Before I set sail, I read everything I could find on optimizing the electrical system on board our Privilege 39 catamaran, Exit Only.

Much of what I read, and almost everything that sales people told me wasn't right for my boat.  They were always quoting the power output from their diesel generator or the power produced by their high output alternators.

I discovered that it was easy to produce tons of electricity at great expense, but there was always a problem.  The acceptance rate of charge by my battery banks was limited.  Even if I could generate a megawatt of electricity, it didn't matter because my batteries couldn't accept all that current. 

Diesel generators and high output alternators work well for the first fifteen minutes of the charging cycle when the batteries can accept bulk charge.  But after that, they burned up a large amount of fuel and produced only a small output during a rapidly tapering three stage charge cycle.  High output devices were not an economical way of charging my battery banks.

I figured out that the acceptance rate of my batteries was the rate limiting step in the discharge/recharge cycle.  I need a source of current that would charge my batteries at a rate that they could accept.


Two options provided the continuous charge that I needed.  Solar panels and Aerogen 6 wind generators could do what I wanted.

In the tropics, my four 75 watt solar panels provided an estimated fifty amp-hours of current each day.  Even more important, the acceptance rate of the batteries meant that almost all of the current would go into the batteries.


My Aerogen wind generators provided a second source of continuous low level current output, and the majority of the time the batteries could accept the full output of the wind generators.  When I cruised in the trade winds, each Aerogen produced ten amps of current in twenty knots of wind.  When the trades were blowing hard, I had more than 400 amp-hours of current available every twenty four hours from the wind generators.  That provided plenty of electricity to run refrigeration, lights, computers, watermaker, and autopilot.

I installed my first Aerogen when I was in New Caledonia to see how good it would work.  Much to my surprise, I went for three weeks without having to turn on my engines to charge the batteries.  That was impressive.  Shortly after that, I installed a second Aerogen when I decided to complete our circumnavigation with four adult electrical consumers on board Exit Only.

The Aerogens did a great job of keeping our batteries charged while sailing offshore.  We had plenty of power for the autopilot, refrigeration, lights, radios, and computers as long as the trade winds continued to blow.

Aerogen Maintenance

There is a zirc fitting on the casing of the Aerogen, and every couple of months it's a good idea to inject grease into the zirc fitting to lubricate the bearing on the front of the wind generator.  The grease also acts to exclude water from the inner workings of the wind generator.

Dump Resistors

Dump resistors are supplied with each Aerogen wind generator.  If the generators produce too much output, the current is shunted into dump resistors which dissipate the excess energy as heat.  You can tell when this is happening because the dump resistors make a high pitch tone that tell you current is being shunted and dissipated.  Alternatively, you can use the excess energy to power the heating element in a DC powered water heater, and you can take a hot shower.

Feathering the Aerogen

Sometimes it's desirable to shut down the wind generators.  The manufacturer says that in winds greater than 40 knots, you should feather the generator to keep it from spinning too fast.  This is done simply by turning the generator out of the wind.    We have a small rope tied to the vane on the back of the Aerogen, and by simply pulling on that rope, we can feather the generator and even stop it from spinning.

Wind Generator Noise

The Aerogens are exceptionally quiet.  There's no high pitch whine created by the spinning blades.  It's one of the quietest wind generators around.

Two Aerogen Wind Generators

Two wind generators create massive redundancy in your boats electrical power generation system.  When you have large electrical demands, you run both generators simultaneously.  When demands are less, you simply feather one generator to save wear and tear on that Aerogen.  We often ran the starboard generator for twelve hours and then switched over to the port one for twelve hours when the trades were blowing hard.

Having two wind generators means that if one generator malfunctions, you have a second one up and ready to go.

Relative Wind Direction and Speed.

Having the Aerogens mounted on the stern provides a continual reference point for the helmsperson to gage the relative wind speed and direction.  If there's a wind shift, it will show up in the orientation of the wind generator.  And if the wind pipes up, you'll see the generator spinning faster.


I sailed halfway around the world without wind generators, and I survived without a problem.  I was always rationing power, and I ran my engines every day to generate electricity.  During the last half of the trip around the world, I had two wind generators working around the clock to meet our electrical demands.  I no longer had to ration power, and I didn't need to run my engines to generate electrical power except on rare occasions.  That meant less wear and tear on the engines, a quieter boat, and I didn't have to endure the smell of diesel exhaust.

Wind generators worked for me because I circumnavigated in the trade winds.  Most of the time the trades were blowing hard, and I had electricity to spare.

If you aren't a trade wind sailor, then a wind generator may not be for you.  You need predictable and reliable winds to make the expense and excess weight worthwhile.



Wind generators are reliable, efficient, and relatively maintenance free.  There's no need for you to ever have flat batteries if you build redundancy into your boat's electrical generation system.  A couple of solar panels, a wind generator, and an engine mounted alternator guarantee that there will be power available when you really need it.

Modern cruising boats are hungry for power, and for us, the easiest way to get that power was with the Aerogen 6 wind generators.