Bill,
So you were getting about 60 watts at 4 or 5 knots? That's right back where this conversation started.... I find it much more effective to talk about watts instead of amps in this kind of discussion due to the varied voltages that are used by different boats.
But I think that you're on the right track. By using a dedicated water powered generator, that entire component can be optimized for extracting power from the water flowing by at the speeds that you expect to achieve regularly. An additional benefit is, like you said, you don't have to take the performance hit unless you choose to harvest power.
The typical problem with using an electric drive for regen is that a prop that is optimized for providing thrust will not be as efficient for collecting energy and vice versa.
I noticed that Robbie stated that he uses 2 dedicated Aquair units rather than the drive unit regen typically discussed here, the Aquairs obviously don't function as drives too. And the same performance data keeps coming up. From the Aquair website "The reason for the choice is that when sailing downwind at 6 knots, the Aquair 100 Water Drive generates approx. 5 amps continuous charge." So they quote 60 watts (5A x 12V) from 6 knots of boat speed. Their chart also shows less than 25 watts from 4 knots of boat speed. That works out to less than 0.5A charging for my 48V boat, or 1 solid week of continuous sailing to charge my 8kWh battery bank from 50% discharged. That assumes no other electrical loads along the way.
So I'm back to my original premise. Regen will not provide any significant charging to a traction battery bank for most conversions being discussed here. Regen or water generators can provide enough to cover most house loads but not much more.
I would personally love to be proven wrong on this premise, but I'm still waiting....
Fair winds,
Eric
--- In electricboats@yahoogroups.com, Steamboat Willie <stmbtwle@...> wrote:
>
> Eric I'd look into a taffrail generator like that sold by Hamilton Ferris. I finally gave mine away after giving up sailing, but it would put out a pretty reliable 4-5 amps at 4-5 knots on my 26' Pearson monohull. It didn't weigh much and would certainly keep ahead of my electrical loads.  I even used it when I was motoring to supplement the rather puny outboard alternator. Â
>
> Nice thing about the contraption is I could bring it aboard when I was more interested in speed than generating... Only problem I had with it was it seemed to have an affinity for seaweed...
>
> Bill
>
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