We fitted a new wind vane in Gibraltar, knowing that an Atlantic crossing under sail would need considerable power to keep both the Autohelm (10 watts at 25% duty) and freezer (40 watts average) going non-stop.
This was belt and braces to an extent. We already had two large solar panels (each 30 watts) and - the first time I had used one - an Aquair 100 tow generator. This proved an excellent device, a transom-mounted generator rotated by a propeller on a long (30m) trailing line. It gave out a reliable 6-8 amps (up to 100 watts) 24 hours a day, as long as we kept moving at around 6 knots, and no doubt we paid a small speed penalty as a result. It also provided an attraction for both dolphins and sharks.
The engine alternator worked through an Ardverc battery management system, claimed to give up to 100% improvement in charging, but only, of course, when the engine is running, which in the event was less than an hour a day on average.
Our last piece of insurance was a Honda generator stowed in a boot locker, so that absolutely nothing could go wrong - in theory.
But it did! An elementary oversight, but the pair of two year old domestic gel batteries had already taken quite a hammering over their life and finally expired after 3 days. Sod's law then kicked in, sending a wave over the stern and into the boot locker, rendering the Honda generator useless just as it was about to be deployed.
We had to choose to keep either luxury food or self-steering, which, as we were short handed, was not really a choice. Nearby sharks must have thought it was Christmas as gifts of food arrived from above. We had made the right decision, although it was a little galling to hear nearby boats exchanging duck recipes as we settled in to yet another evening of pasta.
Luckily the Autohelm held up, with just a little use of the engine to compensate for using running lights and radios. The lesson was clear however and is one I have applied since. Whatever way you do it, generating electricity on board is expensive, so it may be a good idea to think about the following:
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| Fridges can be a real energy drain, but there are alternatives...
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Reduce the requirement for electricity as much as possible
- Do you always need a fridge/freezer, or will a string bag overboard do for beers etc?
- Is gas an alternative energy you could safely use?
- If you aren't using it, switch it off: especially high current items such as radar when visibility is good
Ensure there is adequate charging capacity, remembering:
- Battery management systems help if you rely on engine charging
- Wind vanes - stating the obvious - need wind and generate little at low speeds
- Solar panels need to be oriented properly and are not major providers of power - although good for keeping batteries topped up when not on board
- Tow generators work well, but have a small speed penalty
And above all:
- Make sure your domestic battery provision is adequate - I would suggest twice your estimated daily consumption to avoid discharging too much, too often
- Check your batteries regularly and replace as soon as they show signs of losing their charge.
Follow these simple guidelines and you should have all the power you need for hassle free sailing.
