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Old 02-02-2015, 07:49   #31
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Re: Best generator for day-in/day-out use?

It is possible to build from scratch. I don't think it is practicable. My live aboard friend did it and it was ok but there are a lot of details in the engineering and build development that turned it into an ongoing hobby. The amount of vibrations (not just external but also torsional in the drive system because of the weight on the generators rotor) that can be difficult for tinkerers to get past. After 3 years he bought a production genset and is happy with the new unit. Put fuel in it and change the oil and filters and it just works.
You can't go wrong with Northern Lights. There are some other good choices but I'm not familiar with what is available in the UK. I would also look into the units that use the little Kubota or Isuzu engines.
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Old 02-02-2015, 07:56   #32
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Re: Best generator for day-in/day-out use?

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!
Will address the DIY generator first but have a couple of additional comments from previous posts.

If you're mechanically inclined it would not be too difficult to attach a generator head to a spare diesel engine. BUT then you have to rig all the marine components like the heat exchangers, water pump">raw water pump, water cooled exhaust system and all the pipes and hoses that go with it. THEN you also have to rig an accurate speed control to the engine because engine speed determines the frequency of the output. Spin to slow you get 40 Hz, too fast you get 60 Hz.

So, if you have way more time than money, are willing to expand your electrical knowledge and just cannot resist tinkering with engines and such it is doable. If not, buy a ready made unit.

Other stuff

- would be great improvement to switch lighting, computer/phone/gadget charging and other low power, frequent use things to battery. If that isn't easily accomplished then it would save you many, many hours of generator time by installing an inverter or inverter/charger. You should only consider the kind that will synchronize with your generator so both sources can combine their output to give you higher total power. These combing inverters will let you buy a smaller generator but still have the extra power that some devices need on first startup.

- Read Dockheads advise on battery charging and take it to heart. That is an excellent, simple to follow summary of the best way to keep your batteries happy without running the generator too much.

- I would advise 400-600 amp hours of battery at 12V. Are you 12V or 24V? The high end if you switch more of your use to battery like the lights.

- Switch lighting to LED when you can. Will save you lots of power.
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Old 02-02-2015, 08:15   #33
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Re: Best generator for day-in/day-out use?

Quote:
Originally Posted by skipmac View Post
Will address the DIY generator first but have a couple of additional comments from previous posts.

If you're mechanically inclined it would not be too difficult to attach a generator head to a spare diesel engine. BUT then you have to rig all the marine components like the heat exchangers, raw water pump, water cooled exhaust system and all the pipes and hoses that go with it. THEN you also have to rig an accurate speed control to the engine because engine speed determines the frequency of the output. Spin to slow you get 40 Hz, too fast you get 60 Hz.

So, if you have way more time than money, are willing to expand your electrical knowledge and just cannot resist tinkering with engines and such it is doable. If not, buy a ready made unit.

. . . .

These are good points, but note that most of them apply to AC generators. If you go with DC, then the task is much simplified. You can use a simple belt drive, and you don't need any precise speed control. No torsional vibration issues, either.

But the marinization issues are real and fairly complex (and expensive) to solve. A used marine engine would simplify this a lot since all the marinization parts are there. You could do cooling with an electric raw water pump to simplify that part of it (make sure there's a safety cutoff triggered by lack of power to the pump), standard heat exchangers are fairly easy to find, but the exhaust will be tricky -- and it has to be properly designed and built for safety's sake -- both flooding and carbon monoxide are real serious risks if you get it wrong. I would think twice about running any home-made generator inside the main hull volume, actually; much better if it is in a separate space which does not communicate with the main hull volume, for safety's sake. Note the tragic deaths and criminal charges which resulted in the UK recently from a home-made exhaust for a generator on a power boat used on a lake somewhere.

I think it's doable, but I would sure look hard at solar.
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Old 02-02-2015, 10:58   #34
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Re: Best generator for day-in/day-out use?

We have a boat similar in size modern conveniences.


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Old 02-02-2015, 12:09   #35
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Re: Best generator for day-in/day-out use?

Sorry hit the wrong key... We have a boat similar in size and modern conveniences. However, we have air conditioning that is used sometimes for a few hours when guests come for dinner or once in a while a few hours before bedtime to cool down/ lower humidity for the night. Our 7.6 kW (Westerbeke) seems to be about the right size. However, we cook with propane... both stove top & oven. But we have a AC driven holding plate freezer/frig system. It's this AC holding plate freezer/ refrig system that drives/ paces our gen use/ power budget. We need to top off the freezer/ frig for 30-45 minutes in the morning and evening. This turns out to be about the right run time to all top of the batteries. Given that the gen needs to have this schedule and generators should be loaded with with design capacity for best efficiency/ life... our/ boat's schedule has been modified to try to use the generator's surplus capacity while it's running anyway in order to reduce total run time/ noise and minimize fuel consumption (about 1/2 gal per hour). So our routine goes something like this in the morning:
- start gen with 50a/120v or 25a/240
- turn on frig system (1 0-15a)
- turn on inverter's 100a charger(15a)
- let gen warm up with these loads
they also require longest run times
- turn on water heater (15a)
- those loads total abt 40a, so...
- can't run toaster, microwave, hair
dryer loads at same time so need
learn what is your real time limit &
time or cycle off less immediate
needs for others. But usually the
refrig and 100a charger stay on
because they are most critical/
take longest to complete.
- if no hot water is needed there is
another 10a to play with
- my refrig will cut off when holding
plate reaches -10 degrees
- I have to monitor the amp-hour
battery monitor and decide when it
is time to shut down battery
charging based on status of charge
and expected battery loads before
next charging.
- same routine in evening.
- rarely is generator run except for
morning/ evening 30-45 minutes

As to your question about iPhone chargers, lights, anchor lights,... these are very very low battery/ battery charging generator loads given the generator must be run about 1.5 hours a day and happens in the background when it's running.

Every boat/ boat couple is different. Since we decided to have 120v based refrig system 15 years ago and added air conditioning in Caribbean we haven't had a need for solar panels. If you can live w/o or install an efficient 12v frig, not have air-conditioning or electric hot water, cook w/ propane you can provide all your needs with a well designed/ installed solar system.



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Old 02-02-2015, 12:10   #36
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Re: Best generator for day-in/day-out use?

The power calculation will depend on what devices you will run simultaneously. If you have run all this lot on a marina supply, an upper limit on what is necessary would be the rating of the marina supply. Normal marina supplies are 16Amp which is equivalent to about 3kW. The minimum you could get away with is thus probably about 3500VA. If you had to go for a heavy duty supply then that would probably be 32A or 6kW.

That would be enough to run the washing machine but not much else with it. Do you have a water heater? These can range from maybe 750w to 3kW. Apart from that the fridge will take up to 150w but because the power factor is poor you need to allow 300VA .Generators are usually rated in VA which equals watts for resistive loads(heating) but is higher for motors and anything with electronics.

At least you need to rate it for the washing machine plus fridge and a few lights which about 4kW should do (say 4500VA) provided you are prepared to switch the water heater off while the washing machine is running and probably avoid cooking with electric at the same time. If you want to behave as if you were connected to the mains then yes - you probably do need 6-8kW.

Finally you need to consider the waveform. Some generators are not pure sinewave which is OK for heating and probably the lights but microwaves are notorious for not working properly with modified sinewaves or quasi sinewave. Small switching mode power supplies might not like it so your mobile devices are probably best charged from the batteries using 12v chargers.

Watch the frequency for anything with motors - if you use 50Hz (European equipment with an American generator, even if you get the voltage right it will run 20% faster which might or might not be a problem.
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Old 02-02-2015, 12:13   #37
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Re: Best generator for day-in/day-out use?

FWIW-we live on a 43' Taswell, and have a 6.5kva Onan installed. We have an electric stove and over (the wife hates gas cooking), a 240vAC refer unit(coolbox+freezer box), 2 reverse-cycle aircons, and all the other AC and DC stuff live aboards typically have except for a wash machine. Our battery bank is 6 Trogan T105s connected into 3 12v "batteries"; that gives us 775 AHs. We run the genset 4x per day, to cool the refer/freezer down for approx. 30min per time. In the summer, when its hot and no breeze, we run the aircons for a coule of hours to cool the boat, then use 12vDC fans through the night.
That 6.5kva genset is good for 27+amps at 240v....we rarely see over 16 amp draw. we also have 4-85w solar panels + a windgen connected. We leave the batt charger on, and when we run the genset the batt charger is "On". Between the solar, the windgen, and the periodic batt chrgr input the batts are generally full-not an issue!
The only other thing to be warry of is if you elect to bring your 240v boat to a 110v environment (the US, Caribbean, etc). We did, and had "issues" getting things set up to be able to accept power at a marina (generally 110v). you are 240vAC, 3-wire. While US marinas have 220-240v power, it is generally 4-wire.....not compatible! We ended up buying a 5000w step-up (110v-220v)transformer. The typical power pole is 110v 30amp (approx. 3600w). That equates to the typical European 240v 16amp power pole supply (3800w). It works!...if you have the transformer. Hope this helps!
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Old 02-02-2015, 14:53   #38
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Re: Best generator for day-in/day-out use?

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!
Essentially you are talking about a DC generator which quite a few have done. Expect an AC generator might have a few safety issues unless done by a professional.

Here is a thread on a DC genset by a professional.

Charge Cycle Generator
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Old 02-02-2015, 16:04   #39
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Re: Best generator for day-in/day-out use?

Wow! That's a fair few responses, and detailed! Thanks!

Anything already on the existing batts is 12v (water pump, bilge pump & some lights), the 240 AC stuff is on the mains supply, which is what we'll lose access to when we leave this mooring. We're on the canal on a narrowboat, we're in the UK for good! Our hot water and stove top (& kettle) are propane, our heating is solid fuel stove + a back boiler & radiators, we'll really only need a washing machine, sadly also a dryer (trust me, hang drying the heavier wet fabrics in winter, on water, in England, is a fruitless endeavour!), and various bits of technological gadgetry (computer+monitor, Nintendo, mobiles...). We have no aircon in this part of the world lol! Although do we have an electric microwave/oven combo.

So, if everyone thinks this is a decent idea, as I posted on my other thread, we're thinking lots of battery space, all the bits to make power generation & batt charging more efficient, the smart gauge battery monitor to make sure we keep em in the optimum range. Then: using the boat's existing big, slow, powerful, 3 cylinder Diesel engine to generate as much electricity as can be sucked from it, with the helpful advice (about adding on a real heavy-duty alternator etc) received in this forum as a starting point for that. Also, we'll prob get a 4.5kw petrol(gasoline) gen - Honda or similar - or go the welder-generator route (wouldn't mind an excuse to have my own arc welder either lol!), for backup, as well as going solar for the summer months. Basically, any time a generator, stand-alone or boat's own engine, is running, we'll have a battery charger on that thing to give it its good workout & obvs store any power we can. And yes, definitely converting whatever works to 12v setup - all lights (and yes those to def be LEDs), stereo, chargers, and so on. Does this sound sensible?

And don't worry, I would never do anything dangerous without having done my homework inside out first! And I never do anything I'm not absolutely *certain* I can handle
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