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Old 16-06-2014, 22:08   #181
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Re: Electric Propulsion on Catamarans

How many farads at what voltage?
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Old 18-06-2014, 00:03   #182
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Re: Electric Propulsion on Catamarans

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How many farads at what voltage?
It is off-topic, so don't want to continue the discussion on my car in this thread, so will just leave you with a pic of the caps, peak about 950 HP..
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Old 18-06-2014, 01:00   #183
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Re: Electric Propulsion on Catamarans

I took apart a torqeedo 800 and the motor was identical in specification to a $40 motor from hobbyking. Since the torqeedo was burned out I put in this motor as a replacement and it worked.

The key to efficiency is spinning the motor a lot faster than the propeller because propellers are more efficient slow, and electric motors more efficient fast. This is why torqeedo uses a 14:1 2 stage planetary gear box. The planetary gears are 97% efficient per stage. A 4:1 reduction with etek motors will work but isn't as efficient and also much less cost effective because the motor itself is much larger and heavier.

The torqeedos are also designed for pushing small boats and dingys so are also not very efficient for an actual cruising boat. The larger the propeller the better. You might notice they switched from a funky 3 bladed propeller to a more traditional design. Neither is very efficient.

For a small catamaran, say 30ft long, imagine an outboard with a 1 meter diameter propeller spinning at 20-80 rpm, with a 50:1 gear reduction to spin the electric motor 1000-4000 rpm. At 80 rpm you will be going 5 knots, and this is not very efficient (I estimate 1000-1200 watts), so normal cruising at 30-40 rpm and you would be going 2-3 knots and drawing no more than 200 watts.

With the inefficient torqeedo propellor, 14:1 gears and $40 hobbyking motor my boat goes 2 knots at 120 watts.

When sailing, a completely different propellor (With different diameter and camber) can be installed for charging. The generating propeller is a mirror image (rotated through 4th dimension) so can never be used efficiently for propulsion. It's like the left shoe vs right shoe.
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Old 18-06-2014, 01:22   #184
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Re: Electric Propulsion on Catamarans

Also I might note, torqeedo is terrible. Not because of making false comparisons, but because they refused any support for the broken motor I had, stating that they stopped supporting it 2 months ago. Their engineering is not very refined (lithium batteries didn't have balancing circuits) motor controller didn't have a temp sensor, so the last guy who had the motor melted the copper wire in it, and they have made it as cheap as possible with little concern for longevity.

I simply asked for instructions for how to disassemble it and they told me I could buy a new improved model for 2000 euros instead. I don't recommend their products to anyone because they cost a lot and if they break you are told to buy a brand new one and throw the old one away which isn't very good for the environment. They are also engineered with press-fit gears on shafts instead of keys and in many ways are difficult to adapt to other uses (like swap gear boxes to use a different ratio would be completely impossible) In fact if you strip the gears, it's not possible to use the old motor with new gears. It's like a laptop if the video card breaks, and now you have to throw away all the other working parts.

I cracked it taking the plastic apart and although my improvised solution worked for a few weeks, the 5200 sealant didn't actually work where the crack was and, water leaked in a few weeks later so I am currently without any propellor-based propulsion because they refused a simple explanation which would have prevented my mistake.

They are also not anywhere near theoretical efficiency and much farther from practical efficiency (the situations we will actually use it).
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Old 18-06-2014, 02:25   #185
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Re: Electric Propulsion on Catamarans

boat_alexandra, sorry to read of your bad experience. Thanks for being a pioneer of electric propulsion.

If Torqeedo products are as inefficient and their customer service is as bad as boat_alexandra says (which I cannot confirm or refute), then there is a business opportunity.

I will note that if never overcharged (past 3.5V per cell) then LiFePO4 batteries can be balanced once before installation and will then stay in balance, so there should be no need for balancing circuitry (which could potentially fail in a nasty way) to be installed on a boat. Overcharging can cause an imbalance. I would prefer to invest in extra surety that no voltage significantly over 3.5V per cell will ever be sustained than to invest in risky BMS circuitry.

Also, electric motors can be designed to be efficient at lower speeds (by increasing the number of poles) but this adds cost, especially in smaller motors. Most motors, especially smaller motors, are engineered to be efficient at high speeds. Again, there may be a business opportunity here.
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Old 18-06-2014, 11:18   #186
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Re: Electric Propulsion on Catamarans

Solar powered cruising catamaran nearing completion in Australia. Powered by (2) 13 kw Aquawatt outboards, 40 kwhr LiFePO4, 3200 watts of solar.

Run time at 6 knots* max. 84 nmi | 155 km
Run time at 8 knots* max. 68 nmi | 125 km
Run time at 12 knots* max. 45 nmi | 83 km
Run time at 16 knots* max. 26 nmi | 47 km

*Full sunshine, no head wind or current, 2 passengers

http://www.all4solar.com.au/SOLARPAC...C1045-26pr.pdf

Solar Pacific Cruiser



http://youtu.be/l6a6yGRnjb8
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Old 18-06-2014, 11:56   #187
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Re: Electric Propulsion on Catamarans

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Solar powered cruising catamaran nearing completion in Australia. Powered by (2) 13 kw Aquawatt outboards, 40 kwhr LiFePO4, 3200 watts of solar.

Run time at 6 knots* max. 84 nmi | 155 km
Run time at 8 knots* max. 68 nmi | 125 km
Run time at 12 knots* max. 45 nmi | 83 km
Run time at 16 knots* max. 26 nmi | 47 km

*Full sunshine, no head wind or current, 2 passengers

http://www.all4solar.com.au/SOLARPAC...C1045-26pr.pdf

Solar Pacific Cruiser



THE ULTIMATE SOLAR POWERED BOAT - YouTube
Now that is a sweet looking Solar Power Catamaran
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Old 18-06-2014, 12:14   #188
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Re: Electric Propulsion on Catamarans

It is. I also noticed 600kg max payload (including passengers), 16kw charging per day. Note that their range numbers include the power generated while running, so if you start with full batteries, run 80 miles, you have to spend an additional three days on the hook recharging back to full (assuming no power usage). For an average speed of .89kn.
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Old 18-06-2014, 12:14   #189
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Re: Electric Propulsion on Catamarans

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Now that is a sweet looking Solar Power Catamaran
The only negative (and it is a small one) is the designers flaunting the fact that while on the hook your harvesting more energy than you can possibly use. This is only a 33' X 16' beam cat and to me, weight is the enemy. I agree with the electric galley, electric hot water heater, watermaker, and 2 kw A/C, but their decision on model #1 to include clothes washer and electric dryer and dishwasher is a bit over the top for my tastes.
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Old 18-06-2014, 12:21   #190
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Re: Electric Propulsion on Catamarans

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The only negative (and it is a small one) is the designers flaunting the fact that while on the hook your harvesting more energy than you can possibly use. This is only a 33' X 16' beam cat and to me, weight is the enemy. I agree with the electric galley, electric hot water heater, watermaker, and 2 kw A/C, but their decision on model #1 to include clothes washer and electric dryer and dishwasher is a bit over the top for my tastes.
I agree. That design would be much nicer in a 38 or 40 foot long x16 wide foot print.
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Old 18-06-2014, 12:30   #191
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Re: Electric Propulsion on Catamarans

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It is. I also noticed 600kg max payload (including passengers), 16kw charging per day. So about three days from empty to full on solar assuming you don't use any power while recharging. So an average speed of 1.11kn, which is a little slow compared to, well any sailboat.
It runs 84 nm @ 6 kt on 80% DOD. 80% of 41 kwhr is 32.8 kwhr / 84 = 390 whr per nm.

Greg, if your trying to compute average 24 hour speed and range, you need to know how much solar is harvested and what you consume at cruise speed.

3200 watt X 6 hours = 19,200 ahr / 390 = 49 nm per day. With battery storage you can double that.

At 3 kt of speed, power consumption would be 1/8 of that at 6 kt. It was taking 2.3 kw to run @ 6 kt, so at 3 kt around 300 watts. So at 3 kt your still harvesting more power in a day than what you consume.

How you get 1.11 kt beats the hell out of me.
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Old 18-06-2014, 12:56   #192
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Re: Electric Propulsion on Catamarans

I got my numbers from them. Their advertising copy says they can produce up to 16kw a day. And can run 85nm at 6kn (assuming full sun, no wind, 2 passengers). So you end the 85nm trip with dead batteries. So it works out like the following....

1) travel 85nm 0% charge
2) travel 0nm end day at 41% charge (16/41)
3) travel 0nm end day at 82% charge (32/41)
4) travel 0nm end day at 100% charge (48/41) though you are really fully charged about 1/2 thru the day.

So in 3*24+12 = 84 hours (giving credit for the half day which I didn't before), you get an average speed 85nm/84hours=1.01nm/hr.

If you want to run slower... Well they didn't publish numbers for slower speed, so I won't try and reverse engineer those numbers. But with these hulls my guess is their prismatic coefficient is so high there isn't a huge advantage in going much slower than 6kn. There may be, and it would be interesting if they published those numbers but they didn't. So from their advertising copy they claim an average speed in ideal conditions of about 1 knot. Which is not what I would consider all that impressive.
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Old 18-06-2014, 13:57   #193
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Re: Electric Propulsion on Catamarans

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If you want to run slower... Well they didn't publish numbers for slower speed, so I won't try and reverse engineer those numbers. But with these hulls my guess is their prismatic coefficient is so high there isn't a huge advantage in going much slower than 6kn.
And that my friend is where someone with no experience clashes with folks that have experience.

You'll admit a kayak is efficient, mine will go 40+ miles at 5.5 kt but when I lower the speed to 4.0 kt I get 80 miles. Same holds true for my (3) EVs for road speed.
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Old 18-06-2014, 14:25   #194
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Re: Electric Propulsion on Catamarans

That cat looks pretty good! Certainly the AquaWatt motors are much more appropriate than little torqueedos.

It is the 40Kw of battery that is the killer expense for anyone thinking about EP at minimum $50,000 in raw cells, then add in engineering etc.

My approach is to eliminate the majority of that expense and go with much bigger solar array, and add wind generators, and because I'm not a religious fanatic, use gasoline engines too replace the battery, cutting that $50,000 cost for my boat.

And hopefully this research leads somewhere, and one can generate methanol while on the hook to get long range using it in my engines.

UCLA Engineering researchers use electricity to generate alternative fuel | UCLA

Or other ideas not willing to disclose
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Old 18-06-2014, 14:41   #195
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Re: Electric Propulsion on Catamarans

Jack,

If we can still trust Balqon for delivery of their Winston 700 ahr cells at their clearance price, a 40 kwhr bank would be $10k. Does that price change your project numbers?
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