400AH/144v pack would run you about $20K, Or about $480 a cell with
BMS. You would need 44 cells. But still not chump change.
But I still do not see where you see all the lose at. I think you
assume I am all out all the time maybe 17 knots for three hours would
give me close to my 60 miles. ;-)
But putting around at 6 knots or so I am thinking I would be able to
putt all day? Hard to say till I have the motors in and can measure
the amp draw.
On May 24, 2009, at 7:43 PM, aweekdaysailor wrote:
>
>
> OK, so one assumption I made is that you have a planing, and not a
> semi-displacement hull. Those are not efficient at low speeds. If's
> its a semi-displacement trawler/tug type hull I'll reduce my
> guestimate by 2/3. But I just checked some pictures and they look
> like planing - and you mentioned it as well. I basically took 1/3 of
> 1 of your current engines for the 100KW guestimate.
>
> Let's say I'm off by a factor of 10. That's a 70amp draw off your
> 200AH of battery - 3 hours cruising. Or 6 if you pop $40K for the
> 400AH pack.
>
> At that point I'd say you're not only right, but far richer than I :)
>
> Stumbled on this: http://www.hawaii-
> which might settle the matter.
>
> -Keith
>
> --- In electricboats@
> wrote:
> >
> > 100KW to drive it at what speed? Please supply the math your working
> > in your head.
> > I would be curious what assumptions your making here.
> >
> >
> > On May 24, 2009, at 10:16 AM, aweekdaysailor wrote:
> >
> > >
> > >
> > > Denny is being too nice to say it outright, but what you're
> looking
> > > for isn't practical today. You'd be needing nearly 100KW
> continuous
> > > power to drive that boat -- a minimum of 12 100AH batteries would
> > > last about 4 minutes. So multiply by 10 -- 120 batteries to get an
> > > hour of range (Peukert helps here) at 80% depth of discharge. 120
> > > batteries is ~7000lbs...300 connections to corrode...740 cells to
> > > inspect...and one bad cell to ruin your day (or hour anyway).
> > >
> > > Steyr has some sweet-looking but undoubtedly pricey hybrid diesels
> > > that might be worth looking at - that would give you a short
> period
> > > of "silent running" before needing to power up.
> > >
> > > Otherwise - you can "go green" using biodiesel in conventional
> > > engines. A 30' sailboat is near the practical limit for pure
> > > electric due to hull form and battery weight factors - that's why
> > > they tend to be the focus.
> > >
> > > -Keith
> > >
> > > --- In electricboats@
> > > wrote:
> > > >
> > > > James,
> > > >
> > > > HP is HP, whatever the prime mover. The continuous (not max or
> > > peak) power rating of your motor is the number to use.
> > > >
> > > > The battery bank is the real power constraint anyway, not the
> > > motor. You want to consider speed and range. Not much sense
> setting
> > > up an E boat that will go fast but drain the batteries flat in 5
> or
> > > 10 minutes. Start the design process by defining the speed and
> range
> > > you require, select a possible motor/battery system, evaluate
> cost,
> > > weight, performance. Repeat until you are confident you have the
> > > best compromise.
> > > >
> > > > Get Dave Gerr's "Propeller Handbook" to figure the prop size and
> > > rpm best suited to your boat.
> > > >
> > > > Google the "Peukert Effect" to see how rapid discharge affects
> > > battery capacity.
> > > >
> > > > You will be removing around 2500 - 3000 lbs from the boat. You
> new
> > > installation needs to maintain the original center of gravity or
> the
> > > boat won't float level and if it floats bow down maybe hard to
> steer.
> > > >
> > > > Good luck.
> > > >
> > > > Denny Wolfe
> > > > www.wolfEboats.
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: James Sizemore
> > > > To: electricboats@
> > > > Sent: Sunday, May 24, 2009 3:25 AM
> > > > Subject: [Electric Boats] Any larger electric boat owners out
> there?
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > I see a lot of traffic on this list for smaller conversions
> > > replacing
> > > > A4's and such on 20-30 foot sail boats. Are there any folks that
> > > have
> > > > replaced larger motors on cruisers/trawlers?
> > > > I will be replacing two 427 fords (350hp gas engines) on a 41
> foot
> > > > Chris-Craft. This if for a number of reasons including not
> wanting
> > > > the ongoing expense of buying gas, second I really hate the
> > > monstrous
> > > > complexity of combustion engines. I have a computer science/
> > > > electrical background so I am much much more knowledgeable and
> > > > comfortable with electrical systems. And not to mention the
> smell
> > > and
> > > > noise of combustion engines. The knowledge I lack right now is
> boat
> > > > related: prop size pitch ...etc...etc. I don't need the boat to
> > > plane
> > > > at 17 knots or anything like that, although if it does all the
> > > better.
> > > >
> > > > My current thinking is to replace the fords with a pair of
> (Netgain
> > > > Warp 11'' or Transwarp 11'')'s. The part I can not rap my head
> > > > around is if I go direct drive with the Transwarp's will they
> spin
> > > the
> > > > props to fast? Or should I keep the transmissions that the
> fords are
> > > > bolt to now and go with the Warp's. I would prefer not to have
> the
> > > > extra complexity of the transmissions. The Netgains can move a
> large
> > > > truck at freeway speeds 70+ MPH. My understanding of the
> > > conversion of
> > > > electrical hp to combustion hp is at 144v these motors should be
> > > about
> > > > the equivalent of a 150-200 hp gas motors with considerable more
> > > > torque at the low end.
> > > >
> > > > The boat will soon have a fairly large solar array and already
> has
> > > > 7.5 KWH generator. So keeping the battery bank feed should not
> be a
> > > > problem. I know finding a solar charger/inverter for a 144v
> battery
> > > > pack will be a real challenge. Any recommendations are
> welcome. I
> > > > would also be very curious of other conversions of larger
> plaining
> > > > hull boats, and what motors you use and performance you get now.
> > > Also
> > > > any recommendations on motors/charges/
> boats
> > > > this size would be most welcome.
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > >
> > >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
[Non-text portions of this message have been removed]
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