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ESS,
I played with the throttles quite a bit while underway, and while I could get the amperage to flip from positive to negative in swells, the swing was quite small, biased towards the negative. To add .5kts, you need something like 7A per shaft, far more than you get from regenerating. No way are you getting a knot for free. Remember, you are basically down 1kt from propeller drag in neutral, .5kts when bumping the throttles forward to the max recharge point. If you set the throttles so amperage flips positive to negative, you get a miniscule charging current. Perhaps it would be different in a following sea.
Sean,
As far as weight goes, I think you are comparing the weight of 12 8D batteries at about 150 lbs each (1800 lbs) plus perhaps two hundred lbs of motor (conservatively) versus Yanmar 3YM30's which weigh about 300lbs each. I really think the marketing hype for these hybrids is a bit optimistic. I can see the technology developing in two paths, for two different types of sailors: 1. plenty of battery power and full recharge capability and 2. minimal battery weight onboard with reliance on the genny for regeneration or extended motoring. I'm betting the latter takes off. One type of sailing is good for regenerating--10x ratio of sailing to motoring. Most sailors don't have that ratio and would be better served by a simplified (cheaper) system that gives them enough power to clear the mooring field under electric power and return, foregoing the drag and complexities of recharging underway. I can see this type of system being lighter, cheaper, and more reliable than twin diesel. By the way, I estimated the 10x ratio by estimating how much sailing time it would take me to regenerate the amp hours I used motoring out of the harbor. Or you could think about a discharge rate of 80A vs a charging rate (in very favorable conditions) of 8A.
Brett
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