The problem with lead acid batteries is that during the absorbtion phase re bringing the batteries to full charge from 80% to 100% they will only accept a charge rate of three percent to four percent of their 20 hr AH rating. It is a slow process bringing batteries back to 100 percent and if you only discharge them to 75 percent to 80 percent there is not much point in having a lot of available amps because the battery acceptance rate is so low as you get above 80 percent. Thanks. Steve S.
--- In electricboats@yahoogroups.com, "stmbtwle" <stmbtwle@...> wrote:
>
> Just to be on the safe side I'd size the solar array so it would in theory charge the batteries from dead to full charge in a week. 2 sets of GC's at 225ah = 450 ah + 1 house at 100 ah = 550 amp hours or 7425 watt hours. 7425/5 days 1485 wh/day. Figure about 5 hrs charging time (my experience here in Florida): 1485 wh/5 hrs = 297 watts.
>
> So in my opinion you'll need about 300w of panels. Figure about $600-$800 for new panels (2 big ones will be cheaper than 3 small ones), another $200 for a 25 amp MPPT controller, and $100 for a battery combiner so you can charge both the propulsion bank and the house bank. Somewhere around $1000-$1200.
>
> You might get away with less particularly if you don't run the batteries down or use the boat every week. On the other hand you don't get much on rainy-cloudy days, or in higher latitudes, and there's some inefficiency in the charging. So with the info you've given me those are my figures and I'm stickin' to em.
>
> You could start out with a single 135 watt panel and a 25 amp controller; and see if it's enough. If not buy a second identical panel (the 25a controller can handle both) Don't try to go cheap on the controller; the cheap ones aren't as efficient and if you upsize your array you don't want to have to buy another controller (been there).
>
> Go for it. I have solar on my houseboat and on my home, and love it!
>
> Bill
>
> --- In electricboats@yahoogroups.com, Richard Mair <fullkeel2000@> wrote:
> >
> > Â John.
> > With 5-15 knot winds forget the wind turbine..We had one (air-x) on our alberg 30. At 12 knots the output was still below 1 amp. so less than 12 watts. I did see 250 watts from it at times but not sustained and the wind was over 20 knots. It was rated at 400 watts. It did affect sailing performance as well.Â
> > Â With solar we have 90 watts of panels..If we use 10% of our 9600 watt bank it takes the week to come back up.. This is tied to a dock with the boom off to one side so as not to shade the panels..I should point out that we run the house from a dc/dc converter and there is a computer fan running all the time for the composting head.
> >  On a mooring remember that with tides and wind the boat will be facing different directions all the time so you would have to have the panels above the boom on a mount that  you could remove for racing.
> > Since we are a little further north you may get slightly better results from the panels..Â
> > If the panels are regulated they will not overcharge the batteries if left unattended. I am sure you will get some firm numbers from others but this is what we found.
> > Richard
> >
> > ________________________________
> > From: John <johnpomer@>
> > To: electricboats@yahoogroups.com
> > Sent: Friday, October 14, 2011 8:00:10 PM
> > Subject: [Electric Boats] Opinions Wanted - recharging four (4) GC2 batteries while on a mooring
> >
> >
> > Â
> > During the past year, I have recharged the four (4) GC2 batteries that power a Torqeedo Cruise 2.0 (Tiller model) using shore power at our slip. Next year I would like to eliminate the cost of the slip (~ $2500/year) and use just a mooring.
> >
> > QUESTION:
> > How to size photovoltaic panels and/or wind turbine while still having space on the boat and be "safe" to leave the setup unattended during the week?
> >
> > BOAT:
> > This year we used a Capri 22.
> > Next May we will use our Cape Dory 25 with the same batteries and motor while the Capri "takes a rest".
> >
> > BATTERIES:
> > 4 GC2 6 volt Energizer batteries from Sam's Club ($75 each)
> > 1 12 volt deep discharge "house" battery separate from the motive batteries.
> >
> > BATTERY SPECIFICATIONS:
> > GC2 : SAM'S CLUB
> > Amp-Hour at the 20 hour rate: 225Ah
> > Minutes at 75 amps: 110 minutes
> > Minutes at 25 amps: 447 minutes
> > This is manufactured by Johnson Controls Mexico.
> >
> > ELECTRICAL CONSUMPTION:
> > I have been very pleased with the performance of the Torqeedo Cruise 2.0 and battery setup for our Capri. It is about the same as the 5 HP Nissan (2-cycle) for top end, but MUCH better for all other speeds especially docking.
> >
> > The Cape Dory 25 is twice the mass and has a full keel with a motor well in the lazarette. If the Cruise 2.0 (24 volt) is lacking in power, I would change to the Cruise 4.0 (48 volt) sometime in the future.
> >
> > We typically daysail on weekends and did participate in the Wednesday evening Beer Can races this summer. We also found ourselves motor sailing across Boston Harbor to join in several regattas (since we were running late for the start times).
> >
> > Normal leaving the slip and returning consists of about 30 minutes total at 40 amp draw max. The voltage display starts at 26.2 vdc and drops to 25.4 vdc. On a few rare occasions when we motored at close to full speed for an hour total, the voltage would read 24.5 vdc and would rise to 25.1 after a few minutes of "resting" after reaching the slip.
> >
> > Looking at the usage over this summer, we typically use only 20% of the capacity on daysails. We may use 30-40% when we rush to the starting line on Wednesdays especially if the start is at the far side. Motor sailing around the Boston Harbor Islands (with the tide, but no wind) we still used only about 50% of the capacity.
> >
> > ---
> >
> > So, I am looking into ways not to need shore power to recharge the batteries for this "typical" usage.
> >
> > I would accept a "full charge" only 80% of the time rather than 100%. (I know I can use a generator but will ignore that option for this discussion.)
> >
> > 1) What size photovoltaic panel would allow the batteries to be recharged within 3 days from: 80%, 50%, 20% SOC? (Assume "realistic" sunlight, but ignore "rainy" days.)
> >
> > 2) What size wind turbine would allow the batteries to be recharged within 3 days from: 80%, 50%, 20% SOC? (Assume variable winds 5 to 15 knots.)
> >
> > ---
> >
> > Electric motoring is so nice - quiet, clean, instantly on. We also will "sail" more and have improved are skills.
> >
> > Thank you.
> > John
> > John
> >
>
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