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Old 04-15-2013, 07:57 PM   #1
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Electric Feasibility Study for an Owens

This thread is for me to research the feasibility of converting my 1967 27' Owens Concorde to plug in electric propulsion power. Current power comes via 350 cid Chevy engine with Borg Warner velvet drive transmission(I believe a 1.34-1 gear ratio). Electric head, fridge and 2 burner cook top. 1 rather large (66"x32")solar panel can be fitted to the hard top without affecting the appearance of the boat. 3 additional while possible on the cabin top would affect the use and looks of the boat enough to be less desirable.

Our current use of the boat is mostly day trips of less than 30 miles out and back, however overnight and multi-day trips are in our future. Protected inland waterways with moderately slow tides are the norm rather than the exception in my cruising area. Assume no more than 3 days away from the dock. If longer trips are desired a small generator may need to be compromised into the equation.

I imagine the design will incorporate the use of LiFePO4 battery cells for power storage. The amount of storage needed will need to be determined. The horsepower of the motor would ideally provide for up to 10 kn of speed but 7 or less would be acceptable too. All interior and exterior lighting will be LED.

How close to reality are my expectations to the current state of electric propulsion and battery storage technology? For our purposes here let us assume future resale value is of no concern to me.

Thank you,
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Old 04-15-2013, 09:42 PM   #2
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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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Old 04-15-2013, 09:52 PM   #3
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Craig--- You might want to start by talking to these folks. Electric Boats | Electric Launch | Elco Boats Some of their launches are in operation on Seattle's lake Union.
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Old 04-15-2013, 10:19 PM   #4
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Thanks for that link Marin, good stuff.

Reuben I posted the above "soft requirements" which I knew where way over the top to get the conversation started so to speak. What gave me the idea to do this was Mark's comments about the trimaran solar boat in another thread lacking aesthetics. Some folks, myself included appreciate a boat that looks like our idea of a boat. The possibilities are great so why not look at what is required to convert an existing boat of a design we like. Well I happen to like my Owens.

Your right of course, my planing hull is a very bad candidate for such a conversion Eric's Willard FD hull would be a better candidate IMO. But seeing how Eric didn't start this mess I threw mine into the ring. The horsepower curves are something I have to investigate further along with components. I threw the solar panel idea in more as a why not add one, not all of us have boats that lend themselves to being all solar such as yours.

This is one of those subjects that is difficult to understand fully until we use a tangible example. Ideally cats and tris are better candidates for electric but some of us are die hard mono hull lovers. A wise general once said you go to war with the army you have, not the one you want so that is what this thread is really about.
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Old 04-15-2013, 11:30 PM   #5
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If your old Owens has a stern bracket for a small outboard for trolling, you can get some rough efficiency numbers that way, just remember the prop on a small outboard won't be pitched to allow full rpm because the Owens will be too much of a load. I'd be willing to bet if you roll your own with this motor Motor MotEnergy ME1003 Permanent Magnet DC Pancake Brushed Double Magnet at $589 has a cont. rating of 19.3 hp @ 72 VDC. This controller Controller Kelly KDH07500A 24-72 Volt 500 Amp Series or PM will do the job for $465, you should be able to pull it off for less than $20K.

Find out what speed you can live with for a consumption of 700 w-hr per nm. Might be as fast as 4 kt at 2800 watts. If you need 60 nm range for your outings, then 52.5 Kw-hr (for 80% DOD) would work. Size your solar to handle hotel loads at 12 volts and your propulsion bank will be 72 volts. (24) 700 a-hr cells will get you 54.6 Kw-hr bank at Balqon's clearance price of $560 per cell $13,440. Here is a LiFePO4 charger 20 amp for $465. http://www.cloudelectric.com/product-p/bc-sco7220.htm

The Balqon sale http://www.balqon.com/store.php#!/~/...89&id=18005962

Motor $589
Controller $465
LiFePO4 $13,440
Charger $465

Under $15K if you roll your own.

Keep the trans because the smallest pitched prop might still be pitched too high for the electric motor.
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Old 04-16-2013, 12:00 AM   #6
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Quite frankly 30 miles would probably be more than sufficient. I do not have far to go in any direction to reach a great anchorage. That's just one of the things I love about the Delta.

72 volts DC is what I run in my Gem NEV. Finally, some battery technology I can relate to.
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Old 04-16-2013, 12:27 AM   #7
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Do you feel comfortable rolling you own? By very rough estimates you might be able to cruise at 4 kt on 3.75 hp (2800 watts). The reason I picked a motor with a cont rating of 19.3 hp is that speed increases require a disproportionate increase in power. There will be times you will need or want to run at 8 kt instead of 4 kt, and that power increase would require going from 3.75 hp to 15+ hp. The motor and controller are rated to 400 amps for 1 minute due to thermal conditions, which is 38.6 hp. 200 amps cont rating, which will cover 15 hp. Remember, because of the torque of an electric motor, 15 hp electric rating would equate to much more than an ICE rating.
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Old 04-16-2013, 12:55 AM   #8
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I just noticed no BMS in your above system description George. Is there not one needed? I was under the impression one was mandatory.
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Old 04-16-2013, 01:09 AM   #9
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Who is George? I don't use a BMS. I do a parallel bottom to top balance and use a cell logger with low alarm set at 2.95 volts on discharge and 3.5 volts high alarm for charging. Use an e-xpert to determine remaining capacity. Just stay away from voltage knees and you'll be fine, and that is easy to do on these cells because they have such a small voltage swing during discharge until the knee is reached.
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Old 04-16-2013, 01:16 AM   #10
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Sorry Bob, I'd blame my phone but that'd be a lie. Just a classic case of multi tasking brain spasm


Ok, that makes sense to me and explains the lack of BMS reference above.
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Old 04-16-2013, 01:42 AM   #11
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When someone like Reuben designs systems for the masses, he has to protect the battery investment against careless operators, hence a BMS. You can employ one to be on the safe side, they are cheap insurance against a screw up, but to keep cells balanced which a BMS also does, I have found that if you balance before the install, then stay away from the voltage knees, they stay balanced. The alarm circuit on the cell loggers can always be used to activate a high amperage disconnect for the bank, thus removing it from further discharge and over charge.
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Old 04-16-2013, 01:46 AM   #12
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A sailboat seems more practical if one wants to go "solar." ... Batteries are "nasty" (chemicals, lead, lots of CO2 to produce) especially in the volumes needed for primary propulsion. Spending 50K to 100K for electric conversion would buy a lot of diesel fuel even at several times the current cost.
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Old 04-16-2013, 01:56 AM   #13
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Quote:
Originally Posted by markpierce View Post
A sailboat seems more practical if one want to go "solar." ... Batteries are "nasty" (chemicals, lead, lots of CO2 to produce) especially in the volumes needed for primary propulsion. Spending 50K to 100K for electric conversion would buy a lot of diesel even at several times the current cost.
Just 5 years ago you wouldn't be able to recoup the cost of electric propulsion over the cost of diesel. At the current cost of solar around $1 per watt, combined with the recent drop in LiFePO4 prices, the return on say a converted PDQ 34 trawler would occur in under 25,000 nm. For a full time cruiser, that would be about 3 years of cruising, after that your almost cruising for free.

The time has come to give consideration to electric propulsion.
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Old 04-16-2013, 01:59 AM   #14
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If so cost effective, how come taxpayers need subsidize solar?
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Old 04-16-2013, 02:06 AM   #15
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If so cost effective, how come taxpayers need subsidize solar?
It isn't that cheap due to domestic produced solar but rather China dumping to capture the market. That kind of competition will drive others to bankruptcy. But makes no difference, the result is the same, and that is cheaper propulsion than fossil fuel.
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Old 04-16-2013, 02:23 AM   #16
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Staying with a 1-to-4 gallon-per-hour diesel engine is the smart "non-move" at my life stage.
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Old 04-16-2013, 06:08 AM   #17
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Remember, because of the torque of an electric motor, 15 hp electric rating would equate to much more than an ICE rating.
Bollocks.

Playing games with input power doesn't change the fact that boats are driven by output power measured at the propeller shaft. If your boat takes 15 HP to move through the water at 5 knots, it doesn't make one nanospeck of difference if that shaft is turned by an electric motor, a gas turbine, a squirrel in a cage, a steam turbine, or a diesel engine.

The metrics you guys use to develop interesting numbers for terrestrial vehicles simply don't apply to boats. A propeller doesn't act on the water like a tire on pavement or train wheel on a rail. The availability of high torque at low speed doesn't count for much in a fluid medium unless acceleration is your primary interest and I suspect few here are driving ship assist tugs, ferries, or drag boats.
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Old 04-16-2013, 06:28 AM   #18
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"If so cost effective, how come taxpayers need subsidize solar?"

Because solar folks bundle cash into 1/2 million dollar chunks for democrat elections and get paid back 1000-1 .

Similar questions have been asked on this , link for a decade.

http://www.boatdesign.net/forums/hyb...ain-46834.html

They have a great search function.
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Old 04-16-2013, 06:45 AM   #19
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Old 04-16-2013, 08:15 AM   #20
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Craig

Feasibility Studies always have section called Risk and one called Economics. For Risk, think clearly and ask your insurer. For Economics add a contingency of at least 50 percent.

Ask Bob to give an estimate to Lump Sum the entire job through acceptable turnover to the client and see what the real cost is if contracted out. If not Bob I would assume he knows of an experienced company to Lump Sum EPCM the job through Completion.

BTW, the terms I have capitalized are well defined in Feasibility Study efforts. It is necessary with new endeavors to smoke out the real costs and issues and get beyond the hype. Feasibility Studies can be done on a small scale too, the pencil just needs to sharper.

Last but not least, props move boats as was just stated by the smartest marine engineer on TF.
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