A sailboat electric-energy system
To the editor: Many cruising sailboats have worked out an electric-energy system that works for them; too many others are continually trying to find the right mix. Kathy and I have done the same on our vintage Tartan 34.5 CB sloop. After nearly 28 years living aboard and sailing the same boat, we’ve evolved an electric-energy system we can live with.
When we did our first trans-Atlantic passage we went without refrigeration, solar was in its infancy and the Honda 2000 gasoline-powered generator didn’t exist. Our wind vane, not our electric autopilot, steered the boat at sea. We concluded that we really wanted refrigeration and other electric-energy powered conveniences. Like many sailors we went through a search for a bigger boat, with and without an onboard electric generator and, thankfully, we decided to keep the Tartan: We knew the boat from stem to stern and our trans-Atlantic passages are presumably over.
So, in 1997 I installed a 130-amp, two-belt alternator at the time we installed our new Westerbeke 30-hp diesel. The 130-amp alternator had kept our 390-amp-hour Trojan house battery bank charged at the cost of nearly two-thirds of the 3,700 hours now on the engine-hour meter. To keep track of our electricity use, I installed a Link 10 when it became available several years ago. Finally, I could make sense out of the electricity coming in and being used in the boat. Meanwhile, solar panels became much more efficient, and smaller, quieter, lighter gasoline-powered generators came on the market. Most important, we could cut way down on diesel engine hours if we only used it for motoring and not for charging batteries (the Honda 2000 costs about $1,000 new compared with upwards of $10,000 for a new or rebuilt diesel).
Thanks to the Link 10 we know that our daily electric energy consumption is about 70 to 90 amp hours with refrigeration, computers, lights, radios and all. Nearly all the time we’re on the hook or on a mooring in sunny southern waters. My Maine island solar-diesel installation experience led me to choose Kyocera panels. I chose a 130-watt panel because of its high output per square inch, it would fit on top of the dodger and I could devise an adjustment mechanism.
To do an installation like ours, you need to cut four holes in the dodger, through the tube frame to support the quarter-inch by one-inch solar panel supports. The length of the panel supports depends on the fore and aft dimension of the dodger. I put grommets in the dodger holes and used quarter-inch 20 stainless bolts. It took a few tries to get everything to work right. The hinges were bolted to the bottom of the solar panel with wing-nuts securing them to the panel supports. I used two, quarter-inch by one-inch by 24-inch struts to hold the panel up when we lift it fore or aft to face the sun. The lifting struts each had four, quarter-inch 20 bolts, spaced about six inches apart. We poke the threaded end of the bolts through a panel hinge hole as we raise or lower the panel as the sun moves.
Okay, how did this help our daily battery-bank needs? I replaced the 130-amp alternator on the diesel — it failed and was expensive to fix — with the original size, simple, single-belt 50-amp alternator. We use it to charge batteries only when motoring. The 130-watt solar panel provides six to seven amps DC continuously to the batteries providing the sun is shining and we’re reasonably religious about adjusting the panel fore and aft as close to right angles to the sun as possible. Of course, the sun never rises and sets exactly fore and aft over the boat, but close enough for our needs and makes the two-way adjustment mechanism much simpler.
Our 130-watt solar panel provides about one-third of our 60 to 90 amp-hour daily battery bank charging needs; the Honda 2000 provides the remainder. With the mix of solar and generator we run the Honda about an hour each day on a cupful of gasoline depending, of course, on what battery bank deficiency shows on the Link 10. Since we have a four-cycle, 3.5-hp outboard on our dinghy, we use the same gas as the Honda; hence, one three-gallon can of gas lasts about a week for both; a little less than $12 worth.
The solar panel output works through a regular solar charge controller to the three, group 32 Trojan batteries hooked in parallel. The Honda 2000 plugs directly into our shore power input, which in turn feeds into our 1,000-watt Heart inverter-charger. The three position battery switch — OFF, #1 and #2 — is set for the house bank (#2) all day. The group 24 starting battery (#1) is left off and is charged occasionally. I run the Honda in the morning before the sun begins to shine much on the solar panel; fortunately it’s quiet; I don’t wish to disturb our neighbors. When I first start the generator the Link 10 shows as much as 49 DC charging amps. This tapers off in less than an hour as the batteries become charged. I usually shut the Honda down when the DC charging current falls below six to seven amps DC; what the solar panel can provide. It can take many hours to top off a set of batteries so I quit charging when the batteries are at about 95 percent of full charge.
I keep looking at the latest solar panel specs in hopes of finding one having more output that will fit on top of the dodger. I expect to replace the solar panel every five years as efficiency improves.
—Dick de Grasse is a USCG veteran with a USCG master license. He and his wife Kathy live on their 34-foot sloop in southern waters in the winter, and summer at their home on Islesboro, Maine.