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  1. #1
    Join Date
    Aug 2019
    Posts
    1

    Default Electric boat conversion

    Hi All,

    Does anyone have experience or knowledge around converting a boat from using a diesel engine to a hybrid electric power system.

    So this would mean a large battery bank powering a electric motor and a generator to recharge the batteries and / or drive the motor when they are empty. The obvious advantages would be a completely silent boat when running on batteries and a mostly silent boat when the genny is running, altho this is dependent on sound insulation etc. Would also mean that you could recharge when hooked up to shore power and trickle charge with a solar panel. At a high level the diagram below describes the ideal scenario

    https://www.fischerpanda.co.uk/res/4...V_GENSET_1.pdf

    I currently have a 38' Broom cruiser with a Perkins diesel which runs very well so probably not something that I'm going to do soon but the idea of a silent boat with a fully electric drive system is awfully appealing! The boat itself should be well set up to do this (I'd hope anyway). The engine comp is quite large and very accessible, currently has a hydraulically driven prop but I'm guessing I would just connect the motor direct if I converted? Depending on cost, I'm thinking something like a 6 or 8Kw 48V Generator with a 600a Li-ion battery bank.

    Wondering if anyone has done this or has any advice etc.

    Thanks,
    Ian

  2. #2
    Join Date
    Jun 2010
    Posts
    964

    Default Re: Electric boat conversion

    Perfectly possible if you have more money than sense, but the viability of it is low as the huge extra weight of the batteries and the complex charging needs alone would outweigh any advantages in such a small boat, and it would lead to poor handling and the loss of space. Other issues would be insurance as a home installation would bring huge potential liabilities and the resulting huge premiums and this is even before the risks which are currently known and one risk is Li-ion batteries exploding, and once they explode they are difficult to extinguish.

    I could add more.
    I am old and wise because i was young and stupid.

  3. #3
    Join Date
    Dec 2004
    Location
    Barbados (East coast)
    Posts
    4,638

    Default Re: Electric boat conversion

    Maybe have a look at the Greenline Motor Yachts for some design ideas? - They have hybrid power systems.

    https://www.greenlineyachts.co.uk/

  4. #4
    Join Date
    Sep 2016
    Location
    SoF
    Posts
    9,876

    Default Re: Electric boat conversion

    This is a story that I read a while ago, about the conversation of a Beneteau Swift Trawler 34 to hybrid
    https://www.boats.com/reviews/benete...y-good-hybrid/
    https://www.passagemaker.com/cruiser...brid-prototype
    As far as I know it never got beyond this prototype.
    As it piggybacks the Diesel engine, the diesel also recharges the battery bank. And it can be recharged from shore or generator.
    This gives you the option of using your existing Perkins and not buying a generator.
    This could save a lot of money, until you feel that you have a viable system that’s worth investing more money in.
    Neither a Leaver or Remainer be

  5. #5
    Join Date
    Apr 2011
    Location
    Boat- Western Med
    Posts
    5,345

    Default Re: Electric boat conversion

    How about using wind ?
    You could feasibly use a large sheet or something attached to a pole and work out how to harness a breeze using ropes , winches and knots .
    Perhaps go as far a rigging a system to vary the surface area of letís call then ďsails ď to adjust speed and wind conditions .

    You never know you might even be able circumnavigate the globe @ nil diesel expense with a contraption like this

    Solar panels or a wind generator as well but only for the beer fridge

    I realise itís a different mind set on this particular forum ,having a boat that does not rely on its engine(s)

  6. #6
    Join Date
    Dec 2005
    Location
    Live London
    Posts
    3,840

    Default Re: Electric boat conversion

    I was talking to whitelighter about this the other day.

    A d12 weighs 1175 kg empty. Add oil and water probably 1250 I have2 so 2500kg

    I have another 2700kg if diesel

    So 5200 kg in total. I donít know what an electric engine weighs letís day 600kg the pair

    That leaves 4600 kg for batteries.

    Google tells me an 85kw Tesla battery pack weighs 540kg so I can have 8.5 of them giving 724kw of power

    I have no idea what this means in real life on a boat however ... my Range Rover does 30 to the gallon. My boat about 1.

    If a Tesla does 300 miles on a battery using an efficiency of 30:1 suggests my 8.5 batteries will get me about 85 miles. Not my current 250 mile range but itís a start ! Yesterday I did 30 miles ish to es trenc and back. With shore power I am fine to charge. At anchor not so useful !

  7. #7
    Join Date
    Mar 2004
    Posts
    6,067

    Default Re: Electric boat conversion

    if you just do local trips you may be able to rig up a shore charged system
    you'd never recover the install cost

  8. #8
    Join Date
    Sep 2012
    Location
    Henley
    Posts
    820

    Default Re: Electric boat conversion

    Quote Originally Posted by jrudge View Post
    I was talking to whitelighter about this the other day.

    A d12 weighs 1175 kg empty. Add oil and water probably 1250 I have2 so 2500kg

    I have another 2700kg if diesel

    So 5200 kg in total. I don’t know what an electric engine weighs let’s day 600kg the pair

    That leaves 4600 kg for batteries.

    Google tells me an 85kw Tesla battery pack weighs 540kg so I can have 8.5 of them giving 724kw of power

    I have no idea what this means in real life on a boat however ... my Range Rover does 30 to the gallon. My boat about 1.

    If a Tesla does 300 miles on a battery using an efficiency of 30:1 suggests my 8.5 batteries will get me about 85 miles. Not my current 250 mile range but it’s a start ! Yesterday I did 30 miles ish to es trenc and back. With shore power I am fine to charge. At anchor not so useful !
    Even with shore power it would take 80 hours to recharge on 32A supply if drained to 20%, assuming no other losses or power consumption going on. If you’re enjoying air con etc while you charge it would take even longer!

  9. #9
    Join Date
    Dec 2005
    Location
    Live London
    Posts
    3,840

    Default Re: Electric boat conversion

    Quote Originally Posted by Anders_P42 View Post
    Even with shore power it would take 80 hours to recharge on 32A supply if drained to 20%, assuming no other losses or power consumption going on. If youíre enjoying air con etc while you charge it would take even longer!
    Most Marianaís I goto have 3 phase power which will help

    I am not suggesting I do it but the power range etc is better than I thought !

  10. #10
    Join Date
    Mar 2002
    Posts
    17,639

    Default Re: Electric boat conversion

    Quote Originally Posted by jrudge View Post
    I am not suggesting I do it but the power range etc is better than I thought !
    Are you sure it is, J?
    I am not saying that your train of thought is totally wrong, but your conclusions make me suspect it could be.
    I mean, an electrical-only planing boat which gives, for the same total weight, one third of the range of the equivalent diesel version with the same performance? Without doing any math, that just doesn't pass a quick sanity check, imho.

    I suspect that you might have not considered the "same performance" bit.
    Of course if you are assuming to use the boat at D speed only it makes a helluva difference, but in this case you should make the comparison with a single diesel of less than half the size of each of your D12s...
    Which brings the diesel range well into 4 digits, as opposed to the 250 you mentioned.
    Which is bound to be at P cruising speed, surely?

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