-school design don’t offer the same abundance of space as newer production boats. My original plan was to mount flexible panels on the dodger, but I quickly realized that the surface area there was too limited. With deck space also scarce, the next best option was the stern rail, where I could mount a rigid panel. (I’ll dive into the specific hardware and customizations that I pieced together for that installation below!) It was time to dive into panel options - which were admittedly quite limited by dimensions.
The team at Xantrex introduced me to several of their offerings, and after all the education they provided me with on the battery front, I was confident in pursuing their products. Mary told me about their brand new bifacial solar panel that was designed specifically for dynamic marine applications.
The main reasons I chose a bifacial panel was because it made the most of the limited space available on Maui. The way it works is simple: the panel harnesses energy from both sides, capturing sunlight reflected off the deck or water, along with direct sunlight from above. This dual-sided design optimizes performance even in shaded areas—something every boater (especially sailors) can appreciate. By utilizing both sides to capture sunlight, I knew I could maximize power output, even with my limited mounting options. For an off-grid, low-maintenance setup on a classic boat like Maui, bifacial panels just made sense.
“Xantrex Bi-Facial Solar panels are rated for the front face of the panel only, meaning all of the energy you harvest from the sun on the back side of the panel is bonus! This is especially impactful for sailors that spend their days cutting through the refracting light over the water.” -Mary Morgan, Xantrex
These bifacial panels come in several sizes, from 90W to 490W, with higher wattage meaning a physically larger panel. Given Maui’s compact setup, I opted for the 90W panel— a perfect start for my simple system and ideal for the stern rail space available.
I’ll get to the step-by-step installation process soon, but this next part of my solar education and product selection was easily the most valuable. Before I officially committed to the 90W bifacial panel, I had the opportunity to meet over Zoom with Xantrex applications engineer, Gregg Inscore (a huge perk that Xantrex offers to their consumers). Before our meeting, I provided Gregg with an amp-draw chart for every single electrical system on Maui—from the bilge pump to the cabin lights to the fridge. Gregg used my chart to calculate the total power draw on Maui, and he told me how much time I could use my systems with my current battery bank before I need to recharge the system for optimal battery health, along with how adding solar would affect that runtime on my batteries. I was able to see how adding more batteries, switching to lithium, or increasing to a higher solar wattage would affect run time, and even how much solar I would need to eliminate using the alternator completely.
Chart 2: Solar Impact on Maui, provided by Xantrex
Note: Based on this information, I learned that I would needs 390 amp-hours (AH) of lead-acid batteries to run my current system for 24 hours without needing a charge. This is equivalent to six 65 AH batteries, like the ones I currently have. At 37 lbs each, those six lead-acid batteries would weigh a total of 222 lbs.
The chart indicates that a single 240 AH lithium battery can replace all six of these batteries, weighing only 69.4 lbs.
During our call, Gregg walked me through the impact of adding a 90W bifacial solar panel specifically to Maui and explained the science and math behind it all. I learned that the 90W bifacial panel, which harvests 20% more than its rating, could actually produce up to 108W per hour in full sunlight. Since calculations were based on a ‘daily sunlight average’ for my geographical region here in the northeast, we estimated about 5.5 hours of usable sunlight per day. Under those conditions, the panel would add approximately 45.54 AH to my battery bank every sunny day.
With one 65 AH lead-acid battery having a usable capacity of 32.5 AH, that means one 90W solar panel is essentially like adding another battery to Maui. I walked away feeling confident—not just in installing and monitoring the system, but in really understanding how it all worked. Plus, It's not every day you get to collaborate with pros at this stage of a DIY project, and I’m truly grateful for the knowledge and clarity I gained.
The Installation Process Breaks Down into Three Main Parts:
While waiting for my Xantrex solar kit to arrive, I got started on DIY-ing a mount that would allow the panel to hinge on the curved 1” stern rail. At the time, I was on the hard at a local boatyard in Maine and sought advice on how to piece it all together. Huge shoutout to Bob, a technician in that boatyard, who kindly offered to guide me through his recommendations (thank you, Bob!). This project would have taken much longer without his shared knowledge, and by sharing the specific hardware and resources I used, I hope to pay it forward to someone else in need of a little direction!
The most creative part of this step was templating, designing, and ordering a custom stainless bracket that was straight on one side, and matched the curvature of the stern rail on the other. This bracket would allow for the panel, once mounted, to hinge down on the flat side when in tight quarters.
To build this bracket, I used heavy card stock, taped it below my stern rail, and traced the curve with a Sharpie. From there, I cut the template out, took some key measurements, and started researching how to get the custom bracket cut from a sheet of ¼” stainless steel. After asking around at local metal shops, it became clear that the most efficient way to get this built was through an online service like SendCutSend.com or OshCut.com.
My card-stock template I traced and cut out to start the process
The only catch? To use an online service, I needed to upload my template as a ‘CAD’ file. I’m no engineer and had never used CAD software in my life, so I had to troubleshoot. After a few ad-hoc requests to engineers I knew, my colleague here at Dockwa, Elliott, came through as a CAD pro! By the next morning, Elliott had sent over the file, and I was able to ship the template off to be cut. A few days later, it arrived! Thank you, Elliott!
Note: If you don’t know how to use CAD and can afford to wait a few extra days, you can physically mail your template to these services and let them handle it. I needed the CAD file as I was in a rush to get my panel installed before my annual cruise.
Additional Hardware for the Rail Mount:
With the custom bracket ordered, it was time to get the more ‘accessible’ hardware for the project. Note, my stern rail is a curved 1” diameter tube. Here are the products I ordered to complete mounting the panel:
From left to right: TACO Jaw Slide/ SS hinges, Suncore Multidirectional Cap/ SS tubing, 1/4" rivets
With all my products staged, it was time to get to work! Here’s how I installed the panel:
1. Rivet the hinges to the panel
Pro tip from Bob: Make sure your panel is slightly angled, so water runs off keeping the surface clean for solar absorption!
3. Run wires to the charge controller
I received 15 feet of 10-gauge wiring from Xantrex, with pre-spliced male/female panel connectors. I ran the wires from the stern rail through a clam shell cover on the deck, down through the lazarette, and right up to the cabin bulkhead, where I planned to install the control panel. I secured the wiring in place with zip ties to keep everything neat and secure.
4. Cut a hole in the cabin bulkhead for the charge controller
The charge controller sits flush with the surface, so I carefully cut out a space in the cabin bulkhead to recess it. Secure the panel to the bulkhead with appropriate screws.
5. Prepare for wiring!
With the panel mounted and the charge controller in place, I was ready to wire everything up.
2. Connect the charge controller to the house battery bank
Using additional 10-gauge wire, connect the charge controller to your house battery bank, ensuring secure connections at both points as indicated in the instructions. I also added a 35-amp inline fuse to this section of the wiring, as recommended in the charge controller's user manual.
And voilà! The charge controller powers up directly from the solar energy, allowing you to track a variety of important metrics for your battery health. Just like that, you’ve set up a simple solar system, delivering free power straight into your battery bank!
We wrapped up the installation only two hours before pushing off from the docks at my homeport marina, ready to go completely off the grid for 7 days. On our first leg up the coast, Jack started saying, “The sun is keeping our vegetables cold!”—and that quickly became the motto of our entire trip. After all, the sun truly did keep our vegetables cold!
We were able to monitor the effectiveness of solar power right on the charge controller, which cycled through key metrics like Voltage, battery temperature, amperage, battery charge, and kWH (see chart 3 below).
|
Parameter on the Xantrex PWM Charge Controller |
What does this parameter measure? |
Value and importance of this parameter |
|
Voltage |
Voltage from solar panel and the battery |
By tracking both voltages, the controller can convert the higher voltage from the solar panels to the appropriate voltage needed for charging the battery, optimizing the overall efficiency of the solar power system |
|
Amperage |
Current from solar panel and battery |
The controller ensures that the battery is charged efficiently and safely by providing the appropriate amount of current based on the battery's state of charge |
|
Battery temperature |
Track the battery temperature |
Controller adjusts the charging voltage and current based on the battery's temperature to ensure optimal charging conditions and increase safety, optimize performance, extend lifespan, and ensure more effective management of your battery systems |
|
Battery charge |
Manages the flow of current from the solar panels to the battery through multiple stages (Bulk, Absorption, and Float charging) |
Ensures battery health and longevity, maintaining safety, optimizing performance, and achieving cost effectiveness in solar power systems |
|
kWh |
The total energy produced by the solar panel |
Helps users to track the performance of the solar system and optimize energy use |
Chart 3: Charge controller parameters explained - provided by Xantrex
The impact of adding solar to Maui was noticeable. Our 12V fridge ran from sunrise to sunset, and our house battery bank never dropped below 12.2V. To make it even sweeter, we used less than 5 gallons of fuel for the entire week… meaning that with the winds in our favor we barely ran the engine and the alternator wasn’t contributing much power. Plus, it was beautifully sunny every day—perfect conditions to test the full impact of solar!
I learned so much during the research and installation process, and I’m especially thankful for Mary’s advice to start simple, rather than overcomplicating things with a full battery upgrade. If you are considering adding solar to your boat, but are feeling a bit intimidated about all the advice out there, here’s your sign to find a system that works for you, and take on the project at your own pace. I am happy to share more about my experience if you have any questions, just shoot me an email and we can find a time to connect!
At the end of the day, I’m thrilled with the results of my 90W solar addition. I’m grateful for the guidance I received from my network and the team at Xantrex, and I’m still excited about this upgrade! Is a lithium house bank in my future? Probably. But for now, the sun is keeping my vegetables cold, and for that, I couldn’t be more thankful!