Barney,
Hull speed at 5Kw seems optimistic. 5Kw is less than 3.5 hp at 100% efficiency, your earlier estimate of 10Kw seems more realistic. That said, 3Kw should get you above 4 kts but probably not 5 kts.
I prefer to keep my expectation conservative, or the actual results could be very disappointing.
Fair winds,
Eric
Marina del Rey
--- In electricboats@
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> Many thanks for the replies.
>
> My thoughts have progressed to the following, and i would be very interested in what people think:
>
> I have figured that my boat needs almost exactly 5Kw to push it through the water at hull speed (6.5 knots), which is roughly 1 hour's travel with a 200ah 48v set up (discharging the batteries 50%). For 95% of my travels 4 - 5 knots will be ample, which drops down my power requirements to about 3Kw (in ideal conditions). I would plan to recharge using a Honda EU20i generator, which I could run simultaneously with the electric motor, and would slow my discharge rate by approximately 1.5Kw.
>
> My battery set up would be two packs of four batteries (12v x 200ah), which I could over time increase to three battery packs. With a three battery pack setup, I should go close to recharging one pack as the pack in use runs out of juice - again depending on the conditions.
>
> My choice of motor at this stage looks like either the Mars brushless, or the PMG132 would suit my purpose fairly well.
>
> Interested to hear people's thoughts, and any suggestions welcome.
>
> Barney
>
> --- In electricboats@
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> >
> > --- In electricboats@
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> > >
> > >
> > > --- In electricboats@
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> > > >
> > > > --- In electricboats@
> > > > >
> > > > > Hello all, lots of fascinating information on this group site!
> > > > >
> > > > > I have a 7.6 metre timber launch that I've just finished restoring, and I have put a 26Kw diesel in it, which pushes the boat past hull speed comfortably. Unfortunately, its extremely noisy, and after spending three months redesigning and building a new engine enclosure, its still far too noisy.
> > > > >
> > > > > So, I'm seriously considering selling the diesel and converting to an inboard electric system.
> > > > >
> > > > > I have lots and lots of questions, and thought it might be useful to ask to be pointed in the direction of some posts / case studies of people with similar projects. Any suggestions and considerations would also be very welcome.
> > > > >
> > > > > The details of the boat are:
> > > > > 7.6m LOA, approx 7m LWL
> > > > > Max WL beam = 2m
> > > > > Displacement = approx 3000kg
> > > > > I estimate that 10 kilowatts is what the hull form needs to be driven to hull speed (hence a 26Kw engine running at 60% capacity at present)
> > > > >
> > > > > The boat is currently sitting above its lines, so weight for batteries is not a concern - especially after the diesel is removed.
> > > > >
> > > > > Very interested in any suggestions people may have for me.
> > > > >
> > > > > Barney
> > > > >
> > > >
> > > >
> > > > Hello Barney,
> > > >
> > > > I can maybe help by passing on information and data from my boat conversion from last year. My powerboat is 26'long with a 9' beam and 5,200 lbs. I installed a 5KW BLDC 48Volt motor, 100Amp Controller and a 3:1 reducer and she goes along at a little over 5 MPH running at 50 amps of current. I installed two battery packs (48 volt x 100 AH) and run the boat off one battery pack at a time. For the speed control I put in a Merritt Joystick which also gives me forward and reverse. I also installed a Converter to take off 12Volts for the lights, bilge pump, key switch, etc. I was happy with the performance of the boat except I would like more power and speed. Also, consider a water cooled or forced air cooled motor because with an inboard motor installation you may need to cool the motor. I hope this is helpful.
> > > >
> > > > ebdrives
> > > >
> > > Thanks very much for that. It sounds like our boats are very similar in size. Sounds like you have a nice setup, but I have to agree with you - it would be nice to have the option to exceed 5MPH if required. What about your stern gland? And were you able to use your existing propeller?
> > >
> > > Cheers,
> > >
> > > Barney
> > >
> >
> > My electric boat drive attaches to the existing 1" diameter shaft and 15" diameter propellor. Let me know if you need any help with your electric conversion. No charge...
> >
> > ebdrives
> > ebdrives
> >
>
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