Alternators, Gensets, I am confused

[PeterC]

On a 50 foot yacht intended for blue water use are you better have a large alternator and lots of battery capacity or two Gensets?

It seems to me a big alternator and high battery capacity means you can quickly charge the batteries while motoring and "carry" a lot of power and if the Genset fails you have another means of producing power.

On the other hand with two Gensets presumably the chance of both failing is small so you get the redundancy that way and presumably a Genset has the ability to charge very quickly.

I appreciate two Gensets is a more expensive solution.

 

[jonjo]

On a 50 foot yacht intended for blue water use are you better have a large alternator and lots of battery capacity or two Gensets?

Why restrict yourself to two polarized options. Most people are happy with a middle option comprising of a regular engine alternator, 400 amp hours of capacity and a single genset.

If you don't know, noise while charging from the main engine is the issue.

 

[sailorman]

This is a Sobering Read

On a 50 foot yacht intended for blue water use are you better have a large alternator and lots of battery capacity or two Gensets?

It seems to me a big alternator and high battery capacity means you can quickly charge the batteries while motoring and "carry" a lot of power and if the Genset fails you have another means of producing power.

On the other hand with two Gensets presumably the chance of both failing is small so you get the redundancy that way and presumably a Genset has the ability to charge very quickly.

I appreciate two Gensets is a more expensive solution.

http://www.sailwhisper.com/logs/news_20080225.php

posted earlier

 

[tudorsailor]

I doubt there is room for two gensets on a 50footer. If you really want an alternative back up to the genset and engine, why not get a towable generator? Then you could keep radar and autoplilot powered most of the time and then use the genset to top up battery less often

Tudorsailor

 

[ccscott49]

I have two gennys, one is really an emergency jobbie, aircooled mounted in my lazarette. Having a fisher panda main genny, I have to have backup systems, when it fails again (which it will) I will instal a better simpler make.
I will (when I have the money) install a 140a 24v alternator with smart regulator on one of my engines, that way all can be achieved with the engine running. I also have a BIG (550ah @ 24v) battery bank.

 

[Marsupial]

The real issue is why use the main engine to charge batteries? its the worst use for it. A 230v genset gives battery charging and the option to run other devices, like watermakers and dare I say it hair dryers - dont look at me I dont have any! hair that is. . .

 

[Dockhead]

Why two gensets? You're going to have an engine anyway, right? It will come with an alternator or two on it anyway, right?

The classical setup for a bigger cruising boat is to use a single diesel-powered genset (mounted in a sound enclosure in your engine space) for AC power and for charging a big battery bank, with a big alternator on the engine for the purpose of (a) getting a free charge onto the battery bank when you're motoring anyway; and (b) to back up the genset in case you have trouble with it.

You would not run your main engine to charge batteries except in case of a generator failure, unless you are motoring anyway, in which case you get a free charge. You would not need to run your generator all the time, either, as most of your systems will run for a day, more or less, on battery power. With a robust battery charger connected to your generator, you can run the genset a couple of hours a day to keep the batteries up (and make water, if you have a watermaker, and perform other high power draw tasks).

You can't run a genset when you're heeling, keep in mind. So I guess that's the third use of your big main engine-mounted alternator: charging the batteries on a long passage when you're heeling too much to run the genset.

That's the classical setup and I wouldn't think you would want to do something different. Wind and solar are good supplements to all of the above, but do not really produce enough power to be the main source of power on a bigger cruising boat, unless you are very frugal indeed. You can tow a water-turbine generator behind you when you are sailing on a long passage, but likewise this is better to keep as a supplementary power source, if your boat is bigger and not spartanly equipped.

 

[Dockhead]

I have two gennys, one is really an emergency jobbie, aircooled mounted in my lazarette. Having a fisher panda main genny, I have to have backup systems, when it fails again (which it will) I will instal a better simpler make.
I will (when I have the money) install a 140a 24v alternator with smart regulator on one of my engines, that way all can be achieved with the engine running. I also have a BIG (550ah @ 24v) battery bank.

Is your backup genset petrol-powered? Is your laz sealed off from your bilge? Beware of petrol vapours, which are heavier than air and as explosive as dynamite. You do not want them in your bilge.

 

[sailorman]

Is your backup genset petrol-powered? Is your laz sealed off from your bilge? Beware of petrol vapours, which are heavier than air and as explosive as dynamite. You do not want them in your bilge.

i believe ccscott knows a thing or two about boats

been around these parts 5 yrs

 

[boatmike]

Too many polarised answers on here. I think if you are truly blue water rather than offshore you need to ask how many hours you will want to run the engine for propulsion. If the answer is "not a lot" then running it to charge batteries is not economical on diesel and also not good for the engine unless you load it by driving the boat along too. Generally when offshore day cruising, most will use the engine anyway and get (in effect) free charging. If you will be under sail for days without needing the donker then a small gen set is better (diesel of course). I would also think wind gennies and solar panels are worth spending money on rather than rely heavily on a generator all the time. However I would think with the engine as a fallback if the genny fails a spare genny is a bit OTT. If you have a good quality set in the first place they are pretty reliable bits of kit. If you have spare cash buy solar panels instead.

 

[sailorman]

Too many polarised answers on here. I think if you are truly blue water rather than offshore you need to ask how many hours you will want to run the engine for propulsion. If the answer is "not a lot" then running it to charge batteries is not economical on diesel and also not good for the engine unless you load it by driving the boat along too. Generally when offshore day cruising, most will use the engine anyway and get (in effect) free charging. If you will be under sail for days without needing the donker then a small gen set is better (diesel of course). I would also think wind gennies and solar panels are worth spending money on rather than rely heavily on a generator all the time. However I would think with the engine as a fallback if the genny fails a spare genny is a bit OTT. If you have a good quality set in the first place they are pretty reliable bits of kit. If you have spare cash buy solar panels instead.

Apparently NOT the Fisher Panda. see my post

 

[PeterC]

So the yacht already has an 8 Kw Fischer Panda as it happens. There is less than 30 hours on it. By the sound of it I can expect lots of problems?

There is room to fit another Genset.

I also intend to upgrade the alternator to the largest possible. What would be sensible and what battery capacity and type would peole recommend please?

 

[sarabande]

I really cannot see the logic behind having another big genset. OK, there are risks one one genset going down (less if you are rigorous in maintenance, of course), but you have a backup system in the main engine and alternator and inverter.

If your system redundancy plans demand a third source of mains power, then I'd fill the space (I've never seen a boat which had too much storage BTW)
with a suitcase genny, so that you can lift it out on deck, plug into the mains system, charge batteries, run power drills in the dinghy, even take it ashore on tropical islands to run fairy lights if you wish. All at 1/4 of the price of another big genny, with associated holes in the hull and fuel lines and storage and crossover switches and remote instruments...

 

[Capt'n Pugwash]

Have you considered fuel-cell as an alternative to a genset? They seem to be getting popular with both camper and yacht owners.

I came across a system that works with methanol instead of hydrogen. Keeps the batteries topped up on demand.

Google "Efoy" for more details.

Disadvantage of course if initial cost, but if you carrying petrol for the genset then you can carry methanol cartridges too. And the sealed cartridges are only available from dealers.

Advantage, no moving parts and little or no noise.

 

[Dockhead]

i believe ccscott knows a thing or two about boats

been around these parts 5 yrs

Did not intend to insult anyone's intelligence.

I've seen a boat or two explode; I have always thought such things worth mentioning, on the off chance . .

 

[boatmike]

Apparently NOT the Fisher Panda. see my post

I can't claim to have any experience of Fisher Panda. Most of my experience has been with larger Onan sets which I have found very reliable. I have looked at budget priced DC only set at boatshows and can't say I have been over impressed. I read your blurb on your problems and I think I would agree with your conclusion that it's asking a lot from a little 6HP Kubota and would not want to rely on one like that long term, so in that sense you are right. Perhaps the answer is to buy a bigger one?

 

[sailorman]

I can't claim to have any experience of Fisher Panda. Most of my experience has been with larger Onan sets which I have found very reliable. I have looked at budget priced DC only set at boatshows and can't say I have been over impressed. I read your blurb on your problems and I think I would agree with your conclusion that it's asking a lot from a little 6HP Kubota and would not want to rely on one like that long term, so in that sense you are right. Perhaps the answer is to buy a bigger one?

Not my probs i just copied what another forumite found 2 days ago.
life is just to short for those experences + the dosh he had spent buying the thing & keeping it going

 

[Ex-SolentBoy]

I have 1000 amp hours of battery and a big alternator to charge them. We also have one of those new generators that fits to the back of the engine and generates 4kw AC when the engine is on. If you fit a standalone generator as well you have redunrancy at a fraction of the cost!

 

[Malcolm3]

In defence of Panda I have run one for 2 hours every day for the last year with only routine maintenance and no problems at all. I have on another boat had Panda Problems but that may have been contributed to by taking too much from them . An 8KW panda shouldnt be expected to give 8KW and shouldnt be run for more than a few hours at a time.
If you are going offshore I would add a towing generator (Aquair) and again my experience with them has been good despite above
Malc

 

[ccscott49]

Did not intend to insult anyone's intelligence.

I've seen a boat or two explode; I have always thought such things worth mentioning, on the off chance . .

No worries I'm not easily insulted and I agree with you sometimes mentioning something is very useful.

Its a diesel genny, air cooled, with the dry exhaust out the transom. The lazerette on Englander is a separete compartment with a watertight (Crash) bulkhead, so no worries there. I just open the hatch and run the genny, it gets plenty of cooling air and its not that noisy, well it is, but emergency (standby) only.