Green machines

Michel Bouffard, of Sept-Iles, Quebec, Canada, asks:

“I’m installing a 75-Watt solar panel and an AirBreeze 200 wind generator on my Hunter Legend 35.5. I have two 12-volt deep-cycle batteries, one starting battery, one combiner and a Perko (Off-1-Both-2) battery switch. I’m planning to use the solar panel and wind generator when I am sailing, but I also want my starting battery to be full. How should I hook up these two pieces of gear?”

Nigel Calder replies:

I would run the solar panel and wind generator directly to the house batteries—include appropriate fuses—and run the combiner (or an equivalent paralleling relay) between the two house batteries and the starting battery. When you are on the boat, leave the battery selector switch in the “1” (house battery) position and use this bank to start the engine: keep the cranking battery (“2” switch position) for an emergency start. I’m almost positive that your alternator is wired to the starter solenoid, and then to the load terminal on the battery switch. If so, when the switch is in the “1” position, the alternator output will go to the house batteries whenever the engine is running. The batteries’ voltage will rise, the paralleling relay will close, and the power will go to top off the dedicated start battery.

When the engine is off there’ll be no load on the cranking battery, and the solar panel and wind generator will help keep up the house batteries even when you are not aboard and when the battery isolation switch is turned off. To avoid overcharging the batteries, be sure to install a voltage regulator on the solar panel; the AirBreeze wind generator has one built in. And be sure to size the wind generator cables so there is no more than a 3 percent voltage drop. Because the voltage regulator is inside the wind generator, the reading comes from that point and not at the batteries. Undersized cables could produce more than the minimal voltage drop and that would cause the circuit to shut down prematurely.

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