Very small generator

[Drascomber]

In persuit of my long term project to build a generator capable of making (say) 5 amps for hours at a time (Solar and wind are not options) I have come accross these
Windstream Power
I am surprised at the size and weight compared with a 60s car dynamo of much higher output.
Apart from motive power obviously, do I need anything other than a regulator to use it for battery charging and does the team know of any alternative and possibly more compact devices.

 

[ccscott49]

The reason its larger and heavier, is it's a permanent magnet type of generator.
I wouldnt even consider it against a small alternator. Much more powe4r for less weight.

 

[MASH]

You can buy a 1.5KVA genset new for little over £100 if you look at the power tools adfs in the newspapers. Why on earth build your own? What are you going to drive it with - tide?


At $299 for a genny alone it is no wonder wind "power" is so ridiculously expensive!

 

[Drascomber]

Hi Englander,

Trouble is I can't find a small alternator. Do you know where I can find one? There must in any case be a reason why these things are made - so a permanent magnet DC generator presumably has some advantage. I just wonder what it is. If I can't find anything else I am just going to have to get one of these. /forums/images/graemlins/frown.gif

Hi Mash,
I have no where to put a 1.5KVA genset neither do I want the fuel consumption of such a beast. Even one half that size is too big and ten times overkill.

 

[richardabeattie]

Problem seems to be that we don't know what you are trying to achieve.

 

[William_H]

The thing to be aware of with this generator is that being permanent magnet type the voltage will be proportional to the speed. It is described as a high speed generator. You don't say what is going to drive it but my guess is that most likely sources are low speed so it will need a speed increasing drive syste with usual power losses.

You will hopefully need to regulate the voltage to limit the current into the battery or voltage into the system. This is best achieved by a series linear or switch mode regulator. The linear type wasting a lot of power.

An ordinary car type alternator will be more reliable not having a commutator to wear but will be less efficient in the losses in the diodes and the field current. But certainly vastly cheaper. A car alternator will also require fairly high speed drive.
good luck olewill

 

[DownWest]

5 amps is not much. Mate and I were looking at a strimmer with u/s gearbox and wondering if a direct drive to a small car alternator would be viable as a stand by generator. In my heap of bits there is a 2CV 25amp alternator, so we may go ahead wth the idea. Bit noisy perhaps, but as an emergency battery charger could be useful.
Andrew

 

[ccscott49]

Lots of small alterntors around, look for ones from small electric start petrol or diesel generators or electric start pumps etc. or small cars, lots around, cant understand how you cant find one, or you're not looking in the right places. Scrappies are the place!!
Permanebt magnet generators are there, so you dont have to have a battery to excite the field to produce electricity and can produce electricity straight away, but are limited to output and heavy. The old car generators, didnt need a battery either, as they relied upon internal "residual magnetism" to start the field excitation.
Alternators need external excitation.
Wow, didnt know I remembered all this stuff!

 

[Billjratt]

There are now some (physically) small gensets which have the windings embedded in the flywheel, and synthetically create a sine-wave (50cps AC output) if space is your main concern. Have you looked in the motorcycle scrappy ? or tried winding your own coils and fitting to the outboard ( I assume you have one)

 

[fishermantwo]

I have an old generator off a 3 cylinder Kubota that I have saved for a future project. Looks like an overgrown bike generator from the "50's.

Lots of small generators or alternators out and about.

 

[Drascomber]

Are we saying that an underdriven 25Amp alternator will be a better way of getting 5Amps?

Bike Alternators are a) not much lees powerful and b) seem to be built into the engine and transmission rather than a separable unit - until you get into the Vintage replacement market.

Thanks William. The "High speed" model was chosen simply because it was the smallest one rated for continuous duty of more than 5Amps.

A variety of power sources are under consideration but silent running is one of the requirements so low speed (say under 2500rpm - much less if practical) is desireable. If you assume a belt drive then 2 to 1 up or down shouldn't be a problem.

Hi Bill. Yes I have an outboard and the 2 Amps it already produces at cruise would suffice if I ran it 24/7 but I have a sail boat not a motor boat and I want to produce enough power when I am sailing in the day time to last 24hrs.

If I knew enough about the electrical side of this stuff to wind my own coils rather than assemble a set of bits I reckon I would have had a protoype running LAST winter.

 

[Anonymous]

Have you ever read "Trustee From the Toolroom" by Neville Shute? The protagonist is a toolmaker who writes for a modeling magazine, and among other fascinating models, we are given details of a tiny scale model generator. It's a good read especially for yachties, very boaty.

 

[DownWest]

Funny you should say that, I was also thinking of model engines. ( And the book is excellent) A look in a recent model mag. showed me how far the engines have come since I had an ED racer diesel. There are loads of small 4stroke multi-cylinder engines. Even radials for authentic periode aircraft.Price might be a problem.... I still think one might be better off with a garden implement engine, many of the new ones are 4 stroke which would be a help to keep it quiet. I had a Mase 600 genny some years ago. Small, very quiet and 20amps at 12v.for charging. Don´t know if they still make
them.
Andrew

A quick search on their Italian website says no.

 

[ccscott49]

For 5 amps and use during the day, have you considered solar?

 

[Guest]

[ QUOTE ]
A variety of power sources are under consideration but silent running is one of the requirements so low speed (say under 2500rpm - much less if practical) is desireable.

[/ QUOTE ]
If silent running is what you're after, then a 'suitcase generator' would probably be the best way to go.

[ QUOTE ]
I have an outboard and the 2 Amps it already produces at cruise would suffice if I ran it 24/7 but I have a sail boat not a motor boat and I want to produce enough power when I am sailing in the day time to last 24hrs.

[/ QUOTE ]
Just about the best solution (imho) to generating power on a small boat was published in a yachting mag a few years back, where some guy had strapped a small car alternator to the top of an outboard engine, which was rigged to pump out serious current to a battery whilst the outboard was held in neutral.
A few hours of generating 5-10 Amps might then see you though the day ?
Colin

 

[thalassa]

Son nr 1 recommends a motorbike alternator for the required output. The ones with the axle-encased ones are very well protected too.

Cheers

 

[alexrunic]

i might be missing the point here but there are a lot of cheap Chinese 2 stroke 600 watt generators about even B & Q were selling them at one time. can't remember the cost but between £50 - £100. they are very small and light weight.

 

[Drascomber]

Hi Down West
A highly modified (for slow and quiet running) small single cylinder four stroke petrol engine is one possible power source but It is difficult to spec the power requirement without knowing what you have to drive.

Hi Englander
As I said in the original post solar is not an option. When sailing the only available mounting sites that get a clear view of the sun on both tacks are the top of the mizzen mast, a bracket that starts a meter behind the transom or a bracket in front of the bow. None of these is acceptable.

Hi SAE140
Precisely. But all available suitcase generators are way too big. What I want to do is make a small one.

Alternator on top of the outboard - an interesting thought but not very elegant don't you think. Bit noisy and thirsty too.

Hi Thalassa,
We discussed that above. Not easily seperable (and still more powerful than necessary) but may be forced to do the engineering if no smaller stand alone alternative presents itself.

Hi Alexrunic.
600W units are cheap yes but small and light is relative. I need a cube a quarter or less of that size and bear in mind that I only want an output a tenth of that. I have found a smaller one just over half the cube of a 600W unit but it is still not small enough.

 

[gjeffery]

Reaches 12 volts at 2200 rev/min

12.0 volts is insufficient charging voltage for a 6 cell lead acid battery

 

[Drascomber]

Yes but presumably if I drove it a little faster I would get extra volts?

However, since the team seems to think that a permanent magnet generator has no advantage for this application and I haven't found any suitable alternator searches have lead to a supply of 250W and 350W 24Volt 2,750 rpm electric scooter motors on EBay that are cheap enough for experimentation. With suitable electronics to stop the battery driving the motor do you think one of these might become a suitable generator?