Electric motors - Do they need to be so expensive

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

  1. Kaptin-Jer
    Joined: Mar 2004
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    Kaptin-Jer Semi-Pro

    In a thread for hybrid engines I got sidetracked and asked about electric. I found that the Basic price to replace a 50 hp diesel is $8,770.00. Not counting the extra batteries and a few other things. (The Government should be giving them away!) An electric system is the right way to go on a sailboat because you are limited to hull speed. We need to start a forum on electric motors and see if some of our resident electrical experts can design a do it yourself system that us novices can put together with Radio Shack parts. I believe that this a project worth considering, or am I missing something in my naive enthusiasm.
    It is getting to that stage where new developments, products and "market prices" can be found at one point.
    This parallels BATTERIES at
    and hybrid power at

    Solomon Technologies...
    Some reference sites
  2. masalai
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    masalai masalai

  3. Kaptin-Jer
    Joined: Mar 2004
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    Kaptin-Jer Semi-Pro

  4. kistinie
    Joined: Aug 2007
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    kistinie Hybrid corsair

    Low Cost


    this kit can do for 10 hp to 30 hp equivalent when you use single or twin motor



    By the way, i am looking for the parts do do this reduction, especially the big bearing receiving the propeller shaft (25mm in my case !)

    If you use a high efficiency propeller, it will help

    And do no expect as much HP as on a gas motor.
    Often less HP is more than enough...If you sailing boat is able to go upwind easily. If it is not the case, i would keep a big diesel engine.
  5. masalai
    Joined: Oct 2007
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    masalai masalai

    kistinie, Thanks for the post the mars link can be found elsewhere as well - infortunately your youtube links do not link to any target? can you fix? Thanks....

    Kaptin-Jer, I am looking at the Torqeedo legs http://www.torqeedoaustralia.com/Torqeedo_Australia/Home.html for Australia and there are links to other countries....
  6. kistinie
    Joined: Aug 2007
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    Location: france

    kistinie Hybrid corsair


    Hi Australia !
    the trimaran i'm electrifing is a little part of your country...as it is a CROWTHER TWIGGY MKII lengthed to 37 feet

    Torqueedo is fine techno, but no regen, not because it cannot but because it is not compatible with the lithium battery
    Torqueedo told me they could upgrade this later...and may be in a pod version

    Utube Links repaired !
  7. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    The problem with all electrics still remains storage capacity. The Torqeedo uses some nice technology, but costs more then gas for the same power and doesn't have much range.

    I had a chance to use their little one, on a dinghy this summer and it pushed it to hull speed easily enough, but was dead in two hours. When used again, this time with reduced throttle, it was markedly slower and didn't really save much on battery time.

    I've been waiting with bated breath for three decades now on the "next battery break through" that will revolutionize the industry. At least this is what everyone keeps asking, but it just isn't comming. We've had some recent advances, but damn for the cost of some of these systems, compared to what you get out of it, it's still waiting on "the next big break through" thing again.

    Maybe it's just physics and we should be considering very small nuclear reactor driven devices instead. Buy it pre-fueled up, in a sealed container, let it run for 10 years or so, then trade it in for a new one. Oh hell did I just stir up the bee's nest? Look satellites have been using decaying isotope power cells for decades, why can't people get a head around the idea of this source of energy.
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  8. kistinie
    Joined: Aug 2007
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    Location: france

    kistinie Hybrid corsair

    Low cost energy

    Low cost energy is impossible for the moment, even earthship houses are quite expensive to build.

    For mobility, at 100 or even 145$, petrol is the less expensive energy available if you forget the total over all cost, rising litre after litre.
    Electric cost is stable and do not cost much more each time you use it

    My will to go electric on my boat is not for cost of petrol reason as i use less than 100 litres a years, but to gain, security, space, weight repartition, less noise, no odour, less maintenance, having a powerful hydro generator (easy on most multihull and in general on light boats) and as a blue boat not being obliged to go "hunting" for petrol during long trips gives you more freedom and in fact autonomy which is the aim.

    All energies costs and are limited. Even sun is limited to 50% of a day. This being said, some solutions are worst than others

    One anecdotal solution i use for my cars, truck and boat.
    I get my batteries from scrapyard and desulfat them or hot air solder if the polyethylene is broken.
    This works also for NiCAd.
    This is not an easy job...but works fine. You just need to be careful with acids, and lead, cadmium, vapour, hydrogen gas, fire...
    Battery life is extended, the earth and your wallet will both feel better, you can create jobs.
    Ask for this regeneration/equalization function from power devices sources, solar chargers, generator/motor controller, industrial ad-on cost is a minor fraction of the gain you will make on battery's life.
    in a more general way, we can improve massively the performance and longevity of our actual equipment. It is the simplest way to make then less expensive

    But of course, batteries is THE problem, and the problem is impossible to solve if we stay on this actual principle of electric potential difference between different metals... as metals rarefaction such as Zinc, antimoine, or lithium will increase the difficulty and rise price just like for petrol.
    Nuclear fission is 100 years, it is the past.
    We need to discover something different.

    Fundamental research is compulsory as we never know from where we will find the solution, important discovers are often side effects when looking for something else.
    In this spirit, space research on dark energy is this:


    As far as time is concerned, new big discover like fission was, could take 20 to K.years to find
    So it is the reason why we should be more earth wealth, than penny-wise

    And it is a fact that our actual energies are ALL based on a limited stock materials.

    So the higher the price of this material is the longer it will last.
    When you ask to pay less for these materials, you accelerate the extinction of theses materials.
    The induced stress you create creates chaos, chaos is increasing discoveries and extinctions

    When you ask to pay more for the material you slow down the extinction of the material.
    You peaceful and slow down the system. If research is slowed down too, you slow your changes and evolution.
    When research is increased, you improve your adaptation skills.

    Now till the moment we find a solution...
    The best thing is to have a light sailing boat that ...sails fine, motor is just comfort for a short time, a good energy source when not motoring.
    This is the same for cars or bikes, they need to be light and aerodynamic
    So forget about all not compulsory devices. Air conditioning, electric winches and other gadgets.
    Energy saving is often sweat...and good for health.

    Weight is a potential enemy for your health, in other's car, for your money, for the plane you will fly, and your boats too.
    Weight is preferred outside a moving object,
    If weight is inside the inertia is controlled and used an Kinetic energy resource.

    Your best energy is the one you do not need.
    Last edited: Mar 7, 2009
  9. Guest625101138

    Guest625101138 Previous Member

    There is a reasonable solution using current technology. There is a price break point around 5kW. Above this level you are into serious engineering. Below this level you are in the low end EV market. The motor and controller comes in around USD700:
    Mars motor with 200A Kelly controller on 48V system will peak at 9kW and continuous at 4kW.

    You then need to look at a hull. Trimaran gives the best solution but it only needs to be a trimaran below the water per the rough lineplan attached. This design will achieve 8kts with 1050W. Rated power of 4.5kW will achieve over 12kts.

    Then the boat needs to be built light. Would most likely be carbon fibre over corecell. Total bare hull weight 400 to 500kg.

    You could use lithium batteries to keep weight down but 10kWh of VRLA batteries are acceptable, much cheaper and will provide adequate ballast:
    Need 8 of these or similar.

    You would need 5 of these as the low weight alternative battery but lots more expensive:

    The prop design is the critical element. Needs to be designed for high efficiency and high thrust. This is the key aspect to get the best from the limited power. 20 x 20 prop for plenty of grip. Will achieve 85% efficiency at 8kts and bollard pull of 1.4kN with 9kW peak power.

    Now you add solar panels something like these:
    Four of these will give you reasonable energy in sunny areas. Having the solar cells re-encapsulated in a light weight panel is also feasible. Ends up about 1/3rd of the weight.

    The solar collection could be supplemented with wind energy:
    Something like this mounted on the cabin top would be able to generate on the move or at anchor.

    Overall the objective is to maintain steady speed of 8kts while keeping the batteries near full charge. Boat will have least drain when weather is calm. Range without any energy collection would be around 70Nm at 8kts and 110Nm at 6kts. Range is only limited by the ability to carry food as some sort of energy collection will always be possible.

    So right now it is technically possible and not horrendously expensive if the whole boat is purpose designed. In the long run lithium batteries will get more price competitive. I think this technology will explode as electric cars become common place. Then larger motors and controllers will be much cheaper.

    My next car will be all electric or hybrid electric. I am working on the electric boat.

    Rick W

    Attached Files:

  10. kistinie
    Joined: Aug 2007
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    kistinie Hybrid corsair

    Great ideas !

    And for peace of mind.
    Two smaller rather than one bigger
    Also certainly i will make my installation full redundant with two (energy sources/engines/controller/batteries) group, belt or chain connected to one shaft, one rotation able sail drive, two shafts or two pods.

    Two propeller on each side of rotation centre of the ship will give you a very high mobility.
    And the chance to loose all your propulsion and energy system for material failure is dramatically reduced.
  11. kistinie
    Joined: Aug 2007
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    Location: france

    kistinie Hybrid corsair

    You are right about the wind energy.

    But with such a size (1.8 meters), on less than 60 meters boats, great care should be taken to the effect on the boat balance and behaviour in extreme wind above 60 knts. Foldable wings on the wind generator, would be an efficient safty modification to do
    But if a variable pitch is installed, it may give a very decent safety
    Last edited: Mar 7, 2009
  12. Guest625101138

    Guest625101138 Previous Member

    I have a second Mars motor and controller to be used for the wind generator. I intend to use a 2-bladed turbine with high aspect blades. When stalled it will have very little windage. The controllers I have are 4-quadrant so can be used to generate or motor. The wind generator could be used for propulsion if required.

    My intention is for a single motor drive as it provides adequate power. THe wind generator is the emergency back up.

    Rick W
  13. masalai
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    masalai masalai

    Rick, your project is becoming more and more sophisticated every time I review your work - would be nice to meet on the water as I hope to be mobile in about a year from begining April 2009...

    Thanks Rick & kistinie...
  14. mydauphin
    Joined: Apr 2007
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    Location: Florida

    mydauphin Senior Member

    I don't like electric boats. As anyone that has been on a boat will tell you, bettween corrosion, electrolysis, the constant banging of the boat, salt water splashing, water leaks and the general theory of Murphy's Law. Water and electricity don't mix.

    I have Mechanically inject diesels that will run underwater as long as they have air intake, and fuel. Even the starters are air powered and can run underwater.

    When the water hits the fan, what boat do want to be on - Your electronic wonderland or a boat that will function with water rising in the bilge and get you home.

  15. Guest625101138

    Guest625101138 Previous Member

    Must be a primitive boat if you have no electrics. I guess you use a sextant for navigation - maybe you do not go far offshore. You also need a good time piece for navigation so I suppose you have a wind up clock - no crappy battery or solar powered stuff for you.

    I imagine you only use kero lamps for the nav lights but I expect a bit of a pain to get going when it is windy.

    You no doubt tolerate the poor efficiency of the diesel given it has no electronic fuel management.

    Look at all those deluded fools that make spark ignition outboards. Pity there is no market for these as all the sane people only buy diesel outboards with air starters. Never ever would sane people consider electrics on a boat!!!!!!

    Rick W.
    1 person likes this.
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