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Old 04-15-2013, 08:42 PM   #2
rjtrane
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City: Palmetto Bay
Vessel Name: Sunshine
Vessel Model: Island Pilot DSe 12m Hybrid
Join Date: Apr 2013
Posts: 268
Do you have any current data on HP needed for the speeds for which you are looking? Any sea trial info? It's simple math once you determine your HP needs.
Most likely 5 knots will be a realistic speed. Since your boat is not designed to be truly efficient at slow speed, it may take a bit more power to go 5 knots. Assume you can go five knots in calm conditions with a 10 kw motor. 30 miles is 6 hours or 60 kw/ hours. At 48 volts, this is 1,250 amp hours for day-trip propulsion only. Assume you build your battery with 32 each, 700 ah cells for a total of 1,400 ah. Each cell is $770.00 from Balqon or about $25,000 with freight. Add a BMS (battery management system) for a couple thousand dollars and shore charger another several thousand, your investment for the battery is $30k.

We have 28 PV panels your size on Sunshine with a rated output of close to 6 kw. 4 panels will keep your refrigerator and pumps going, but not much else.

Finally, you have the motor. Good thing about a 10 kw motor and controller is they are not too costly - maybe around $10,000 depending on type and make. You won't need your gas motor or gear box. Hook up the motor directly to your shaft.

For overnight trips, a small 48v DC generator could recharge your battery overnight.

Total materials will be around $50k - $60k plus labor.

Any extra money you have in your budget spend on more battery. You cannot have too much.

Oh, and forget about 10 knots.

Note: my estimates are based on guessing you can use a 10 kw motor to get your 5 knots. If you have any powers curves for your boat, you can make a closer estimate on the size motor you'll need for the speeds you desire. Smaller would save you some money - larger would cost you more.
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Reuben Trane
"Sunshine" - Island Pilot DSe 12m
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