Sun Power: Solar Battery Chargers for Your Boat

Like many boaters, and particularly sailboaters, I have always been cognizant and even enamored by wind power, but I didn’t give much thought to solar power other than negatively as a source of sunburn. In the last 20 years or so, I have come to appreciate the enormous advances in solar power as a green alternative to petro dollars for all boaters. For boaters, solar power has become a viable solution in several areas: onboard ventilation and battery charging. I know that many of you will also tout the sun-warmed shower bag as a great invention for boaters of all stripes, but it is ventilation and battery charging that I want to explore with you.

A compact hard solar panel battery maintainer like this Sunforce brand 125ma unit costs only $28

First of all, don’t think of solar power as free — it takes an investment to get the right equipment, but once you’ve made that initial investment the payback is immediate and long-term. Twenty years ago I refurbished an O’day DaySailor and had added running lights with a small 12V motorcycle battery to power them, but wasn’t sure how to keep the battery charged. The solution was adding a small hard solar panel that could trickle charge the battery while it sat otherwise idle on the mooring.

A Sunforce brand 30 amp charge controller

What has changed since those early days of solar power? Well, just about everything! First, the panels are better, made with either flexible thin-film, crystalline silicon, or amorphous silicon technology. Back when I first explored solar power afloat there were no regulators or smart chargers to control charging—resulting in cooked batteries. Today we have those items and also controllable panels. The use of diodes to control power drops in shady conditions while also preventing backflow of charge from the batteries that could overheat the panels is new. And finally the plethora of accessories is new.  Anything that can be charged, such as cell phones, GPS, laptop computers, to AAA Nicad batteries now has an available adaptor that can plug in and harness the power of the sun.

From a small 1-foot by 2-foot panel you can sustain a 5W .45a charge for the one time investment of $160.  If you have greater power consumption or charging needs try a bigger 80-inch by 14” array that can produce 28W and 1.8A for less than $500. Today’s more advanced flexible solar panel with an embedded smart charger that lays over the boom or on the cabin top to keep batteries at peak charge is a good solution for most any boat. All these products are available commercially at your local West Marine.

Solar powered vents come in a variety of sizes and finishes

I recently acquired a solar ventilator for my boat that fits in the passive air vent on the bow. It was an older stainless model with a plastic fan inside that I got at the marine consignment shop I visit.  My solar vent doesn’t have any of the modern features available on new units such as the ability to change from intake to exhaust, a damper to control flow, insect screens, or a simple on off switch.  Putting a solar powered vent on both ends of your boat to maintain fresh air and reduce mildew is something that is inexpensive to do and easy to install—particularly if you already have the passive air vents. Units with all those features that can move 1000 cubic feet of air per hour cost approximately $80.  One more feature to look for is the day/night ability of units that have a rechargeable nicad battery embedded, so when the sun goes down, the fan works off the stored battery power all night long.

The cost of power isn’t likely to get cheaper anytime soon so a small one-time investment of a few hundred dollars to automatically keep your batteries charged, your hand-held conveniences powered, and your cabin cool sounds like smart sustainable green boating to me.

Written by: Peter d'Anjou

A USCG licensed captain and former merchant mariner, Peter d'Anjou is now a freelance writer and editor. A one-time executive editor at Sailing World magazine, he writes about his passion for racing and boating. Having managed a large yacht repair facility in the NE U.S. his background in boat construction and repair translate to the practical side of boat ownership.