Electric motors - Do they need to be so expensive

Discussion in 'Propulsion' started by Kaptin-Jer, Mar 28, 2008.

  1. sigurd
    Joined: Jun 2004
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    sigurd Pompuous Pangolin

    electrics can be sealed.
    there has been a lot of development in the big RC brushless motors the last years. you can get a plettenberg 17kw under 2-3kg if I remember correctly. The torqeedo is a torcman.de motor. There are slow, big power, light motors coming for the paraglider market. Naturally with 2000rpm at 11kw it is a bit larger than the plettenberg I mentioned.
    The big controllers are far apart and expensive. DIY variants has been developed in the RC and EV crowd.
  2. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Actually, I have three fully redundant electrical systems. Two monitoring systems and several computers. It is a big boat and I need the help navigating and just seeing which of 5 tanks, 6 bilge areas or three battery banks need attention. I also have 4 solar panels in two separate banks. But that said. My engines, steering, throttles, and all emergency system can operate manually or mechanically.
  3. Guest625101138

    Guest625101138 Previous Member

    So while you warn others of the dangers of electrics you place huge reliance on electrical systems.

    Rick W
  4. mydauphin
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    mydauphin Senior Member

    Simple. I don't think that hybrid technologies are yet at the level of performance, price or reliablity to be used in most marine applications.
    Just because people sell it doesn't make worth while. Torpedo Electric outboard is a perfect example. I can buy 3 outboards for the price of one electric and get better performance. Sure I have to pay for gas and some maintenance but over the next 5 years a gas outboard is more reliable and I am ahead enough to buy another one, all the fuel and everything else. What is life span of Torpedo battery and its cost?
  5. Guest625101138

    Guest625101138 Previous Member

    The forum is about boat design. Boat design needs a practical edge but it also needs to be looking to the future and the forces shaping the future. Electric power will be the motive force of the future and is already practical at certain levels such as auxiliary for sailing boats.

    Lithium batteries, electronic controllers and PM electric motors have already made IC motors obsolete for model planes. The electric systems provide twice the power to weight and cost about 1/2 of the IC motor for the same power. This technology is just starting to filter into larger applications.

    There are only a few electric outboards around right now but as more brands get into the market you will see prices drop. An electric outboard can be made with one moving part and a set of bearings. The only items manufactured to tight fit tolerance are the bearings and housings. Compare that to what is required to produced an IC outboard.

    The Lithium batteries have only been in the pipeline for about 10 years. As they become highly developed the performance will improve and the price will come down with higher volumes.

    As far as durability goes, the most arduous application I have ever come across is a submerged sewerage pump. Would hate to place an IC engine in that environment. Electric motors in these applications last for decades. Simply a matter of designing for the application. Electric motors work at design efficiency unless they are stopped. IC engines deteriorate from the first day they are operated and performance degrades until they are overhauled.

    You can be content with your noisy, smelly, polluting outboard but others, me included, want to dabble in the future; not to be driven solely be current economic sense. In any event within 10 to 20 years I can see legislation prohibiting use of liquid hydrocarbons for non-commercial applications or taxes that make its use prohibitive.

    Rick W
  6. masalai
    Joined: Oct 2007
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    masalai masalai

    or appropriate fuel prices as a consequence of scarcity (depletion of a finite resource).... Once USA and many other developed countries go belly up in a major depression the stupidity of manipulating various commodities and currency values will force a significant change of attitude.... the $140 / barrel price of crude will seem like a gift in about 5 years time....
  7. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    My point is that, on a boat safety is number one and that means getting home.
    As far as lithium batteries, they are not economical or practical or sustain use. Case in point, I am marine contractor, when we build a dock, if we used the best most expensive li-battery screwdriver for 45 minutes the battery is dead. It would take like nine batteries to do what a $50 regular drill does very easily and well. Why am I going to spend $300 and go through all kinds of aggravation if a $50 tool does the same or better.

    Electric motors have been used in boats for nearly a century, their advantages and disadvantages are well known. The navies of world with almost basically unlimited budget have done a lot research. You have basically two systems that work. Nuclear power driving a turbine generator, producing electricity and using super excessive electric power to drive electric motors. Or using a series of diesel/turbine generators to drive electric motors.

    Both these system require lots of money, lots of space, engineering, and knowledgable personnel to operate. They also breakdown and it would not be the first time they got towed.

    KISS is the king of sea, these electrical system require, generators, power controllers, cooling and multiple system to maintain. They still suffer from rules of physics.

    If you get a 100kw diesel, install a transmission driving a shaft, you might get 90kw to prop.
    If you used a 90kw electric motor to drive shaft then you need 100kw generator . The 10k is lost in controller, heat, restistance etc.. Guess what the 100kw generator is 160kw diesel that consumes more fuel and polutes more that original 100hp diesel.

    Oh by way, my old diesels are old. Over 10,000 hours, been rebuilt twice for the heck of it and run better today than new thanks to upgrades. They also pollute less thanks to cleaner fuels, Fuel/Air sep filters and better tuning.

    Oh and if the United Socialist State of America persists in telling boaters and everyone else what they can and can't do. They and I will move to a less sociallist country like China, France, Canada. You can stay in USA by yourself on your electric motor boat that each motor cost $1,000 per hp. I will be somewhere else burning diesel at alarming rates, enjoying 600hp, spending a lot less money and enjoying myself traveling the world.
  8. Guest625101138

    Guest625101138 Previous Member

    You would expect someone so taken with all things internal combustion would not be bothered with electric tools. Why not use an IC powered drill? The advantage of the battery powered tool is the avoidance of dragging around an electric cable.

    Navies use electric drive because of their efficiency, simplicity and overall operating economy. The same reason large earth bound traction machines use electric transmission.

    Compare the number of moving parts in any internal combustion engine and transmission with an electric motor. The IC is intricate with tight tolerances all subject to wear.

    The shortage of oil is a fact of life. Anyone using it wastefully will be a social outcast. Good luck going to China, Canada and elsewhere to get low cost fuel. USA, the middle east and other OPEC countries are the few that don't already levy significant taxes on fuel. I have attached some numbers from Europe. To save you doing the sums it currently works out around USD5.30/USG.

    Oil was the trigger for the current financial problems and its availability will continue to limit the ability of economies to recover. Governments have to encourage alternatives otherwise there will be serious problems. Right now there will be a huge number of oil projects being shelved. This does not bode well for the next boom/bust cycle.

    I look at brand new IC cars as being close to scrap. They are already heading toward obsolescence before they get off the assembly line. All car makers are hurting right now but the product lines with growth are electric hybrids and those with greatest growth potential are battery electric. The underlying technology will filter into boating applications and the boats will adapt to make the best of the technology.

    A solar powered boat with infinite range is already technically viable. Sailing boats already circle the globe faster than IC powered craft. Many forces are working to make IC powered pleasure boats obsolete. My preference is to look forward rather than stick resolutely to the past.

  9. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Let me go point by point. Every energy form has its best use, advantages and disadvantages. Electric, gas, diesel, coal, nuclear, Solar, wind and others have their place it is very hard to replace one with another.

    One of the main uses of electric motors in ships is because of silences during operations i.e. submarines. Other are used because it is hard to throttle a steam turbine driven by a nuclear generator to steer a ship. You just go forward, reverse, idle on a steam or regular turbine. Another perfect example is locomotive that has diesel electric powerplant, need a variable throttle and those big engines run on constant speed.

    But notice the key word diesel electric, something needs to generate the electricity. Power is lost in transmission, heat, adjusting power levels. There is no such thing as pure electric anything. There is a power source, your ultimate efficiency is that of power producer.

    Then lets talk power. Lets say I have a 50 foot boat, not a very powerful boat with only two 300hp diesel engines. Usually boats this size have at least 450hp each. Then lets say I have 600 gallon fuel tank. On this boat, it should have a range of about 400 miles at about 20knots. Do that with batteries

    You need this power to tackle the seas. To break through the waves, current, against the wind. It sounds to me like you have never really been on a boat, on a not so shining day, outside the protected bay.

    A solar boat may have infinite power, but if you got top full of solar panels, of a 50' boat by lets say 20'. How many kilowatts of power could you develop. Perhaps 10, 20 lets say even 100kw that converted to the give you about 100hp. I am being very generous here with effiency. That is not enough to push a 50 foot boat not much beyond idle. For that give me sails, it will be faster.

    Electric boat people talk about 10kw, 15 kw maybe 40kw at max... Please my tender has 50kw... Get real and the engine only weight 200lbs complete.

    Now let's look at cars. The best hybrid out there gets good gas mileage but the same can be gotten by properly designed gas or diesel car. There is a couple of small diesel cars, Volkswagen I believe, that get 60mpg My wifes Honda Fit get 50mpg on the highway, only cost $15,000, and I dont have to throw out a **** load of batteries every few years to pollute the environment. By the way the only crappy cars are the one being made by US auto companies under pressure from the government. Mercedes, Bmw, Toyota, Nissan, Hyundai, Honda, and many others make really fine cars. Amazingly they are not going bankrupt.

    As far as government is concern, look at todays headline,"Venezuela's Hugo Chavez tightens state control of food amid rocketing inflation and food shortages" Venezuela once one of the riches country per capita in the world is now one of the poorest via government controls, and socialism.
    Or look at California the most progressive state in the USA, also the most broke. Why is that? Unfortunately reality and dreaming are two different things. That applies to government and electric boats.

    One final note: Electrics have their place, may be one day when we all have personal nuclear powerplants do they have the power to propel boat, yachts and ships properly. Until then we are dependant on diesel or gas main power. And solar power, wind generators are used to charge batteries for electronics and may be some refrigeration.

    Oh and by the way, I am a Electrical Engineer by schooling and a boat builder by hobby. I have been a boater since I was 12, built countless boats. And have enjoy boating, freedom and the free markets very well thank you. I am also a envirnomentalist by nature, or a naturalist by nature. Believe in recycling, conservation and using latest technology.... But only if it make sense... not propaganda or wishful thinking
  10. kistinie
    Joined: Aug 2007
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    Location: france

    kistinie Hybrid corsair

    Full Solar and wind propulsion with or without sails is a viable
    Light electric boat concept is realistic, actual prototypes are impressive.
    Multihulls are made to receive this technology

    Production should be helped, and motivated.

    We must turn to lighter and simpler boat with less gadgets.
    The times of heavy things is over,

    We need light boat with low needs.
    Do it like you want as long as it is light, universal and efficient.

    Free energy is the one you do not need
  11. marshmat
    Joined: Apr 2005
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    marshmat Senior Member

    Wow. I wasn't expecting this thread to become so politically charged.

    I must admit, I too am rather mystified by how expensive electric drive systems are. Having worked on several solar cars, using some of the most efficient electric drive systems ever built (we had a motor rated for 97.6%), I think the main reason for the high costs comes down to economics and marketing.

    Look at the standard marine gas engines- the 4.3 V6, 5.0 V8, etc. The basic engineering of these things is decades old. They have been used in numerous applications- boats, cars, trucks, stationary generation- with only minor modifications.

    Now, looking at electric motors: The big guys- GE, Westinghouse and the like- design and build semi-custom stuff, at significant expense, for industrial clients. There's a significant market for stock industrial motors in the few-kilowatts range, but they all have severe restrictions: most require some particular type of 3-phase supply, or are restricted to single-speed operation, or need an elaborate VFD controller. Few of these industrial motors are suitable for vehicle applications, so electric car and bike hobbyists have to resort to smaller manufacturers, who may or may not be reliable, and may or may not believe in compatibility with other suppliers. The engineering costs are spread out over relatively few units, so the unit price goes up and less money is available for engineering.

    I think there would be a good market for a range of motor/generators in the 5-50 kW range, that are simple, require only a very basic controller (none of this frequency-varying synchronous stuff), and can be configured for a decent variety of DC or AC supply voltages. Alas, I have yet to find any such product line at a reasonable price, that is widely available.
  12. Guest625101138

    Guest625101138 Previous Member

    You need to go back to your text books and work out the difference between power and thrust. If you are what you say by education you should know this.

    10kW on the right prop can produce plenty of thrust to move a seaworthy craft against the severest conditions.

    You do not seem to grasp the simple fact that oil resources are rapidly diminishing. Untethered use of this resource will place even greater pressure on the world economy. This resource cannot be used wastefully until alternatives are established.

    You have moved way off topic trying to justify a dumb stance on not using electric propulsion. The question was about the expense of electric. The short answer is that it is not expensive if the whole system is scaled down to what is made for mass consumption. Until we see mass market production of higher powered electric devices we are stuck with paying industrial prices for robust higher powered units.

    Rick W
  13. mydauphin
    Joined: Apr 2007
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    mydauphin Senior Member

    Rick, I trying to explain that the ocean, sea, or even bay doesn't care about your arguements against oil. The sea water, ever present moisture, salt air, waves poundings will in a shorrt time destroy your batteries, and your boat if you do not have the horsepower to get out of a storm front. Have you ever been on a boat at sea or even a bay. 10kw wont even move a 14' boston whaler properly. Get real - Go buy a boat, go out 20 miles, listen to the radio, have a couple of cool beers, fish a little, trolling prefered then come back in a few hours at 20 knots. When you can do that in a electric boat I am all for it. Otherwise the PERFORMANCE is not there. Otherwise you have a electric paddle boat or canoe... Not a boat.
  14. Guest625101138

    Guest625101138 Previous Member

    I realised a long time ago that my boating was for relaxation. It takes time and needs to be savoured. I am long past pounding my guts out belting across waves at 20 to 30kts. I did that as kid and wasted far more than my fair share of oil. Have caught fish until I got sick of catching fish in the best fishing waters in the world. I am past all that.

    You cannot relax in the way I want to relax if you do not have time. If I can do 8kts safely and efficiently then I will be happy and relaxed. The boat I described earlier will do that speed in calm conditions with 1.05kW. It will have 9 times that power if required. It will have a bollard pull of 1.4kN. It will be seaworthy - unsinkable if completely swamped, self-righting. It will be easily managed by one person and beachable. It will be trailerable and can be stored on land. It will suit one or two people for extended cruising.

    Again I must point out that power and thrust are very different things.

    Most boats, even yours apparently, rely on batteries. To say they cannot stand up to the conditions is nonsense. They can be made reliable and long lasting. Battery technology is advancing rapidly right now. No reason why they cannot last a lifetime. I currently have a couple of Ni-Cd batteries I have used continuously in various applications since I purchased them in 1986 - they must have been well made.

    Rick W

  15. kistinie
    Joined: Aug 2007
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    Location: france

    kistinie Hybrid corsair

    Well said !

    Thanks rick for telling true facts
    Demonstrating it works will make things change.

    For information my actual electric project is "sail/electricity hybrid", no oil exept an old 3.5HP outbord and a 48V DC group if space and money for , electricity will be IP68 inside hull up to 1 meter high minimum.
    UFO can come and do holes in hull, motor and boat still sail and drive
    Price of such device will be under a fuel motor installation cost.
    24 to 48 volts - 150 amp/h - 5 Kw brushed or brusless motor, both are reversible
    Maintenance close to zero
    Weight inferior to the fuel option
    Electric autonomy far better than fuel option, as 100% paid when you sail and camp.

    I'm sure you will love it
    I keep you informed of the results when done and tested !
    And as use to say my grandfather "do not discuss with a wheelbarrow, push it"

    Solar and wind boat users accept that their performance during a travel depend on weather.
    They will run slow when low sun and low wind, and fine rest of the time.
    This for at least 25 years, with low maintenance and no carbon as they are simple boats

    This is a difficult technical point
    to listen at when you have to much oil in the ears...
    We could try with more volume to be heard ?
    Volume of Ev boats that cruise...
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