Alternators, Gensets, I am confused

[syfuga]

Alternators and Gensets..

Nobody seems to have stated the vital first step: you need to make a list of your power requirements under way and while stationary. This needs to be in terms of ampere-hours over a 24 hour period. You will find that continuously running kit, fridges, freezers, air conditioning, inverters (idle and under load) computers will be the significant draw, followed by instruments etc. Electric toilets, anchor winches, halyard and sheet winches, if carried, may take lots of amperes, but their duty cycle is very short, so the power required is not so great.

This then governs the balancing act that you must follow:

That should give you a clue as to the size of your service batteries. The greater the capacity, the less percentage discharge, the more efficiency and longer life you will obtain. If you aim to draw no more than 20% of your theoretical capacity per day, you are about right.

Once you have the battery bank, you need to consider how to charge it within a reasonable time. Large battery chargers are expensive, and create heat, so that needs to be taken into account.

People say that AGM batteries are better and can be charged quicker. My experience (I fitted some) is that they do not fulfil their promise and are horrendously expensive.

We started out by fitting a small diesel generator (3.5kw). Until this year it has been very unreliable, but we have had a very good year from it. Nevertheless it cost £4K in 2003, and an additional £2K in bits and pieces to plumb it in. While we would not be without it, because it keeps us at anchor, it was a very poor investment, working out at £3 per hour so far, excluding all the spares and hassle.

Do not be sold on a larger generator than you sensibly need: it will simply be less efficient, and is far better under reasonable load. You would be a masochist to fit two big ones!

We do not have a wind generator. One of the better ones would give much better value if you reckon to have wind where you are going. In the Med, they are only of benefit sporadically. Say £1200 or so. With a reliable wind you are going to get perhaps 60AH+ most days.

You don't say what HP engine you have. This may govern the sensible limit of any alternator. You may want to put an auxilliary drive and have a second alternator, as some power their refrigeration this way. Over 80A you need a hefty drive belt or dual drive. As others have said, your engine is not efficient for charging batteries unless it is used for propulsion, and it is indeed bad for the engine as it will polish the cylinders under low load. Our engine uses 3 litres an hour (48HP) but our generator uses one third of a litre an hour. Make sure you have an intelligent voltage sensing charge controller fitted to your alternator: it turns the engine into a 4-stage charger, and will bring the batteries up faster.

A much better investment is solar power. Consider a gantry, and any way you can get more of them deployed, the better. They are silent, trouble free, and efficient in terms of cost per ampere generated. We carry 150W, but would like more. Again, you need a regulator.

We carry a towed generator. We have never used it, but my son took it around the world. It is a nuisance to deploy and recover, and will slow you down a bit, but it is a source of reliable power on long journeys. You can reckon on about 6A at 5 knots I believe.

If you are not electrically savvy, find someone who is to help you.

 

[PeterC]

Thank you everyone so much for your contributions.

As you probably gather I am new to long term cruising.

Let me try and fill in some blanks.

The intention is to blue water cruise to reasonably remote destinations and to live in reasonable comfort while on longer passages and at anchor. In other words to be independent of marinas where possible and desirable.

I am therefore trying to assess what is possible.

The engine is a Yanmar 100hp. I am already lead to understand the alternator is inadequate so will be replaced. What would make the perfect replacement?

The equipment list is as follows. The yacht already has twin Raymarine E series with radar, sat phone, and VHF, heating, twin electric loos, twin showers, electric davits, electric windlass and twin electric main winches. Fortunately I think the furling is all manual, aside from the fore mentioned electric winches. There is a fridge and freezer. We will be adding air con to the three cabin areas, and a washing machine.

I should add as an explanation for posting at this stage that my offer for the yacht has been accepted and we are waiting to complete over the next few weeks.

Within reason we are lucky in that cost is not a limiting factor, we would rather do the job as well as we can and spend a little more if that makes sense.

Oh, and I also gather the battery bank is of inadequate size for our purpose and in any event all the batteries require replacement.

I would be so grateful for your guidance on the perfect size of the battery bank, the recommended make, the size and make of alternator and any other improvements that could be made. As I indicated earlier the Genset is a Fischer Panda 8Kw.

Thank you

 

[ccscott49]

Air con is a massive drain, you need a fairly big genny to run them. (which you have)Everything else is handleable, in fact almost identical to us, but no power winches. and we have icemaker and an extra fridge. 8kw will be enough for all your needs and a bit of intelligent planning will allow you to live at anchor indefinitely. I would include a watermaker.

How big is your domestic battery bank and what size charger(s) do you have?

I also have 360w of solar, which helps.

This is how I run our boat.

Use the genny every other day, charge batteries, make water.

Next time I run genny, charge batteries, use washing machine/hoover.

and carry on with that regime. I do not use the aircon, unless in a marina or if it gets unbearable, then only to cool the sleeping cabins, use fans and windscoops normally.

We do have the spare air cooled genny, (4kw) built in, but it only gets used to test and keep it free and if our FP 4.5 claps out again, main reason is to keep us cruising, until we can repair/get repaired our main genny.
Seriously thinking of replacing the FP in the next year or two, for a 6kw 1500rpm set. Not FP, I might add.

The balmar high output alternators have a good reputation, along with one of their smart regulatros, I would go for 140amps.

 

[pugwash60]

Based on experience of an 18Kva panda you will be doing yourself a favour if you remove it, sell it somewhere whilst it has some value and is still working and fit something else. I heard these rumours aboout the Panda before fitting one at the same time as a Northern Lights one on a big yacht. The Nl was 25 Kva, we went for the Panda for various reasons not least being that we could get it into the Engine room without dismantling. We were persuaded that the problems from F P had been put behind them and were impressed with the quality of the castings, manual and general appearance of quality. Big mistake. We never got through a period between services (50 hours as I recall) without a breakdown. Sometimes it turned out to be trivial like shorting wires where the insulation had somehow beeen stripped on internal wiring, sometimes major like sealed bearings which had been changed in the design from greased bearings to ones supposed to be in an oil bath but the manuals hadn't been updated and the bearing hadn't been filled. It was a complicated beast with electronics needed to be working for it to work. The Northern Lights one we fitted by contrast had clocked up 3000 hours without a missed beat. We did get the panda up to just over 2000 hours eventually but every time it started and went on the board we were just waiting for it to stop again. Overheating was often also a problem, particularly in warm waters. No one will ever persuade me that it is worth fitting one. Another thing to bear in mind is that the worldwide dealer network isn't that great and although the engine is based on a good one (ours was a kubota) it isn't the engine side that breaks down, spares are exoensive. The chaps in Germany are adequate but not particularly helpful.
From what you say it sounds as though you are needing to run a generator most of the time, I'd recommend fitting a great battery bank if you can fit one in and these days you can mount them on their sides, we used sonnenschein sealed batteries which come in cells of 2 v. I'd fit two generators possibly of different powers so that you can load them up ie if you have a load of 40 a with air con and 15 without then look at something like a 60 and 25 amp capacity ( you don't want one running on light load, it's bad for them and they end up making a lot of black smoke) say 12 and 6 Kva. Put a high output alternator on the main engine going to the house batteries and leave the current one going to the start batteries. Fit 4 stage, so called intelligent, controllers on the alternators and a big battery charger so that you can charge the batteries with either the main engine or generator.
Having said all that I think from a personal point of view now if I was doing it for myself (above experience was being paid to do it for somebody else) I'd go for the KISS approach, not have air con or anything much else, the trouble with all this gear is that it all needs to be fixed and maintained all the time, you are constantly on the internet chasing down little thingumijigs that you want to carry as spares or need yesterday to get it going again. Or if you're not that keen to do it yourself spending all the money you had budgeted for fun things on contractors. You will get to meet some great and helpful characters however. Be as involved as possible with all the fitting of stuff so you know as much about it as you can for when you need to work on it later. If you haven't already bought Nigel Calders big book on boat maintenance then I'd add it to your list - worth it's weight in saffron.
Hope some of this is interesting and doesn't sound too much like a lecture.
Good luck.

 

[PeterC]

I should have added the yacht has a water maker.

The alternator is currently 80ah and the inverter is 250W. The compressor for the fridge and freezer is water cooled.

The water maker can be operated both from an AC and DC supply.

I am interested to know how much use people make of the AC circuit to run just off the batteries? For example I would like to have a PC on board, but I guess this would run off the AC circuit. In the same way I am assuming the fridge / freezer would run off the DC circuit (I havent checked yet?)

Thanks for the book recommendation.

Any other thoughts on the best make of alternator and batteries and the ideal battery bank size.

I appreciate the wisdom of KISS. However I am afraid I equally realise I rather like technology so there is soemwhat of a conflict!!

The FP is 8Kw as I mentioned earlier. What is the collective wisdom on the most relaible make of Genset. I ahev heard it said Onans are very good.

 

[Marsupial]

I should have added the yacht has a water maker.

The alternator is currently 80ah and the inverter is 250W. The compressor for the fridge and freezer is water cooled.

The water maker can be operated both from an AC and DC supply.

I am interested to know how much use people make of the AC circuit to run just off the batteries? For example I would like to have a PC on board, but I guess this would run off the AC circuit. In the same way I am assuming the fridge / freezer would run off the DC circuit (I havent checked yet?)

Thanks for the book recommendation.

Any other thoughts on the best make of alternator and batteries and the ideal battery bank size.

I appreciate the wisdom of KISS. However I am afraid I equally realise I rather like technology so there is soemwhat of a conflict!!

The FP is 8Kw as I mentioned earlier. What is the collective wisdom on the most relaible make of Genset. I ahev heard it said Onans are very good.

OANA is a very good genset - its the weight of thing that put me off it.

My genset is used primarily to run the run the watermaker and battery charging. The Pajero will operate at 25 deg so it can be used while sailing. As far as reliability is concerned its all to do with the way the equipment is installed and how well its maintained, with that goes the requirement to use it under load for fairly long periods - say not less than 1 hour per start.

 

[PeterC]

Northern Lights and Mase also seem to have a very reliable reputation. Anyone experience of these?

If I replaced the FP (rather than install 2 Gensets) would it have much second hand value - it has less than 10 hours, but is three years old.

 

[pugwash60]

I'd stick the FP on ebay someone will buy it.
I'd use a laptop plugged into the dc system, you can use an invertor and modern ones are getting more efficient but it's sllly to take dc, convert it to AC to transform it and convert it back to dc which is what most of the computer will run on anyway when a laptop with car charger will do the job from the dc circuit anyway.
If you're expecting to run the AirCon most of the time then you'll probably have the generators on most of the time; you really need to decide whether you want to get the boat to 'go' for significant spells without a power source running and plan around that with the biggest battery bank that'll fit the space probably 1000 - 20000 amp hours, or accept that you'll have a genset or engine on all the time anyway and just have a couple of hundred a h batteries and spend the money on the gensets instead, I'd go for the former
and try to use energy efficient appliances that will run on the dc circuit like LED lights and so on. If your fridge/ freezer is well insulated then you can turn the fridge circuits off for longer too, you might want to add solar and wind power circuits but they'll only give you about enough to run a fridge and or freezer so don't expect miracles, and if you're expecting to run with air con then it's hardly worth the bother as you'll need hydrocarbons to keep up with the power demands.
With your water cooled condensor (fridge circuit) it will pay you to get into the habit of cleaning the sea strainer at least once a week particularly in the tropics, and if you haven't a decent strainer already then fit one, it's amazing how quickly fish, barnacles, jellyfish, bags, seaweed and general marine growth congregate inside a sucking pipe. If the strainer is a distance from the seawater inlet then that hose will need to be cleaned too but only every month or two and the fridges have a real sense of humour failure if they don't the expected flow of water, from that point of view air cooled ones are better but they add to the hot air in the boat too - nothing is easy!

 

[ccscott49]

Keel cooled type external cooling pipes for fridges work well, but I went with air cooled and have no problems in the meddy. (you can always fit a cooling fan to switch on when the fridge switches on) I also went with domestic fridge and freezer, on mains, running off my inverter. The cost was the factor, 1200 quid for 24v fridge and freezer, or 258 quid for domestic. I see no difference in thickness of insulation on them. The pure sine inverter is said to be 92% efficient, so not much of a loss there.

For a long term liveaboard, I would strongly reccomend, 2v-6v or even 12v true deep cycle batteries, of the open wet type, (rolls etc) much longer lasting and the charge can be whacked in, ok you will need to check the levels, but so what, not a difficult job.

I have also changed all my lights aboard, for LED's they are great and use next to naff all. Not cheap initially, but last for ever. Wish they made LED pumnps!! hehe

 

[mandlmaunder]

6v

On our cat after many hours of research and asking around about the pro's n con's of which batteries were best for us Trojan 6v 105's were the best option giving 225ah per 12v pair. Battery capacity is 675ah, you will probably need twice that amount.
Trojan now make a taller version of this battery now. giving more amp per square foot of storage space if you have the hight.
We also have a wind gen, KISS 28amp at 25knt and solar panels 180watt which run the fridge and freezer all day no problem.
Our mains power is from inverters but most things on board have slowly become 12v
We dont have AC on board and only wish for it about 2 hours 4 days a year as a sun shade and water catcher (double duty) drop the temp hughly.

Why go to a remote anchage to "get away from it all" and take your own noise and air pollution with you? (just a thought). The more hours or days with out starting an engine the more you will enjoy your quiet spots, but if you want or need all the bells n toys you will be miserable without sufficient power to use all the good stuff you have.
Except when in marinas (about 8 days every 2 years ) we mainly anchor so face into the wind.

The more engines on a boat the more time spent maintaining them! obvious I know but some thing to think about.

All this is what works for us on our boat and your comfort levels and minimum requirements will be different from any one else, with experience you will find what is best for you.

As an aside we work on a 50ft cat with all the bells n toys including AC and have a Northern lights 6.5 kva genny which works fine if services on time. Battery bank 900ah , genny runs most days about 8 hours but no AC when genny is off

Mark

 

[boatmike]

I should have added the yacht has a water maker.

The alternator is currently 80ah and the inverter is 250W. The compressor for the fridge and freezer is water cooled.

The water maker can be operated both from an AC and DC supply.

I am interested to know how much use people make of the AC circuit to run just off the batteries? For example I would like to have a PC on board, but I guess this would run off the AC circuit. In the same way I am assuming the fridge / freezer would run off the DC circuit (I havent checked yet?)

Thanks for the book recommendation.

Any other thoughts on the best make of alternator and batteries and the ideal battery bank size.

I appreciate the wisdom of KISS. However I am afraid I equally realise I rather like technology so there is soemwhat of a conflict!!

The FP is 8Kw as I mentioned earlier. What is the collective wisdom on the most relaible make of Genset. I ahev heard it said Onans are very good.

Only you can estimate power requirements based on your own usage. Some specific answers to your questions however.

Aircon is VERY power hungry. Think this out carefully. Livaboards rarely run Aircon for long and nearly always on AC with a gennie running. That's a very expensive option and frankly you will be airconditioning the oggin a lot of the time!
Personally with that engine I would up the alternator to about 110 Amp/Hours, fit a Stirling smart controller and REWIRE THE CHARGING CIRCUIT! Most charging circuits have undersize wiring in the first place and you don't need a fire. A PC is best run off the DC circuit. Many DC transformers are available for this purpose and its more efficient than AC to DC. Compared with the fridge, freezer and the watermaker the PC consumes very little though so either will be OK. You need to look at the watermaker. The main pressure pumps will be either AC or DC. AC is best but will need the genny to produce AC if that's what you have. I still think the high load items are best on AC and you will run the gennie more than the engine. One way of providing AC back up is to have a big invertor which can run off your batteries rather than have a spare gennie which is a bit OTT IMHO on a 50 ft yacht.

It's true that Onan gennies are heavier than little suitcase jobbies like Panda but that's probably because they are not built like a meccano set. They are certainly very reliable.
HOWEVER when installing one make sure you can get at it. Most small gennies die either of lack of maintenance or overheating, both caused by installing them in inaccessable corners of sometimes wet lockers. Running the fridge and freezer off DC is preferred in my case because they are on all the time. Make sure they are as well insulated as possible to keep current usage down and consider balancing this load with solar panels. That's what I have on my boat and the hotter it is the more current they produce. Exactly what you need when the fridge is working overtime!

Before you decide on anything though look at the current requirements of all the stuff you have on board and estimate the time of possible usage. This will give you the size of gennie you need and the capacity of the battery bank. When you have both numbers double them! You will not be far wrong in the end.....

 

[Marsupial]

Boatmike, Agreed! it just wish I had the time to write it all out, a point on the weight of the ONAN, it not just against the suitcase jobbies its heavier but against almost everything else its over double! True they tend to use 2 cylinders at 1500 rpm where others use 1 at 3000 but the extra weight and size was a big issue for me, I couldnt get one through the locker opening let alone instal it and have the boat upright! - good kit though.

My initial concept was to make a 12v boat but it soon become apparent that 12v watermakers are not worth the bother and anything that needs power like drills and polishers cleaners, washing machines etc must have 230v to be effective. So with that in mind the genny is sized to meet the desired load (water making battery charging and water heating) when operating at 75% of capacity - not peak capacity. Also looked at windmills and solar panels and inverters but on balance found the battery life is very short if running a powerful inverter. So that is the choice, lots of battery and bits hanging off the topsides or a diesel genny.

The best bit of kit for saving 12v is the keel cooler we have on the fridge - magic and with no fan the fridge is now silent.

Time will tell.

 

[boatmike]

Boatmike, Agreed! it just wish I had the time to write it all out, a point on the weight of the ONAN, it not just against the suitcase jobbies its heavier but against almost everything else its over double! True they tend to use 2 cylinders at 1500 rpm where others use 1 at 3000 but the extra weight and size was a big issue for me, I couldnt get one through the locker opening let alone instal it and have the boat upright! - good kit though.

My initial concept was to make a 12v boat but it soon become apparent that 12v watermakers are not worth the bother and anything that needs power like drills and polishers cleaners, washing machines etc must have 230v to be effective. So with that in mind the genny is sized to meet the desired load (water making battery charging and water heating) when operating at 75% of capacity - not peak capacity. Also looked at windmills and solar panels and inverters but on balance found the battery life is very short if running a powerful inverter. So that is the choice, lots of battery and bits hanging off the topsides or a diesel genny.

The best bit of kit for saving 12v is the keel cooler we have on the fridge - magic and with no fan the fridge is now silent.Time will tell.

You are of course correct on all counts. As I have spent most of my life fitting out "superyachts" and ferries I suppose I tend to forget they are somewhat lumpy beasts
for a smaller yacht . My point regarding inverters was not in fact that you should rely on one as main AC power but that with the main engine running they can provide back up power if the gennie goes down especially if you have a smart controller on the alternator. Without the engine running you are dead right that the inverter would soon flatten a battery bank. Solar panels are great for the reasons I stated but won't ever make enough power for more than a fridge and instruments etc. unless you fit loads of them so it's really a matter of "everything has it's place" I guess....

 

[ccscott49]

Boatmike, just as an aside, solar panels become less efficient the hotter they get, a cool panel with lots of sun is what gets it.
Small gennies are OK, its just the FP's that seem to have the major problems, dont know why, they do look well made.
I also agree with you that AC is best for washing machine, watermaker etc, thats how I do it and I've seen quite a few liveaboards, having done so permanently for 15 years.
I have tried over the years, different ways of doing things, electrically, and as I stated above, is the way I do things now. Works for me.
By the way, I do rely on my sine wave inverter to supply mains for my fridges etc. But then again I do have 550AH @ 24v battery bank, which gets a regular charging, plus 360 watts of solar to keep them going during the day.
I also have my solars on wander leads, so I can position them best for the sun, when anchored, helps a lot.