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Sailboat Life

Sailboat Cruising and Lifestyle Magazine.

Sailboat Solar Systems and How-To

Solar on a sailboat goes together like hands and gloves, but sailboat solar systems can be installed in a variety of ways. The solar components themselves create an infinite combination of possibilities for off-grid sailing. Victron Energy chargers, Renogy Panels, Sunpower Yachts, BlueSea Systems, and many more brands have entered the marketplace, and that’s not including the lithium battery companies.

To simplify things, we’ve compiled three sailboat solar systems videos to give you an overview of what’s possible. And to help you decide on your own simple solar panel setup for sailing.

How-To Install Solar Panels on Your Sailboat

This system from Zingaro shows flexible panels summing 300w of power on a 38′ catamaran.

300W Solar System:

• Three 100w solar flexible panels
• 1 MPPT Solar charger controller

View on Amazon >>

100W HQST Flexible Solar Panels $100-$200

20amp Solar Charge Controller by Victron Energy $150-$200

Simple Sunpower Solar System

This simple solar system from The Fosters shows a quick and easy setup with limited space on top of a bimini.

Sunpower Solar Panels are considered by most in the industry as the gold standard. They use the highest-efficiency solar cells and have top-notch build quality. In this simple installation, three 50w panels are just enough to get you started. Plus, it’s the most affordable installation!

150w Starter Solar System

• Three 50w Flexible Solar Panels
• A Single 15amp solar charge controller

50W Sunpower Solar Panels $150-$200

75v/15amp Solar Charge Controller by Victron Energy $100-$124

Off-Grid on a DIY Solar Powered Sailboat

Here’s a special installation that turned a derelict sailboat into an off-grid sailing machine!

Simon has transformed this derelict sailboat into an epic off-grid solar-powered and fossil-fuel-free cruising catamaran. He’s been living aboard and renovating the boat for the past 3.5 years We’re excited to show you the transformation as well as how he plans to propel the boat without the use of diesel or fossil fuels!

5280w Solar System for Electric Powered Catamaran

• 16 Rigid solar panels (330w each)
• 20kwh of Lithium Batteries

240W Rigid Solar Panels $250-$300

200AH Lithium 4d Battery $1200-$1200

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What You Need To Know About Boat Solar Panels

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Sunshine and boats are a natural together, so why not use all that free energy? Here’s the lowdown on solar panel selection and installation

I first embraced the idea of solar power while up a pole (literally) in the Atlantic Intracoastal Waterway replacing dead batteries. It was the early 1980s, and I was maintaining buoys, beacons, and other such Aids To Navigation (ATON) for the U.S. Coast Guard, replacing massive, nonrechargeable batteries with rechargeable solar-powered ones. The higher-ups said the solar rechargeables would last six years – twice as long as the one-shot batteries. As the deck-ape in charge of lugging all those batteries up and down the ladders, my back and I immediately appreciated the whole “free power from the sun” thing, a concept I continue to embrace.

The strategy behind s olar energy onboard is simple: A solar panel converts sunlight into electricity, after which wiring conducts it to your batteries for storage until needed. Solar panels are used to keep batteries or banks charged rather than to power equipment directly. This arrangement allows the panels to store generated power whenever produced, while providing a steady source of power to a piece of equipment even when the panel is producing no power.

While they do require an initial outlay, solar panels can easily pay for themselves in money saved and independence gained over their service life. They’re noiseless, have no moving parts, and they provide free electricity for years with minimal maintenance. Solar panels also have the benefit of being modular, letting you start small and add more as your power requirements increase.

The benefits of solar

Almost any boat can benefit from solar power. Whether at a slip, mooring, or on a trailer, boats can keep their batteries topped off without the need for external power. You can also use solar power to supplement or even replace other onboard charging sources, reducing or eliminating the need to run engines or generators to keep batteries topped off (a wasteful practice that burns fuel while wearing down the costliest pieces of equipment onboard).

While underway, it’s a plus to be able to recharge a dead battery in an emergency – say, to operate a VHF radio or navigation gear. While dockside, solar panels keep batteries charged and vital systems (such as bilge pumps) up and running without the need for shore power.

Just about any boat can benefit from solar power, whether it’s to keep batteries topped off or supplement other onboard charging sources.

Mount solar panels where they are exposed to maximum sunlight but do not interfere with operation of the vessel. 

Bottom: Something as simple as the shadow of a line or shroud can reduce or halt output.

Types of panels

Solar panels contain photovoltaic cells – small silicon semiconductor devices that convert sunlight into electricity. Each cell generates between 0.45 and 0.5 volts, depending on exposure to direct sunlight. Cell size determines amperage, with a 3-inch cell producing roughly 2 amps, a 4-inch cell a little over 3 amps, and a 5-inch cell around 5 amps.

Construction-wise, the three main types of solar panels are monocrystalline, polycrystalline, and amorphous (or thin-film) technology.

Monocrystalline panels have been around the longest and remain the most popular. The panels are constructed of thin slices of crystal silicon (each cell is cut from a single crystal) housed in a rigid, aluminum frame and covered with tempered shatterproof glass. The panels have a uniform black, blue, or gray appearance and are generally quite rugged, although they can be cracked or broken if subjected to extreme abuse.

Monocrystalline panels have the longest service life of the three types. With a conversion efficiency of around 17%, they’re also the most efficient and have the highest electrical output per area, but they are also the most expensive.

Polycrystalline cells are sliced from a cast silicon block and have a shattered glass appearance. Built in much the same way as monocrystalline panels, they’re rectangular, giving the panel itself a tiled look. Their life span is similar to monocrystalline panels, and while their conversion efficiency is lower (by 14%), they’re also a bit less expensive.

Amorphous panels are made by placing a thin film of active silicon on a solid or flexible backing (such as stainless or aluminum sheeting) depending on whether the panel is to be rigid-framed and glass-fronted or flexible. Flexible amorphous panels, in which cells are sandwiched between rubber and polymer covers, are light and tough enough that you can walk on them and, in some cases, even roll them up for storage.

This type of solar panel is also better if shade is an issue. With crystalline panels, even the thin shadow of a rope or shroud across one cell can reduce or halt output of an entire module. Amorphous panels have “bypass” diodes that essentially turn off shaded cells and provide a current path around them. Some monocrystalline panels also have bypass diodes, but this feature comes at an increase in cost.

Amorphous panels are the least expensive of the three types, but their efficiency is also lower – around 8%, or roughly half that of a monocrystalline type. This lower output is somewhat mitigated in newer panels, however, which use three-layer construction. Each layer absorbs different colors of the solar spectrum, so the panel will deliver more power longer each day and during lower light conditions than the other two types.

The charge controller should be mounted below decks and as close to the battery as possible. 

Follow manufacturer instructions for wire connections.

Planning the system

While factors such as cost, mounting options, and output are important, a successful installation depends on knowing what you want the system to accomplish. Is the goal to float-charge a single battery or supplement an overall vessel energy plan? Answering these questions up front will help determine the type, size, and number of panels required.

To understand the process better, let’s walk through the basic steps to determine power requirements and installation considerations for a single solar panel installation. While the example itself is simple, the steps are the same used to plan more complicated installations.

For our example, the goal is to install a solar panel to provide charging for a single 12-volt, 100-amp-hour wet-cell battery used to power an automatic anchor light on a moored vessel.

The first step is compiling a daily power consumption estimate to determine how much solar power is needed.

The daily self-discharge rate for a wet-cell battery is roughly 1%, meaning our 100-amp-hour battery requires one amp every 24 hours just to maintain the status quo. The anchor light draws 50 milliamps per hour of operation, and we’ll assume it operates 10 hours each night. Multiplying current draw (50 milliamps) by hours of daily operation (10) generates a daily energy expense of 500 milliamps or .5 amps.

This means our solar panel must meet a minimum daily energy tab of 1.5 amps – one amp of battery self-discharge rate plus .5 amps of power draw for the anchor light.

Next up is figuring out panel size and the best mounting location. For our example, let’s assume the panel will be a horizontal, fixed-mount installation. A 10-watt horizontally mounted panel should generate between 3- and 5-amp hours per day.

We’ll need at least 13 volts to fully charge our 12-volt battery. As most solar cells generate at least 0.45 volts, you’ll want a panel with a minimum of 33 cells, which should provide around 14.85 volts.

Keep in mind that’s the minimum needed, which may not be enough once you factor in a few cloudy days. Most panels are designed to generate between 15 and 20 volts to overcome problems like cloudy days or inherent electrical resistance within the panel or installation components. While this higher voltage lets you make up for less electrically productive days, it also means you’ll want to install a solar charge controller (voltage regulator) to avoid battery damage due to overcharging.

Attempts to plan a system that tries to use the output of the panel and capacity of the battery to prevent overcharging (and avoid the installation of a charge controller) is false economy and should not be done. The system will never meet its full output potential and, worst case, can damage the battery due to overcharging.

A word on ‘charge controller confliction’

If your vessel has multiple charging sources, such as solar panels and a wind turbine, a crucial but often overlooked consideration is “charge controller confliction.” In short, this is an issue where the charge controller for your solar panel and the charge controller for your wind turbine are internally adjusted to the same maximum charge voltage set point. This means they are constantly fighting each other to be the dominant power source, which results in diminished overall charging output and performance. An in-depth article on this issue can be found at ­missioncriticalenergy.com (in the website footer, click “Superwind Turbine Manuals & Technical Bulletins.” Under the header “Charge Controllers,” select the document “Resolving Charge Controller Confliction”).

While this article addresses charge controller confliction at remote, off-grid sites, the information provided is also applicable to vessel installations. — F.L.

Location and mounting

Solar panels should be mounted in a location where they are exposed to the maximum amount of sunlight but do not interfere with operation of the vessel or the movement of passengers and crew. Solar panels will typically be either fixed or mounted on some type of movable bracket that allows you to actively point the panel toward the sun for maximum output. Both methods have their pros and cons. Fixed panels (which are normally mounted horizontally) don’t produce as much power as a panel that can be adjusted to face the sun. The downside is that adjustable panels must be aimed throughout the day to maximize their output.

Use good quality, marine-grade heat shrink connectors (top) and liquid electrical tape (right) to create airtight, waterproof seals and reduce corrosion.

Installation

After choosing and mounting your panel, it’s time to connect it. The first thing you need to determine is the size (gauge) of the wiring to be used. Multiply your panel’s rated amp output by 1.25 (which adds a 25% safety factor). Then measure the length of the entire wiring run, panel to battery, and multiply by 2. Once you have these two numbers, refer to the American Boat and Yacht Council’s (ABYC) 3% voltage-drop table for wire size. Ancor Products offers a handy wire calculator on its website ( ancorproducts.com/resources ).

Always use good quality marine grade connectors  and tinned, multi-stranded copper wire with vinyl sheathing. The wire will run from the solar panel to the charge controller first, then to the battery. Try to keep the wire run as short as possible, and if it transits an external deck or cabin house (it likely will), be sure to use an appropriate weatherproof deck fitting.

The charge controller should be mounted below decks and as close to the battery as possible. You’ll always want to follow the manufacturer’s instructions for connections, but in a typical installation you’ll connect the solar panel’s positive (red wire) lead to the charge controller’s positive input wire or terminal and the negative (black wire) lead to the charge controller’s negative input wire or terminal.

Next, connect the charge controller’s negative output to the battery negative terminal and the controller’s positive output to the battery’s positive terminal via an appropriately sized in-line fuse (or circuit breaker). ABYC recommends these be installed within 7 inches of connection to the battery or other point in the DC system. To reiterate, the installation of the charge controller can vary among models, so follow the manufacturer’s installation instructions.

Finally, ensure all connections are waterproof and secure any loose wire runs with wire ties and cable clamps for a neat installation. Then get ready to lean back and soak up some free sun.

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Frank Lanier

Contributing Editor, BoatUS Magazine

Capt. Frank Lanier is a SAMS-accredited marine surveyor with over 40 years of experience in the marine and diving industries. He’s an author, public speaker, and multiple award-winning journalist whose articles on boat maintenance, repair, and seamanship appear regularly in numerous marine publications worldwide. Contact him via his YouTube channel “Everything Boats with Capt. Frank Lanier” or at captfklanier.com.

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Top 3 Best Solar Panels For Sailboats

Choosing whether or not to install solar panels on your sailboat is a big decision. They are not exactly cheap, though they can start to pay themselves off pretty quickly.

This article is going to cover not only why you might want to use solar panels but all the benefits they provide. You will also find a helpful guide on which solar panels would be best for you and your budget. Hopefully, by the end, you will feel confident in your decision to install solar panels on your sailboat and even have an idea of which ones you might like.

Table of contents

Are solar panels on sailboats necessary?

Whether or not you should be installing solar panels on your boat is a matter of choice, not out of necessity. Sailboats get their power from the wind, by harnassing it in their sail. So if you plan to be sailing for the afternoon you probably don’t need solar panels.

You could charge a battery pack from the marina and that will probably see you through several trips. The problems only really start to arise if you are planning to be on your sailboat for longer periods, or even permanently. If you plan to live on your sailboat year-round, even if you spend 80% of it in a marina, you would be better off with some solar panels. Even if it is just as a backup source of power.

Are solar panels on boats safe?

Solar panels are generally pretty safe. They have no moving parts and typically have a very strong protective cover over them so you never come in contact with the electrics themself. So, as a source of power, they are generally pretty safe. The only time they may become unsafe is if they are badly damaged.

Solar panels are often covered by glass plating that keeps them safe. It also helps them absorb sunlight and warmth. This is great, except when the glass breaks. If the glass protective cover on your solar panels should crack and splinter you are at risk of serious injury from sharp shards of glass. Not only is the glass itself dangerous at this point, so are the electronic components inside. They have powerful currents running through them, and if you come in contact with them you may be in for a shock.

Furthermore, if these electronics get wet they can become deadly. Electricity and water do not mix well at all. Being as you are on a sailboat, at sea, the chances of them getting wet is very high. Luckily, the chances of them breaking in the first place are slim to none. The only real way they would break, besides vandalism, is by debris hitting them during a bad storm. There is not often debris at sea, so this shouldn’t be too much of a problem.

What are the benefits of having solar panels on a sailboat?

There are so many great benefits of having solar panels on a sailboat. They can be a lifesaver if you find yourself at sea for a long time. There benefits range from trivial comforts to being the difference between life and death. Here are some of the benefits you might not have considered about having solar panels installed on your sailboat.

Money-saving

Solar panels are not cheap, it is far cheaper to just run a generator or charge your batteries from the marina the whole time. At least, it is in the short term. Over time, it can start to become very expensive. With solar panels, you are looking at a big initial cost (the solar panels themself) and then it’s smooth sailing. You don’t need to pay for power again. Solar panels last for about 40 years before they start to become too inefficient at producing power. The cost of a few solar panels upfront compared to 40 years of marina fees and gasoline for a generator is the financially savvy move.

Emergency power

If you find yourself at sea, the wind dies down (or becomes too strong), and you find yourself stuck bobbing around waiting for more favorable conditions you may run into trouble. Depending on how long you are out there, you may find yourself with dead electronics. Be it a satellite phone, radio, or secondary engine (depending on the boat). Having a set of solar panels and a power bank can be a genuine lifesaver in these situations.

Comfort amenities

Whether you are day sailing or making a week-long voyage, having access to the comforts in life can make the whole journey so much more enjoyable. The amenities may not be available to you without having a constant source of power at sea. Having access to a kettle, tv, videogame system, radio or microwave oven may be the only thing keeping you going at rougher times. As exciting as sailing can be, when you aren’t sailing and are just bobbing around it can be quite dull. The sea is beautiful, but there is only so much time you can spend looking at the water before you miss the comforts of land. With solar panels, you can bring those comforts with you.

Eco-friendly

There are only two alternatives to solar panels. A gasoline generator, and taking power from the grid. Neither of these is good for the environment. Luckily, solar panels are a great third option. Solar panels are completely eco-friendly and are great for the environment. This is not just great for the earth, and your conscience, but for the journey itself. If you are running a gasoline generator at sea you are going to be listening to it thrumming away and smell the burning gasoline. Wouldnt you prefer silence and nothing but the smell of the sea breeze?

How much do solar panels cost?

How much solar panels cost is almost entirely tied into both their voltage/wattage and whether or not they are portable panels. Portable solar panels are great for people who don’t spend a lot of time on their boat or are happy enough living off the marina’s power grid. Permanent solar panels, the kind that may need to professionally installed, can end up costing far more. They are also likely to be far superior and you can pretty much forget about them once they are installed.

Portable solar panels will cost just a few hundred dollars each. You will need a few to be sustainable, but that’s not going to be much of a problem. These portable solar panels can just be rolled out on the deck of your boat, weighed down, and then hooked up to a battery pack. The battery itself here is going to be the most expensive part of the whole set up. A decent-sized battery could set you back a $1000. But, when charged fully it will last days. Even with constant use.

Permanently installed solar panels can cost one or two thousand dollars in some cases. The advantage here though is once they are installed that’s it, you can forget about them. You don’t have to put them up, take them down, and find somewhere to stow them every time they need using. They too will need to be hooked up to a battery, the battery is still only going to cost you $1000. If you are installing permanent solar panels because you plan to be making long voyages, it is ideal to have two or perhaps even three large batteries hooked up to your boat. One to run off, one or two for emergencies.

How do I maintain my solar panels?

Solar panels, unlike gasoline generators, are generally pretty easy to maintain. They have no moving parts and are thus pretty self-sufficient. They don’t need taking apart and they last as long as 40 years. That being said, if they do break they need repairing as soon as possible. The exposed electrics can be deadly when water is thrown into the mix. Which, on a boat, is almost always. The glass cover will need replacing and the electronics inside may need repairing, though not always. Don’t ever attempt to do this yourself unless you are experienced at making these repairs. The cost of hiring someone to do it for you is preferable to being dead. Solar panels have very powerful electric currents, that when in contact with water and yourself can be fatal. As mentioned above, these panels rarely break so you will likely not ever run into this problem. If you do, hire a contractor.

Do my solar panels need cleaning?

Solar panels work by converting the light and heat of the sun into useable power. The process itself is rather complicated but the results are simple to understand. That being said, there are some reasons that your solar panels will stop working as effectively. They all revolve around a lack of sunlight. It could be because it is night time. It could be because it is very cloudy. Or, it could be because they are dirty. If solar panels become too dusty, dirty, and become too covered in grime they stop operating at maximum efficiency. This is not as much of a problem at sea, the sea spray stops dust settling. The biggest thing you will need to clean off your solar panels is salt build-up and slime. This is easy enough to do with some warm soapy water. Freshwater, not seawater. You want to be removing as much salt as possible. Salt is corrosive to electronics, so removing it is important. Never clean your solar panels using pressure washers as they can crack the glass.

Which are the best solar panels for sailing?

There are so many options on the market at various price points. Here are three very different options that will all make good choices, depending on your needs. It is important to consider not just price but power output. Spending a lot of money on solar panels now might not feel ideal, but it is the most cost-effective decision.

1. Renogy Starter Kit

This starter kit is going to be perfect for installing on almost any sized boat. There are four solar panels, each can be fitted permanently to the boat. They can be mounted (and unmounted) easily, for your convenience. They do require a flat surface, but they are small enough that that likely won’t be too much of a problem. This starter kit is very middle of the pack price-wise but should provide enough power for a small to medium-sized vessel easily. It is also possible to buy extra panels individually should you need them.

Wattage: 400/4 (100 per panel)

2. Nature Power Rigid

The nature power rigid is a large, powerful, single solar panel. If you are looking for the right panels to power your entire boat comfortably, these are the ones for you. They are very large so they will need a large flat surface area. alternatively, they can be hung vertically from rails. This is an inefficient way of using them, so you would need to buy more this way. Nature power makes various solar panels so you could find some smaller ones of the same brand to supplement it. This one is not so easy to install, you might need to hire someone to install it for you.

Wattage: 165

3. Nature Power Monocrystalline

Nature power makes a portable solar panel that fits inside a special briefcase. It is perfect for stowing away easily and only taking it out when it is needed. It is decently powerful considering its portable, but there is the inconvenience factor of having to set it up each time. If you planned to buy the nature power rigid, buying one of these portable panels might be ideal for supplementing your power supply when it is especially sunny. Though, it may be cheaper for you to just fit more of the Nature Power Rigids.

Wattage: 120

Hopefully, you now have a good idea about whether solar panels would be right for you and your sailboat. Sailing is great, but the lack of power at sea can be dreadfully boring. Luckily, there are so many great options available on the market. Not just the ones mentioned above. Buying a solar panel is an investment, the initial cost is minor compared to the steady return from all the savings you will make.

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Daniel Wade

I've personally had thousands of questions about sailing and sailboats over the years. As I learn and experience sailing, and the community, I share the answers that work and make sense to me, here on Life of Sailing.

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Picking the best solar panels for a sailboat: Buyer’s guide

• 18 Aug 2022

You might have already heard of brave sailors that conquer the oceans with nothing but wits and solar panels. For instance, this year 83-year-old Kenichi Horie became the oldest person to sail solo from the US to Japan on a solar-powered boat. These stories are inspiring, but picking panels for your boat yourself can be a small challenge in itself. That’s why we wrote a short article about the best solar panels for sailboats and how to recognize them.

Start from type of solar panels

When it comes to solar panels for sailboats, their weight and size matters more than with PV modules for residential systems. Efficiency is important but power — not that much, because the energy needs of a boat are relatively low. The first thing you’ll have to decide about your panels is their type.

Generally, you’ll choose between thin-film panels and monocrystalline modules. While polycrystalline panels are still around and they are indeed cheaper than mono panels, they are much less efficient, which means they’ll need more space and add more weight to your boat.

Thin-film panels are light and cheap

Thin-film or flexible solar panels bend well and they are very easy to install which makes them a great choice for boats with difficult configurations. Some sailors say that flexible panels are the best choice for fast boats because they don’t impact the aerodynamics of a vessel as much as rigid panels do.

The downside of flexible panels is their low wattage. If there are many appliances on board, you’ll need several panels and you’ll need to find the right place for each of them. They also age faster than rigid panels — a thin-film panel generally lasts for 10-15 years.

Monocrystalline panels are powerful and reliable

Rigid solar modules, monocrystalline and polycrystalline, are heavier and bulkier than thin-film panels. You can fix flexible panels with adhesives, but rigid panels require drilling. They are also more expensive than flexible panels. 

On the other hand, monocrystalline panels are the most efficient type of panels which means that they provide more power for less space. Even one powerful mono panel can be enough for everything that you’ve got on board. They are also much more reliable and will survive any storm that is coming your way. A monocrystalline panel lasts for at least 25 years.

Panels for boat should be efficient and sturdy

The best solar panels for sailboats don’t have to be powerful, but they better be efficient — find the number in the datasheet. For rigid panels anything over 18-19% is fine. Panels also should be sturdy enough to withstand seastorms. You generally also want good shading tolerance since panels often get shaded by masts and sails. Finally, good performance in low-light conditions is appreciated.

Picking bifacial panels, 72/144-cell panels or larger, anything too powerful generally doesn't make a lot of sense. Performance at high temperatures matters less than it does with home systems. Warranties also play a lesser role. You won’t be able to make use of them because they generally have effect only for residential installations.

The markets of thin-film and rigid panels are different. Generally, a manufacturer of flexible panels doesn’t offer mono- or poly-panels. Canadian Solar, Q CELLS and Jinko Solar are good choices when it comes to monocrystalline modules for boats. Renogy , WindyNation and PowerFilm make fine thin-film panels.

Do the math before purchase

The amount of power for your boat depends on the number of appliances on your board. There are two main ways to determine the size of installation that you need. You can take a test trip and see how much of your battery’s charge you’ve spent in one day. You can also do the calculations manually: write down all the appliances on the board with their power rating and number of hours in use per day. You can read about it in detail in our article " How much solar power to sail the seas? " It doesn’t make sense to oversize a marine PV system, because all the excess power will just go to waste.

Keep in mind that adding photovoltaics doesn’t make your vessel a solar boat, unless you have a solar-powered motor. You can switch your boat to solar energy fully, especially if it’s small, but you’ll have to calculate your energy needs accordingly.

Once you’ve purchased your panels, you’ll have to install them properly. You can order professional service or do it yourself. The most popular places for solar panels on a boat are a stern rail, masts, deck and canvas. Thin-film panels can even go on the sails. Ideally, you want a place where panels wouldn’t be shaded by masts on any other parts of a boat.

List of solar panels for a sailboat

We’ve asked our engineer to pick the panels that would complement a small boat well. These are his choices:

ZNShine Solar ZXM6-NH120-370/M

Solar panels from ZNShine Solar are inexpensive and fit all kinds of applications, including boat systems. ZXM6-NH120-370/M provides 370 Watts of power with a 19.88% efficiency. It performs well in low-light conditions. Graphene coating increases power generation and allows self-cleaning. The only downside is a lower wind tolerance, compared to other models: it is rated to withstand 2400 Pa pressure which is comparable to 140 mph wind.

Mission Solar MSE345SX5T

MSE 345 is a simple solar panel for all kinds of applications, including boat installations. Mission Solar panels are manufactured in Texas. The module provides 345 Watts of power with 18.7% efficiency. It is certified for high snow (5400 Pa) and wind loads (4000 Pa). The model is resistant to salt mist corrosion.

Suntech STP 365 S

Suntech is a Chinese company that offers quality budget-friendly solar panels. The STP365S model stands out in line because of its great performance in weak light, such as cloudy weather and mornings. It is designed to withstand harsh weather conditions, and the module is certified to tolerate wind of over 170 mph. Half-cut design makes cells sturdier and improves shading tolerance. Overall, this panel earns a place among the best boat solar panels.

Andrey had been a news editor and freelance writer for a number of medias before joining A1SolarStore team. Climate change and its impact on people's lives has always been among his interests and it partially explains his degree in Philosophy and Ethics.

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Adding Solar Power to a Sailboat

• By Emily Fagan
• Updated: October 18, 2019

During our nearly four-year cruise of Mexico, my husband, Mark, and I lived almost exclusively on 555 watts of solar power charging a 640-amp-hour house battery bank. We anchored out virtually every night aboard our 2008 Hunter 44DS, Groovy , and relied on the sun for power. During one 10-week stretch, while we waited for a replacement engine alternator to arrive, our boat’s solar panels were our sole source of power. We had no backup charging system to turn to, and yet we lived and sailed comfortably the entire time. Mounting solar panels on a sailboat was not difficult, but a few key decisions made a huge difference in how effective our panels were.

A solar-power installation on a sailboat is made up of two independent systems: one system to charge the batteries, and another system to provide 120-volt AC power for household appliances. In the charging system, the solar panels convert sunlight into electrical current and deliver it to the batteries via a solar charge controller. Similar to a voltage regulator, the charge controller acts as a gatekeeper to protect the batteries from receiving more current than they need as they are being charged. In the AC power system, an inverter or inverter/charger converts the 12-volt DC power in the battery into 120 volts AC whenever it is turned on.

Panel Positioning and Wiring Considerations

One of the biggest challenges for sailors installing solar power on a sailboat is finding a place on the boat where the panels will be shaded as little as possible. Just a few square inches of shade on one panel can render that panel all but inoperable. Unfortunately, between the mast, radome, spreaders and boom, shadows cross the deck all day long, especially as the boat swings back and forth at anchor.

What’s worse, if the panels are wired in series rather than in parallel, this little bit of shade can shut down the entire solar-panel array. When we installed solar power on Groovy , we had already lived exclusively on solar power in an RV for over two years. Our RV solar panels had been wired in series, and we had witnessed the array shutting down current production when just half of one panel was shaded.

Choosing whether to wire the panels in series or parallel on a boat affects the wire gauge required, which is why many solar-power installers lean toward wiring the panels in series. Panels wired in series can be wired all the way to the solar charge controller with a thinner-gauge wire than those wired in parallel. This is because the voltage of panels wired in series is additive, while the current remains constant, so the current flowing is just that of a single panel. In contrast, the current flowing from panels that are wired in parallel is additive, while the voltage across them is not. This means that in a parallel installation, the current going to the charge controller is several times higher and requires much thicker cable to avoid any voltage loss over the length of the wire.

Not only is thinner-gauge wire less expensive, but it is also more supple and easier to work with, making the job of snaking it in and around various crevices in the boat and connecting it to the solar charge controller much less of a struggle. Thus the choice between series and parallel wiring boils down to a trade-off between system performance, expense and ease of solar system installation.

Luckily, the size of the wire can be reduced if higher-­voltage solar panels are chosen. Since watts are determined by multiplying volts by amps, a higher-voltage panel that generates the same watts as a lower-voltage panel will produce less current. Therefore, selecting nominal 24-volt panels instead of 12-volt panels allows for the use of thinner wire sizes no matter how they are wired.

Our Marine Solar Panel Design Choices

In our installation, we decided to mount three 185-watt, 24-volt (nominal) Kyocera solar panels high above the cockpit, well aft of the boom, as far away as possible from potential shade. Our Hunter came with a big, solid stainless-steel arch, and we turned to Alejandro Ulloa, a brilliant metal fabricator at Baja Naval Boatyard in Ensenada, Mexico, to build a polished stainless-steel solar-panel arch extension onto the existing structure. He designed the arch extension with integrated telescoping davits to hoist our dinghy as well as support the solar panels. These davits were strong enough — and the lines and blocks had enough purchase — that either of us could lift our light Porta-Bote dinghy with its 6-horsepower outboard without a winch.

We spaced the panels about a half-inch apart and wired them in parallel. Using two twin-lead wires, we snaked the three positive leads and one common ground down through the inside of the arch tubes so they wouldn’t be visible, and placed wire loom over the exposed wires under the panels.

The junction points for the three parallel panels were on positive and negative bus bars inside a combiner box, all mounted in a cockpit lazarette. Inside the combiner box, we installed three breakers, one for each panel. This gave us the ability to shut off any or all of the panels if we needed to (we never did).

We mounted a Xantrex solar charge controller (model XW MPPT 60-150) in a hanging locker, as close to the batteries as possible, in a spot where it was easy to monitor and program. We ran twin-lead wire from the combiner box to the charge controller and from there to the batteries.

Our boat came with three new 12-volt Mastervolt 4D AGM house batteries, all wired in parallel, for a total of 480 amp-hours of capacity. We wanted a bigger house battery bank, and because it is best for the age, type and size of the batteries to be matched, we added a fourth new Mastervolt 4D AGM house battery, which brought our total to 640 amp-hours. Our batteries were installed at the lowest point in the hull, below the floorboards, and they ran the length of the saloon, from just forward of the companionway stairs to just aft of the V-berth stateroom door.

The best way to charge a bank of batteries that are wired in parallel is to span the entire battery bank with the leads coming from the charge controller. We did this by connecting the positive lead from the charge controller to the positive terminal of the first battery in the bank, and the negative lead from the charge controller to the negative terminal of the last battery. By spanning the entire bank, the batteries were charged equally rather than having the charging current focused on just the first battery in the bank.

We feel that AGM batteries are superior to wet cell (flooded) batteries because they can be installed in any orientation, don’t require maintenance, can’t spill (even in a capsize), and charge more quickly. Our Mastervolt batteries, like almost all AGM batteries on the market, are dual-purpose, combining the very different characteristics of both deep-cycle and start batteries. Our batteries work well, but if we were doing an installation from scratch today, we would consider the new Trojan Reliant AGM batteries. These batteries are engineered strictly for deep-cycle use and have been optimized to provide consistent current and maximize battery life.

Our boat came with a Xantrex Freedom 2,500-watt inverter/charger wired into the boat’s AC wiring system with a transfer switch. The inverter/charger performed two functions. While the boat was disconnected from shore power, it converted the batteries’ 12-volt DC power into 120-volt AC power, allowing us to operate 120-volt appliances, like our microwave. When the boat was connected to shore power, it charged the batteries.

Because this inverter/charger was a modified-sine-wave inverter, mimicking AC ­current with a stair-stepped square wave, we also had a 600-watt pure-sine-wave inverter to power our potentially more sensitive electronic devices. We chose Exeltech because its inverters produce an electrical signal that is clean enough to power medical equipment, and they are NASA’s choice for both the Russian and American sides of the International Space Station. For simplicity, rather than wiring the inverter into the cabin’s AC wiring, we plugged ordinary household power strips into the AC outlets on the inverter and plugged our appliances into the power strips. Like the charge controller, the inverter must be located as close to the batteries as possible. Ours was under a settee.

Shade’s Impact on Sailboat Solar Panels

Once our solar installation was completed on our sailboat, we closely observed the effects of shade on our solar-panel array. We were often anchored in an orientation that put the panels in full sun. Just as often, however, we were angled in such a way that shade from the mast and boom covered portions of our panels. It was fascinating to monitor the solar charge controller’s LCD display whenever the sun was forward of the beam — the current from the panels to the batteries fluctuated up and down as we swung at anchor.

Taking notes one morning, we noticed that the charging current was repeatedly creeping up and down between 9.5 and 24.5 amps as the boat moved to and fro. When the entire solar-panel array was in full sun, it generated 24.5 amps of current. When we moved so the mast shaded a portion of one panel, the array generated 15 amps. When it shaded portions of two panels and only one was in full sun, the array produced just 9.5 amps. Of course, it would have been preferable to see a steady 24.5 amps all morning, but this sure beat watching the current drop to zero whenever a shadow crossed a panel.

We discovered that shade makes a huge impact while sailing, too. Surprisingly, it is far worse to have the panels shaded by the sails than to have the panels in full sun but tilted away from its direct rays. One afternoon, we noticed that while we were on a tack that tilted the panels away from the sun, they generated 24.5 amps of current, whereas on a tack where the panels were tilted toward the sun but two of the three were partially shaded by the sails, the current dropped to a mere 10 amps.

Reflections On Our Solar Panel Installation

A wonderful and surprising side benefit of our large solar panels and arch system was that the setup created fabulous shade over the jumpseats at the stern end of the cockpit. Our metal fabricator, Alejandro, placed a support strut at hand-holding height, and sitting in those seats feels secure and comfortable while sailing, no matter the conditions.

After living on solar power for eight years of cruising and land-yacht travel, we’ve learned that you can never have too much solar power. Groovy’s 555 watts was enough to run all our household appliances as needed, including our nearly 4-cubic-foot DC refrigerator, two laptops, a TV/DVD player, and lights at night. However, it was not quite enough power to run all that plus our stand-alone 2.5-cubic-foot DC freezer during the short days and low sun angles of the winter months without supplemental charging from the engine alternator every few days. For the 10 weeks that we did not have a functioning alternator, our solution was to turn off the freezer, which enabled our batteries to reach full charge every afternoon.

Solar power made a world of difference in our cruise. Not only did it allow us to live comfortably and with ample electricity for weeks on end when our engine alternator went on the blink, but as a “set-it-and-forget-it” system, it also gave us the freedom to anchor out for as long as we wished without worrying about the batteries. In our eyes, the solar-panel arch enhanced the beauty and lines of our boat, giving her a sleek and clean appearance. It was true icing on the cake to discover that the panels and arch system also provided much-needed shade over the cockpit and helm from the hot tropical sunshine. If you are preparing for a cruise, consider turning to the sun for electricity and outfitting your sailboat with solar power.

The Installation:

Emily and Mark Fagan offer cruising tips and share their stories and photos on their website, roadslesstraveled.us . They are currently enjoying a land cruise across America aboard an RV.

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Sailing with solar power: A practical guide

• Duncan Kent
• November 13, 2020

The latest solar technology makes self-sufficient cruising much more achievable. Duncan Kent gives the lowdown on everything you need to get your boat sorted

SOLAR POWER ON BOARD

Solar power is fast becoming the most popular and economic method of keeping the batteries charged on a boat.

Particularly now that the efficiency of photovoltaic (PV) panels, charge controllers and batteries is improving every day.

Furthermore, the latest technology in regulators and charge controllers has brought about a noticeable increase in useable power output, so the problems of shading and non-alignment can be compensated for more easily.

Not only has PV equipment become more efficient and cost-effective, but many of the modern devices we want to use on a boat have become less power hungry.

This means it is now far easier to provide your entire yacht’s electrical needs, both 220Vac and 12/24Vdc, from natural energy resources – particularly solar power, even if you are planning on a fully electric boat .

Thinking carefully about how much power you need and how much your boat can accommodate is key to planning a solar array. Credit: Graham Snook

WHAT DO YOU NEED?

For instance, a boat with two new, good quality, deep-cycle house batteries of 100Ah each would supply 100Ah of energy to consume between charges, if you only use the recommended 50% of available charge between each charge cycle to protect the batteries.

From this you could run:

• a modern 12Vdc fridge (approx. 1.5Ah, or 36Ah over 24hrs),
• all LED lighting (say 20Ah per day),
• various small device chargers (20Ah)
• and a number of other items such as water pumps, TVs and stereos (25Ah/day)
• Totalling around 100Ah.
• For this you’d need 400W of solar capacity.

Of course, if you like to run a lot of AC devices off-grid such as hair dryers, microwaves, toasters and the like, then you’re going to need a DC/ AC inverter, which will take you to another level in power consumption terms.

But even then, with careful planning, solar could provide a large portion of the power you need before resorting to engine charging or a generator.

THE AVAILABLE SPACE

In practical terms, a modern 40ft monohull would have the space for around 1,200W of PV panels (cockpit arch, sprayhood top, deck), maybe 1,500W with the addition of a few portable panels for use at anchor.

The 1,200W of fixed position solar array could produce around 360Ah on a sunny summer’s day (zero shading) or more likely 250Ah on the average UK summer’s day.

So that’s enough for your 100Ah general DC consumption plus another 150Ah of AC consumption via the inverter.

Of course, to do this you’ll most likely need to increase your battery capacity to around 400-500Ah for maximum flexibility (you’ll need to store as much as possible during daylight hours), a typical figure for a 40-50ft offshore cruising yacht these days.

Get your solar charging right and you may never need to hook up to shore power

Typical daily inverter loads for a cruising yacht off grid might be:

• induction cooking plate (20min) 60Ah
• microwave (15min) 30Ah
• coffee maker (20mins) 25Ah
• hair dryer (5min) 15Ah
• laptop charger (2h) 10Ah
• or around 140Ah in total.

The trick is to monitor the batteries’ state of charge (SOC) at all times and vary your use of the inverter to suit.

For example, you might want to cook supper mid-afternoon, when solar is in abundance, and then reheat it in the evening when you want to eat it.

In some cases, when you’re cruising in warm climates such as the Med, you might end up with excess charge from your solar panels .

In this situation, many long-term cruisers devise a method of ‘dumping’ the extra energy by heating water for showers.

Do bear in mind if you’re planning to live aboard full time , then it’ll be a whole different story on cloudy days and during the winter, when inverter use might need to be knocked on the head entirely.

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POWER DISCREPANCIES

There’s often confusion as to how much power you can harvest from a solar installation.

A PV panel is nearly always advertised stating its theoretical peak output power (Pw).

But in reality, on a yacht where there are limited areas in which to mount them, they will more likely produce a maximum of 60% of their peak output if mounted horizontally, increasing to 80% if tilted towards the sun and regularly adjusted.

The latter is rarely achievable on a boat, however, as even at anchor it can swing through an arc of 180° in wind or tidal shifts .

Flexible panels can be mounted on sprayhoods or awnings to add power when it’s needed at anchor or in harbour

INSTALLATION

Having trawled through hundreds of ‘deals’ to get the best price on the most efficient panels you can afford you now need to know how to install them to best fulfill your energy generation needs.

The output, even from the highest quality photo-voltaic array, will only be as good as the installation itself.

So following our guidelines should ensure you extract every last drop of energy from your investment.

PANEL MOUNTING

Sailing boats are not the ideal structure on which to mount wide, flat PV panels.

So before you go ahead and purchase what looks like the biggest and best, take a few minutes to decide on exactly where you can mount them, as this will affect what size and type of panels you should buy.

In many cases the first choice would be on an arch, davits or gantry aft, especially if you already have, or plan to fit one.

Dinghy davits, particularly on multihulls, can support a huge solar capacity

These allow a solid metal framework to be constructed that will be strong enough to take the heavier, more productive rigid PV panels.

You can also build in some form of adjuster to the framework that will allow the panels to be orientated towards the sun for the best performance.

With luck (or careful planning) a gantry will also keep them aft of the boom, thereby eliminating loss of output caused by boom shading.

The next most popular position for mounting the panels is on a cockpit sprayhood or bimini, although this will often mean using the flexible or semi-flexible panels, which are generally less efficient than the rigid ones for the same area.

ELEVATED MOUNTING

Alternatively, there are kits available for mounting panels onto lifelines, which can allow their elevation to be manually adjusted to a certain degree.

Pole-mounted panels can be used for maximum adjustability

Finally, panels can be fitted directly onto the deck by either gluing them down using mastic or attaching them onto a rigid support frame.

Once again you will probably need to use semi-flexible panels – especially if the deck surface is curved.

Rigid, glass-coated panels will obviously not be suitable for deck mounting in an area that is frequently walked over.

Don’t be tempted to drill through the panels, even along the edges, as this will invalidate the warranty and possibly damage the panel.

With solid panels, the ability to adjust the angle can add significantly to output

It might seem obvious, but the key to an efficient system is to avoid shading wherever possible.

It’s no good fitting expensive, high-efficiency PVs right under the boom as they’ll perform little better than the cheaper types.

Saying that, in good quality panels each cell will be isolated from the next by a series of diodes (one-way electrical valves), so that if one cell is shaded at least it won’t drag down the other cells within the same panel.

Older panels often didn’t have these, so the slightest partial shading caused the output of the entire panel to cease.

OVERHEATING

Another important factor that is often ignored when installing the panels is that of overheating.

If a PV panel gets too hot, which is quite likely if mounted directly onto a flat surface without an air gap behind, its output will drop quite noticeably.

To allow for some air circulation behind the panels it’s best to apply mastic adhesive in numerous large dabs.

This is best achieved by placing wooden spacer strips between the dabs until the mastic has completely cured, after which the spacers can be removed.

You might need some form of trim around one or more of the outside edges, though, if they are positioned where sheets and other lines might get caught under them.

Raising the panels up will also help water to drain off and thereby helping to avoid possible delamination from sitting in water for too long.

CHARGE CONTROL

A PV module cannot supply an electrical device directly due to the changeability of the sunlight, which in turns varies the current it can produce.

Therefore, it has to be connected to a battery, which stores and smooths its output.

Whatever the size of your solar array you will need to fit a regulator, or charge controller as they are now more commonly known, to the system in order to control the output and to help extract as much power from the panels as possible.

There are two types of PV charge controller.

The older designs, called Pulse Width Modulation (PWM) types, were fairly basic voltage regulators and simply output volts at just above battery level.

The latest controllers use Multi Power Point Tracking (MPPT) technology and can accept much higher input voltages (up to 240Vdc).

MPPT controllers can be up to 30% more efficient as they use the peak output of the panels to charge the batteries, even compensating for partial shading.

BEWARE FAKE GEAR

If you buy online do be careful to ensure you’re getting what you pay for.

There are a huge number of fake MPPTs out there, which are simply the much cheaper PWM dressed up with fake labels.

It’s hard to tell which is which, but the old adage of ‘if it looks too good to be true, it usually is’ makes good sense.

MPPT controllers are usually bigger and heavier than PWMs, but if in doubt call or email the supplier to discuss the pros and cons of their kit before buying.

If they’re not happy to chat and advise you then I would steer clear of their gear.

Some good MPPTs are made in China, but unless they have a UK supplier, I wouldn’t bother with them as you’ll have no follow-up advice.

To calculate what size controller you need simply divide the panel’s peak power in Watts (Wp) by the battery voltage, which will give you the maximum current (Amps) they could theoretically supply.

For example 240W/12V = 20A. Although it’s unlikely you’ll ever get near the peak output from any PV panel, it’s best to go for the maximum possible.

Induction cooking is now a reality on board, even without shore power

PV panels come with a short length of cable, usually around 1m long.

Some are supplied with MC4 connectors already attached but most only provide bare wires.

The latter can be easily extended using proper waterproof connections but thought must be given as to the current rating and voltage drop (usually max 3%) for the size of cable you intend to use.

If in doubt, bigger is better!

Panels can sometimes be ordered with the wiring on the back so that the cable can go straight below deck through a hole under the panel.

You may need to fit extra battery capacity if you want to run an inverter from solar charging

SERIES OR PARALLEL?

A commonly asked question is ‘should I wire my PV panels in series or in parallel?’

The simple answer is, if there’s any danger of frequent shading to one or more of the panels then install them in parallel.

If wired in series the shading of a single panel will drag down the output from all of the others in the same series.

PARALLEL IS PREFERRED

Most commonly, multiple panels are wired together in parallel to a single charge controller, with diodes protecting each panel from discharging the others should one become partially shaded.

With the advent of MPPT controllers, however, there can sometimes be a benefit to wiring two or more identical panels into a series bank, thereby presenting a higher voltage to the controller.

It’s worth noting that, like batteries, wiring PV panels in series increases the voltage only – the current capacity of the array remains the same as for a single panel.

‘Where’s the benefit of wiring them in series then?’ you might ask.

Well, the higher the voltage fed into the MPPT, the more consistent it will be with its output, which could, in some cases, prove more efficient than a parallel installation with PWM controllers.

It’s also likely to be necessary if you have a 24V domestic system.

SERIES WIRING

Series wiring is usually only done when the cable runs are long, as it helps negate the voltage drop caused by the resistance of the cable.

While a decent controller will have no problem handling the output from four or even five panels wired in series, it is often inappropriate for sailing yachts as shading just one of the panels will reduce the output of the entire series array.

If you need to do so in order to reduce cable runs then it’s best to split the panels between each side of the boat – a series bank on each side.

If you do this, then you would ideally fit a separate controller to each series PV bank and then connect their outputs together in parallel to the battery bank.

Note, however, that panels wired in series must all be the same types with an equal number of cells per panel.

Furthermore, the charge controller needs to be sized for the total of all panel voltages added together and the current rating of one individual panel.

Differently rated panels can be connected together in parallel but only if each panel has its own controller.

The outputs of the individual controllers can then be joined together to go to the battery bank.

BATTERY BANK QUESTION

Another frequently asked question is ‘Can I connect another charging source to the battery bank while the solar array is charging?’

The answer is yes.

Any decent PV controller will be protected against feedback from other charging sources.

Think carefully about where shade from mast, boom and rigging will fall. Credit: Graham Snook Photography

CABLE SIZE AND CONNECTORS

A frequent cause of reduced output from PV arrays is wiring that is too small.

The resistance of a wire conductor increases in direct proportion to its cross-sectional area, so go as big as is practicable for the least cable loss.

Each panel should be supplied with the correctly sized cables for its own maximum output.

But if you’re combining panels, either in parallel or in series, you will clearly need to rate the single feed cable to suit the maximum current available at theoretical peak solar output and to minimise voltage drop.

Likewise, the cable from the controller to the batteries should be sized to suit the controller’s maximum output current and protected with a fuse.

For outside it’s important to use exterior grade cable, which is double- insulated and UV-proof.

WEATHERPROOF CONNECTORS

And wherever possible use compatible weatherproof connectors (usually MC4) to those found on the panels rather than cutting off the plugs and hard-wiring them.

Field- assembly MC4 plugs are available, so you don’t have to drill large holes in the decks or bulkheads when feeding the cables through.

When joining more than one panel together try to use the approved multiway connectors; not only do they keep the wiring neat and tidy, but they also offer a greater contact area than budget terminal blocks.

If you have to use screw-type connectors make sure to fit proper ferrules to the wire first to avoid any stray wires in the multistrand shorting across the terminals.

When feeding a cable from above to below deck, try to go through an upright bulkhead where possible to minimise ‘pooling’ of water around the access hole.

Also, use a proper watertight deck seal that matches the cable you’re using.

If drilling through a cored deck you need to drill a larger hole first, fill it with epoxy resin and then drill the required size hole through the epoxy to ensure no water gets into the deck core.

Ideally, the charge controller should be mounted no further than 2m from the battery bank.

If you need to go further, you’ll require larger cabling to reduce the voltage drop.

A generous solar array will keep you self- sufficient indefinitely. Credit: Graham Snook Photography

CONTROLLER LOAD TERMINALS

There is often confusion over the ‘load’ output of a charge controller (often depicted by a light bulb) and what can safely be connected to these terminals.

Rarely explained in the manual, the load terminals should be pretty much ignored in a marine installation as the output on these terminals is usually very limited (10A max).

Some attach an LED light to them to indicate the controller is operating, but all your usual electrical loads should remain connected to the batteries with the battery terminals on the controller connected directly to that battery bank via a fuse.

It is possible, though, to control a high-current switching relay in certain conditions.

Parallel installation is more resilient to shading, but a series installation will increase peak charging outputs. A combination of the two offers some of the benefit of both

CIRCUIT MONITORING

Unlike most cheap PWMs, the majority of good quality MPPT charge controllers come with an alphanumeric LCD screen to let you know what is going on.

This can either be a remote display or simply one on the front of the box.

It’s obviously a lot better to have a proper numerical display than to rely on a few flashing LEDs to tell you when something’s not right.

So if your chosen controller doesn’t have one be sure to fit a battery monitor (the shunt type) into your solar circuit between the controller and the batteries.

It doesn’t have to be a very ‘smart’ monitor, just one that can display the voltage and current being supplied by the panels.

For smartphone addicts there are several wifi apps that will do the job remotely on your phone or tablet.

DEVICE PROTECTION

All good quality PV panels feature built-in diode protection between each cell to prevent a shaded cell from dragging down the productive ones.

In addition, there will be internal blocking diodes on the final output to protect the panel from polarity reversal and to ensure that the batteries can’t discharge back into the panel during the night.

The latter can be added externally, the former can’t, so check before you buy.

A fuse, rated just above the maximum current available, should be fitted between each panel and the charge controller.

Another fuse should then be installed between the charge controller’s output and the batteries.

In the case of multiple arrays, this second fuse will be rated higher than the individual panel fuses and should match the maximum current rating of the cable.

With this protection installed other charging devices can be connected in parallel at the battery, meaning the solar can be left connected even when you are hooked up to shore power and the battery charger is operating.

In some circumstances, however, this arrangement can affect the sensing of the battery by the charger, causing it to fall back into float mode.

If this becomes apparent it can be overcome by installing a manual/auto switch to disconnect the solar array when on shore power.

Check the flex of the solar panel is sufficient for your deck

EXCESS POWER DUMPING

A solar charge controller works by disconnecting the supply from the PV panels when the batteries are fully charged.

But for some full-time liveaboards in sunny climates that can be considered a waste, when the excess power could be put to good use – heating water, say.

This is commonly done using an inverter to supply AC power to the heating element.

Alternatively, you can now buy a 12Vdc element for your calorifier (hot water tank) and supply this directly from your battery bank.

Both of these methods would require a voltage sensitive relay (VSR) to disconnect the element should the battery voltage drop below a pre-set level.

Don’t expect boiling hot water, as there will probably only be enough spare power to take the chill off it before your battery bank reaches its lower threshold voltage.

A 600W/12V element will draw some 50A, from the batteries, whereas a 1kW AC element run through an inverter will need close to 100A.

A small, semi-flexible panel will be sufficient for keeping batteries trickle charged, but not for heavy use

RIGID, FLEXIBLE, OR SEMI FLEXIBLE?

Despite massive recent improvements in semi-flexible panels in recent years, the solid glass panels still offer a higher power density.

That said, they are heavier, more awkward to mount and can’t be walked on, so unless you have a dedicated gantry aft, you’re better off choosing the more rugged semi-flexibles.

Modules incorporating monocrystalline cells also have a better output than those with polycrystalline cells (that’s cells made from a single slice of silicon as opposed to layers of smaller pieces).

Output voltage also depends on the number of cells on the panel.

In the past this has commonly been 32, but now some 36 and even 40 cell panels are available.

That said, they’re larger, of course, so an array of interconnected smaller panels might be a better solution.

Module efficiency is now more often around the 20% mark, as opposed to 12-15% for older models and semi- flexible (up to 20° bend) are usually better than flexible (up to 180° bend).

A rigid panel is more efficient, but less robust

There are a huge number of panels on the market, but many use the same cells.

Sunpower Maxeon cells are exceptionally good, as are the Panasonic HIT range and LG, but they are pricey.

If the maker is offering a 25-year guarantee instead of a 3-5 year one, you can be pretty confident they’re good.

When it comes to charge controllers it’s definitely worth paying a little more for a decent MPPT.

A cheap PWM might be okay just to keep a small starter battery charged with a 30W panel, but the MPPT will give you much more when it comes to heavy service.

Victron are probably top of the range, while cheaper brands like MakeSkyBlue and EPever are also good value – but treat imports of unclear origin with care.

ABOUT THE AUTHOR

Duncan Kent has been evaluating and reviewing yachts and marine equipment for the past 30 years

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• Inside Practical Sailor

Estimating Solar Panel Size for Boats

The starting point for a successful solar panel installation is quantifying your requirements. We present here a simple analysis based on the test boat used for our recent report on choosing and installing a solar panel. Some values are from experience, and others are accepted rules of thumb. For more details on choosing and installing a solar panel, see the March 2018 issue of Practical Sailor online.

Energy Balance

Look up the current draw of each piece of equipment (confirm with panel ammeter if available) and estimate the number of hours operated. Record the number and capacity of your batteries, recognizing that you cannot draw below 50% charge without shortening their life, and that you will seldom charge past 85% while away from the dock-as a result, only 35% of nameplate capacity is really useable. Finally, total your charging sources, including engine, wind, and solar. For solar, take the rated wattage x 5 hours/12 = amp-hours while on passage and wattage x 7 hours/12 = amp-hours while at anchor (sails do not shade and the boom can be rigged out to the side). This is far below the rated capacity-sailors in the tropics will do better, and sailors farther north or sailing in the winter more poorly-but this is an accepted starting point.

Estimating Panel Output

How many days can you manage with poor generation? Are you willing to economize during a long cloudy stretch? Will you recharge at a marina or by running the engine periodically? Long-term cruisers appreciate an abundance of power, while the occasional cruisers may be satisfied with less.

Saving Power

Every AH (amp-hour) consumed has a real cost in weight, panels, and dollars. If you can reduce consumption by 50 AH/day you will save a battery (the useable capacity), a 120 watt panel, and perhaps a mounting arch. The cost savings might be $500 and 150 pounds for just a few bulbs.

• Lighting. Switch from incandescent to LED and fluorescent lighting, starting with the lights you use most. We use LEDs and fluorescent for the anchor, salon, and cockpit lights, but since we seldom run at night, we left the running and steaming lights alone. Likewise, the deck light and many task lights remain halogen or incandescent; they are not used enough to matter.
• Go to bed at night and get up with the sun. Big savings in juice and more time to play.
• The gas solenoid is a big user for us; it runs the propane fridge and cabin heater, so it is on for long hours, but we can turn it off at night or go without refrigeration now and then.
• Fans. Run them on low speed and watch the hours. A wind scoop doesn’t use power.
• Instruments. Do you actually need GPS and other instruments full-time on passage? Twenty years ago they didn’t even exist. Balance the sails to minimize the load on the autopilot.

If you’re not sure if it’s time to upgrade or replace your solar panels, the upcoming June 2023 issue offers detailed guidance on evaluating old solar panels and house batteries. If you are upgrading your boat’s electrical system, adding new accessories, or just replacing some wires, our recently updated six-volume ebook Marine Electrical Systems covers everything you need to know about electrical systems–including Batteries, System Installation (including rewiring and lightning protection), Panels, Monitors, Charging, Alternative Energy, and AC Systems.

Power Usage Table

Drew Frye is a frequent contributor to Practical Sailor. He blogs at www.saildelmarva.blogspot.com

RELATED ARTICLES MORE FROM AUTHOR

On watch: this 60-year-old hinckley pilot 35 is also a working girl.

Good subject; article can not be understood by most people.

What people need to know is: I have a x feet sailboat; my boat sits idle y days/week, I live in z area; how many watts will I need most of the time?

What people need to know is; do I have enough places to put the panels, are there panels designed to work well vertically, are flexible panels practical?, etc.

There really isn’t any way to get a realistic daily usage estimate without an amp-hour meter. Do you actually know how many hours per day the fridge compressor runs? They cost a couple hundred and take a couple hours to install.

On my boat, it’s the fridge that is the energy hog. Long ago, I replaced almost all lights (cabin, navigation, and anchor) with LEDs. Cut energy use significantly and worth the money. Newer electronics also have lower draw than very old units. Radars now work at a tenth the prior draw.

Can any readers comment on solar panel output for various mount locations? Bimini, dodger, rotating on stanchions, cabin top What’s best? What’s acceptable?

BTW Boats with a head and galley qualify as second homes and thus are eligible for federal credits for solar panels and batteries bigger than 250 amp-hours. 30% off

After communicating with someone cruising in the Pacific I followed his advice…”Put up as much solar you have room for and you can afford.” With that advice I installed 4x140W (560W) Kyocera panels; 2x140W over the dodger and 2x140W on a new stern arch on my Tayana Vancouver 42. The panels are permanently fixed and I never worry about adjusting them for the best angle. On my roundtrip to Hawaii I never had to start the diesel engine to charge the batteries and I don’t have a genset. I did use the Pacific Cup 2012 Sample Energy Budget as a template and modified it for determining my energy use and highly recommend it. I strongly second the comments about being reasonable in your use of electrical power as it is the easiest and most cost-effective way to manage that requirement…take a very hard look at everything that uses electrical power; do you really need it or use it as much as you do?

I don’t understand the reference to just LA/Flood batteries…

I havev all LiFePo4 both main bank and 12v house and never have any power issues…

I simply maxed out as much as physically possible on my narrow beam 40ft sloop both PV and storage…

A couple items i dont understand. The ‘charging chart’ above has engine charging at 2 amps. This seems very low. Most alternators output in excess of 50 amps. Plus the chart has 2 amps for 5 hrs with a total AH of blank. Also dont understand the ‘solar charging row’. The number just dont jive.

The 2 amps is easy; the example boat had two 9.9 hp outboards that charge 1 amp each. Yes, 2 Amps x 5 hours should have been 10 Ah. Of course, many days the engine does not run.

The refrigeration on the boat in the example was propane, thus no usage.

Additionally, it should be obvious that not all of the items will happen every day. Passage making and at-anchor are different.

Every boat is different. The idea is that by estimating usage, generation, and inventory (batteries) you can better understand your system.

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Field test: PV Modules

A real world comparison between Mono, Poly, PERC and Dual PV Modules.

* This is a field test and the results are specific for this installation on this location please research which is the best solution for your own situation as the results can be different based on environmental influences.

Total solar yield as of 27/03/2023 when the results were reset: Mono: 9158 kWh Split-cell: 9511 kWh Poly: 9113 kWh Perc: 9471 kWh Perc-east: 1970 kWh Perc-west: 1730 kWh

Enjoy the sound of silence

Harnessing the power of the wind makes sailing an unforgettable experience. All you want to hear is the sound of the wind blowing and the waves breaking. But what is the best way to power the on-board electronics while the engine and generator are switched off? Victron combines energy storage and solar generation to provide the power you need. In absolute silence.

Whether you’re sailing away for the weekend or planning a trip around the world, big chance the very same Victron solution could support both. It’s the level of comfort that really determines your optimal solution aboard. With Victron you can power just about any plans, but as an example we illustrated ‘normal’ and ‘heavier’ power profiles in the below for the ‘average’ sailing yacht.

Consumption

• Power Profile
• Complete system

How much do you need?

A modern sailing yacht is packed with a lot of electrical equipment. Most things used to run the boat usually use DC, bigger (household) appliances need AC. When it comes to estimating power consumption, many just add up the Watts. Time is equally important. A microwave might use 1000 Watts, but only for 2 minutes. A fridge might consume as little as 50 Watts, but is turned on 24 hours a day.

For inspirational purposes we’ve outlined 2 system examples based on ‘normal’ and ‘heavier’ use.

1.2 - 2.4 kWh / day

'normal' and 'heavier' energy consumption. Read more

The microwave uses 1000W an hour but is only on for 2 minutes a day. 1000W / 60 x 2 = 0.03 kWh / 2 minutes

The fridge uses 50W an hour but is on the entire day (actually cooling ½ the day). 50W x 24hrs/2 = 0.6 kWh / day

Storage & conversion

How much energy should be stored.

Storing energy allows you to live of shorepower at sea or lets you use solar power harvested during the day over night. The inverter will convert the stored power to 230V. Sailing yachts typically experience long intervals between battery recharges, so your house battery should have a generous capacity. As a rule of thumb, we’re calculating with 48 hrs on board without shore power shore/engine/generator/solar power. Multiply the daily power consumption x days for even greater independency.

The storage capacity of a lithium battery should be two times the daily power consumption.

Due to its ±50% smaller discharge capacity, the storage capacity of a lead-acid battery should be four times the daily power consumption.

The inverter should be sized to handle the average load continuously and should match the expected peak power current, which our inverters handle very well (on average 2 x their continuous current).

Where does the power come from?

Sources of power, power profile.

Normal and heavier power profiles in kWh, based on the daily energy consumption, which should be in balance with the generation.

Storage batteries in Ah, double the capacity using lead-acid batteries.

It seems like your browser does not support the latest technologies. To see this section properly, consider using a modern browser.

System diagram

For a lithium and lead-acid battery based system.

How do the system design considerations translate into a robust system?

GX 4G modules

The professionals choice:

You’ll want to bring small devices on board for your trip. Or use household appliances like a microwave. These usually run of an AC outlet. Think of:

• Phone charger
• Refrigerator

Being able to plug-in these device saves you the trouble of finding a DC version.

Boat engines

Sailing yachts have one or two diesel engines (Catamarans) to get from harbour to horizon. The engines come with alternators to charge the engine batteries, drive fuel pumps, etc.

Once the starter batteries are recharged, the engines can also power the boat electrics and recharge the house battery. On bigger yachts you’ll find power hungry DC equipment such as anchor windlasses and bow thrusters. The engines have to be running before you can use them.

BatteryProtect

Discharging your battery too far will damage it. Adding a Victron BatteryProtect will disconnect the boat’s electronics when the battery voltage drops below a pre-set level. It will also automatically reconnect everything when the battery is sufficiently recharged.

There is more to a Victron BatteryProtect. The built-in shutdown delay ensures that vital electronics aren’t disconnected in error, i.e. when starting the engine causes a short drop in battery voltage.

Battery Management Systems

Battery management systems take excellent care of Lithium batteries, protecting the individual cells of LiFePO4 batteries against over voltage, under voltage and over temperature and will shut down or reduce charging (VE.Bus products only) or disconnect the loads when this occurs.

Victron Energy offers several BMS options, in general the VE.Bus BMS and smallBMS signal separate devices to disconnect the charging (Inverter/Chargers, Cyrix-Li, DC-DC chargers) or disconnect the loads (BatteryProtect, Inverter/Charger), the modular Lynx distribution system features the Lynx BMS and other modules for more control over the DC busbar. For vehicles and boats all-in-one functionalities are available in the Smart BMS versions for Victron Lithium batteries, but also include current limiting to protect the alternator from overheating and BatteryProtect-like functionality to shut down the loads when pre-set critical battery conditions are met.

Victron Energy also offers full flexibility when it comes to selecting a third-party off-grid battery bank (and their BMS) of choice. A large number of well supported Lithium battery manufacturers can be easily integrated through the use of a mandatory GX-device. This flexibility enables our customers to perfectly match their off-grid needs for their unique power situation. When working with unsupported brands, a Victron Energy Battery Monitor is required to pass on accurate state of charge readings to the wider system.

Battery Monitors

BatteryCombiner

The Cyrix BatteryCombiner is the only safe way to connect the house battery to the starter battery (to start your boat’s engines). With a BatteryCombiner you can charge the house battery from the alternator without running the risk of draining the starter battery (which always should be ready to go). When other sources of power are available (eg. shore/solar/generator power), the Cyrix BatteryCombiner will allow bi-directional charging from the house battery to the starter battery.

When the Voltages of the starter and house batteries are the same, use a Cyrix: its current rating should be equal or bigger than the current rating of the alternator. If the house battery is Lithium and the alternators Amperage is smaller than the house battery, or when the Voltages of the starter and house battery are different: use a Orion or Buck-Boost.

Boat Network

Keeping grips on all the systems on board can be a hassle. The solution: tie everything together in a single boat network using NMEA communication standards. Your boat network can include navigation equipment, tank senders, battery monitoring and much more. The status information can trigger alarms and shutdowns, adding to the safety on board. The Cerbo GX now supports the NMEA2000 out protocol, allowing you to monitor your boat’s network of systems from wherever you are.

The BMS 12/200 is a dedicated battery management system (BMS) that protects Victron Smart 12,8V LFP batteries against deep discharges, overcharging and high temperatures with up to 200 Amps maximum DC current. When critical values are exceeded, the BMS acts immediately: loads are disconnected physically in case of a deep discharge and charging is stopped when there is a risk of overcharging. High temperatures trigger an immediate end to both charging and discharging.

This is the only BMS that can be directly connected to an alternator, protecting them from overload/overheating. This works with a combination of an AB fuse (rated in accordance with the expected max load current of the alternator) and an internal programmable input (which limits the input current electronically to 80% of the AB fuse).

Please check your manufacturer for the maximum charging current of your alternator and size AB fuses of the BMS 12/200 accordingly, see manual.

When different Lithium batteries & higher voltages are used, other solutions are needed, such as the VE.bus BMS and Lynx Ion BMS.

Boat Electronics

A sailing yacht is home to several electronic devices. These are all connected to the house battery. Think of:

• Boat control panel
• Log/depth sounder
• Chart-plotter or GPS
• Navigation lights
• Bow thruster
• Interior lighting
• Music player

The Victron Cerbo GX is the communication-centre of your boat’s installation, allowing you to always have perfect control from wherever you are and maximises its performance. Simply connect through our Victron Remote Management (VRM) portal, or access directly, using the optional GX Touch 50 screen, a Multi Functional Display or our VictronConnect app thanks to its added Bluetooth capability.

The Victron Cerbo GX is an easy to use visual system. Instantly monitor the battery state of charge, power consumption, power harvest from PV, generator, and mains, or check tank levels and temperature measurements. Easily control the shore power input current limit, (auto)start/stop generator(s) or even set quiet periods to avoid starting the generator in the middle of the night. Change any setting to optimise the system, follow up on alerts, perform diagnostic checks and resolve challenges remotely. The Cerbo GX turns any power challenge into an effortless experience.

DC-DC chargers

DC-DC converters, or battery-to-battery chargers (converters with built-in charge algorithms) are used in dual battery systems, where the (smart) alternator and the start battery are combined with the service battery (of equal or different voltages) to charge it. They can also be used to charge applications that have dedicated batteries (eg. bow thrusters), or to power applications that have a voltage different than the service battery bank.

Most DC-DC chargers can be used in 12V or 24V systems and all are suitable for both lead acid and lithium batteries. Some DC-DC charger models can be parallel connected to increase the output current. DC-DC chargers are a perfect and safe solution to charge Lithium battery banks from smart alternators (and lead-acid batteries for that matter).

Charging lithium batteries from the alternator Most alternators cannot be directly connected to lithium batteries. A lithium battery will draw more current than the alternator can supply, which may result in permanent alternator damage. To not damage the alternator, current limiting is one of the options to stay within the safe zone of the alternator.

Victron offers multiple solutions to solve this problem, of which one of them are the DC-DC converters:

• DC-DC converters act as a current limiter between the alternator and the battery: the battery can be safely charged without blowing up the alternator.
• Victron also offers alternative solutions for dual battery systems powered by alternators. Some (smart) BMS products physically limit the current drawn from the alternator, in other systems, battery combiners might be a solid option. See the datasheets for more info.

GX GSM Dongle

The Victron GX GSM is a 3G cellular modem that enables GX devices with mobile internet for the system and connection to the VRM Portal, allowing you to monitor your system from remote. When the boat is in range of a 3G network, it will send data to the VRM website and you can monitor the boat from your smartphone. The GSM module adds tracking the boat, recording your trips and putting up a geo-fence around the boat. You will get an alert via mail when the boat travels outside the geo-fence area.

The Victron Energy Cerbo GX is the communication-centre of your systems installation, allowing you to always have perfect control from wherever you are and maximises its performance. The optional GX Touch 50 is a companion to the Cerbo GX, it’s five inch touch screen display gives an instant overview of your system and allows you to adjust settings in the blink of an eye.

Instantly monitor the battery state of charge, power consumption, power harvest from PV, generator, and mains, or check tank levels and temperature measurements. Easily control the shore power input current limit, (auto)start/stop generator(s) or even set quiet periods to avoid starting the generator in the middle of the night. Change any setting to optimise the system, follow up on alerts, perform diagnostic checks and resolve challenges remotely with the free Victron Remote Management (VRM) portal.

Galvanic Isolator

A galvanic isolator prevents electrolytic corrosion. The isolator is mounted directly behind the shore power connector on board. It blocks DC currents that might leak through the shore power earth terminal. These currents can cause corrosion to all metal parts under water, like the hull, propeller, shaft, etc. The galvanic isolator should have the same power rating as the incoming shore power.

It’s a misunderstanding that galvanic corrosion occurs only in metal and aluminium hulls. In fact it can occur on any boat as soon as a metallic part (the shaft and propeller) is in contact with water. Galvanic corrosion will quickly dissolve your sacrificial anodes, and attack the shaft, propeller and other metal parts in contact with water as soon as the boat is connected to the shore-side supply. It might therefore be tempting not to connect the ground conductor: this is however extremely dangerous because Ground Fault Current Interrupters will not work nor will a fuse blow in case of a short circuit to a metal part on the boat.

The safe option is to use a Galvanic Isolator for non-metal smaller boats, or use an isolation transformer for metal boats or boats with bigger systems.

House battery

The house battery stores power for the boat’s electrical system. Sailing yachts typically have long intervals between battery recharges and the house battery should have a generous capacity.

For a house battery you can choose from two types: lead-acid and lithium. There are various reasons to favour one over the other. Here are a few common ones:

Inverter/Charger

The inverter/charger is the heart of the system. In the marina, it charges the batteries from shore power. While sailing it inverts the energy from the boat’s battery into AC power for household devices. The switch from charging to inverting and from inverting to charging is seamless.

• Victron inverter/chargers come with a handful of outstanding features:
• PowerControl: automatically manage battery charging to prevent an overload of the generator or shore power.
• PowerAssist: uses the battery as a buffer to assist the shore power during peak power demand.
• Perfect power: even sensitive devices run flawlessly on the pure sine wave power.
• High peak-power: use motorised equipment without overheating.
• Low self consumption.

For this power profile we would recommend:

We would recommend our Multiplus-II inverter/charger. If you have a generator on board you’ll need a Quattro inverter/charger, which has an extra input (shore power and generator).

We strongly recommend 24 Volts for new boats. The higher voltage is simply a better choice when it comes to meeting the power demands of a modern sailing yacht. If your boat’s system is based on 12 Volts, select a 12 Volts unit instead.

MFD GX Integration

The Victron integration between our GX range and several leading Multi Functional Display manufacturer brands enables you to easily connect an MDF to the heart of your power system such as the Cerbo GX, or the GX enabled Multiplus-II GX. Once connected you can easily monitor and control your boat’s power system, right on your Glass Bridge.

Shore Power

In the marina, the boat will be connected to shore power. Shore power recharges the batteries. It can also be used for maintenance and to run large AC loads.

Often shore power is limited in how much power you can draw, i.e. just 10 Amps. Berths with higher ratings might not always be available. Victron inverter/chargers allow you set a maximum shore power current. Now you can charge your batteries and turn on any equipment without blowing a fuse.

Sometimes shore power is less than perfect. You might run into voltage drops if you’re at the far end of the harbour. There could also be power surges, which could harm sensitive equipment on board. Victron’s inverter/chargers smooth out these problems and turn bad power into perfect power.

Solar charger

A solar charger- also called MPPT controller, harvests the power from the solar panels to charge the house battery. Solar chargers have the same charging cycles as our regular, fully automatic, battery chargers. When your boat is moored without shore spower, solar power is a great way to keep the batteries charged.

In a marine environment, the performance of solar panels changes constantly. Victron’s solar controllers use ultra fast maximum power point tracking to squeeze up to 30% more power out of your panels.

The rating of the solar charger is defined by the size of the solar panel. For solar panels of less than 150W or less, choose a 75/10 charger. If your solar panel produces between 150 and 220W, pick a 75/15 instead.

Solar panel

More and more sailing yachts area equipped with solar panels. After all, they extend the autonomy range without the noise of a diesel engine and… for free. Victron offers a wide range of small, highly efficient, solar panels that are just perfect for boats.

Starter Battery

The starter battery is needed to start your boat’s engine. These batteries are different from house batteries and engineered to deal with a large discharge current. The starter battery should always be ready to go. It’s best to isolate the important starter battery from all other electrical circuits on board, so it cannot be accidentally drained of power.

VE.Direct Bluetooth Smart dongle

The Bluetooth dongle enables you to use the VictronConnect app with VE.Direct enabled devices (without Bluetooth built-in). With the app you can have real-time insight and full control, and you can access all VE.Direct enabled devices such as the smaller VE.Direct inverters, the BMV 70x series battery monitors or MPPT solar controllers.

VictronConnect

All Victron products on your boat can be monitored and controlled from the palm of your hand. Just connect the VictronConnect App via Bluetooth and you’ll have direct access to values like battery voltage and current. You can also turn devices on or off, as well as change their settings.

VRM - Victron Remote Management

Monitor and manage.

Monitor and manage your Victron Energy systems from anywhere and catch potential issues early by setting alerts and alarms. With VRM you are always in perfect control from wherever you are.

VRM works with a GX-device such as the Cerbo GX with internet connection, the GlobalLink 520 or GSM LTE 4-g for smaller systems.

Monitor the battery state of charge, power consumption, power harvest from solar, generator and mains in real-time. Optimise the energy harvest and usage with history graphs and detailed analytical reports. Catch potential issues early by setting alerts and follow up on alarms to prevent definitive system failure.

Easily control the shore power input current limit, switch on the inverter, (auto)start/stop generators or even set quiet periods to avoid starting the generator in the middle of the night. With VRM you can change any setting, follow up on alarms, perform diagnostic checks and resolve challenges from wherever you are.

Lynx Smart BMS

The Lynx Smart BMS is a dedicated Battery Management System for Victron Lithium Smart Batteries (for non Victron Lithium batteries, see below). There are multiple BMS-es available for our Smart Lithium series of batteries, and the Lynx Smart is the most feature rich and complete option. Its main features are:

• Built-in 500A contactor, used as a fallback safety mechanism and also suitable as a remote controllable main systems switch.
• Battery monitor, indicating state of charge percentage and more data.
• Pre-alarm signal: provide a warning before the system shuts down due to -for example- a low cell.
• Bluetooth for use with our VictronConnect App, for setup and monitoring.
• Local and remote monitoring using a Victron GX device, for example the Cerbo GX.

Battery Management System

The dedicated battery management system (BMS) protects Victron Lithium Smart batteries against deep discharges, overcharging and high temperatures. When critical values are exceeded, the BMS acts immediately: loads are disconnected physically in case of a deep discharge and charging is stopped when there is a risk of overcharging. High temperatures trigger an immediate end to both charging and discharging.

Battery monitoring

Lynx Distribution system

Non Victron Lithium batteries

Lynx Distributor

The Lynx Distributor is a modular DC busbar, with locations for four DC fuses. It will monitor the status of each fuse, and indicate its condition with a LED on the front. When connected to a Lynx Smart BMS or Lynx Shunt, the status of the fuses will be visible in VictronConnect and VRM (when the Lynx Smart BMS is connected to a GX-device).

Multiple Lynx Distributors can be used to connect all the DC-loads and charge sources on one side of the BMS, on the other side, a Lynx Power In (without fuses) or another Lynx Distributor (with fuses) can be used to connect the battery bank to the modular busbar.

This product is part of the modular Lynx busbar system that also provides the Lynx Smart BMS, a dedicated Battery Management System for Victron Lithium Smart Batteries (for non Victron Lithium batteries, use the Lynx Shunt).

Power consumption will vary from yacht to yacht and from owner to owner, even on sailing yachts. Here are two examples - with a normal and a heavier daily energy consumption - of what an Optimal Energy plan for a sailing yacht could look like. Please note that many more factors come into play when designing and installing your optimal solution: your Victron Professional will gladly help you with that.

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Best Solar Panels For Sailboats of 2024

Sailing uses the power of the wind to move, so why not use the power of the sun to charge your batteries? Solar panels offer the best way to charge boat batteries. This method can also save the engine from being used just for charging. Getting the best solar panels for sailboats means choosing the right size and power for your boat.

But, how much power will you need? Will your panels be able to keep up even on cloudy days? Do you plan to sail in cold water or deep in the tropics? Do you need the panels to sit on a curved surface? There’s a surprising amount of factors to consider when purchasing sailboat solar panels.

Whether you’re replacing old panels or buying for the first time, let us do the hard work of comparing the best solar panels for your boat.

For more of our top sailing gear recommendations, check out the Best Wind Generators for Sailboats . 

QUICK ANSWER – THE BEST SOLAR PANELS FOR SAILBOATS 

• Nature Power Monocrystalline
• Nature Power Rigid
• Renogy Starter Kit (4 panels)
• Newpowa Poly Solar Panel
• Acopower Polycrystalline
• Nature Power 90W Rigid
• Newpowa 150W
• Suaoki SunPower
• Eco-Worthy Semi-Flexible

SAILBOAT SOLAR PANEL REVIEWS

Nature power monocrystalline.

Check out the latest price on: Amazon  | West Marine

BEST FOR: Efficient high-power use

WEIGHT: Unspecified

WATTS/AMPS: 120W/6.6A

SIZE: 45.1” x 33.6” x 3”

PROS: Foldable for easy storage and portability, pop-out legs that allow it to easily sit at an angle, sturdy design

CONS: On the upper end of the price spectrum, short warranty

NATURE POWER RIGID

BEST FOR: Energy-hungry boats

WATTS/AMPS: 165W/9.4A

SIZE: 57.8” x 26.3” x 1.4”

PROS: Powerful and efficient, scratch resistant and anti-reflective coating, well-built aluminum frame, easy-to-use connections

CONS: Powerful but expensive, only suitable for larger boats with a big flat space to set it up on

RENOGY STARTER KIT (PACK OF 4 PANELS)

Check out the latest price on: Amazon

BEST FOR: Large boats needing lots of power

WEIGHT: 18.0lbs

WATTS/AMPS: 400W/22A

SIZE: 4 x 47.0” x 21.3” x 2.0”

PROS: Includes x4 100W panels along with a charge controller and everything else needed to set up, ideal for sailors looking for a lot of power, easy mounting system, great price for a comprehensive kit

CONS: Rigid solar panels can only be on flat surfaces or mounted on rails, included charge controller might not be the charge controller for your needs

NEWPOWA POLY SOLAR PANEL

BEST FOR: Keeping small battery banks topped up

WEIGHT: 6.3lbs

WATTS/AMPS: 30W/1.7A

SIZE: 27.0” x 14.3” x 1.9”

PROS: Sturdy design, small and slim making it ideal for stern rail, wattage should be enough to trickle-charge medium battery banks, very affordable

CONS: Rigid design means placement is limited, heavy for a small panel

ACOPOWER POLYCRYSTALLINE

BEST FOR: Larger sailboat trickle-charging

WEIGHT: 6.9lbs

WATTS/AMPS: 35W/2A

SIZE: 29.9” x 16.1” x 1.7”

PROS: Looks neat with silver aluminum frame, should be able to easily keep batteries topped up and contribute to energy requirements when boat is in use, very affordable and slim, other wattages available

CONS: Weighty, aluminum frames can have sharp corners

NATURE POWER 90W RIGID

Check out the latest price on: West Marine

BEST FOR: Permanent mounting

WEIGHT: 15.2lbs

WATTS/AMPS: 90W/4.9A

SIZE: 33.7” x 26.5” x 1.0”

PROS: Sturdy frame can be mounted on gantry rails permanently, good power output and small enough to be mounted alongside an identical panel for double power, long warranty, reputable brand

CONS: Awkward to move about the deck so not ideal for portable panel, fairly heavy

NEWPOWA 150W

BEST FOR: Medium to large sailboats

WEIGHT: 24.4lbs

WATTS/AMPS: 150W/8.3A

SIZE: 58.4” x 26.6” x 1.2”

PROS: Great for permanent mounting, powerful and well-built,

CONS: Very heavy, only comes with 3ft of cable which may well be too short and require extension

SUAOKI SUNPOWER

BEST FOR: Smaller, lightweight sailboats

WEIGHT: 4.8lbs

WATTS/AMPS: 100W/5.6A

SIZE: 43.3” x 22.4” x 0.1”

PROS: 30-degree curve possible making this ideal for boat coach roofs, very thin makes for less dirt buildup and less wind resistance, good price for a powerful panel

CONS: Cable connections are on the top of the panel which may encourage corrosion and UV damage

ECO-WORTHY SEMI-FLEXIBLE

BEST FOR: Coach roofs and curved deck areas

WATTS/AMPS: 100W/5.5A

SIZE: 47.4” x 21.6” x 0.1”

PROS: Capable of a 30-degree curve making it suitable for coach roofs and curved decks, thin and durable construction

CONS: Connector on top allowing salt build-up and accidental damage

COMPARISON TABLE – THE BEST SOLAR PANELS FOR SAILBOATS 

HOW TO CHOOSE THE BEST SOLAR PANELS FOR SAILBOATS

1. required energy.

Buying solar panels for your sailboat involves more than going over a few models at random. You need to know how much power you’ll need daily. Also, you need to determine whether you will rely solely on solar power or use the engine as well.

SOLAR AND ENGINE

Will you use solar power most of or all the time? If yes, then you will need higher power, larger or more solar panels. If you plan to use the engine more, then you won’t need as much solar power.

Your sailing goals come into play in this decision. If you want to cruise the intercoastal waterways, chances are you’ll be using your engine a lot. If you plan on cruising the Caribbean, you can often rely on good winds for sailing.

Once you’ve worked out how you plan on powering your sailboat – solar and engine, or just solar – you’ll need to work out your daily amp draw . If you’ll be running a fridge, freezer, water maker, VHF and SAT NAV all day long, you’re definitely going to need a lot of power!

It can be difficult to determine how many amps your sailboat will need, especially if you still don’t have all the electronics you plan to bring on board. Some products will give you an idea of their power draw in their technical specifications. For others that don’t provide that information, you may have to settle for an estimate.

Once you have an idea of your daily amp draw, then you can work out the solar output required to keep up with that power draw. But there are other considerations too, namely, actual output vs maximum output.

ACTUAL OUTPUT VS MAXIMUM OUTPUT

While a 90W solar panel might sound like it’ll give out 90W, remember that this is its maximum output. That is, it refers to a clean panel in full sunshine. It won’t be giving anywhere near that output on cloudy days. In the case of a fixed panel, ask yourself if the sail will be casting a shadow over it on one tack.

Unless you plan on running the engine to top up the batteries on cloudy days, you will find yourself needing enough solar panel output for these times. Make sure to also consider the times when your panels aren’t giving out their optimum performance.

TEMPERATURE CHANGES

If you’re starting in Nova Scotia, your fridge won’t take much power to keep it at a cool temperature. But, what happens when you sail south to go diving in Mexico ? Suddenly, the water temperature is higher and the fridge would have to work twice as hard to stay cool. While good insulation is a bonus on a sailboat, it’s important to remember that atmospheric changes like temperature may mean an increase (or decrease) in your power requirement.

ARE WE TALKING AMPS OR WATTS?

While you need to know how many amps your sailboat will draw on a daily basis, solar panels are sold by watts. There’s no need for that to be confusing though, as we’ve also provided the amps in the chart. You can read more about watts and amps to get a better understanding.

2. HOW MANY SOLAR PANELS DO YOU NEED?

Many sailboats have more than one solar panel. This means you won’t need to move the panels to follow the sun or as the boat shifts at anchor. Having multiple solar panels also allows you to have smaller panels, which tend to get in the way less. Your required power output can be divided among them as well.

If you need 200W a day, then you could have three 90W solar panels on different parts of the boat and be covered power-wise, even on different tacks.

How much space do you have on deck? Where you place your solar panels is very boat and sailor dependent. Day-sailing in hot places? Solar panels on the bimini rack are an easy solution. Long-distance cruising? You’ll need solar panels that are efficient yet out of the way to improve windward performance.

If you spend a large amount of time on board, your energy consumption will be higher. You’ll need your solar panels to be as efficient as possible. Many cruisers have panels on top of gantries on the stern to keep them in sunshine all the time. This is terrible for sailing performance, so you have to think about where you want to compromise. Don’t forget to consider the other on-deck items, such as your paddle board , as well.

Solar panels generally come in two types: mono- and multicrystalline and amorphous thin film silicone. However, all solar panels listed in this article will be mono- or multicrystalline as they are the most effective.

MONO- AND MULTI-CRYSTALLINE

Efficient and sturdy, these panels will probably make up your core solar panel collection. For everything on board like lights, fridge, radio and navigation electrics, mono-and multicrystalline are your best bets. They aren’t forgiving on cloudy days though, and even a shadow over the corner of a panel will pull down the output by a lot.

AMORPHOUS THIN FILM SILICONE

Not as efficient as crystalline panels, amorphous panels are cheaper and flexible. They’re good for trickle-charging batteries while the boat is left unattended.

Solar panels are expensive, but their prices have been dropping over the years. If you only use your sailboat for summer weekends, chances are you won’t need pricey, hyper-efficient panels. You just need enough to keep up with your power consumption for two days a week and let the trickle-charge solar panel do the rest.

Take your solar panel budget and split it between the number of solar panels you think you’ll need. Keep in mind though that you’ll most likely need to buy a charge controller as well.

For more of our top sailing gear recommendations, check out these popular buyer's guides:

Sailboat Anchors

Sailboat Winches

Sailing Shoes

Solar Panels for Sailboats

Bilge Pumps

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Owning a boat can be expensive; you have to pay an upfront cost to purchase it, and you'll also have to spend money on maintenance and fuel charges. Solar panels may be the answer if you're looking for a reliable, cost-effective way to power your boat.

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How do solar panels work on boats?

Solar energy systems on boats work similarly to other portable , off-grid systems. There are four important components to a marine solar panel system:

Solar panels

Charge controller

Most marine solar panel systems require charge controllers to prevent the batteries from receiving more voltage than they can handle. Without charge controllers, you risk overcharging and damaging your battery.

Depending on your boat's electrical setup and the appliances you need to power, you may also need an inverter to convert direct current (DC) electricity into alternating current (AC) electricity. Some boat electronics use DC and don't need an inverter. However, if you use everyday household appliances on your boat (i.e., TVs, microwaves, or hairdryers), they likely run on AC electricity, and you'll need an inverter.

You can buy all of these components separately, but you can find solar panel kits that include some or all of the necessary parts. Some marine solar panel kits include the wires, cables, and mounting equipment required to get your boat's solar panel system up and running.

Best solar panel kits for boats

Below are a few products tailored to off-grid marine solar power systems.

Boat solar panel options

If your solar panel kit does not include an inverter or charge controller, you must buy those components separately. Battery storage products occasionally have built-in inverters and/or charge controllers.

Should you install solar panels on your boat?

There are numerous benefits to powering your boat with solar energy. One of the most attractive benefits of marine solar power systems is the monetary savings. You'll need to invest money upfront to purchase solar equipment; however, once it's up and running, you'll generate free electricity for your boat. Alternatives to electrifying your boat, like gasoline-powered generators, require purchasing fuel on an ongoing basis. Switching to solar power can reduce these purchases while protecting you against rising fuel costs.

Another benefit of marine solar panel systems is the quietness of operation. Running a generator can be a noisy disturbance for those going out on the open water to experience nature. Powering your boat with solar allows you to enjoy peace and quiet without losing power.

Furthermore, you can also safely generate electricity and charge your battery with solar power while you're away from your boat. This isn't feasible with generators - running a generator requires manual operation and monitoring. With solar panels, you can produce usable electricity during the day and then use it for weekend boating adventures.

However, there can be obstacles to installing solar on a boat, perhaps the largest of which is available space. Ideally, your solar panels can be installed in an area with uninterrupted sunshine. Depending on your boat type, this space may be easy or difficult to come by. While you likely get a lot of sun out on the water, the area may be too small or have too many obstacles that make fitting the number of solar panels necessary to generate your electricity needs difficult.

Consider your boat's deck or canvas when you're looking for spots to install a marine solar panel system. Remember that the positioning of your solar panels will also impact the type of equipment you should purchase – you may be able to use traditional monocrystalline and polycrystalline solar panels if you're installing on a fixed, rigid section of your boat. However, if your only open space available isn't suitable for fixed mounting, installing lower-efficiency flexible solar panels may be a better option. Some flexible solar options have an adhesive backing, so you won't need to worry about the constraints of traditional mounting and racking materials.

How many solar panels do you need for your boat?

Unsurprisingly, a yacht has very different power requirements than a sailboat. The number of solar panels you'll need for your boat not only depends on the type and size of your boat, but also the quality of the equipment you choose, how many sun-hours the boat sees, and the amount of electricity you require. Some boats can get by with one 100-watt solar panel (or even smaller), while others need a multi-panel setup.

Calculating your electricity load is the first step in determining how many solar panels you need. Below are some common appliances you may use on your boat and what they draw for power.

How many solar panels do you need for common appliances?

The last column of the above table is the amount of energy you'll consume in watt-hours running each appliance for the number of hours identified in column three. One 100-watt solar panel that receives direct sunlight for 5 hours will produce approximately 500 Wh of electricity (5 hours x 100 W = 500 Wh). Not considering conversion losses, that's enough electricity to power a mini-fridge for 24 hours or power a boat's GPS display for 10 hours. Running all of the appliances above for everyday use will require multiple 100-watt solar panels or fewer higher-wattage panels.

Install solar to save on electric bills

You can save money by installing a marine solar panel system, but you'll save even more by installing solar on your home or business. If you want to evaluate your solar options, check out the EnergySage Solar Marketplace . You can receive up to seven custom solar quotes from local installers to compare. You can also try our solar calculator for a quick estimate of solar costs and savings on your property.

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• Solar Systems

Small Sailboat Solar System Comments Suggestions

• Thread starter Thread starter Capt Y Knot
• Start date Start date Mar 24, 2020

Capt Y Knot

• Mar 24, 2020

Hello All, While the boat is still on land and finishing up the solar installation I wanted to submit the wiring diagram to the forum members for review. I apologize for the screen shot. Thank you All, Mike  

Attachments

Solar Wizard

For a 50w panel I wouldn’t mess with either of the 2 fuses you have between the panel and SCC. You DEFINITELY want a fuse between the battery and load panel. As close to the battery as possible. Where do you sail? I boat on Lake Erie  

Unofficial Forum Librarian & Perpetual Newbie

Capt Y Knot said: Hello All, While the boat is still on land and finishing up the solar installation I wanted to submit the wiring diagram to the forum members for review. I apologize for the screen shot. Thank you All, Mike Click to expand...

• Mar 25, 2020

Thanks for the reply's. From what I have read about electricity and "shorts" its good practice to protect the wires. The # 10 wire from the panel to the controller is snaked through the bulkhead and not easily accessible. The in-line fuses, at the panel and the controller, are marine rated and water proof. I understand that breaks in a wire are potential weak points but I can get at the in-line fuses to trouble shoot. On the battery positive post is a MRBF Terminal Fuse (300 AMP). Also the # 8 wire has a Bussmann 25 AMP Breaker that is switchable. This is my first go with solar, its practical and exciting! Thanks for the comments. JoeHam, Y Knot is moored in Narragansett Bay Rhode Island, a great location with predictable south- south west winds most afternoons. Close to Newport, RI and the open Atlantic. Fair Winds  

Capt Y Knot said: Thanks for the reply's. I understand that breaks in a wire are potential weak points but I can get at the in-line fuses to trouble shoot. Click to expand...

Thank you, a second opinion is always welcome.  

@Capt Y Knot You are taking a prudent and sensible approach to fusing and it sounds like you've done your due diligence. Circuit protection between the PV array and the SCC is a bit different. Have a look at this article to learn the basics of how it differs. The gist of it is for a small solar array short circuit protection is (1) unnecessary, and (2) impractical. Unnecessary because if a short was to develop, the current will not exceed the short circuit current (Isc) of your solar array, in your case that's probably <4A. Impractical because for a fuse to be effective it would need to be above your panels maximum operating current (Impp) but below the short circuit current (Isc), that is probably about a 1 amp window, maybe less for your 50W panel. That said, it rarely hurts to err on the side of caution, and this logic only applies to shorts, lightning strikes would be a whole different conversation (one that i'm not informed enough to speak on).  

Thank you Dzl, the explanation makes sense and thanks for the article link. This is my first go with solar and appreciate the helpful advise from the forum members. Being responsible for crew, boat and systems I do tend to be over cautious. I will check back with results and performance of the solar system as the season progresses. Thanks again, Mike  

Capt Y Knot said: Thank you Dzl, the explanation makes sense and thanks for the article link. This is my first go with solar and appreciate the helpful advise from the forum members. Being responsible for crew, boat and systems I do tend to be over cautious. I will check back with results and performance of the solar system as the season progresses. Thanks again, Mike Click to expand...

• Apr 9, 2020

I agree with the others that the 2 fuses between the panel and the controller are unnecessary and the extra connections add potential problem areas. A solar panel - like an alternator - is self limiting. It can not output more than it is designed for. As long as the wiring has the ampacity to carry the max current from the panel there is no reason for a fuse, much less 2. Solar panel wiring is typically 10 awg which has an ampacity of many times the panel output. The 25 amp breaker could just as easily - and less expensively - be replaced with a 10 amp fuse.  

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