Re: [electricboats] Time to re-power

Thanks, Eric.  I'm looking at the spreadsheet and the photos you generously posted.  I have a follow-on question, but first, appreciation, I would say one thing.  Certainly some folks who'd developed such a knowledge base as you have might have tried to monetize it by publishing a book!  Life gets in the way for many, I'm sure, who attempt such a project on their own, and those who've simply paid someone to do it would have little interest in a group like this one.  But for someone like me who has the desire to do something personally and globally beneficial but lacks the appropriate theoretical or practical background, it's a much slower process!
Now, back to my follow-up question.  Your prop is a 4-blade 13" dia. X 15.5" pitch wheel.  (Being 4-blade, I presume you let it freewheel while under sail so that it does not add drag while getting the "gift" you mentioned earlier of 0.7 amp of regen.)  In your photo of the motor installation, it appears that you've connected it to an old transmission.  What is the reduction ratio, please?  Your spreadsheet shows motor RPM and I'm interested in translating that into prop shaft RPM.
With respect to your statement about cost of LiFePO4 batteries, you mentioned paying ~$0.45/Wh, which if my arithmetic is correct, works out to ~$230 per individual 3.2v cell.  But after some trial and error (and non-trivial cost!), I've located a source in China that will deliver genuine 200Ah CALB LiFePO4 cells for ~$125 ea (including freight & customs) which works out to under $0.20/Wh.  Adding a Thunderstruck BMSC and EVCC brings the cost for the pack up to ~$0.26/Wh.  These are the same battery cells that Electric Car Parts Co sells for $253/ea (T'struck price for 180Ah CALBs is ~$250 also.)  Something I've spent quite a bit of additional money on is what I'll call "user interface", convenience, and compliance materials (an EV Display from T'struck, meters, tachometer, wiring, connectors, switches, lights, alarms, etc).  But that's a topic for a different post!
[-tv]
Tom VanderMeulen
Grace O'Malley
Cape Dory 27
Monroe, MI

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