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Old 01-02-2015, 18:06   #16
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Re: Next question: best 6-8kw generator for use several hours daily?

I have NL and I like it but I wish I would have installed more Solar and Wind generators instead of that...

A small Honda eu2000i portable generator can help in an emergency.
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Old 02-02-2015, 03:59   #17
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Re: Next question: best 6-8kw generator for use several hours daily?

Ok, bear with me here, the first paragraph below is a kind of 'disclaimer', in the second one I get to the point!

I don't, as yet, have any familiarity with mechanics, electronics, or engineering in general... However, God bless the Internet for instructions & contextual information, and trust me when I say this is the kind of subject matter I'm capable of learning thoroughly and quickly. And I've got friendly acquaintances specialising in all kinds of relevant fields who would help in the case of hiccups...

Now the point: how hard would it be to build my own generator using an old but sound tractor engine & a suitably heavy-duty alternator (& all other parts)? 'Cause I can get pretty much anything from local breakers, if anyone can point me in the direction of what I need to know (basically I know nothing), and decent how-to guides, that kind of thing.

Again, all & any advice gratefully received!
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Old 02-02-2015, 04:13   #18
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Re: Next question: best 6-8kw generator for use several hours daily?

Quote:
Originally Posted by melissiti View Post
Ok, bear with me here, the first paragraph below is a kind of 'disclaimer', in the second one I get to the point!

I don't, as yet, have any familiarity with mechanics, electronics, or engineering in general... However, God bless the Internet for instructions & contextual information, and trust me when I say this is the kind of subject matter I'm capable of learning thoroughly and quickly. And I've got friendly acquaintances specialising in all kinds of relevant fields who would help in the case of hiccups...

Now the point: how hard would it be to build my own generator using an old but sound tractor engine & a suitably heavy-duty alternator (& all other parts)? 'Cause I can get pretty much anything from local breakers, if anyone can point me in the direction of what I need to know (basically I know nothing), and decent how-to guides, that kind of thing.

Again, all & any advice gratefully received!
Not that hard -- a lot of us have done it. A DC generator with a school bus alternator is the most common type for home build.

If you trawl through the archives, you'll find plenty of information.

You have to fabricate brackets and get the right sheaves and drive system. Then, you have to figure out how to mount it in your boat, and sound insulate it.

You have to match the power curve of the engine to the power at various RPM of the alternator, to get the right drive ration.

The most common engine used is the Kubota one cylinder diesel, but if it is water cooled there's a fair amount of expense and trouble involved with marinizing it -- arranging exhaust, heat exchanger, etc. Air cooled is much simpler but much noisier, and you have to arrange a sufficient quantity of air flow, plus a dry stack exhaust.

This will not be either quiet or durable or reliable like a proper heavy duty genset, but is a lot better than nothing, and can be done pretty cheaply if you find a used engine. The good news is that such a thing is so simple that it's never a big deal to fix it, or exchange broken bit of it when necessary.
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Old 02-02-2015, 04:19   #19
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Re: Next question: best 6-8kw generator for use several hours daily?

[QUOTE=melissiti;1739024]Ok, bear with me here, the first paragraph below is a kind of 'disclaimer', in the second one I get to the point!

I don't, as yet, have any familiarity with mechanics, electronics, or engineering in general... However, God bless the Internet for instructions & contextual information, and trust me when I say this is the kind of subject matter I'm capable of learning thoroughly and quickly. And I've got friendly acquaintances specialising in all kinds of relevant fields who would help in the case of hiccups...

Now the point: how hard would it be to build my own generator using an old but sound tractor engine & a suitably heavy-duty alternator (& all other parts)? 'Cause I can get pretty much anything from local breakers, if anyone can point me in the direction of what I need to know (basically I know nothing), and decent how-to guides, that kind of thing.

best bet would be to find a 2nd hand marine engine on ebay,take the gearbox and housing off and fit a twin pulley on the flywheel.
then find a fixed bearing generator to suit the horse power of the engine. match up your pulleys to get the right rpm.
mount on a frame,and plumb in onboard.

pretty easy if you have access to a work shop and a welder to make up the frame

link to stand alone alternators in the uk,6-8 kw cost about 500

Mecc Alte S.p.A.
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Old 02-02-2015, 04:46   #20
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Re: Next question: best 6-8kw generator for use several hours daily?

AWESOME I can work steel and weld myself, and I do have access to a workshop (neighbour on the other side of the canal is a pro welder & says I can use his kit), plus my husband works at a second-hand car dealers', so they can help with breakers' contact details, as well as friendly mechanics who'll check over anything I might buy, and another canal neighbour is an electromagnetics nerd who can advise if needed...

Sounds like all-systems-go! Many thanks for your help again, this forum is the best thing since sliced bread!
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Old 02-02-2015, 06:12   #21
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Re: Next question: best 6-8kw generator for use several hours daily?

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Originally Posted by melissiti View Post
AWESOME I can work steel and weld myself, and I do have access to a workshop (neighbour on the other side of the canal is a pro welder & says I can use his kit), plus my husband works at a second-hand car dealers', so they can help with breakers' contact details, as well as friendly mechanics who'll check over anything I might buy, and another canal neighbour is an electromagnetics nerd who can advise if needed...

Sounds like all-systems-go! Many thanks for your help again, this forum is the best thing since sliced bread!
OK, great!

There's a guy on here called Flying Cloud who built a really nice DC generator himself -- he might give you some tips, or you can find all the details in the archives.

The first question you will face is whether to produce AC or DC power. There are pros and cons to both, but I would suggest doing like most people and making DC. Power output will vary according to RPM and so you can regulate that, which will keep the engine loaded better and make it run more efficiently.

If you go this way, you shouldn't oversize it. 200 amps at 24v is the most you could possibly use, and anything from 100 will probably be fine.

Since you will be making DC power, you will need to match this with a good inverter. 3 kW nominal is usually enough for anyone without air conditioning and so you can back into the alternator capacity you need -- so if its around 160 amps at 24v, then you will never need full alternator output to power maximum load on your inverter, and there will always be something left over for charging your batts.

You can do your own googling, but there are tables which show you the engine power your need to power such a thing -- roughly 9 horsepower, I guess. A used marine engine (as Atoll suggested) might be the easiest thing since it will already be marinized. If you can find it. So a one or two cylinder Yanmar or something like that in the right horsepower range.

If I were you, I would buy two identical school bus alternators, if you're going to do this -- one for the generator, and the other for the main engine. Then you have redundant power sources, and you will also get an efficient charge (and be able to run your AC gear) when the main engine is running.

The economy version of this is to skip the generator and just put the school bus alternator on your main engine, and use that. Depending on the size of the main engine (the smaller the better, so that it's loaded decently when charging), this can be ok.

So to summarize, using the DC plus inverter approach, here are the main system elements:

1. School bus alternator (150 amps or so at 24v) on the main engine (that would be a priority if I were you). Important: alternator must be externally regulated, Balmar, Adverc, etc.

2. Another similar school bus alternator on a home-made generator.

3. Adequate battery bank, the bigger the better, at least 400 amp/hours at 24v, better 600. Using real deep cycle batteries, not "leisure" batteries (cheap golf cart batts are fine).

4. 3kW inverter, which will give you a practical 2.5kW. If you ever have shore power, then you will want for this to be a combo charger/inverter with power boost. If you can't manage your loads to live within 2.5kW at a time, then take the next inverter size up from that (and increase alternators a bit).

5. Merlin Smart Gauge to monitor the battery state. Maybe plus Victron battery monitor with shunt so that you can monitor currents in real time, too.


With such a system, you have up to about 2.5kW of power on tap at all times for AC equipment, which is generally enough even for large boats, as long as you're not running air conditioning. Of course you have to manage your loads and not run, for example, an electric kettle and washing machine at the same time. You run the generator or main engine when you have peak loads, and charge once or twice a day to keep the batteries between 50% or 60% and 80% or 90%. Don't let them fall below 50% or you will shorten their lives. You will need some way to top them off once and a while, preferably not less than once a week. Either shore power, if you can go into a marina periodically as I do, or solar.


Solar is absolutely brilliant, if you have space for it. You're on a canal boat, right? It should be easy to mount solar panels. Instead of a generator, you could consider a large solar array. With the school bus alternator on the main engine for bulk charging when you need it. It won't be more expensive than even a home made generator, and will be vastly easier to use, is silent, zero maintenance, no fuel cost, etc., etc., etc.

My father's boat lives like that -- big solar array plus alternator on main engine. His needs are more modest than those of many people (37' sailboat without a lot of electrical equipment), but he lives comfortably. He can go for days at anchor (which he loves to do) without running the engine at all. Solar is quite efficient in the UK outside of the dark winter months, because of the long days and cool temperatures. In the summer, a given solar panel will produce more power in the UK than it does in Florida.
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Old 02-02-2015, 06:13   #22
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Re: Next question: best 6-8kw generator for use several hours daily?

If you are going to permanently mount the generator on shore there are many alternatives. You don't have to use a marine generator for that. You can buy a Generac petrol powered unit here in the US new for $999.00. It does not have an enclosure so you need to think about covering it.

You can buy a LP gas powered 8kW generator at a big box hardware store (e.g. Home Depot) for less than $2,500.00 US. It has a full enclosure and ready to mount on a small concrete pad. These things are extremely reliable. There are thousands of them installed outside homes in the US for standby electricity service. They work extremely well.

I am pretty sure the similar things are available in the UK at various price ranges. I think you will have a hard time throwing something together from the scrap yard for less money if your time is worth anything at all.
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Old 02-02-2015, 07:07   #23
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Re: Next question: best 6-8kw generator for use several hours daily?

Solar would be ideal for summer, but "summer" only really happens at all between mid April and mid October, and you'll only get reliable runs of several days at a time really in May and June. So we definitely need both options. We may or may not be told to keep the gen strictly on the boat & off the land, so that'll dictate what we end up doing to some extent. In any case, I quite fancy the challenge of going DIY - besides which, we have very little cash we can drop in one go, we're leaving our residential mooring cause were flat broke in the first place! And I don't have much in the way of work just now, for medical reasons, so I might as well find a vaguely productive distraction Thanks for the help on how to do it myself, I think that leaves me all set for the time being, but I'll definitely be using this place for an info source when needed Cheers, all!
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Old 02-02-2015, 07:33   #24
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Re: Next question: best 6-8kw generator for use several hours daily?

Dan hit on my question: if you're planning a shoreside installation, why look at a marine Genny? There are literally dozens of industrial gensets that would fit your application.
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Old 02-02-2015, 07:35   #25
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Re: Next question: best 6-8kw generator for use several hours daily?

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We may or may not be told to keep the gen strictly on the boat & off the land, so that'll dictate what we end up doing to some extent.
I have some concern that the issues of exhaust, engine cooling, fuel supply, noise, and wiring requirements have not been completely addressed for your project. It is unclear if you intend to make this a part of your boat's system, or to use it off the boat.
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Old 02-02-2015, 08:38   #26
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Re: Next question: best 6-8kw generator for use several hours daily?

I would suggest that anything you build should be part of the boat its self rather than something to put on shore. How big is your main propulsion engine? If it is in the 100 hp range I would consider trying to put enough generator on the main engine to load it enough to get the cylinder temps up enough to keep it from glazing the cylinders. Do you have 12 volt or 24 volt DC system? A couple of 500 amp 12 volt driven by a cogged belt (or a multi ribbed belt, don't try to do this with v belts) may load up the main engine enough.

(I replied on your other thread that I don't think building your own genset is practicable. I was thinking of a real 240V AC machine. I still think that stretching the budget for a commercial unit would be more satisfactory in the long run. I think you would spend less money in the long run with a built in diesel genset. If short term expenditure is driving the decision you should look hard at the small Honda and Yamaha gas generators. )
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Old 02-02-2015, 08:39   #27
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Re: Next question: best 6-8kw generator for use several hours daily?

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Dan hit on my question: if you're planning a shoreside installation, why look at a marine Genny? There are literally dozens of industrial gensets that would fit your application.
Absolutely. If the job is to have power in a fixed location, then a land-based generator is far simpler than a marine one.

And even simpler than that is to bring mains power
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Old 02-02-2015, 08:44   #28
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Re: Next question: best 6-8kw generator for use several hours daily?

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. . . If short term expenditure is driving the decision you should look hard at the small Honda and Yamaha gas generators. )
Good point!

This is so much cheaper than an installed diesel generator, even a home-made one, that it's definitely worth considering. The Honda and Yamaha ones (others not so much) are quieter than most diesel generators. They are somewhat more expensive to operate and have a much shorter useful life, but it would take many years for a diesel genset to pay for itself in this.

Solar supplemented with suitcase generator for the dark months plus school bus alternator on the main engine can be a great solution.
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Old 02-02-2015, 08:45   #29
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Re: Next question: best 6-8kw generator for use several hours daily?

you might look on ebay ideal if you have somewhere to put it outside

5KVA SILENT RUNNING LDE6800T DIESEL GENERATOR 5KVA | eBay
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Old 02-02-2015, 08:49   #30
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Re: Next question: best 6-8kw generator for use several hours daily?

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Dan hit on my question: if you're planning a shoreside installation, why look at a marine Genny? There are literally dozens of industrial gensets that would fit your application.
Furthermore, many of these are reasonably portable, so that you can store them on the boat and set them on land when you use them, with great advantages in terms of safety (CO), noise, etc.

Here's 3kW for only 450 quid:

3Kva Diesel Generator - Electronic Key Start | eBay

Beware, however, that such units are extremely noisy -- 89dB

That will wake the dead for a mile around - a Honda or Yamaha petrol generator will be vastly quieter.
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