Uprate your boats alternator

UPDATE: I say at the end of the video that there will be ad update in EP4, well we hadn’t done enough testing to do it there, but there are regular references to it in later episodes. Here is a written summary:
ALTERNATOR UPDATE:
For those of you who have watched the ‘Uprate your alternator’ video I did promise an update on how it performed in this episode. We didn’t actually do enough motoring to properly test it however so apologies for not having that in this film. We will give a video update in a future episode, but in the meantime I do have some stats from using the alternator a bit now so will write out what I’ve found here:

Firstly on advice from experienced marine engineers that you get much more longevity by running the alternator at below full capacity I set the ‘belt manager’ to 3 on the regulator. This means you will not get full capacity out of the alternator but it will be less stressed and last longer. having the belt manager on 3 is supposed to drop the output by 21% and it seems I get about 95 Amps at cruising revs when the batteries are able to accept full charge so that seems about right. There are also some comments on the alternator film that people have experienced Balmar failures due to excessive fan belt dust. I would always do everything possible to avoid creating fan belt dust, that’s why lining up pulleys and tensioning the belts properly is important. You need a tensioner on a twin belt system, levering the alternator over and tightening it up won’t cut it!
In real life use, after a night at anchor I’m typically at 60-70% state of charge on the house bank (580AH AGM) So running the engine to leave the anchorage and raise the sails, usually about 1 hour, gets my state of charge up around 15% so 75-85% This is about right as the internal resistance of the battery goes up to a level where bulk charging is slowed to such an extent that solar is a much better option anyway.
A no wind passage where you’re motoring for a period of time will easily bring the batteries back to full charge which is good for the batteries. We get enough days like that in the Med. to give the batteries an occasional full charge so we don’t have to rely on shore power to do that.
Basically then I think the alternator is doing the job it needs to do & I’m happy. I’m still a bit shy of total power for long term voyaging without resorting to the Generator. We only used the Genny once in the last 4 months. But the power I’m short of is more the lower amperage long term charge which for me will probably be more solar. We could go to wind, but I’m very reluctant because of the noise, even the best modern designs are intrusive to some degree. Hydro is also an option, but difficult to fit on a canoe stern.
Also reducing power draw is always something to look at. I’ve done everything possible for the moment I think, but there is one big saving we could make which is to fit wind vain steering at not use the autohelm. This is an attractive option for all the other benefits it brings, but it has the same problems of fitting to a canoe stern and is expensive.

If you’re interested in the technical aspects of sailing, i’ve uploaded some maintenance videos of the boat lift to the ‘Tech Corner’ page of our website…
http://www.sailingfairisle.com/tech-c…
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Uprating your alternator is high on the list of things to do for a cruising boat. This technical corner is all about choosing, wiring and fitting a larger alternator and external regulator.
There’s more to consider than you might think. Uprating to a serpentine or double V belt, changing and aligning the pullys. Lots of wiring, alternators work MUCH better with external regulators and you need to be able to program the regulator, standard regulators are shocking when it comes to charging house banks.
This video walks you through the whole process.

If you like this tech video there are many more in the tech series and we also have lots of tech tips and tricks in the regular episodes so don’t miss them.