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  #11  
Old 09-07-2009
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argle the yanmar 1 gm spec is slightly over 1 pint an hour at cruise rpms. i just did the math and i was wrong it about 6 days. so 8 hours or so per gallon.

i did the math a few months ago and dont know where i was wrong, but i was.

i still dont think battery tech will get much further. it will always be a space and weight issue, more space than weight.

the real issue will be using over run to regenerative charge the batteries. ie you set speed for 6 knots and a wave pushes you to 6.25 for a second. if you could get that .25 back then it would help not much but it would.

once again the whole issue of drag is the killer using current car tech will not roll over
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  #12  
Old 09-07-2009
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All the discussion of electric not being capable of motoring for 10 or 20 or 30 hours misses the real point which is that a vast majority of sailboats simply don't do that. I know the boats at my marina that get the most use are the race boats and at least the one I crew for only visits the fuel dock once a season. Electric may not ever work for a long distance bluewater setup but for the 18-25 foot weekender (which is far and away the largest segment of sailboats by sheer numbers) it is a reasonable solution. Even for the 30+ footer that spends its entire working life in the Chessy electric is likely a practical solution. I have a 20' boat that I use a trolling motor exclusively to maneuver to and from the dock, for me it's completely sufficient.
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  #13  
Old 09-07-2009
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Quote:
Originally Posted by tager View Post
I have stated this so many times. The watt is a power unit, not an energy unit. Watts per hour is a nonsense unit.
tager: i dont think anyone on this thread ever used a "W/h" unit. i do use kWh which, although not an SI unit, is a standard accepted unit of energy which is equal to 1 000 W x 1 hour = 1000 J/s x 3600 s = 3 600 000 J = 3.6 MJ. its kind of like saying an amp hour (Ah) for a battery which is also a unit of energy, at 12 Volts equal to:

1 Ah = 1 A x 12 V x 3600 s which is equal to
1 Ah = 1 Coulomb/s x 12 Joule/Coulomb x 3600 s = 43.2 kJ

so, since 1 kWh is 3.6 MJ, there are (3.6 MJ/kWh)/43.2 kJ/Ah = 83 Ah/kWh.

so, the 56 kWh Li ion battery bank in a Tesla Roadster electric car is the equivalent of a 12 Volt bank of batteries with 56 kWh x 83 Ah/kWh = 4600 Amp hours or about 40 marine house batteries each rated at 110 Ah.

i dont pretend to be an expert about batteries or electric motors or marine propulsion, just an interested layperson, but i am an electrical engineer and i do try to keep my units correct. if anyone used "W/h" i'm sure it was a typo.

scottyt: i accept your quoted fuel consumption. seems considerably better than the rules of thumb for fuel consumption per horsepower i have read. are you sure that gives you 8 hp at 1 pint/h?

Li-ion will make a huge difference in energy density per weight, but not per volume as you pointed out. there are some very high energy density storage solutions coming down the pipeline that will make further considerable gains. right now they are where Li ion was maybe 10 years ago.

Last edited by ArgleBargle; 09-07-2009 at 03:26 AM. Reason: typo
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  #14  
Old 09-07-2009
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Quote:
Originally Posted by scottyt View Post
argle the yanmar 1 gm spec is slightly over 1 pint an hour at cruise rpms. i just did the math and i was wrong it about 6 days. so 8 hours or so per gallon.

i did the math a few months ago and dont know where i was wrong, but i was.

i still dont think battery tech will get much further. it will always be a space and weight issue, more space than weight.

the real issue will be using over run to regenerative charge the batteries. ie you set speed for 6 knots and a wave pushes you to 6.25 for a second. if you could get that .25 back then it would help not much but it would.

once again the whole issue of drag is the killer using current car tech will not roll over
hi

not to belabour this, but in a previous post i found reference to following Yanmar tech data sheet for 1GM10

http://www.yanmarmarine.com/uploads/...0_TechData.pdf

fuel consumption at 2800 rpm about 0.31 gph. this would make it 7.5 hp/0.31 = 25 hp/gph with respect to the crankshaft.

also, there was a Yachting Monthly (British publication) article from march comparing 2 hp outboards (admittedly a very different aimal from a diesel inboard) and included the Torqeedo 801. It did very comparably to the 2 hp gas outboards, beating some in propulsive force (which was their measure). it is an 800 W unit, which when converted to heat units should only be about 1 hp. so, as a first approximation, it may be fair to say that 750 W electric is more the equivalent of 1.5 to 2 hp internal combustion rather than the oft quoted exact thermodynamic equivalent of 750 W/ 1hp.

see:

http://www.torqeedo.com/uploads/medi...english_UK.pdf

Last edited by ArgleBargle; 09-07-2009 at 04:13 AM. Reason: typo
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  #15  
Old 09-10-2009
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Watts/Schmatts.....................Yanmar/Battery............Ya know what kills electric powered sailboats? Marketing. They have to market to the lowest common denominator and that's the person who asks, "Yeah, but how to we get home if the wind quits and we're 20 miles from home? Who's going to feed the dogs at home?.................I think we should get one with an engine."
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Quote:
Originally Posted by tager View Post
I have stated this so many times. The watt is a power unit, not an energy unit. Watts per hour is a nonsense unit.
If someone says 100 watts per hour I'm happy to let it slide because it is obvious what they mean, and it also provides more useful information than watt-hours because you can usually assume 12vdc and see the load they have on the battery bank, and as we all know the amount of current being drawn as a percentage of capacity affects the overall capacity of the bank. If they just used a technically correct measure like watt-hours we wouldn't know anything, and we'd lose the inferred rate of discharge given by watts per hour. I'm guilty of using watts per hour as short hand myself and I'm not losing any sleep over it, as far as I know nobody is publishing these posts in IEEE.
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  #17  
Old 09-10-2009
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Sounds like everything should work out ok.
ArgleBargle is going to put his money where his mouth is.
If he is right and makes a ton of money he can buy his new battery powered 35 footer even if it cost more.

Sounds fair to me.
Good luck ArgleBargle and if we are racing don't even think of spinning that prop even if it too quiet to hear.
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Old 09-10-2009
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Quote:
Originally Posted by casioqv View Post
I disagree- I use an electric drive system on my C22 and it works awesome. Total cost was about $500 for an 82lb thrust saltwater trolling motor, 2 large deep cycle batteries, and a promariner 3 channel shore charger. Total weight is about as much as a motor and fuel tank, but the batteries are near the keel instead of the transom. I don't know the full battery life (never ran them dead), but it move the boat at 3-4 knots for many hours. I use it only for docking and for pointing windward when raising and lowering the sails.
This is interesting.
What boat do you have exactly. Catalina 22, what is the displacement?
What motor do you have?
What batteries do you have?

What is the longest you have run on battery?
What water are you in? lake, current, tides how much?

Sorry about all the questions. Inquiring minds want to know?
Did this really work out cheaper than an outboard?
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  #19  
Old 09-11-2009
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I'd be moe interested about using these "hybrid" lithium batteries for my house bank. There was a thread some time ago about this but I can't be bothered going searching for it.

I was at that time led to understand that these batteries could seriously revolutionise electricity (other than electric drives) on boats. What has anyone to conribute to that aspect (or does that constitute thread hijacking?)
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  #20  
Old 09-11-2009
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I think of it like this: Electric motors run on coal. IMHO, more specifically, electric cars (or boats) get charged somewhere and it costs money to do that charging. If we start plugging our electric drives into shore power, for sure we'll start seeing marinas charge extra for sailboats with electric drives.

Hybrid cars make sense because of all the breaking that they do. Recapturing that energy makes sense. For boats, I think the equivalent is the extra sail power you have up once you reach hull speed. So, for "old shoe" designs that don't really plane, the extra energy is there to recharge batteries from the prop moving through the water. Owners of sailboats with more modern designs, which get extra speed from planing or partially planing, would be less inclined to want hybid drives since it would slow them down. Also remove from this group those "old shoe" designs that are used for living aboard, since they have their own power needs and are less inclined to have the ability to charge engine batteries, especially when (mostly) sitting on the hook.

The other category would be infrequently used sailboat engines that have solar panels to make a dent in the needed charging, and don't go far from home. I picture these as "non-docked solar day sailors", since it's far easier to store energy (motoring distance) as gas or diesel than as batterines -- I'musing 10 miles as the range, pick another number if you want. Since day sailors seem to be the most likely to incorporate modern hull designs that can exceed theoretical hull speed, they are stuck with solar or extension cord charging. If you are at a dock, it's far easier (lighter weight, cheaper) to charge from the power grid (coal) that solar.

So in terms of investment, where it makes sense is with electric drives on sailboats are:

1) old shoe designs that are not at a dock and not live-aboards, capturing prop charging (hybrid drives)

2) any sailboat that doesn't go far from home and is either
2a) infrequently used (solar charging) or
2b) at a dock (coal-based charging) (using edison batteries, see below)

and let's add in this one too...

3) any sailboat that does go far (>10 miles) from home, which has a generator

So I'd invest in making those options viable for people. For #1 that means businesses that retrofit older boats with hybrid systems. For #2 and #3 that means simple, inexpensive, lightweight electric engines and battery systems.

---

While I'm taking up space on your screen, I'm actually thinking 1) that hybrid sailboats need to use the weight of lead-acid batteries to their advantage with a battery keel. If you are really revamping sailboat designs, use that 8,000 pounds I have as a place to energy storage. That would change the equation a lot by giving you tons of motoring distance.

And 2) that edison battery technology be used along with lead-acid batteries(or any other type of battery that doesn't have many charge-dischage cycles). The edison battery would be used for the first part of discharge and the lead-acid is used for the infrequent final part of discharge. This utilizes the best characteristics of both:

Edison battery: near-infinite charge/discharge cycles, 2% power loss per day, short term overcharging possible in more sophisticated designs.
Lead Acid: very few charge/discharge cycles, 0% power loss per day, no overcharging possible.

All this is IMHO, of course. Hope this helps.
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