Exactly.
As Steve pointed out in referencing Torqeedo’s website referring to “overall efficiency”:
> > > The Torqeedo website shows the 801 motor has an overall efficiency of 40% to 45% at inputs of 300 to 400 watts. The Cruise 2 efficiency is 30% to 35%. Your batteries would give you more range with the 801 at three knots than the Cruise 2. For a 23' sailboat I would think the smaller motor is a better choice if you are concerned about range. Thanks. Steve S.
But to show how even these efficiency ratings are meaningless without considering the hull, consider driving a 20-ton vessel with one. The overall efficiency would be dismal. Prop size and shape needs to be appropriate for the hull being driven. Failing to get that somewhat right, the results can be disappointing. The 40-45% overall efficiency noted above, while not sounding too great, is probably not too bad if you consider motor efficiency around 85-90% and prop/gearing efficiency of, at best, 70%...ie… your overall efficiency goal should be to get as close to 65% as feasible thru proper choice of prop, gearing, drive motor and controls/wiring/batteries.
-MT
From: electricboats@yahoogroups.com [mailto:electricboats@yahoogroups.com] On Behalf Of epowermarine
Sent: Saturday, December 18, 2010 7:54 PM
To: electricboats@yahoogroups.com
Subject: [Electric Boats] Re: Torqeedo Cruise 2 and charging methods
The really important thing here is 'overall efficiency', meaning propulsive force for whatever it is you are trying to move through the water. Since most of the systems we use have some sort of reduction drive, the efficiency of that must of course be included. The motor, controlling circuits, hydrodynamics of the housing, wiring, voltage, battery size and chemistry all contribute (or detract) from the overall efficiency rating. After all they are working as a complete system, not independently.
These discussions usually end up with a bit of ebb and flo, and likewise there are many reasons to choose one product over another. On the water conditions are hardly ever similar to a test tank, and the more powerful motor might be a better choice to provide a safety net when weather or other conditions necessitate. It's nice to know that now more than ever there are real choices available, any you can put together a system truly tailored for your application.
Capt. Todd
www.epowermarine.com
--- In electricboats@yahoogroups.com, "Steve" <sstuller@...> wrote:
>
> This is an interesting discussion about electric motor efficiency. I believe that you are saying that the motor efficiency is a constant from zero power input to maximum power input. If this is true then you are correct. If not, then a smaller motor that reaches its peak efficiency at lower power inputs then the larger motor is a better choice for smaller boats that would normally operate at these levels. Thanks. Steve S.
>
> --- In electricboats@yahoogroups.com, "epowermarine" <todd@> wrote:
> >
> > Regarding Torqeedo efficiency:
> > Perhaps there is an error with the information you were looking at. I have been selling Torqeedo products for 3 years and we are seeing incremental efficiency gains every year with each new product release. The 'old Travel 801' is not more efficient than the 'Cruise 2.0 tiller' at any speed, especially if it is a recent 2.0 tiller that shares the same motor/controller from the Cruise Remote series.
> >
> > The new Travel 503/1003's are also more efficient than the old Travel line was. It's not only the motors themselves, but the propellers are getting better as well. In 2011 you will see multiple propeller choices so you can better tune the motor to your application, be it a small lightweight skiff or a larger heavy boat.
> >
> > In a month or so the new catalog will be out with lots of background data relating to efficiency and other test results.
> > Best,
> > Capt. Todd
> > www.epowermarine.com
> >
> > --- In electricboats@yahoogroups.com, "Steve" <sstuller@> wrote:
> > >
> > > The Torqeedo website shows the 801 motor has an overall efficiency of 40% to 45% at inputs of 300 to 400 watts. The Cruise 2 efficiency is 30% to 35%. Your batteries would give you more range with the 801 at three knots than the Cruise 2. For a 23' sailboat I would think the smaller motor is a better choice if you are concerned about range. Thanks. Steve S.
> > >
> > > --- In electricboats@yahoogroups.com, "millsy321" <millsy321@> wrote:
> > > >
> > > >
> > > > I have, finally, about completed my e-drive installation on my 23' sailboat. Recently purchased a Torqeedo Cruise 2, powering through (6) 100 AH agm batteries (slightly used- in good condition) in a watertight keel cavity, also acting as ballast. I have only used the motor a few times but have so far been happy with the results: 50 amp max @ 24VDC; 25 amps gives me speed enough even against head winds; 15 amps keeps me moving at 3 knots.
> > > >
> > > > Torqeedo is very down on connecting multiple batteries together and I have divided them up into (2) 24VDC banks: Bank 1 has 4X batteries in series/parallel. Bank 2 has 2X batteries in series (I might add another two batts to this bank later on and place them elsewhere on the boat). I also have the option of connecting both 24V banks in parallel through a battery switch. On order is the Expert Lite battery monitor and Quick Charge OB24 with agm charging profile from Evolve Electrics. The Quick Charger I will connect through a battery switch with the idea in mind that I will be able to charge the idle bank through a small Honda genset eventually.
> > > >
> >
>
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