Generating Electricity

As I wanted to avoid having a separate diesel generator I had to have an adequate enough system to satisfy my needs. I planned to use the engine as the main source of charging the batteries but backed up by some alterative sources: wind generator, solar panel, towing generator.

Aventura’s engine is fitted with two alternators,

a standard 55 AH alternator and a 120 AH model that needed to be fitted with a double pulley and two belts. The 120 AH alternator charges the house batteries whereas the standard 55 AH alternator charges the engine starting battery and also supplies power to the anchor winch as it is normally only used when the engine is running. As a useful backup either alternator can charge both banks on its own and a switch allows the house batteries to be used to start the engine. However, I do make sure that the banks are always kept separate and, in fact, I never have had to use both banks to start the engine as the engine battery is more than adequate for the limited use it gets.

An 80-watt rigid solar panel is mounted on the coachroof and provides around 5 AH on sunny days. A Rutland 930 wind generator puts in an additional 1 to 4 AH depending on the strength of wind. On all long passages I tow an Aquair water generator that is highly efficient as it provides enough power (approximately 1 AH per knot of speed) to run the autopilot and fridge. There are two disadvantages to the towing generator, one that I cannot troll a fishing line and tow the turbine at the same time, so if I want to fish, I have to haul in the turbine and its 100 foot line. This is not an easy operation if the speed of the boat is over 3 knots, and at 6 knots virtually impossible.

Slowing down Aventura once she gets going, even if I am prepared to drop the sails, which I would never do, is a waste of time, so it’s either no fish for dinner or, on passages where I expect to have to do some motoring at some point, as in the Mediterranean, I do not use the towing generator and as soon as we are out of port the fishing line is let out instead.

To prevent chafe I regularly check the knot at the generator end and also make sure that the line runs out without any obstructions. To prevent chafe at the turbine end I pulled a two metre length of clear plastic hose over the end of the line that connects to the turbine. Having used the towing generator extensively over these last five years I have the highest praise for it and, as the saying goes, would never leave home without it.

Gradually I have come to the conclusion that, depending on one’s cruising area, there may not be any real need for an additional diesel generator. Personally I found that even when not going far but just moving from one anchorage to another the engine is used enough to keep the batteries charged up. With so many charging options on the current Aventura I felt there was no need for a separate diesel genset.

Two other improvements that I made while in New Zealand was to acquire a better 30 AH battery charger for the times when I am in a marina, and to upgrade the inverter to 1500 watt as the previous 1000 watt model was not able to cope with some of my electrical appliances. Whereas the previous system had a combined charger/inverter unit, the current inverter is a stand-alone model, which I installed myself. I realized that by wiring the inverter into the boat’s mains power network I ran the risk of forgetting to switch off the inverter when I plugged into shore power, so I bought a large mains switch, which has three positions: 0 - all power off, 1 - inverter on, and 2 - shore power on. Simple and foolproof.

My generating system has worked satisfactorily during my long voyage and coped well with my energy requirements. The addition of a higher capacity alternator in New Zealand was a useful improvement and made it possible to bring the batteries to a full charge in a shorter time than before. The solar panel and towing generator provided a useful boost on long passages but, under those conditions, the wind generator was a disappointment. In nine years I had to replace the batteries once every three years, which is far from perfect but is probably the price I paid for leaving the boat unattended for several long periods when the batteries could not be charged under optimum conditions and had suffered as a result. I am now convinced that for my kind of sailing the system was perfectly adequate and should I ever have to make such a voyage again I would probably choose a similar system.