conversion diesel to electric

Discussion in 'All Things Boats & Boating' started by maitlot, Mar 5, 2008.

  1. maitlot
    Joined: Mar 2008
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    maitlot Junior Member


    Conversion from diesel to electric and would like some basic advice on where to begin.

    What would be the best forum for beginners.

    Thank you.
  2. Guest625101138

    Guest625101138 Previous Member

    I expect you are talking about a boat and not a truck.

    What type of boat - there is already a thread going for diesel electric.

    Is it a sailing boat? Do you intend to use batteries?

    There are package electric/controller drives available from some suppliers.

    Batteries range in cost depending on how well sealed. Flooded lead acid are the low end and VRLA gel type are the top end of practical betteries. You can go to certain lithium ion if you want to spend big and go fast.

  3. kach22i
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    kach22i Architect

    Interesting link.

    I suggest doing a advanced forum search, I think there has been some discussion on this. Most of it not as actual or direct application though.
  4. maitlot
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    maitlot Junior Member

    conversion d-e

    I apologise for the poorly expressed question.

    I’m neither an electrical or mechanical engineer.

    The forums I have been reading, many, are way over my head and I need a beginners guide on this.

    I would like to convert my ship from diesel to electric propulsion.

    My first questions will indicate my level of understanding of this subject.

    I would like to go straight electric? No hydrocarbon fuels?

    Would generate my ‘fuel’ with wind turbines.? Stored in batteries?

    Should I go ‘AC’ or ‘DC’ for the drive motor?

    Where might I find a forum/thread at my level of understanding on this?

    Particularly a discussion on the ‘AC - DC’ question.

    I will really appreciate any input, suggestions on this.

    Thank you.


    12.2 metre sloop, fin keel.

    Data below based on keel removal.

    keel = 3,000 kilo = 6,600 #

    With keel, displacement = 7,300 kilo = 16,060 # dry

    Without keel = 4,300 kilo = 9,460 # +

    used 13,000 # displacement

    Reference: Calder, Nigel. ‘Marine Diesel Engines’; International Marine/McGraw-Hill. 1992 pg. 173

    Speed (s) / Length Ratio LWL 34 feet

    √34 = 5.83 X 1.34 = 7.813 knots

    S/LR = 1.34 = 55 # per Long Ton

    13,000 / 2,240 = 5.8 LT

    5.8 X 55 = 319 # = R

    S/LR = 1.34

    Effective HP = R X s X 0.003
    EHP = 319 X 7.813 X 0.003 = 7.48 EHP

    Propeller Factor 7.48 / .5 = 15 HP = 11 kW

    S/LR = 1.0
    R s
    EHP = 319 X 5.83 X 0.003 = 5.58 HP = 4.2 kW EHP

    Propeller Factor(PF)5.58 / .5 = 11.2 HP = 8.3 kW
  5. safewalrus
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    safewalrus Ancient Marriner

    Asimple question - where will you be putting these wind turbines? You'll need a fair sized one to generate enough power to shift that boat!
  6. maitlot
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    maitlot Junior Member

    I’m new to this, but I imagined the ‘power’ would come from the battery bank, not the turbine/generator. I expect there will be room on the 12.2 metre (40 foot) for the turb/gen.

    Very interested in hearing of your experience.

    Thank you.
  7. Guest625101138

    Guest625101138 Previous Member

    I have done the analysis for a Solar-Wind powered boat. There is a good deal of discussion here:
    and here:

    What you are proposing is practical. How much do you want to spend?

    To drive your hull at the 5 to 7 knot mark you will need decent batteries and turbines.

    I gave a link to drives in the earlier post. You would find that a Perm PMG-132 motor on minimum of 48V would do the job. Maybe need to go to 72V to get some good top end speed.

    Your power calculations are reasonable.

    There are some nice commercial wind turbines around. You would probably want two around the 3 to 5kW size. There are issues with hazard from high speed blades that you have to contend with.
    The boat will actually power directly into the wind without actually using battery power if you select the water prop right.

    You may find there are benefits in using solar power as well. I do not want to wait for wind to operate. In fact I would prefer to travel when the weather is calm so I have designed as much solar collection as wind collection.

    It is not a cheap option to get something that will work well. It will be as expensive as rigging the boat with mast and sails plus auxiliary power. The benefit is never having to worry about buying fuel again.

    You do not need to worry about matching voltage levels for the turbines, batteries and solar panels as you can get controllers to look after this. They will automatically load the units to maximise power recovery.

    All these things are proven but I do not know of any single boat having all combinations. I guees the USD30k to 40k you need to do it properly for a large boat is a turn off.

    Rick W.
  8. maitlot
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    maitlot Junior Member

    Rick Willoughby,

    I can’t thank you enough for your time and the links.

    My thinking is as follows:

    The first project has to be electrical generation and storage.

    Learn how to generate and store enough electrons to drive the vessel for five(5) hours at five knots.

    Build a ‘VAWT’, , or similar.

    Horizontal turbines, with there flaying ‘butcher knives’, would turn the foredeck into a “no man’s land’.

    I really don’t have a good understand of all this, but should ‘clue in’ after I have built, installed my first turbine/generator.

    I would appreciate your opinion on the ‘VAWT’.

    Propulsion must come later.

    I’m an older guy, septuagenarian, not as nimble or strong as I used to be, but the only way I can stay on the water, is power.

    But as Ratty said to Mole,
    "There is nothing -- absolutely nothing -- half so much worth doing as simply messing about in boats.”

    Again your input is most important, and I thank you very much.

    Oh, as to your question, “How much do you want to spend?”

    As little as possible ;-).

    I believe I have an adequate budget.

    With your assistance, I expect I’ll find out how adequate soon enough. ;-)

    Now off to peruse your links.

    Thanks again.

  9. safewalrus
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    safewalrus Ancient Marriner

    there's one thing positive - with all the batteries you'll need you've got no problem with ballast! The main problem (apart from money!!) is topping up those batteries!! Solar will help but I guess every deck spot will be covered in panels (GLASS!!) and many 'whirling dervishes' or wind turbines would make life slipping about the glass decks fraught with danger every time you stood up!! The Good thing is improvements ARE being made all the time! But are they good enough yet?

    the concept is as stated possible, but.................................I wish you luck. One other thing - you need a certain amount of emergency power at all times, this either means reducing your range / endurance or increasing your capacity (and if it's blowing a full gale what happens to those fans? they may take off eventually - a fail safe may stop the engine - dead!!!

    Sorry to sound so negative but if you can solve all the problems before they actually become problems life will be easy when you get afloat - ain't that what it's all about?
  10. maitlot
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    maitlot Junior Member

    “Sorry to sound so negative but if you can solve all the problems . . . .”

    AWWW shucks Penzance, I waz hope’n you would solve ‘em fer me !

    After I deep six the mast, I wuz tinking I’d fly a kite.

    Tanks fer wishing me luck.

    “Now you take care of yourself, ya hear.”
  11. Guest625101138

    Guest625101138 Previous Member

    I appreciate the link to test result on the vertical axis turbine. This looks nice for a simple stationary unit. I have played with similar units but my blades were not as clever as the ones shown. The Cd change through the rotation would be about 2:1 so this would give effective drive.

    However, I doubt that such a simple configuration would be useful on a wind powered boat. There are VAWTs with adjustable vanes that would have much better power to force ratio.

    Going into the wind in a turbine driven boat requires the water prop to provide sufficient thrust to overcome the wind drag on the turbine and hull as well as the water drag on the hull. Using fixed vanes on the VAWT would condemn the system to poor windward performance. A high proportion of the energy collected would be required to overcome the drag on the turbine.

    I personally believe you can make a high speed horizontal axis turbine safe. For example you could provide simple mesh guards over the deck areas that prevent accidental contact with the blades.

    You could make a development strategy.
    1. First stage would be to buy an electric motor and controller. The perm PMG-132 is a good choice as this will do the job of a decent sized diesel. These will give continuous of 7.2kW on 72 volts and peak at more than twice that power. You would need to gear it to get best results and swing say a 24 x 20 prop.

    2. You need to buy say 4 off 12V batteries to get started and a controller. You really need around the 200Ah range for serious testing.
    This would give you a range of around 15nm at about 5 knots - this is guessing. I could do it accurately but I would need to model your hull. I have my own test set up on a small boat. So I can play with the technology.
    The motor on this boat cost USD45 and controller USD18. I purchased batteries in Australia but they are around USD25 for the small ones shown. I think that it is reasonable that two small batteries give me a range of about 7km at 7kph.

    3. Next step would be to buy a small turbine to charge the batteries when the boat is not in use and add a little extra range. Surprisingly the best value units seem to be in the UK.
    Mounting one of these high enough to avoid accidental contact would not be difficult. It is not much bigger than the battery charger turbines for boat auxiliaries.

    4. If you are happy with it so far than you jusy keep adding. Next step is 2 more batteries to get you to 72V system. This will extend the range accordingly.

    5. In this step you add some solar cells. You could use these as cockpit awnings and side deck awnings. (They would act as turbine guards if you wanted to lower the turbines). The best I have found so far are Sunpower:
    I have not purchased any yet but they are available and they are competitively priced although expensive. The 215W units are around 5ft by 3ft. Eight of these are going to set you back a bit but then you give over 1.5kW in reasonable sunlight.

    6. Next step would be to add 2 more wind turbines.

    7. To finish the picture add another full set of batteries. This give 400Ah at 72V; equivalent to 28.8kWh.

    The end result is 3kW of wind collection in 25 knot wind; 1.6kW of solar power in full sunlight overhead; range of about 30nm at 5kts without any energy collection; ability to reach hull speed if required and ability to sustain maybe 5kts crossing an ocean.

    The boat you have is not ideal for the application but with good design it could be an impressive demonstration of an easily handled, ocean capable vessel.

    I am happy to do performance calculations if you want to pursue something like this. The initial design would be based on the final configuration. You would have an experienced based development process, learning along the way and gaining confidence with ability to predict performance and estimate costs. Given the current interest in renewable energy, you might find a sponsor to help you pay the bills.

    Rick W.
    1 person likes this.
  12. Guest625101138

    Guest625101138 Previous Member

    Has the existing boat got a bolt-on lead keel. Have you seen the price of lead lately. Three tonne of the stuff sold in the right place should get you going on batteries with money to spare.

    The question of AC or DC does not mean much these days. The electronic controllers are very flexible. The high efficiency motors will have permanent magnets. DC motors will normally have brushes. You can get DC motors that are actually AC motors but they have in-built electronics. AC motors do not have brushes but with the right controller they operate from a battery.

    You will see that you can get 4-quadrant controllers, electronic reversing or just variable voltage. For your application you would not need 4-quadrant controllers. These are only required if you want to generate from the water prop. Might be useful if the boat is moored in a tidal stream. I prefer electronic reversing to just variable voltage - it keeps wiring simpler.

    The Perm motor has a good reputation and I doubt that the brush life would be a concern in your application. This motor achieves a peak efficiency of 92% and only weighs 11kg.

    Modern DC systems use voltage chopping so you do not need to get overly concerned about exact matching of voltages. For example you should have no problem charging a common battery from 24V turbines and 32V solar panels providing each has a regulator.
    I have selected 48V battery because it gets more expensive to go above this voltage. Also I do not need more than 9.6kW on my prop.

    The other things that most systems have are a converter for battery voltage to 12VDC and an inverter for battery voltage to 220VAC (or your 110VAC).

    Rick W.
  13. safewalrus
    Joined: Feb 2005
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    Location: Cornwall, England

    safewalrus Ancient Marriner

    Rick, in theory very good, my only concern is these batteries, for the amount of 'juice' your going to need some hefty beasts, looking at the way you glibly buy batteries remember they have to go somewhere! And low down they are bloody heavy! Other than the fact you can't get inside the boat it looks good - if expensive!
  14. Guest625101138

    Guest625101138 Previous Member

    For my boat I have selected 100Ah and they weigh in at 28kg. They fit lengthwise end-to-end in a long keel. I figure I can manhandle these into position.

    The 200Ah units proposed on this thread weigh in at 66kg but they will be placed in the bilge of a 12m hull. Should be ample room for two people to get them into position. It would be possible to double the number of batteries with half the capacity to reduce unit weight. Page 10 of the pdf here has the detail on the Haze batteries:

    The boat needs a strong, secure battery box as there will be 800kg of batteries that need to be held to the bilge. I would replace the lead keel with a small stainless keel aimed at adding some roll damping and through-bolt this to a stainless or fibreglass battery case.

    One of the problems with the conversion is the reduction in roll inertia. Getting the batteries down low will increase the inertia and ensure self-righting. Placing the turbines a few metres above the deck will reduce interference and also increase roll inertia. The turbines also add damping as they will resist rapid speed variation as the boat rolls in a beam sea.

    Rick W.
    1 person likes this.

  15. Guest625101138

    Guest625101138 Previous Member

    I took a closer look at the performance of ML-12E.

    I used the Delftship default hull with minor modification. Adjusted draft for 800kg of batteries in a 4.3t boat - total 5.1t. Exported Michlet file and produced ship_output_by_speed file.

    Energy source 72V 400Ah
    Calm conditions
    88% motor/controller efficiency, 85% prop efficency 5% other losses giving 70% overall propulsion system efficiency (these efficiencies are possible)
    battery discharge to 90% of capacity

    The range at 6 knots is 84nm.

    Range increases to 137nm at 5 knots.

    The top speed at allowable full power of 13kW is 8.3kts.

    There is a bit of effort involved in getting the efficiencies stated but they are possible.

    Rick W.

    Attached Files:

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