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Go Back   SailNet Community > On Board > Gear & Maintenance > How desirable is a diesel generator?
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Thread: How desirable is a diesel generator? Reply to Thread
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Topic Review (Newest First)
12-22-2011 09:24 AM
bdietrich Bchaps: you won't need air-conditioning on the hook in the Bahamas.

I removed an old Onan diesel genset out of my boat, and was glad to get rid of the weight and free up engine-compartment space and simplify the boat. But mine was a much easier choice: much older genset which had some problems, air-conditioners which had some problems, AC freezer which had some problems.

A genset is a nice backup in case engine alternator fails (but I guess you have solar), nice to power tools, nice to run a microwave or coffeemaker or whatever. But I live just fine on solar and propane now. And burning less fuel is a very good thing.

And a working genset and air-conditioner is part of the value of your boat, at present.
12-21-2011 05:09 PM
hellosailor Rudders, rudderposts...
I *know* I've been tiaght sufficient math to figure it out, I just have no anywhere near real or recent experience to consider things like "how much torque, twist, pressure, does a rudder impose on a rudder post when the boat is moving laterally against 20' seas in 45mph winds at 5 knots under bare poles?"

Somewhere amongst us are the engineers or nautical architects who, one can dream, have the formulae all meatly typed up somewhere to make the plug-n-play....

I think the three little piggies has similar questions before the huffing and puffing began. (G)
12-21-2011 09:41 AM
Zanshin Hellosailor - we won't quibble about capability or potential here, sort of like saying that a Ferrari can only travel 60MPH top speed....if you leave it in first gear

The lost rudder was 2 boat ago, but the cause was a mix of a probable grounding with slight stock bend early on in the charter career before I got the boat, then crevice corrosion set in and heavier weather did the rest. But on my new boat I am very careful about keeping the forces on the rudder as low as practicable so that I won't have to go through anything like that again in the future.
12-20-2011 02:27 PM
hellosailor "5400W equates to a charging capacity of 450amps at 12V."
I think our casual misuse of wrods is at the heart of this.

5400W at 120VAC does not equate to a charging capacity of 450A @12VDC. It equates to a potential charging capacity, if someone invests in an expensive 1:10 stepdown transformer and some 1000A-rated diodes to rectify the AC into DC. Or these days, into a still expensive switched power supply to provide the DC.

The difference is that capacity depends on what was bult and how it was built, and these days everything is built to a price and for a purpose, a target market. Even Honda, whose gensets are widely acclaimed, states flat ou tin the manual for some that the DC output is suitable only for battery charging, and not for any other purpose, because the DC waveform is so dirty. That's made for a purpose, battery charging.

The OP's Fischer Panda apparently is made to provide AC power, with a smaller capacity DC to charge a small battery bank, or perhaps DC loads. (Who knows how clean that DC is?) Whether it is "right" or "wrong" for the built-in DC output to only provide 40A, depends on what it was built for, as well as whether it is working to spec.

Heck, my *lunch* has the capacity to power a small ship for a week. Capacity, yes, but the Mr. Fusion converter is lacking, so someone won't be able to make that happen this week. :-)

Zanshin, some time ago you lost a rudder and there was a long thread about how the post failed. What ever became of that, did anyone figure out why it broke?
12-20-2011 07:25 AM
Zanshin Captainjay - Ahh, I see; I was misled by the initial sentence in your original post and only scanned the rest of the text. It does sound as if the OP has issues outside of the power producing capability of his genset.

Postscript - Text written while running my genset and pumping 210Ah into my battery bank (at 24V!) using a big hefty Victron inverter/charger and another Cristec charger. I no longer have a Fischer-Panda but a Cummins-Onan genset aboard this boat.
12-20-2011 06:35 AM
captainjay
Quote:
Originally Posted by Zanshin View Post
I beg to differ - 6Kw is a significant generator. Without taking too many factors into consideration, let us take 6000W and de-rate by 10% for various losses. 5400W equates to a charging capacity of 450amps at 12V. Depending upon your battery bank size and battery type and charger you most likely won't be able to use all those amps.

If you have the Fischer Panda soft-start system, you can even crank up a Bauer dive compressor (running it is easy once the system is running). The genset will run 3-4 air conditioning units and could cool a 49 foot boat in the tropics (I had a 49DS in the caribbean with a 5Kw Fischer Panda which did the job).
Zanshin,
You misunderstood what I was saying. The OP said he was only getting forty amps charging out of the generator. The standard alternator on the generator has a very small, I believe less than 10 amp alternator designed to maintain it's own starting battery. The generator is fully capable of running a large onboard a/c powered charger or charger/inverter. The boats in our fleet that have this generator are equipped with 2.5 kw inverter chargers capable of putting well over 100 amps DC into the battery banks. My point was that his charging issues with the generator have nothing to do with the generator and everything to do with the charger he has on board.
jay
12-19-2011 09:14 AM
Zanshin
Quote:
Originally Posted by captainjay View Post
The generator doesn't have the capacity to charge your house batteries. The 6kw has a very small charging system designed to keep a dedicated start battery charged...
Jay
I beg to differ - 6Kw is a significant generator. Without taking too many factors into consideration, let us take 6000W and de-rate by 10% for various losses. 5400W equates to a charging capacity of 450amps at 12V. Depending upon your battery bank size and battery type and charger you most likely won't be able to use all those amps.

If you have the Fischer Panda soft-start system, you can even crank up a Bauer dive compressor (running it is easy once the system is running). The genset will run 3-4 air conditioning units and could cool a 49 foot boat in the tropics (I had a 49DS in the caribbean with a 5Kw Fischer Panda which did the job).
12-19-2011 01:47 AM
Capt Len Even the old fashioned (cheap) Trace inverter puts out at 125amps dc as a charger from shore or gen set. And 2500 watts ac from main engines alt.Sound to me like there are some useful options here if you keep the gen set.
12-18-2011 09:59 PM
captainjay The generator doesn't have the capacity to charge your house batteries. The 6kw has a very small charging system designed to keep a dedicated start battery charged. The on board 110 volt charger or charger/inverter does the charging under generator power just like when you are plugged into shore power. If you are only getting 40 amps then it's a charger issue. I would learn to maintain it, fix or upgrade your charger and keep it as a back up. You will never say I wish I only had one way to charge the batteries. Also the ability to dry the boat out with the on board air conditioning for a few hours will come in handy on still days, or rainy nights.
Jay
12-17-2011 04:42 PM
hellosailor Bill-
" but only charges at 40 ah which seems to never peak the batteries " Is it spec'd to only put out 40A? And with what kind of voltage or regulation? It may not be topping off the batteries simply because it is malfunctioning, or not putting out the voltage they need.
If you don't need it and can make better use of the space, by all means travel lighter and sell it. But if that AC sometimes comes in handy, it might be worth looking into whether it can be made to work better. If it is simply wired up as a 6kW AC genset with a small capacity for DC, the answer may be to add a "shorepower" battery charger (or use the one you may have?) and convert the higher power AC output for charging.
Not all gensets have equal abilities on their AC and DC sides, some are designed with very lopsided abilities.
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