SailNet Community - View Single Post - Electric drive owners need some advice
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post #6 of Old 02-14-2009 Thread Starter
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the person that has a knee jerk reaction that says it cant replace 10 horse diesel is the person that don't know what he is talking about that's why I was wanting to hear from other actual owners. Its simple as a horsepower consumes 750 watts regardless of the power source here is the difference. your diesel can ONLY create the 10 horsepower at full power and max torque close to the same. A 8hp electric motor creates the same torque that your diesel does but from the time it starts turning regardless of RPM. All alternators are motors and all motors are alternators. Just spin them backwards that's it. When your sailing the prop spins and charges the batteries and you have endless power when you are sailing.

eMKay I totally agree with your Car project and thanks for the site I have been looking for that forum and couldn't remember the name of it. any way in a car yes your right, however we are talking about a boat that has a wave pushing it that's why it takes so little power to push a boat at hull speed. in a boat system i think for my own personal reasons i think 96v should be the smallest amount of power that should be used. i actually prefer 144v the amp draw at cruising speed should be in the 6000 watts range for a 30 to 32 footer and around 45-50 amps figuring in line losses.

another difference is the batteries in a boat you don't need the super fast discharge capabilities of the LiFePO4 batteries. They actually work against you and Trojan T105's would be a great choice. 220AH @ 20 hours with 144v in the system its 24 batteries a little heavy yea but factor this in at 50% discharge there is 2640 usable amps (of course you arent going to use them all at once) and thats a 50 hour or so burn rate and a (no wind no wave ideal condition) range of around 260 miles. when you get back under sail the system charges its self.

ok this is the plan I am puttin together

Oh and the "Gearing" is no more (on 90% of the systems) than a 2:1 pully system to slow down the electric motor to about 600 to 800 rpm

A long time ago, my mother said something about not being able to sleep at night worrying about me. I told her, "Don't be foolish, I don't skydive at night."

"You gain strength, courage and confidence by every experience in which you really stop to look fear in the face...You must do the thing you think you cannot do."
Eleanor Roosevelt
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