Here are a couple excerpts from postings at the electricboats group which may be of interest.
I've seen some regen on Current Sunhsine which has a Cruise 4. Its
not recommended by Torqeedo, so keep that in mind if you want
experiment with this. If you do it you may lose warranty.
If I set the throttle at around 50 watts or some other low number,
then when the boat is sailing the power requirement quickly drops back
to zero, and then from around 5 or 6 knots I begin to see 1 or 2 amps
coming in. I've seen as high as 18 amps when she was doing about 13
knots. And it has been regenerating when I've had her at 25 knots and
the motor was screaming but I did not get a chance to see what the
amps was. That was accidental :) But it didn't blow up the motor, so
I think they could be robust enough for more genatle use.
This regen is at 48 volts so at 18 amps that was a respectable 900
watts coming in. But even at 2 amps, thats 100 watts and is enough to
easily meet my house load requirements and a bit more besides.
And another aspect of this is the advantage of this in fickle winds, such around Pittwater (Australia) where I have the boat, and where the waterways are fiord-like and can generate fickle winds on the narrow creeks. When the prevailing wind is say 10 knots, the wind at water level can be 5 to 15 knots and changing from moment to moment. Then by running the Torqeedo at a low speed, say 150 watts, it is enough to help her through lulls and knocks, and to keep her going through a tack, especially with just the jib up. Then when the wind picks up to over 10 knots it will be regenerating. So this kind of sailing is "for free" in that the power used in the lulls can be won back in the gusts. As well as being much easier to sail cos she doesn't keep stalling, and just as quiet :)
I wonder if this works with all trolling motors?