Ned,
Perhaps not surprisingly, I've got 8kWh of LiFePO4 batteries (16 Thundersky 160Ah cells and 200 pounds) going into my 30' ketch with a Yamaha EF2000is for backup. Using a PFC charger, you should be able to get about 1400W into your driveline from the generator running full blast. I should be able to confirm that later this summer.
Since you're taking a big leap in the hull design and driveline, you might want to do your initial test runs with a cheap set of L/A batteries to measure your power requirements. A guy on the EV board loaded up his car conversion with deep cycle batteries from Sams Club for about $70 and 65 pounds each. I don't believe that the batteries have great capacity or lifespan, but they would allow you to work out your drive, gearing and controls and empirically set your performance expectations before laying down the cash for Li batteries.
If you're lucky, you'll hit your cruising requirements with about 4000W (5.3HP) out of the motor, which should be about 5000W out of the batteries. Your 8kWh pack will last about 70 minutes while "silent running", running the generator the entire time will only add about 40 minutes of range. If your hull turns out to be even more efficicent then you'll be ahead of the game.
If by then it looks like your project is still on track, then adding another 8kWh set of batteries (after your pocketbook recovers) will push your silent range to almost 2.5 hours.
Fair winds,
Eric
Marina del Rey.
--- In electricboats@yahoogroups.com, Ned Farinholt <nedfarinholt@...> wrote:
>
> Sirdarnell, Eric, Myles, redu, et al,
>
> Thanks for the inputs. I am now convinced of the need to go to LiFePO batteries but 600 lbs busts the budget. 8 kWh of battery and a Honda EU2000 is now my thinking.
>
> An intriguing thought, which probably shows my ignorance of hydrodynamics more than anything, is the use of a boxed keel. The recent article in Wooden Boat about the efficiency of the Atkins Rescue Minor at S/L of 2 to 3 got my attention. It would seem that L/B ( > 12) allows one to exceed Fn of .4. So if the keel carries 50-75% of the displacement, the hull will be very lightly loaded and generate very little wave drag. The surface resistance of the keel could be minimized by making it mostly semicircular cross-section. The keel would be ballasted with batteries of whatever type and the motor generator. The Honda is only 11.4 inches wide. Naturally, there would be a bilge pump in the keel and the boat would be mostly decked. The keel would be open to the inside the boat and formed with the hull. The hull above the keel could be a canoe or a light planing hull ala Atkins. So the keel acts as a high L/B displacement hull above which is a light planing hull. LOA about 25', keel about 20' displacement including batteries, motor, m/g, passengers and hull less than 1000 lb. What do you think?
> Thanks for you patience,
> Ned
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