It's a pretty common mistake to use published battery ratings for maximum range, but the rating that you quote below is for a 100% depth of discharge. Using the accepted 50% DOD for maintaining healthy wet cells, the 8 T105s will have a usable capacity of 66 minutes and the 12 T105s will have a usable capacity of 110 minutes at a 3000w load.
This is why many people run AGMs that can be run to 65% DOD without negative effects or LiFePO4 batteries that are rated for over 2000 cycles at 80% DOD. AGMs are also less affected than regular wet cells by the Peukert effect, the reduced capacity of batteries under high amperage loads, and Lithium batteries even less so.
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@
>
> Thanks for the numbers James. I assume that 3KW @ 5.75MPH is measured performance from your Catalina, right? Sounds reasonable.
>
>
> The Trojan T105s are rated for 115 minutes at 75A, so lets say an easy 2 hours at 3000W (62A). That'll give you 10 miles at 5 KT.
> If you go to a 72V system (4 more batteries), the range should about double.
>
> Not sure what my point is, but it's an interesting comparison.
>
> Cheers,
> Jim
>
>
>
> --- In electricboats@
> >
> > A Catalina 30 consumes 3 KW at 5.75 miles per hour continuous,
> > provided the bottom is clean and there are no obstructive though hulls.
> >
> > It takes 8.7 hours to motor 50 miles at this speed.
> >
> > it takes about (3 x 8.7) 26 KWH to motor 50 miles. However,
> > there are probably going to be wind and waves along the passage, so
> > add another 20 percent for weather.
> >
> > It will most likely take 32 KWH to run 50 miles.
> >
> > A 2 panel solar array constantly aimed at the sun may produce 420
> > watts for 8 hour on the longest day or 3.3 KWH.
> >
> > this leaves battery capacity required at 28.7 KWH.
> >
> > Lithium Iron Phospate battery packs by Thundersky are rated at 160
> > amp hours @ 48 volts = 7.6 KWH of which 80 percent is useable or 6.1
> > KWH. A 48 volt pack of these batteries costs around $3,000. You
> > would need 5 packs which would yield 30.4 KWH.
> >
> > Each one of these battery packs weighs 200 lbs, so total weight would
> > be 1,000 lbs, still less than the AGM pack I have on my Catalina 30,
> > Kapowai.
> >
> > You could install the batteries under the aft bunk, under the
> > starboard settee and next to the engine, and if necessary under the
> > front bunk.
> >
> > Approximate price of all components would be
> >
> > Drive Unit: $5,000
> > Batteries: $15,000
> > Battery Chargers: $3,000
> > Cables etc. $1,000
> >
> > Estimated Total: $24,000 plus installation and options.
> >
> >
> >
> >
> > James Lambden
> > Propulsion Marine
> > 805 455 8444
> >
> > www.propulsionmarin
> >
> >
> >
> >
> > On Mar 22, 2010, at 4:58 PM, MarkH wrote:
> >
> > > Hello to all. I bought a Catalina 30 3 years ago, (30 foot sloop
> > > sailboat, 10,500lbs). It's a 1986 model with a 21hp 3 cylinder diesel.
> > >
> > > Ironically, I'm not having any problems right now. However, a
> > > diesel is noisy, smelly, requires constant maintenance of filter
> > > replacement, oil changes, fuel, etc… You guys know this, I'm
> > > preaching to the choir.
> > >
> > > Electric propulsion is an attractive option for me; but I do have
> > > some concerns.
> > >
> > > 1) I know electric propulsion will work for 90% of my sailing; 15
> > > minutes out, an hour or three later, 15 minutes of motoring back to
> > > the dock.
> > >
> > > 2) BUT, my concern is how this will work when I cruise up the canal
> > > from Elizabeth City North Carolina to Portsmouth Virginia, a 50
> > > mile, 8 to 10 hour journey … can I do this with electric
> > > propulsion?? This trip cannot be done at a slow 3 knots or less to
> > > conserve amps; one must keep up 5 knots or so, to make the lock
> > > schedule, and to keep out of others way coming up behind you in the
> > > relatively narrow canal.
> > >
> > > In other words, can one feed charging juice to the batteries with
> > > either solar, wind, and/or generator while still moving at 5 knots,
> > > without stopping to recharge, making it possible to make a 50 mile
> > > trip at full speed non-stop?
> > >
> > > The title about being crazy … fellow members of my yacht club think
> > > I'm from Mars when I suggest converting to electric. This may
> > > simply be I'm a reader and keep up a bit more with current events
> > > than many others; although this topic isn't exactly current events
> > > since electric powered sailboats have been around for many years.
> > >
> > > I also realize new lithium-ion battery technology may change the
> > > formula significantly in the near future … that's what I'm hoping
> > > for anyway.
> > >
> > > BTW … anyone want to take a stab at what a 25 year old, 21hp 3
> > > cylinder, model M25 Universal diesel in working condition, worth?.
> > > The exact hours unknown. It was showing 1,000 hours when purchased,
> > > but the hour meter wasn't working at that time.
> > >
> > >
> >
>
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