Sounds like Bill has a sweet setup and a great approach. I love to build boats so I designed and built my own, but I'm sure I spent much more than the used-sailboat approach. My boat design has a box keel angled toward the aft, where the bilge pump is. The six Trojan T 105 6 volt lead acid batteries are in the box keel and lend a great deal of stability with a flat floor. The boat weighs about 900 lbs empty (just a guess, really). The 7200 watt hours in my battery bank recently took me on a 15 mile round trip and left me with 74%. This at 5+ mph with about 500 lbs of crew. I also have photovoltaics on the roof pumping in 350 watts or so. This can move me at 3.0 mph on sunlight alone at high noon. When we docked in Bar Harbor I got about 3% back while we had lunch and a beer. I also have an on-board charger but didn't use it. I'm thinking of taking it out.
If you are not on salt water you may get away with an open motor like the ME 1003. I have pictures of what the magnets look like after 3 years from my ME 0909. If you can enclose the motor far away from the water it would be good. Mine is covered, but in a well with saltwater a foot or so below it. As I said, I switched to the ME 1007 totally enclosed motor. It runs at a lower RPM and so is well suited to outboards. This winter I'll open it up to see what the salt air did to it. I don't think EV Drives carries it, you may have to inquire at motenergy.com in Wisconsin.
I chose 36 volts because I wanted only 6 batteries. If I did it again, I would go to 48 volts because 36 volts is sort of an odd duck for finding parts like motor controllers, charge controllers (for photovoltaics) and DC to DC convertors for auxiliary 12 volt (lights, stereo, etc). This would argue for a longer boat, say 21 feet, but I was limited to 18 feet because of my garage.
Your question about range is complicated. Six knots will require lots of watts, double that of 5 knots if your displacement design is maxed out at 6 knots. My guess is that if you had a longer boat with top displacement speed of 7 knots, 6 knots would be more economical than with the boat which maxed out at 6. The best I can do to answer your question is to show my results, on calm water, one person, no wind and little contribution from solar (9 AM in Maine, about 150 watts):
0 watts (solar input of 150 watts) 1 MPH
<100 watts 2.4 MPH
200 watts 2.9 MPH
300 3.3
400 3.7
500 4.0
600 4.2
700 4.5
1000 4.8
1200 5.0
3000 6.1
I don't like to drain my batteries below 50%, so I really have only 3600 watt hours to work with. If I were to run at 6.1 MPH I'd be down to 50% in 72 minutes (7.23 miles)! Things improve when you slow down to 5 MPH, 3 hours, 15 miles. Having just done this with 74% left shows the positive effect of photovoltaics and a strong tail wind on the way back. Hope this helps, Bruce. Electric Boat Range Revisited
Posted by: affordableacadia@gmail.com
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