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Go Back   SailNet Community > General Interest Forums > Gear & Maintenance
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  #21  
Old 02-26-2010
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The Honda on deck in any weather would last about 1 hour
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If a dirty bottom slows you down what do you think it does to your boat
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  #22  
Old 02-26-2010
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Med, even running full time, the generator's output would not keep up with the power demands of the motor. The 12 volt output is only 8 amps., less than 25% of the motor's rating, and the power still has to be stepped up to 36 volts. A generator any larger would definitely not fit in the available space.

I also have some concern with the re-e-power approach of hanging the motor in a pod under the hull. Unfortunately, it maybe a tough fit with my hull, and would present some structural issues.

Last edited by bljones; 02-26-2010 at 12:52 PM.
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  #23  
Old 02-26-2010
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BLJ, the direct DC output of the honda is indeed too small. That's the point of using the Xantrex charger and 3 x 12volt batteries is to use the full 120volt output of the genset and step it up to 36volts. If you don't like the outside EPOD approach there are some companies that use direct to your existing shaft type installs.

Another thought is that instead of using top shelf parts (like the honda and Xantrex) you could do the ghetto-DIY option as listed here:
Building your own generator.
You could still use a brand new honda OHV engine, a bomar high capacity alternator and a fancy regulator and you'd be doing everthing in DC voltage and come out cheaper than the original system I reccomended.

Another thought still is to use a DC power supply instead of the xantrex and the batteries.

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Last edited by MedSailor; 02-26-2010 at 01:09 PM.
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Old 02-26-2010
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As with the 3 million fuel savers "invented" for automotive use over the years, I ask the question: If a motor manufacturer could save 40% on the fuel consumption (as claimed by most fuelsaver inventors) they would slaughter the car market - it would be worth billions of $. But even with their annual $200m R&D budget, they can't come up with a working solution. So how does the inventor in his suburban garage do it? Well, in truth he doesn't - they're all scams.

It's the same with your challenge. If a wealthy yacht-builder with a substantial R&D budget could provide silent endless propulsion they would also slaughter the market.

But have they?

No.

Why not?

Because it can't be done with the technology available today.

Like I said in another thread - get over it - fix your diesel.
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Old 02-26-2010
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Omato, I am not looking to get out of rebuilding my diesel. My intention here was to see if there was a viable alternative, maybe prompt some backyard tinkerer/lurker here to come forward and say, "hey, here's what I did," start a dialogue a little more focused than the usual blue sky electric boat threads by presenting a specific problem, and an incentive to solve that problem.
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Old 02-26-2010
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Quote:
Originally Posted by bljones View Post
Omato, I am not looking to get out of rebuilding my diesel. My intention here was to see if there was a viable alternative, maybe prompt some backyard tinkerer/lurker here to come forward and say, "hey, here's what I did," start a dialogue a little more focused than the usual blue sky electric boat threads by presenting a specific problem, and an incentive to solve that problem.
I suppose I should have put some smilies and stuff in my post to indicate that I'm not on the attack - just offering an opinion.

The reason why the other posts on this subject are of "blue sky" quality is that with the technology available now, that's all it can be.

And like I said - a tinkerer is not likely to achieve something that the best engineering genius in the world with an almost unlimited budget can't.

Like some earlier posts alluded to - putting the kind of tech required into a 24 foot boat is a contradiction in terms - you'd have to use the electric boat to tow the one you're travelling in because there wouldn't be enough space for you in the electric boat. (see, there's the smilie)
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  #27  
Old 02-26-2010
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MedSailor,

The question that I have with the system that you outline is whether it meets the power output requirement. The batteries that you included have so little storage, it is essentially negligeable over 30 hours. That means that the generator needs to power the motor directly. The generator is rated at 2kw feeding a charger (~90% efficient), powering a motor controller (~95% efficient for a really good one) giving you power to the motor of 1.7kw to the motor best case scenario. This is 2.3hp which is very unlikely to push the OP's boat at hull speed. You might well get to 1/2 of hull speed in calm conditions but it doesn't meet the spec of maintaining hull speed. What you are proposing would most likely work if you went to a 4kw generator and the associated increase in charger size but this would significantly increase the cost and size of the system. Of the options posted, yours is the closest to meeting the specs but it still doesn't come close to meeting them in my book.

My issue with hybrids in boats is a separate issue. Their overall efficiency is lower because of all of the energy conversions and you really violate KISS. I have built 3 electric cars and 1 hybrid racecar and a hybrid is a real nightmare from the standpoint of what can go wrong. The reason that hybrids get better fuel economy in cars in the city is that they are parallel hybrids and the vehicle keeps accelerating and decelerating. In a boat, a parallel hybrid just doesn't make sense since we run constant rpm. The two applications are completely different (continuous versus intermittant).
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Old 02-26-2010
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FWIW:
I'm a pretty good tinkerer, and have an electric drive. My suggestion when you need to scale back on the requirements to match 2010's physical realities is to drop the requirement for hull speed. That's where you'll get the biggest bang for the buck. My system uses about 1.2KW to push the boat at 3kn in a calm protected harbor. Hull speed can be reached, but at a cost of 7.2KW. If my math is correct, that is a six fold increase. To do that for just a few minutes makes me weep for the batteries.
Sidenote: story on NPR the other day saying there will be a manufacturing glut for Lithium Ion batteries in 2012! Maybe by then the charging algorithms and systems can be marinized and come down in price, too.
Yeah, I'm not holding my breath...

And if someone does design the system your looking for, let me know! I'll buy stock in that one!
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