The website www.polardcmarine.com describes dual output diesel DC generators with dual DC outputs so that you can charge batteries and run a propulsion motor at the same time. Thanks. Steve S.
--- In electricboats@yahoogroups.com, "v40beth" <mrkgillis@...> wrote:
>
> Eric and Steve-
> Thank you so much for responding. I can make my own plumbing and sew my own sails, but this hybrid stuff is new to me. A number of people are pressuring me to get the Beta genset which is rated at 9.5 KW. Eric, my calculations were along what you did, And I was thinking that on batteries alone I could pretty well do everything I wanted to do, but the genset will be there for extended times on the hook and for those little things that tend to drive the volts down in the batteries. ( I will be using AGM's BTW) As I have read Nigel's study on this, I need a genset sized to the average draw, not the acute draw of a panic move on the motor, or 10 minutes on a stove etc. My battery set needs to be big enough, but if I have the genset just to top it off, or run through slack water (dead calm) in the ocean, why do I need a 500 lbs flesh eating monster? (the smaller genset is 210 lbs)
> But you guys have been there and done that. I am only speaking theory. I have the bucks to do either, but I do not want to turn my boat into a large party boat where the fun never stops (ie entertainment via electricity)
>
> --- In electricboats@yahoogroups.com, "Eric" <ewdysar@> wrote:
> >
> > Hi v40beth (?),
> >
> > With a displacement of just over 11 tons, you are correct that you should aim for a drive with at least 11hp or about 8.5kW continuous rating.
> >
> > Unfortunately, not many people have posted "watts to knots" performance data for boats in the 10+ ton range, so I have to extrapolate the data that we already have. I've seen that the recommended 1kW per ton drives seem to hit 90% hull speed at full power. Your boat has a hull speed around 7.5kts with its 34' waterline, so your 8.5kW (175A x 48V) should push the boat at about 6.8kts in calm conditions. If we assume that halving the power drops the speed by 1kt (a little optimistic, but close enough for this conversation), then 90A will be around 5.8kts and 50A will be around 4.8kts. Let's check that premise with another comparison. My 30' ketch Serenity, a boat with half the displacement, getst 5kts out of 2500W (50A x 50V); however, by displacement alone your boat may be closer to 4kts in calm conditions at that power setting. Your increased waterline offsets some of that speed loss to displacement, so I'd guess that your boat would be right around 4.5kts at 50A.
> >
> > Let's check out your range on your 20kWh battery bank alone. If you're planning on flooded batteries, then a 50A load will take the batteries from fully charged to 60% depth of discharge in 3hrs 45min. If you're travelling 4.5 kts, that's 17nm. That falls right in line with the range target for many conversions of 20nm at about 4kts. If you chose AGM batteries that are less influenced by Peukert's Effect and can handle deeper discharges more often, then 20kWh will support 50A for 5hrs 6min to 70% depth of discharge. That pushes your battery only range to just about 23nm.
> >
> > You mentioned regen. You'll have a big prop which is good, but I've only seen reports of less than 100W at 5.5kts and 150W between 6-6.5kts. So you need to think about your average sailing speed during a passage. If you're pulling 150 mile days, you'll probably average about 3.6kWh from regen. Add in 2kWh from the 400W solar panels and you've got a 5.6kWh daily allowance in optimum conditions. I have no idea what your all electric house demand will be, but you should figure that out to see what kind of reserve is available for your traction batteries.
> >
> > The 5.5kW generator seems OK, it should support a 45A load at 120V. Modern 48V chargers that run on 120V seem to max out around 35A, that works out to a 18-20A A/C draw by the charger. If the generator supports 230V A/C, then a 50A charger isn't that hard to find. Your 15A 12V charger won't be much load at all. I'm guessing that your galley (electric range) will be the biggest draw at peak loads.
> >
> > All in all, it sounds reasonable. Just be sure to work out your energy budget as well as you can ahead of time so that you don't get many big surprises later, after you've spent so much money and time putting it all together.
> >
> > Fair winds,
> > Eric
> > Marina del Rey, CA
> >
> > --- In electricboats@yahoogroups.com, "v40beth" <mrkgillis@> wrote:
> > >
> > > Alright guys, I know I don't post here much (never) but I would like your opinion.
> > > About 3 years ago I acquired an old Valiant 40 (one of the first 20 made) and I have slowly been restoring and renewing her. I am a sailor not a powerboater, and the old Westerbeke 4-107 as been leaking oil and embarrasing me whenever the bilge pump goes on. I have dreamed of electric with regen for along time, I realize that I can't do it completely, but this is what I want to do....
> > > I did my calculations- it looks like I need about 11 horsepower to do whatever I need with an auxillary. With the genset powering 50 amps of 48 volts, I think I can cruise at about 5-6 knots. But I usually motor in and out of port, and use my diesel to face into the wind to deploy the main- that is about it. For the engine – a 180i. I just don't think I will need more. If I have to carve off a lee shore during a storm, my sails will make or break me anyway. My Westerbeke has about 20 hp total- probably less than that at the propeller. I rarely use it above 2000 rpm. I just use the wind to go places.
> > > Two banks of batteries- 12v 450 a-hours (which I already have in place) for the house bank.
> > > 400 a-hours 48 volt to power the motor.
> > > A Next Generation kubota genset 5.5.KW with battery chargers going to 48 volt (25 amps) and using my current battery charger (I think it is 15 amps) to the 12 volt bank.
> > > Now here is where it gets tricky. I will have a Mastervolt inverter to cover the galley, microwave, and Big screen TV. I will go all electric stovetop and thus eliminate propane entirely from my boat (except the outdoor grill) I use all of these very rarely anyway. I will have a set-down transformer to convert the 48 vdc to 12 vdc when on the hook for extended periods. And I will keep enough solar panels (400watts) to keep everything charged when I am away from the boat. During passagemaking, the regen/solar will keep the 48 vdc and housebank charged. When I am cooking a meal downstairs, I will either have the batteries all topped off already, or just start the genset for an hour.
> > > Speaking of the genset, I will pipe the freshwater heating to the hot water heater, and then to a radiator (for winter heat) or a keel cooler (for tropical cooling)
> > > In the future- I will put in a low watt startup heat pump for cooling and heating.
> > > So there you have it- I get rid of two rather bothersome systems (propane and big diesel) and relace with a multifunctional genset and lots more batteries. What do you think??
> > >
> >
>
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